are compound components usually placed in the primary air
loop as the sole component. On the zone equipment side they
are usually connected to one or more zones through
uncontrolled terminal units (i.e., AirTerminal:SingleDuct:ConstantVolume:NoReheat
objects). The maximum or design air flow rate through the
furnace or unitary system should usually be set equal to the
sum of the maximum air flow rates through the terminal unit
objects. However, the simulation program can usually account
for unequal air flows if the user wishes to model this
scenario.
The following HVAC equipment types are allowed in the air
loop. The component matrix shows which coils and fans are
allowed with which equipment models.
The AirloopHVAC:UnitarySystem object is intended to replace
all other air loop equipment, although other system types are
still available. This system is unique in that it can
accommodate all fan and coil types whereas other system types
are specific to the type of fan and coil available for
simulation. Additionally, although the
AirloopHVAC:UnitarySystem is intended for use in the primary
airloop, this object can be modeled as zone equipment (i.e.,
listed in a ZoneHVAC:EquipmentList) or as an outside air
system component (i.e., listed in a
AirLoopHVAC:OutdoorAirSystem:EquipmentList). Water coil
controllers are not required when these coil types are used
with the AirloopHVAC:UnitarySystem object (i.e., leave the
controller list name blank in the AirLoopHVAC
object if water coils are used exclusively within the Unitary
System).
The AirLoopHVAC:UnitarySystem
object is a “virtual” component that consists of a fan
component (OnOff, ConstantVolume, VariableVolume, or
ComponentModel), a cooling coil component, a heating coil
component, and a reheat coil as shown in Figure 1.
When a draw through configuration is desired, the fan is
placed directly after the heating coil. If dehumidification
control is selected, a reheat coil component is also required.
If the reheat coil is present and the dehumidification control
type input is not specified as CoolReheat, the reheat coil
will not be active. All of the fan and coil components are
optional which allows the AirLoopHVAC:UnitarySystem
object to be configured for fan-only, heating-only,
cooling-only, or both heating and cooling. It may also be
applied without a fan, controlling one or more coils, similar
to the function of CoilSystem:Cooling:DX.
When the AirloopHVAC:UnitarySystem object is modeled as an
equipment on an air loop with an economizer, and when the
system is using either a Coil:Cooling:DX:Multispeed, Coil:Cooling:DX:VariableSpeed,
or a Coil:Cooling:DX
object, two types of economizer staging operation are
available, see the Economizer Operation
Staging input of the
hyperref[controlleroutdoorair]Controller:OutdoorAir
object.
Schematic of the EnergyPlus
Unitary System [fig:schematic-of-the-energyplus-unitary-system]
Links to the fan, cooling coil, heating coil and reheat
coil specifications are provided in the unitary system input
data syntax. In addition, the control zone name and the system
design operating conditions are specified by the unitary
system inputs.
For unitary systems, don’t use the night cycle manager. Use
a scheduled availability manager and let the system be always
on. Then use the Supply Air Fan Operating Mode Schedule Name
in the unitary system to switch between continuous fan (for
ventilation) during occupied periods and switch to cycling fan
for unoccupied. The system will cycle on as the thermostat
requests, and this way it will run just enough to meet the
load - no need for a minimum cycle time.
Multi-speed fan chilled and hot water coils Air Handling
Unit (AHU) can be modeled using Airloop Unitary System HVAC
object (AirloopHVAC:UnitarySystem). AHU with chilled and hot
water coils is setup by specifying Fan:OnOff
and DesignSpecificationPerformance:MultiSpeed objects in
Unitary System. The design specification performance object
allows running the chilled and hot water coils capacity
control using a multi-speed supply air fan. The multi-speed
fan capacity control for chilled and hot water coil AHU is
performed by modulating the supply air flow rate while
maintaining a constant water flow rate. The chilled or hot
water flow rates is set at maximum fixed flow rate when there
is cooling or heating load and the water flow rate is set to
zero when there is no load. Such control strategy is called
two-position cooling or heating coil control. The fan speed
selection depends on the current load, at lower load the fan
is operated at minimum speed (Speed = 1) and the fan speed
level increases progressively as the load increases until it
reaches the maximum speed level specified. The multi-speed fan
operation is modulated between the speeds to meet the current
load. When the supply air fan is cycling between consecutive
speeds levels, the speed ratio is calculated that indicates
what fraction of the time step that the system run at the
higher of the two speeds. At lower load, the fan may cycle
on-off or run continuously depending the fan operating
schedule specified. When the fan is cycling a part-load ratio
is calculated to reflect the proportion of the system timestep
the fan and coils were operating. In continuous fan operating
mode only the coil cycles on-off and the part-load ratio
applies to the coil only. Multi-speed fan capacity control is
allowed with load based control type only.
This alpha field contains control type i.e. load based or
setpoint based for the unitary system. Valid choices are
Load, SetPoint and
SingleZoneVAV. Load and SingleZoneVAV control
requires a Controlling Zone
name. SetPoint control requires set points at each coil outlet
node. A single set point at the outlet of the system is
allowed but not recommended. If setpoint control is used and
the system represents a heat pump (i.e., cooling and heating
coils are both DX coils) then only one of these coils may
operate at a time. SingleZoneVAV requires two distinct fan
flow rates, namely the Cooling and Heating Supply Air Flow
Rate and a lower No Load Supply Air Flow Rate which is used
during times of reduced cooling or heating loads.
SingleZoneVAV allows load control at low speed fan until the
load exceeds available capacity or the outlet air temperature
exceeds the specified limits where the fan speed is then
increased. For the SingleZoneVAV control type, temperature
limits are identified in the input fields for Minimum and
Maximum Supply Air Temperature. Additionally, specific coil
types are required for the SingleZoneVAV control type. The
cooling coil types are Coil:Cooling:Water,Coil:Cooling:Water:DetailedGeometry,Coil:Cooling:DX:SingleSpeed,
and Coil:Cooling:DX:VariableSpeed
while the heating coil types are Coil:Heating:Water,Coil:Heating:Fuel,Coil:Heating:Electric,Coil:Heating:DX:SingleSpeed,
and Coil:Heating:DX:VariableSpeed.
If alternate coil types are used they are modeled using the
load based control method.
Field:
Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where
the thermostat controlling the unitary system is located. This
field is required when Load or SingleZoneVAV control type is
selected.
This alpha field contains the type of dehumidification
control. The following options are valid for this field:
None - meet sensible load only, no active
dehumidification control. None is required when Control Type =
SingleZoneVAV.
Multimode - activate enhanced
dehumidification mode as needed and meet sensible load. This
option is used to model DX equipment with a controllable heat
exchanger assisting the DX cooling coil for improved
dehumidification. It is valid only with cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted.
CoolReheat - cool beyond the dry-bulb
temperature set point as required to meet the high humidity
setpoint. If cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted,
then the heat exchanger is assumed to always transfer energy
between the cooling coil’s inlet and outlet airstreams when
the cooling coil is operating.
The default is None. For the other
dehumidification control modes, the maximum humidity setpoint
is used. This must be set using a ZoneControl:Humidistat
object. When extra dehumidification is required, the system
may not be able to meet the humidity setpoint if its full
capacity is not adequate. If the dehumidification control type
is specified as CoolReheat, then two
additional inputs (reheat coil type and name) are also
required as shown below. Although the reheat coil is required
only when CoolReheat is selected, the
optional reheat coil may be present for any of the allowed
Dehumidification Control Types. If the reheat coil is present
and the dehumidification control type is not specified as
CoolReheat, the reheat coil will not be
active,
This alpha field contains the schedule name which contains
information on the availability of the unitary system to
operate. A schedule value equal to 0 denotes that the unitary
system must be off for that time period. A value greater than
0 denotes that the unitary system is available to operate
during that time period. This schedule may be used to
completely disable the unitary system as required. If this
field is left blank, the schedule has a value of 1 for all
time periods.
This alpha field contains the unitary system air inlet node
name.
When the UnitarySystem is used to serve a zone as a zone
equipment unit, this node name must be either the name of a
zone air exhaust node (Ref. ZoneHVAC:EquipmentConnections) to
draw air from a zone directly or an induced air outlet node
(Ref. AirLoopHVAC:ReturnPlenum) to draw air from a return
plenum, when the zone return node is connected to a return
plenum.
This alpha field contains the identifying type of supply
air fan specified for the unitary system. Fan type must be
Fan:OnOff,Fan:ConstantVolume,Fan:VariableVolume,
or Fan:ComponentModel.
Fan:ConstantVolume
is used when the Supply Air Fan Operating Mode Schedule values
are never 0 and the fan operates continuously. Fan:OnOff
is used when the fan cycles on and off with the cooling or
heating coil (i.e. Supply Air Fan Operating Mode Schedule
values are at times 0). Fan:VariableVolume
is used for variable air volume systems or multi- or
variable-speed coils. The Fan:ComponentModel
may be used in place of the ConstantVolume or VariableVolume
fan types to more accurately represent fan performance.
This alpha field has two choices:
BlowThrough or DrawThrough.
The first choice stands for “blow through fan”. This means
that the unit consists of a fan followed by the main cooling
and heating coils and supplemental heating coil. The fan
“blows through” the cooling and heating coils. The second
choice stands for “draw through fan”. This means that the unit
consists of the main cooling/heating coil(s) followed by a
fan, with the supplemental heater located at the outlet of the
fan. The fan “draws air through” the cooling/heating coil(s).
If this field is left blank, the default is blow through.
Field:
Supply Air Fan Operating Mode Schedule Name[LINK]
This alpha field specifies the name of the supply air fan
operating mode schedule. The supply air fan operating mode may
vary during the simulation based on time-of-day or with a
change of season. Schedule values of 0 denote that the unitary
system supply air fan and the heating or cooling coil cycle on
and off together to meet the heating or cooling load (a.k.a.
AUTO fan). Schedule values other than 0 denote that the supply
fan runs continuously while the heating or cooling coil cycles
to meet the load. The SingleZoneVAV control type is only
active when the supply air fan runs continuously (i.e., during
cycling fan operation the Control Type = Load model is
used).
This alpha field contains the identifying type of heating
coil specified in the unitary system. The hot water and steam
heating coils require specifying plant loop, branches, and
connector objects to support the heating coils, and are placed
on the demand side of the plantloop. Only specific coil types
are allowed when Control Type = SingleZoneVAV as noted.
Allowable coil types are:
This numeric field is used to adjust heat pump heating
capacity with respect to DX cooling capacity. It is used only
for DX heat pump configurations (i.e., a DX cooling and
heating coil is used).
This input field enables DX Cooling coils to be used for
100% outdoor air dedicated outdoor air system applications.
There are two choices Yes or No. If Yes, the DX coil is used
as 100% outdoor DX coil. If No, the DX coil is used as regular
DX coil. This input field is optional and the default is
No. No should be specified when selecting the SingleZoneVAV
control type.
When Use DOAS DX Cooling Coil is specified as Yes, this
input field is the DX Cooling coils leaving minimum air
temperature for frost control. The DX cooling coil leaving air
temperature is not allowed to exceed this minimum air
temperature. The DX cooling coil frost controller adjusts or
limits the desired coil outlet air setpoint temperature when
the coil outlet temperature exceeds this minimum temperature
limit specified. The minimum and maximum values of this input
field are 0.0\(^{o}\)C and
7.5\(^{o}\)C, and the default
value is 2.0\(^{o}\)C. This
field is not autosizable when the input for Use DOAS DX
Cooling Coil = Yes. When Control Type = SingleZoneVAV, enter
the minimum air temperature limit for reduced fan speed in
cooling mode. For SingleZoneVAV, the maximum limit for the
minimum supply air temperature is 20.0\(^{o}\)C. Additionally, for the
SingleZoneVAV model this input does not limit the minimum
supply air temperature resulting from cooling coil operation
at high fan speed.
This alpha field defines the latent load control method.
Available choices are SensibleOnlyLoadControl,
LatentOnlyLoadControl, LatentWithSensibleLoadControl, or
LatentOrSensibleLoadControl. The default choice is
SensibleOnlyLoadControl. The SensibleOnlyLoadControl choice
will operate to meet only a sensible load and is also required
when SingleZoneVAV control is selected. The
LatentOnlyLoadConrol will operate to meet only a latent load.
The LatentWithSensibleLoadControl will operate to meet the
latent load only if there is a sensible load. The
LatentOrSensibleLoadControl will operate to meet either a
latent or sensible load.
This alpha field contains the identifying type of
supplemental heating coil specified in the unitary system. The
hot water and steam heating coils require specifying plant
loop, branches, and connector objects to support the heating
coils, and are placed on the demand side of the plant loop.
The Coil:UserDefined
object must be configured as a heating coil. Supplemental
heating type must be one of:
This alpha field contains the identifying name given to the
unitary system supplemental or reheat coil object. This coil
provides supplemental heat during heating mode operation, or
reheats the supply air during dehumidification mode operation.
For set point based control, all coils will control to their
respective outlet air temperature set point.
This alpha field defines the supply air flow method during
cooling operation. Available choices are SupplyAirFlowRate,
FlowPerFloorArea, FractionOfAutosizedCoolingValue,
FlowPerCoolingCapacity. For each of the choices, a
corresponding air flow rate for cooling must be specified. If
the system does not have a cooling coil a 0 may be entered for
cooling air flow rate and/or no load supply air flow rate to
turn the fan off when cooling is not required.
This numeric field defines the supply air flow rate leaving
the unitary system in cubic meters per second when the cooling
coil is operating. Values must be greater than 0 if the
cooling coil is present or this field is autosizable. Required
field when Cooling Supply Air Flow Rate Method is
SupplyAirFlowRate.
Field:
Cooling Supply Air Flow Rate Per Floor Area[LINK]
This numeric field defines the supply air flow rate per
floor area leaving the unitary system in meters per second
when the cooling coil is operating. Values must be greater
than 0 if the cooling coil is present or this field is
autosizable. Required field when Cooling Supply Air Flow Rate
Method is FlowPerFloorArea.
Field:
Cooling Fraction of Autosized Design Cooling Supply Air Flow
Rate[LINK]
This numeric field defines the fraction of autosized supply
air flow rate leaving the unitary system when the cooling coil
is operating. Values must be greater than 0 if the cooling
coil is present or this field is autosizable. Required field
when Cooling Supply Air Flow Rate Method is
FractionOfAutosizedCoolingValue.
Field:
Cooling Supply Air Flow Rate Per Unit of Capacity[LINK]
This numeric field defines the supply air flow rate per
unit of capacity leaving the unitary system when the cooling
coil is operating. Values must be greater than 0 if the
cooling coil is present or this field is autosizable. Required
field when Cooling Supply Air Flow Rate Method is
FlowPerCoolingCapacity.
This alpha field defines the supply air flow method during
heating operation. Available choices are SupplyAirFlowRate,
FlowPerFloorArea, FractionOfAutosizedHeatingValue,
FlowPerHeatingCapacity. For each of the choices, a
corresponding air flow rate for heating must be specified. If
the system does not have a heating coil a 0 may be entered for
heating air flow rate and/or no load supply air flow rate to
turn the fan off when heating is not required.
This numeric field defines the supply air flow rate leaving
the unitary system in cubic meters per second when the heating
coil is operating. Values must be greater than 0 if the
heating coil is present or this field is autosizable. Required
field when Heating Supply Air Flow Rate Method is
SupplyAirFlowRate.
Field:
Heating Supply Air Flow Rate Per Floor Area[LINK]
This numeric field defines the supply air flow rate per
floor area leaving the unitary system in meters per second
when the heating coil is operating. Values must be greater
than 0 if the heating coil is present or this field is
autosizable. Required field when Heating Supply Air Flow Rate
Method is FlowPerFloorArea.
Field:
Heating Fraction of Autosized Design Heating Supply Air Flow
Rate[LINK]
This numeric field defines the fraction of autosized supply
air flow rate leaving the unitary system when the heating coil
is operating. Values must be greater than 0 if the heating
coil is present or this field is autosizable. Required field
when Heating Supply Air Flow Rate Method is
FractionOfAutosizedHeatingValue.
Field:
Heating Supply Air Flow Rate Per Unit of Capacity[LINK]
This numeric field defines the supply air flow rate per
unit of capacity leaving the unitary system when the heating
coil is operating. Values must be greater than 0 if the
heating coil is present or this field is autosizable. Required
field when Heating Supply Air Flow Rate Method is
FlowPerHeatingCapacity.
This alpha field defines the supply air flow method when
neither cooling or heating is required. Available choices are
SupplyAirFlowRate, FlowPerFloorArea,
FractionOfAutosizedCoolingValue,
FractionOfAutosizedHeatingValue, FlowPerCoolingCapacity,
FlowPerHeatingCapacity. For each of the choices, a
corresponding air flow rate must be specified. The following
fields are also used to specify the lower air flow rate for
the SingleZoneVAV control method with recommendations of
greater than or equal to 67% of the Cooling or Heating Supply
Air Flow Rate when any DX coil is used and 50% for other coil
types.
This numeric field defines the supply air flow rate leaving
the unitary system in cubic meters per second when neither
cooling or heating is required (i.e., main cooling/heating
coils and supplemental heater are off but the supply air fan
operates). This field is only used when the unitary system
operating mode is specified as continuous fan operation or
when the Control Type is specified as SingleZoneVAV. Values
must be greater than or equal to 0, or this field is
autosizable. If this field is autosized, then it is sized to
the minimum of the heating and cooling lowest speed supply air
flow rate. If the Control Type is specified as SingleZoneVAV
and this field is autosized, then the no load supply air flow
rate is set equal to 0.5 or 0.667 times the maximum flow rate
for water or coils, respectively. If the unitary system
operating mode is specified as continuous fan operation and
this value is set to zero or this field is left blank, then
the model assumes that the supply air flow rate when no
cooling/heating is needed is equal to the supply air flow rate
when the compressor was last operating (for cooling operation
or heating operation). This field should not be set to 0 when
Control Type is specified as SingleZoneVAV.
Field:
No Load Supply Air Flow Rate Per Floor Area[LINK]
This numeric field defines the supply air flow rate per
floor area leaving the unitary system in meters per second
when neither cooling or heating coil is operating. Values must
be greater than or equal to 0 or this field is autosizable.
Required field when No Load Supply Air Flow Rate Method During
is FlowPerFloorArea.
Field:
No Load Fraction of Autosized Cooling Supply Air Flow
Rate[LINK]
This numeric field defines the fraction of autosized supply
air flow rate leaving the unitary system when neither cooling
or heating coil is operating. Values must be greater than or
equal to 0 or this field is autosizable. Required field when
No Load Supply Air Flow Rate Method is
FractionOfAutosizedCoolingValue.
Field:
No Load Fraction of Autosized Heating Supply Air Flow
Rate[LINK]
This numeric field defines the fraction of autosized supply
air flow rate leaving the unitary system when the neither
cooling or heating coil is operating. Values must be greater
than or equal to 0 or this field is autosizable. Required
field when No Load Supply Air Flow Rate Method is
FractionOfAutosizedHeatingValue.
Field:
No Load Supply Air Flow Rate Per Unit of Capacity During
Cooling Operation[LINK]
This numeric field defines the supply air flow rate per
unit of capacity leaving the unitary system when neither
cooling or heating is operating. Values must be greater than
or equal to 0 or this field is autosizable. Required field
when No Load Supply Air Flow Rate Method is
FlowPerCoolingCapacity.
Field:
No Load Supply Air Flow Rate Per Unit of Capacity During
Heating Operation[LINK]
This numeric field defines the supply air flow rate per
unit of capacity leaving the unitary system when neither
cooling or heating is operating. Values must be greater than
or equal to 0 or this field is autosizable. Required field
when No Load Supply Air Flow Rate Method is
FlowPerHeatingCapacity.
Field:
No Load Supply Air Flow Rate Control Set To Low Speed[LINK]
This alpha field defines whether the supply air flow rate
leaving the air conditioner in cubic meters per second when
neither cooling nor heating is required is set to the coil
high speed or low speed air flow rate. The valid choices are
Yes or No. The default value is Yes. If the coil type does not
have multiple air flow rates or if Design Specification
Multispeed Object Type = UnitarySystemPerformance:Multispeed
then this field is not used. If Yes is selected and the coil
air flow rate is autosized the No Load Supply Air Flow Rate is
proportional to the number of speeds.
This numeric field contains the design operating air outlet
temperature in degrees C when the unitary system is heating.
If this input field is left blank, the default value is 80 C.
When Control Type = SingleZoneVAV, enter the maximum air
temperature limit for reduced fan speed in heating model. For
the SingleZoneVAV model this input does not limit the maximum
supply air temperature resulting from heating or supplemental
heating coil operation at high fan speed. This field is
autosizable.
Field:
Maximum Outdoor Dry-Bulb Temperature for Supplemental Heater
Operation[LINK]
This numeric field defines the outdoor air dry-bulb
temperature above which the heat pump supplemental heating
coil is disabled. The temperature for this input field must
be less than or equal to 21 C. If this input field is left
blank, the default value is 21 C.
Field:
Outdoor Dry-Bulb Temperature Sensor Node Name[LINK]
This alpha field specifies the name of the outdoor node
which controls the operation of the supplemental heating coil.
If this field is left blank, the outdoor temperature is based
solely on the weather data. If this field is not blank, the
node name specified must also be listed in an OutdoorAir:Node
object where the height of the node is taken into
consideration when calculating outdoor temperature from the
weather data. Alternately, the node name must be specified in
an OutdoorAir:NodeList
object where the outdoor temperature is taken directly from
the weather data.
This field defines ancillary electrical power (W) consumed
during the on-cycle period (i.e., when the cooling or heating
coil is operating). The model assumes that this ancillary
power does not contribute to heating the supply air. The
minimum value for this field is 0.0, and the default value is
also 0.0 if the field is left blank.
This field defines ancillary electrical power (W) consumed
during the off-cycle period (i.e., when the cooling and
heating coil are not operating). The model assumes that this
ancillary power does not contribute to heating the supply air.
The minimum value for this field is 0.0, and the default value
is also 0.0 if the field is left blank.
This optional input field defines the design water flow
rate used if the heat recovery option is being simulated. If
this value is greater than 0.0 then a heat recovery loop must
be specified and attached to the multispeed heat pump using
the next 2 node fields. To determine how the heat recovery
algorithm works, refer to the EnergyPlus Engineering Reference
in the AirLoopHVAC:UnitarySystem
with Heat Recovery section. The units for this input value are
cubic meters per second.
Field:
Maximum Temperature for Heat Recovery[LINK]
This field sets the maximum temperature (in degrees C) that
this heat pump can produce for heat recovery. The idea behind
this field is that the current models do not take temperatures
into account for availability and they just pass Q’s around
the loop without a temperature limit. This temperature limit
puts an upper bound on the recovered heat and limits the max
temperature leaving the component.
As temperatures in the loop approach the maximum
temperature, the temperature difference between the entering
water and the surfaces in the piece of equipment becomes
smaller. For the given heat recovery flow rate and that
temperature difference the amount of heat recovered will be
reduced, and eventually there will be no heat recovered when
the entering water temperature is equal to the maximum
temperature specified by the user in this field. The reduced
amount of heat recovered will diminish if the temperature of
the loop approach is the maximum temperature, and this will
show up in the reporting. This allows the user to set the
availability or the quality of the heat recovered for usage in
other parts of the system or to heat domestic hot water
supply.
This alpha field contains the identifying type for the
design specification multispeed object. This field is only
needed when multispeed cooling or heating coil is
specified.
This alpha field contains the identifying name for the
design specification multispeed object. This field is only
needed when multispeed cooling or heating coil is
specified.
As shown in the example below, correct specification of the
heat/cool unitary system requires specification of the
following objects in addition to the unitary system
object:
Fan (Fan:OnOff or Fan:ConstantVolume)
Cooling coil
Heating coil
Reheat coil
Direct air unit
(AirTerminal:SingleDuct:ConstantVolume:NoReheat) for each zone
served by the unitary system when used in an air loop
AirLoopHVAC:UnitarySystem,
DXAC Heat Pump 1, !- Name
Load, !- Control Type
East Zone, !- Controlling Zone or Thermostat Location
, !- Dehumidification Control Type
FanAndCoilAvailSched, !- Availability Schedule Name
Mixed Air Node, !- Air Inlet Node Name
Air Loop Outlet Node, !- Air Outlet Node Name
Fan:OnOff, !- Supply Fan Object Type
Supply Fan 1, !- Supply Fan Name
BlowThrough, !- Fan Placement
FanModeSchedule, !- Supply Air Fan Operating Mode Schedule Name
Coil:Heating:DX:MultiSpeed, !- Heating Coil Object Type
Heat Pump DX Heating Coil 1,!- Heating Coil Name
, !- DX Heating Coil Sizing Ratio
Coil:Cooling:DX:MultiSpeed, !- Cooling Coil Object Type
Heat Pump ACDXCoil 1, !- Cooling Coil Name
, !- Use DOAS DX Cooling Coil
, !- Minimum Supply Air Temperature {C}
, !- Latent Load Control
Coil:Heating:Fuel, !- Supplemental Heating Coil Object Type
Supp Gas Heating Coil 1, !- Supplemental Heating Coil Name
SupplyAirFlowRate, !- Cooling Supply Air Flow Rate Method
1.7, !- Cooling Supply Air Flow Rate {m3/s}
, !- Cooling Supply Air Flow Rate Per Floor Area {m3/s-m2}
, !- Cooling Fraction of Autosized Cooling Supply Air Flow Rate
, !- Cooling Supply Air Flow Rate Per Unit of Capacity {m3/s-W}
SupplyAirFlowRate, !- Heating Supply Air Flow Rate Method
1.7, !- Heating Supply Air Flow Rate {m3/s}
, !- Heating Supply Air Flow Rate Per Floor Area {m3/s-m2}
, !- Heating Fraction of Autosized Heating Supply Air Flow Rate
, !- Heating Supply Air Flow Rate Per Unit of Capacity {m3/s-W}
SupplyAirFlowRate, !- No Load Supply Air Flow Rate Method
0.2, !- No Load Supply Air Flow Rate {m3/s}
, !- No Load Supply Air Flow Rate Per Floor Area {m3/s-m2}
, !- No Load Fraction of Autosized Cooling Supply Air Flow Rate
, !- No Load Fraction of Autosized Heating Supply Air Flow Rate
, !- No Load Supply Air Flow Rate Per Unit of Capacity during Cooling Operation {m3/s-W}
, !- No Load Supply Air Flow Rate Per Unit of Capacity during Heating Operation {m3/s-W}
50, !- Maximum Supply Air Temperature {C}
21, !- Maximum Outdoor Dry-Bulb Temperature for Supplemental Heater Operation {C}
, !- Outdoor Dry-Bulb Temperature Sensor Node Name
, !- Ancillary On-Cycle Electric Power {W}
, !- Ancillary Off-Cycle Electric Power {W}
, !- Design Heat Recovery Water Flow Rate {m3/s}
, !- Maximum Temperature for Heat Recovery {C}
, !- Heat Recovery Water Inlet Node Name
, !- Heat Recovery Water Outlet Node Name
UnitarySystemPerformance:Multispeed, !- Design Specification Multispeed Object Type
MyMultispeedHPSpec; !- Design Specification Multispeed Object Name
UnitarySystemPerformance:Multispeed,
MyMultispeedHPSpec, !- Name
4, !- Number of Speeds for Heating
4, !- Number of Speeds for Cooling
No, !- Single Mode Operation
, !- No Load Supply Air Flow Rate Ratio
0.235294118, !- Heating Speed 1 Supply Air Flow Ratio
0.235294118, !- Cooling Speed 1 Supply Air Flow Ratio
0.470588235, !- Heating Speed 2 Supply Air Flow Ratio
0.470588235, !- Cooling Speed 2 Supply Air Flow Ratio
0.705882353, !- Heating Speed 3 Supply Air Flow Ratio
0.705882353, !- Cooling Speed 3 Supply Air Flow Ratio
1.0, !- Heating Speed 4 Supply Air Flow Ratio
1.0; !- Cooling Speed 4 Supply Air Flow Ratio
This output variable is the ratio of actual air mass flow
rate through the unitary system to the unitary system’s design
air mass flow rate (i.e., design volumetric flow rate
converted to dry air mass flow rate). For continuous fan
operation mode, this variable is always 1.0 when the unitary
system is available (based on the availability schedule). For
cycling fan/cycling coil operation mode, the actual air mass
flow rate is calculated based on the ratio of the sensible
heating (or cooling) load to the steady-state unitary system
heating (or cooling) capacity. For the cycling fan mode, the
runtime fraction for the unitary system fan may be different
from the fan part-load ratio reported here due the part-load
performance of the unitary system’s heating (or cooling) coil
(delay at start-up to reach steady-state output). In general,
runtime fractions are reported by individual components where
appropriate (e.g., Fan:OnOff). When the speed number is
greater than 1, the value is 1.0.
Unitary
System Compressor Part Load Ratio [][LINK]
This output variable is the ratio of the sensible load
(heating or cooling) to the steady-state capacity of the
unitary system’s DX heating or cooling coil at Speed 1. The
runtime fraction for the unitary system compressor may be
different from the compressor part-load ratio reported here
due the part-load performance of the heating/cooling coil
(delay at start-up to reach steady-state output). In general,
runtime fractions are reported by individual components where
appropriate. When the speed number is greater than 1, the
value is 1.0.
This output variable is the ratio of the sensible load
(heating or cooling) to the steady-state capacity of the
unitary system’s DX heating or cooling coil (Speed 1) for the
entire system timestep. The value is between 0.0 and 1.0 when
the unitary system is cycling on and off its lowest speed
(Speed 1) and 1.0 when the unitary system operates at speeds
above 1.
When Single Mode Operation is specified, the value is
between 0.0 and 1.0 when the heat pump is cycling on at any
given speed.
This output variable is the ratio of time in a system
timestep that the compressor is at rated speed between two
consecutive speed numbers ( [Compressor Speed - Compressor
speed at Speed i-1] / [Compressor speed at Speed i -
Compressor speed at Speed i-1]). The compressor speed ratio
reports (1.0 is max, 0.0 is min) and any value in between as
it is averaged over the timestep. The value is 0.0 during
Speed 1 operation.
The physical meaning of the speed ratio is dependent on the
compressor configuration defined in the field of child coil
object: Apply Part Load Fraction to Speeds greater than 1. The
allowed choice is either Yes or No. When No is entered, one
compressor is assumed for all speeds. The speed ratio
represents how long the higher speed runs as a fraction of the
system timestep, and the lower speed runs in the rest of the
system timestep. When Yes is entered, multiple compressors are
assumed, and each compressor has associated speed. The speed
ratio represents how long the higher speed runs as a fraction
of the system timestep, and the low speed runs in a whole
system timestep.
When Single Mode Operation is specified, the speed ratio is
set to 0 at Speed 1 and 1 at Speed > 1.
This output variable reports the maximum speed needed when
the unitary system operates to meet the sensible load (heating
or cooling) in a system timestep. When the value is 1, the
unitary system operates at Speed 1 (lowest speed). For this
case the cycling ratio is between 0.0 and 1.0, while the speed
ratio is 0.0. When the speed number output variable is above
one, such as i, the unitary system operation is determined by
the speed ratio through linear interpolation. For example,
when the speed ratio is 0.4 and the speed number is 3, the
unitary system operates at Speed 3 for 40% of a system
timestep and at Speed 2 for 60% of a system timestep for a
single compressor. For multiple compressors, the unitary
system operates at Speed 3 in the 40% of a system timestep and
at Speed 2 in the whole system timestep.
This output field is the total (enthalpy) heat addition
rate of the unitary system to the zones it is serving in
Watts. For set point control, this value is calculated using
the enthalpy difference of the unitary system outlet air and
inlet air streams, and the air mass flow rate through the
unitary system. This value is calculated for each HVAC system
timestep being simulated, and the results (enthalpy addition
only) are averaged for the timestep being reported. For load
or single zone VAV control this value is calculated using the
outlet air and zone air conditions.
This output field is the total (enthalpy) heat extraction
rate of the unitary system from the zones it is serving in
Watts. For set point control, this value is calculated using
the enthalpy difference of the unitary system outlet air and
inlet air streams, and the air mass flow rate through the
unitary system. This value is calculated for each HVAC system
timestep being simulated, and the results (enthalpy extraction
only) are averaged for the timestep being reported. For load
or single zone VAV control this value is calculated using the
outlet air and zone air conditions.
This output field reports the sensible heat addition rate
of the unitary system to the zones it is serving in Watts. For
set point control, this value is calculated using the enthalpy
difference of the unitary system outlet air and inlet air
streams at a constant humidity ratio, and the air mass flow
rate through the unitary system. This value is calculated for
each HVAC system timestep being simulated, and the results
(heating only) are averaged for the timestep being reported.
For load or single zone VAV control this value is calculated
using the outlet air and zone air conditions.
This output field reports the moist air sensible heat
extraction rate of the unitary system from the zones it is
serving in Watts. For set point control, this value is
calculated using the enthalpy difference of the unitary system
outlet air and inlet air streams at a constant humidity ratio,
and the air mass flow rate through the unitary system. This
value is calculated for each HVAC system timestep being
simulated, and the results (cooling only) are averaged for the
timestep being reported. For load or single zone VAV control
this value is calculated using the outlet air and zone air
conditions.
This output field is the latent heat addition
(humidification) rate of the unitary system in Watts. This
value is calculated as the difference between the total energy
rate and the sensible energy rate provided by the unitary
system. This value is calculated for each HVAC system timestep
being simulated, and the results (latent heat addition only)
are averaged for the timestep being reported.
This output field is the latent heat extraction
(dehumidification) rate of the unitary system in Watts. This
value is calculated as the difference between the total energy
rate and the sensible energy rate provided by the unitary
system. This value is calculated for each HVAC system timestep
being simulated, and the results (latent heat extraction only)
are averaged for the timestep being reported.
This output field is the electricity consumption rate of
the unitary system in Watts. The consumption includes
electricity used by the DX coils (including crankcase heater
if the fuel type is electricity), fans (indoor supply air fan
and the condenser fans associated with the DX coil[s]),
defrost mode operation (resistive or reverse-cycle), auxiliary
power during on and off period, and the supplemental heating
coil (if electric). This value is calculated for each HVAC
system timestep being simulated, and the results are averaged
for the timestep being reported. Any non-electric energy use
is not reported by the unitary system object but is reported
in the associated coil objects as appropriate.
This output field is the electricity consumption of the
unitary system in Joules for the timestep being reported. The
consumption includes electricity used by the DX compressor
(including crankcase heater if the fuel type is electricity),
fans (indoor supply air fan and the condenser fans associated
with the DX coil[s]), defrost mode operation (resistive or
reverse-cycle), auxiliary power during on and off period, and
the supplemental heating coil (if electric). This value is
calculated for each HVAC system timestep being simulated, and
the results are summed for the timestep being reported. Any
non-electric energy use is not reported by the unitary system
object but is reported in the associated coil objects as
appropriate.
Unitary
System Ancillary Electricity Rate [W][LINK]
This output field is the average auxiliary electricity
consumption rate (including both on-cycle and off-cycle) in
Watts for the timestep being reported.
Unitary
System Cooling Ancillary Electricity Energy [J][LINK]
This is the auxiliary electricity consumption in Joules for
the timestep being reported. This is the auxiliary electricity
consumption during periods when the unitary system is
providing cooling (DX cooling coil is operating). This output
is also added to a meter with Resource Type = Electricity, End
Use Key = Cooling, Group Key = System (ref. Output:Meter
objects).
Unitary
System Heating Ancillary Electricity Energy [J][LINK]
This is the auxiliary electricity consumption in Joules for
the timestep being reported. This is the auxiliary electricity
consumption during periods when the unitary system is
providing heating (DX heating coil is operating). This output
is also added to a meter with Resource Type = Electricity, End
Use Key = Heating, Group Key = System (ref. Output:Meter
objects).
Unitary
System Predicted Sensible Load to Setpoint Heat Transfer Rate
[W][LINK]
This output variable is available only for load based and
single zone VAV control and is the adjusted sensible load
requested from the zone thermostat in watts. This value is
calculated by adjusting the zone predicted sensible load to
setpoint heat transfer rate based on the controlling zone air
flow fraction and the impact of fan heat and outdoor air so
that the thermostat setpoints are met. This value is used for
control purposes within the Unitary System model. Positive
values denote a heating load while negative valued denote a
cooling load. Positive and negative values do not necessarily
represent which coil type is active (e.g., a positive heating
load does not necessarily mean the heating coil will turn on).
This value is calculated for each HVAC system timestep being
simulated, and the results are averaged for the timestep being
reported.
Unitary
System Predicted Moisture Load to Setpoint Heat Transfer Rate
[W][LINK]
This output variable is available only for load based
control and is the adjusted moisture load requested from the
zone humidistat in watts. This value is calculated by
adjusting the zone predicted moisture load to setpoint heat
transfer rate based on the heat of vaporization of water,
controlling zone air flow fraction and the dehumidification
control type (i.e., the moisture load is set to 0 for
non-dehumidification systems). When this value is non-zero and
dehumidification is requested, the Unitary System Predicted
Moisture Load to Setpoint Heat Transfer Rate is compared to
the result of sensible only control and if the coil does not
provide sufficient dehumidification the coil capacity is
increased to meet this moisture load. This value is calculated
for each HVAC system timestep being simulated, and the results
are averaged for the timestep being reported.
Unitary
System Heat Recovery Inlet Temperature [C][LINK]
Unitary
System Heat Recovery Outlet Temperature [C][LINK]
Unitary
System Heat Recovery Fluid Mass Flow Rate [kg/s][LINK]
These outputs are the heat recovery inlet and outlet
temperatures and water mass flow rate for unitary systems with
heat recovery.
For multispeed unitary systems with heat recovery, these
outputs are the recoverable energy rate (in Watts) and energy
(in Joules).
Unitary
System Requested Sensible Cooling Rate [W][LINK]
This output variable is the sensible cooling requested from
the zone thermostat in watts. This value is calculated using
the unitary system outlet air and zone conditions, the
specific heat of the zone air, and the supply air mass flow
rate entering/leaving the system. This value is calculated for
each HVAC system timestep being simulated, and the results are
averaged for the timestep being reported.
Unitary
System Requested Latent Cooling Rate [W][LINK]
This output variable is the latent cooling requested from
the zone humidistat in watts. This value is calculated using
the unitary system outlet air and zone conditions, the heat of
vaporization of water at the current zone conditions, and the
supply air mass flow rate entering/leaving the system. This
value is calculated for each HVAC system timestep being
simulated, and the results are averaged for the timestep being
reported.
This output variable is the sensible heating requested from
the zone thermostat in watts. This value is calculated using
the unitary system outlet air and zone conditions, the
specific heat of the zone air, and the supply air mass flow
rate entering/leaving the system. This value is calculated for
each HVAC system timestep being simulated, and the results are
averaged for the timestep being reported.
This output variable is the ratio of the sensible load
(heating or cooling) to the steady-state capacity of the
multispeed fan chilled water or hot water coil for the entire
system timestep. The value is between 0.0 and 1.0 when the AHU
is cycling on and off its lowest speed (fan speed 1) and 1.0
when the multispeed fan chilled water or hot water AHU
operates at speed levels above 1.
This output variable is the ratio of time in a system
timestep that the AHU fan is at rated speed between two
consecutive speed levels ( [System Load – Capacity at Fan
Speed i-1] / [Capacity at Fan Speed i – Capacity at Fan Speed
i-1]). The fan speed ratio reports (1.0 is max, 0.0 is min)
and any value in between as it is averaged over the timestep.
The value is 0.0 during Speed 1 operation. AHU speed ratio
depends on the system load and the supply air fan speed. The
speed ratio represents how long the higher speed runs as a
fraction of the system timestep, and the lower speed runs in
the rest of the system timestep.
This output variable reports the maximum speed needed when
the system operates to meet the sensible load (heating or
cooling) in a system timestep. When the value is 1, the AHU
operates at Speed 1 (lowest speed). For this case the cycling
ratio is between 0.0 and 1.0, while the speed ratio is 0.0.
When the speed level is above the minimum (speed = 1), the
system operation is determined by the speed ratio. For
example, when the speed ratio is 0.4 and the speed lever is 3,
then the supply air fan and water coil operate at Speed 3 for
40% of a system timestep and at Speed 2 for 60% of a system
timestep.
Unitary
System Zone Load Sensible Heat Ratio [][LINK]
This output variable reports the load sensible heat ratio,
defined as sensible load / (sensible load + latent load) for a
subcool reheat coil. The value is used to determine required
coil output sensible heat ratio.
Unitary
System Cooling Coil Load Sensible Heat Ratio [][LINK]
This output variable reports the cooling coil load sensible
heat ratio, defined as sensible output / (sensible output +
latent output) for a subcool reheat coil. The value is used to
determine mode ratio between coil normal operation mode and
subcool or reheat operation mode.
This field defines the number of heating speeds for the
heat pump, and must match the number of heating speeds defined
in the associated heating coil. The value for this input field
defines the number of airflow rate ratios that must be defined
for heating in the fields below. The minimum value for this
field is one and the maximum value is the number specified in
the coil object. If the heating coil type used in the unitary
system object is not a multispeed coil type, then this field
should be 1.
This field defines the number of cooling speeds for the
heat pump, and must match the number of cooling speeds defined
in the associated DX cooling coil. The value for this input
field defines the number of airflow rate ratios that must be
defined for cooling in the fields below. The minimum value for
this field is one and the maximum value is the number
specified in the coil object. If the cooling coil type used in
the unitary system object is not a multispeed coil type, then
this field should be 1.
This field specifies the coil operation mode for multiple
speed DX cooling and heating coils during each HVAC timestep.
The allowed choice is Yes or No. The No choice allows a coil
works between two adjacent speeds when a system load is
greater than the coil capacity at speed 1. The Yes choice
allows a coil works with a single capacity at a different
speed. The speed number is determined by a system load.
The allowed cooling and heating coil types are restricted
to the following combinations:
This field defines the no load operating air flow rate when
the system fan is specified to operate continuously. The
allowed fractions are between 0 and 1 with a default value of
1. This fraction is usually set to the minimum of heating and
cooling operation lowest speed supply air flow fraction. The
no load air flow rate will be calculated as this fraction
multiplied by the minimum of the cooling and heating high
speed supply air flow rate. If the cooling or heating coil is
not present, this fraction is multiplied by the operating
supply air flow rate.
Field
Group: Heating and Cooling Speeds 1 to 10[LINK]
The air flow through a multispeed coil system is specified
as a group of two air flow ratio inputs, one each for heating
and cooling. If the number of speeds for heating and cooling
are different, inputs for both heating and cooling are still
required for a given speed yet one input may be blank. The
maximum of the inputs for Number of Speeds for Cooling and
Number of Speeds for Heating specified above determines how
many groups of heating and cooling supply air flow ratio
inputs are required. Both inputs for Speed 1 are required and
specify the air flow ratio for the lowest speed, followed by
the inputs for Speed 2, Speed 3, etc. up to a maximum of 10
speeds. These inputs are applicable only to multispeed or
variable speed coils.
Field:
Heating Speed <x> Supply Air Flow Ratio[LINK]
This numeric field defines the ratio of supply air flow
rate leaving the unitary system to the maximum air flow rate
specified in the coil object at maximum speed when the heating
coil is operating at Speed <x>. Values must be greater
than 0. The entered value must be greater or equal to the flow
rate ratio specified for the previous heating speed. If the
‘Number of Speeds for Heating’ is less than <x>, then
this field can be left blank.
Field:
Cooling Speed <x> Supply Air Flow Ratio
{#field-cooling-speed-x-supply-[LINK]
air-flow-ratio}
This numeric field defines the ratio of supply air flow
rate leaving the unitary system to the maximum air flow rate
specified in the coil object at maximum speed when the cooling
coil is operating at Speed <x>. Values must be greater
than 0. The entered value must be greater or equal to the flow
rate ratio specified for the previous cooling speed. If the
‘Number of Speeds for Cooling’ is less than <x>, then
this field can be left blank.
The heat/cool furnace is a “virtual” component that
consists of a fan component (OnOff or ConstantVolume), a DX
cooling coil component, and a Gas or Electric heating coil
component. The blow through furnace configuration is shown in
Figure 2
below. When a draw through furnace configuration is desired,
the fan is placed directly after the heating coil. If the
dehumidification control type is specified as CoolReheat, a
reheat coil component is also required. If the reheat coil is
present and the dehumidification control type input is not
specified as CoolReheat, the reheat coil will not be
active,
Schematic of EnergyPlus
Heat/Cool Furnace [fig:schematic-of-energyplus-heatcool-furnace]
Note: the coil order shown here has been revised from
previous versions (prior to V4.0) of Energyplus to configure
the cooling coil upstream of the heating coil. This
configuration provides uniformity with all unitary equipment.
However, for unitary HeatCool systems that do not use a reheat
coil, the heating coil can also be placed upstream of the
cooling coil. This optional coil placement is retained to
allow compatibility with previous versions of Energyplus. For
input files developed using previous versions of Energyplus,
it is recommended that the coil order be revised according to
the figure above.
Links to the fan, heating coil, DX cooling coil and
optional reheat coil specifications are provided in the
furnace input data syntax. In addition, the control zone name
and the furnace design operating conditions are specified by
the furnace inputs.
This alpha field contains the schedule name which contains
information on the availability of the furnace to operate. A
schedule value equal to 0 denotes that the furnace must be off
for that time period. A value greater than 0 denotes that the
furnace is available to operate during that time period. This
schedule may be used to completely disable the furnace as
required. If this field is left blank, the schedule has a
value of 1 for all time periods.
This alpha field contains the furnace outlet node name.
Field:
Supply Air Fan Operating Mode Schedule Name[LINK]
This alpha field specifies the name of the supply air fan
operating mode schedule. The supply air fan operating mode may
vary during the simulation based on time-of-day or with a
change of season. Schedule values of 0 denote that the furnace
supply air fan and the heating or cooling coil cycle on and
off together to meet the heating or cooling load (a.k.a. AUTO
fan). Schedule values other than 0 denote that the supply fan
runs continuously while the heating or cooling coil cycles to
meet the load.
This numeric field contains the design operating furnace
air outlet temperature in degrees C when the furnace is
heating. If this input field is left blank, the default value
is 80 C.
This numeric field defines the supply air flow rate leaving
the furnace in cubic meters per second when the DX cooling
coil is operating. Values must be greater than 0 or this field
is autosizable.
This numeric field defines the supply air flow rate leaving
the furnace in cubic meters per second when the DX heating
coil and/or supplemental heater are operating. Values must be
greater than 0 or this field is autosizable.
This numeric field defines the supply air flow rate leaving
the furnace in cubic meters per second when neither cooling or
heating is required (i.e., DX coils and supplemental heater
are off but the supply air fan operates). This field is only
used when the furnace operating mode is specified as
continuous fan operation. Values must be greater than or equal
to zero, or this field is autosizable. If the furnace
operating mode is specified as continuous fan operation and
this value is set to zero or this field is left blank, then
the model assumes that the supply air flow rate when no
cooling/heating is needed is equal to the supply air flow rate
when the compressor was last operating (for cooling operation
or heating operation).
Field:
Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where
the thermostat controlling the furnace is located.
This alpha field contains the identifying type of supply
air fan specified for the furnace. Fan type must be Fan:OnOff
or Fan:ConstantVolume.
Fan:ConstantVolume
is used when the Supply Air Fan Operating Mode Schedule values
are never 0 and the fan operates continuously. Fan:OnOff
is used when the fan cycles on and off with the cooling or
heating coil (i.e. Supply Air Fan Operating Mode Schedule
values are at times 0).
This alpha field has two choices:
BlowThrough or DrawThrough.
The first choice stands for “blow through fan”. This means
that the unit consists of a fan followed by the DX coils and
supplemental heating coil. The fan “blows through” the cooling
and heating coils. The second choice stands for “draw through
fan”. This means that the unit consists of the DX coil(s)
followed by a fan, with the supplemental heater located at the
outlet of the fan. The fan “draws air through” the DX coil(s).
If this field is left blank, the default is blow through.
This alpha field contains the identifying type of heating
coil specified in the furnace. The hot water and steam heating
coils require specifying plant loop, branches, and connector
objects to support the heating coils, and are placed on the
demand side of the plantloop. The hot water flow modulation
through the heating coil does not require additional
controller or Controller:WaterCoil
object. The parent object (Unitary Heat and Cool Furnace)
itself provides the “controller” function of modulating water
flow. Allowable coil types are:
This alpha field contains the type of dehumidification
control. The following options are valid for this field:
None - meet sensible load only, no
active dehumidification control
Multimode - activate enhanced
dehumidification mode as needed and meet sensible load. This
option is used to model DX equipment with a controllable heat
exchanger assisting the DX cooling coil for improved
dehumidification. It is valid only with cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted.
CoolReheat - cool beyond the dry-bulb
temperature set point as required to meet the high humidity
setpoint. If cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted,
then the heat exchanger is assumed to always transfer energy
between the cooling coil’s inlet and outlet airstreams when
the cooling coil is operating.
The default is None. For the other
dehumidification control modes, the maximum humidity setpoint
is used. This must be set using a ZoneControl:Humidistat
object. When extra dehumidification is required, the system
may not be able to meet the humidity setpoint if its full
capacity is not adequate. If the dehumidification control type
is specified as CoolReheat, then two
additional inputs (reheat coil type and name) are also
required as shown below. Although the reheat coil is required
only when CoolRheat is selected, the optional
reheat coil may be present for any of the allowed
Dehumidification Control Types. If the reheat coil is present
and the dehumidification control type is not specified as
CoolReheat, the reheat coil will not be
active,
This alpha field contains the identifying type of reheat
coil specified in the furnace. The hot water and steam heating
coils require specifying plant loop, branches, and connector
objects to support the heating coils, and are placed on the
demand side of the plantloop. The hot water flow modulation
through the reheat coil does not require additional controller
or Controller:WaterCoil
object. The parent object (Unitary Heat and Cool Furnace)
itself provides the “controller” function of modulating water
flow. Reheat coil type must be one of:
This alpha field contains the identifying name given to the
furnace reheat coil.
As shown in the example below, correct specification of the
heat/cool furnace requires specification of the following
objects in addition to the furnace object:
fan (Fan:OnOff or Fan:ConstantVolume)
cooling coil (Coil:Cooling:DX:SingleSpeed or
CoilSystem:Cooling:DX:HeatExchangerAssisted)
heating coil (Coil:Heating:Fuel or
Coil:Heating:Electric)
terminal unit
(AirTerminal:SingleDuct:ConstantVolume:NoReheat) for each zone
served by the furnace
Note: the furnace’s fan, cooling coil, heating coil and
optional reheat coil must be connected in the air loop
according to the configuration shown above (Figure 2)
when CoolReheat is selected as the dehumidification control
type. In addition, the volumetric air flow rate specified in
the terminal air unit for the controlling zone should properly
reflect the fractional volumetric air flow rate specified in
the furnace object.
AirLoopHVAC:Unitary:Furnace:HeatCool,
GasHeat DXAC Furnace 1, !- Name of furnace
FanAndCoilAvailSched, !- Availability schedule
Air Loop Inlet Node, !- Furnace inlet node name
Air Loop Outlet Node, !- Furnace outlet node name
CycFanSchedule, !- Supply Air Fan Operating Mode Schedule Name
80, !- Maximum supply air temperature from furnace heater {C}
1.3, !- Cooling Supply Air Flow Rate {m3/s}
1.3, !- Heating Supply Air Flow Rate {m3/s}
0.0, !- No Load Supply Air Flow Rate {m3/s}
East Zone, !- Controlling zone or thermostat location
Fan:OnOff, !- Supply fan type
Supply Fan 1, !- Supply fan name
BlowThrough, !- Fan Placement
Coil:Heating:Fuel, !- Heating coil type
Furnace Heating Coil 1, !- Heating coil name
Coil:Cooling:DX:SingleSpeed,!- Cooling coil type
Furnace ACDXCoil 1, !- Cooling coil name
None; !- Dehumidification Control Type
Coil:Heating:Fuel,
Furnace Heating Coil 1, !- Coil Name
FanAndCoilAvailSched, !- Availability Schedule Name
NaturalGas, !- Fuel Type
0.8, !- Gas Burner Efficiency of the Coil
25000, !- Nominal Capacity of the Coil {W}
Heating Coil Air Inlet Node,!- Coil\_Air\_Inlet\_Node
Air Loop Outlet Node; !- Coil\_Air\_Outlet\_Node
Coil:Cooling:DX:SingleSpeed,
Furnace ACDXCoil 1, !- Coil Name
FanAndCoilAvailSched, !- Availability Schedule
25000, !- Rated Total Cooling Capacity (gross) {W}
0.75, !- Rated SHR
3.0, !- Rated COP
1.3, !- Rated Air Volume Flow Rate {m3/s}
DX Cooling Coil Air Inlet Node, !- Coil Air Inlet Node
Heating Coil Air Inlet Node,!- Coil Air Outlet Node
WindACCoolCapFT, !- Total Cooling Capacity Modifier Curve (function of temperature)
WindACCoolCapFFF, !- Total Cooling Capacity Modifier Curve (function of flow fraction)
WindACEIRFT, !- Energy Input Ratio Modifier Curve (function of temperature)
WindACEIRFFF, !- Energy Input Ratio Modifier Curve (function of flow fraction)
WindACPLFFPLR, !- Part Load Fraction Correlation (function of part load ratio)
CyclingFanAndCompressor; !- Supply Air Fan Operation Mode
Fan:OnOff,
Supply Fan 1, !- Fan Name
FanAndCoilAvailSched, !- Availability Schedule Name
0.7, !- Fan Total Efficiency
600.0, !- Delta Pressure {Pa}
1.3, !- Max Flow Rate {m3/s}
0.9, !- Motor Efficiency
1.0, !- Motor In Airstream Fraction
Air Loop Inlet Node, !- Fan\_Inlet\_Node
DX Cooling Coil Air Inlet Node; !- Fan\_Outlet\_Node
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone1DirectAir, !- Name
, !- Availability Schedule Name
Zone 1 Terminal Inlet Node, !- Air Inlet Node Name
Zone 1 Supply Node, !- Air Outlet Node Name
0.47; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone2DirectAir, !- Name
, !- Availability Schedule Name
Zone 2 Terminal Inlet Node, !- Air Inlet Node Name
Zone 2 Supply Node, !- Air Outlet Node Name
0.36; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone3DirectAir, !- Name
, !- Availability Schedule Name
Zone 3 Terminal Inlet Node, !- Air Inlet Node Name
Zone 3 Supply Node, !- Air Outlet Node Name
0.47; !- Maximum air flow rate {m3/s}
This output variable is the ratio of actual air mass flow
rate through the furnace to the furnace’s design air mass flow
rate (i.e., design volumetric flow rate converted to dry air
mass flow rate). For continuous fan operation mode, this
variable is always 1.0 when the furnace is available (based on
the availability schedule). For cycling fan/cycling coil
operation mode, the actual air mass flow rate is calculated
based on the ratio of the sensible heating (or cooling) load
to the steady-state furnace heating (or cooling) capacity. For
the cycling fan mode, the runtime fraction for the furnace fan
may be different from the fan part-load ratio reported here
due the part-load performance of the furnace’s heating (or
cooling) coil (delay at start-up to reach steady-state
output). In general, runtime fractions are reported by
individual components where appropriate (e.g., Fan:OnOff).
The AirLoopHVAC:UnitaryHeatCool
object is the identical model to the
AirLoopHAVC:Unitary:Furnace:HeatCool object. The heat/cool
unitary system is a “virtual” component that consists of a fan
component (OnOff or ConstantVolume), a DX cooling coil
component and a Gas or Electric heating coil component as
shown in Figure 3.
When a draw through configuration is desired, the fan is
placed directly after the heating coil. If dehumidification
control is selected, a reheat coil component is also required.
If the reheat coil is present and the dehumidification control
type input is not specified as CoolReheat, the reheat coil
will not be active,
Schematic of Blow Through
Heat/Cool Unitary System [fig:schematic-of-blow-through-heatcool-unitary]
Note: the coil order shown here has been revised from
previous versions (prior to V4.0) of Energyplus to configure
the cooling coil upstream of the heating coil. This
configuration provides uniformity with all unitary equipment.
However, for unitary HeatCool systems that do not use a reheat
coil, the heating coil can also be placed upstream of the
cooling coil. This optional coil placement is retained to
allow compatibility with previous versions of Energyplus. For
input files developed using previous versions of Energyplus,
it is recommended that the coil order be revised according to
the figure above.
Links to the fan, DX cooling coil, heating coil and
optional reheat coil specifications are provided in the
unitary system input data syntax. In addition, the control
zone name and the system design operating conditions are
specified by the unitary system inputs.
This alpha field contains the schedule name which contains
information on the availability of the unitary system to
operate. A schedule value equal to 0 denotes that the unitary
system must be off for that time period. A value greater than
0 denotes that the unitary system is available to operate
during that time period. This schedule may be used to
completely disable the unitary system as required. If this
field is left blank, the schedule has a value of 1 for all
time periods.
This alpha field contains the unitary system outlet node
name.
Field:
Supply Air Fan Operating Mode Schedule Name[LINK]
This alpha field specifies the name of the supply air fan
operating mode schedule. The supply air fan operating mode may
vary during the simulation based on time-of-day or with a
change of season. Schedule values of 0 denote that the unitary
system supply air fan and the heating or cooling coil cycle on
and off together to meet the heating or cooling load (a.k.a.
AUTO fan). Schedule values other than 0 denote that the supply
fan runs continuously while the heating or cooling coil cycles
to meet the load.
This numeric field contains the design operating air outlet
temperature in degrees C when the unitary system is heating.
If this input field is left blank, the default value is 80
C.
This numeric field defines the supply air flow rate leaving
the unitary system in cubic meters per second when the DX
cooling coil is operating. Values must be greater than 0 or
this field is autosizable.
This numeric field defines the supply air flow rate leaving
the unitary system in cubic meters per second when the DX
heating coil and/or supplemental heater are operating. Values
must be greater than 0 or this field is autosizable.
This numeric field defines the supply air flow rate leaving
the unitary system in cubic meters per second when neither
cooling or heating is required (i.e., DX coils and
supplemental heater are off but the supply air fan operates).
This field is only used when the unitary system operating mode
is specified as continuous fan operation. Values must be
greater than or equal to zero, or this field is autosizable.
If the unitary system operating mode is specified as
continuous fan operation and this value is set to zero or this
field is left blank, then the model assumes that the supply
air flow rate when no cooling/heating is needed is equal to
the supply air flow rate when the compressor was last
operating (for cooling operation or heating operation).
Field:
Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where
the thermostat controlling the unitary system is located.
This alpha field contains the identifying type of supply
air fan specified for the unitary system. Fan type must be
Fan:OnOff
or Fan:ConstantVolume.
Fan:ConstantVolume
is used when the Supply Air Fan Operating Mode Schedule values
are never 0 and the fan operates continuously. Fan:OnOff
is used when the fan cycles on and off with the cooling or
heating coil (i.e. Supply Air Fan Operating Mode Schedule
values are at times 0).
This alpha field has two choices:
BlowThrough or DrawThrough.
The first choice stands for “blow through fan”. This means
that the unit consists of a fan followed by the DX coils and
supplemental heating coil. The fan “blows through” the cooling
and heating coils. The second choice stands for “draw through
fan”. This means that the unit consists of the DX coil(s)
followed by a fan, with the supplemental heater located at the
outlet of the fan. The fan “draws air through” the DX coil(s).
If this field is left blank, the default is blow through.
This alpha field contains the identifying type of heating
coil specified in the unitary system. The hot water and steam
heating coils require specifying plant loop, branches, and
connector objects to support the heating coils, and are placed
on the demand side of the plantloop. The hot water flow
modulation through the heating coil does not require
additional controller or Controller:WaterCoil
object. The parent object (Unitary Heat and Cool System)
itself provides the “controller” function of modulating water
flow. Allowable coil types are:
This alpha field contains the type of dehumidification
control. The following options are valid for this field:
None - meet sensible load only, no
active dehumidification control
Multimode - activate enhanced
dehumidification mode as needed and meet sensible load. This
option is used to model DX equipment with a controllable heat
exchanger assisting the DX cooling coil for improved
dehumidification. It is valid only with cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted.
CoolReheat - cool beyond the dry-bulb
temperature set point as required to meet the high humidity
setpoint. If cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted,
then the heat exchanger is assumed to always transfer energy
between the cooling coil’s inlet and outlet airstreams when
the cooling coil is operating.
The default is None. For the other
dehumidification control modes, the maximum humidity setpoint
is used. This must be set using a ZoneControl:Humidistat
object. When extra dehumidification is required, the system
may not be able to meet the humidity setpoint if its full
capacity is not adequate. If the dehumidification control type
is specified as CoolReheat, then two
additional inputs (reheat coil type and name) are also
required as shown below. Although the reheat coil is required
only when CoolReheat is selected, the
optional reheat coil may be present for any of the allowed
Dehumidification Control Types. If the reheat coil is present
and the dehumidification control type is not specified as
CoolReheat, the reheat coil will not be
active,
This alpha field contains the identifying type of reheat
coil specified in the unitary system. The hot water and steam
heating coils require specifying plant loop, branches, and
connector objects to support the heating coils, and are placed
on the demand side of the plantloop. The hot water flow
modulation through the reheat coil does not require additional
controller or Controller:WaterCoil
object. The parent object (Unitary Heat and Cool System)
itself provides the “controller” function of modulating water
flow. Reheat coil type must be one of:
This alpha field contains the identifying name given to the
unitary system reheat coil.
As shown in the example below, correct specification of the
heat/cool unitary system requires specification of the
following objects in addition to the unitary system
object:
1) Fan (Fan:OnOff or Fan:ConstantVolume)
2) Cooling coil (Coil:Cooling:DX:SingleSpeed or
CoilSystem:Cooling:DX:HeatExchangerAssisted)
3) Heating coil (Coil:Heating:Fuel or
Coil:Heating:Electric)
5) Direct air unit
(AirTerminal:SingleDuct:ConstantVolume:NoReheat) for each zone
served by the unitary system
Note: the unitary system’s fan, cooling coil, heating coil
and optional reheat coil must be connected in the air loop
according to the configuration shown above (Figure 3).
In addition, the volumetric air flow rate specified in the
direct air unit for the controlling zone should properly
reflect the fractional volumetric air flow rate specified in
the unitary system object.
AirLoopHVAC:Unitary:Furnace:HeatCool,
GasHeat DXAC Unitary System 1, !- Name of unitary system
FanAndCoilAvailSched, !- Availability schedule
Air Loop Inlet Node, !- Unitary system inlet node name
Air Loop Outlet Node, !- Unitary system outlet node name
CycFanSchedule, !- Supply Air Fan Operating Mode Schedule Name
80, !- Maximum supply air temperature from unitary system heater {C}
1.3, !- Cooling Supply Air Flow Rate {m3/s}
1.3, !- Heating Supply Air Flow Rate {m3/s}
0.0, !- No Load Supply Air Flow Rate {m3/s}
East Zone, !- Controlling zone or thermostat location
Fan:OnOff, !- Supply fan type
Supply Fan 1, !- Supply fan name
BlowThrough, !- Fan Placement
Coil:Heating:Fuel, !- Heating coil type
Unitary System Heating Coil 1, !- Heating coil name
Coil:Cooling:DX:SingleSpeed,!- Cooling coil type
Unitary System ACDXCoil 1, !- Cooling coil name
None; !- High humidity control
Coil:Heating:Fuel,
Unitary System Heating Coil 1, !- Coil Name
FanAndCoilAvailSched, !- Availability Schedule Name
NaturalGas, !- Fuel Type
0.8, !- Gas Burner Efficiency of the Coil
25000, !- Nominal Capacity of the Coil {W}
Heating Coil Air Inlet Node,!- Coil\_Air\_Inlet\_Node
Air Loop Outlet Node; !- Coil\_Air\_Outlet\_Node
Coil:Cooling:DX:SingleSpeed,
Unitary System ACDXCoil 1, !- Coil Name
FanAndCoilAvailSched, !- Availability Schedule
25000, !- Rated Total Cooling Capacity (gross) {W}
0.75, !- Rated SHR
3.0, !- Rated COP
1.3, !- Rated Air Volume Flow Rate {m3/s}
DX Cooling Coil Air Inlet Node, !- Coil Air Inlet Node
Heating Coil Air Inlet Node,!- Coil Air Outlet Node
WindACCoolCapFT, !- Total Cooling Capacity Modifier Curve (function of temperature)
WindACCoolCapFFF, !- Total Cooling Capacity Modifier Curve (function of flow fraction)
WindACEIRFT, !- Energy Input Ratio Modifier Curve (function of temperature)
WindACEIRFFF, !- Energy Input Ratio Modifier Curve (function of flow fraction)
WindACPLFFPLR, !- Part Load Fraction Correlation (function of part load ratio)
CyclingFanAndCompressor; !- Supply Air Fan Operation Mode
Fan:OnOff,
Supply Fan 1, !- Fan Name
FanAndCoilAvailSched, !- Availability Schedule Name
0.7, !- Fan Total Efficiency
600.0, !- Delta Pressure {Pa}
1.3, !- Max Flow Rate {m3/s}
0.9, !- Motor Efficiency
1.0, !- Motor In Airstream Fraction
Air Loop Inlet Node, !- Fan\_Inlet\_Node
DX Cooling Coil Air Inlet Node; !- Fan\_Outlet\_Node
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone1DirectAir, !- Name
, !- Availability Schedule Name
Zone 1 Terminal Inlet Node, !- Air Inlet Node Name
Zone 1 Supply Node, !- Air Outlet Node Name
0.47; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone2DirectAir, !- Name
, !- Availability Schedule Name
Zone 2 Terminal Inlet Node, !- Air Inlet Node Name
Zone 2 Supply Node, !- Air Outlet Node Name
0.36; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone3DirectAir, !- Name
, !- Availability Schedule Name
Zone 3 Terminal Inlet Node, !- Air Inlet Node Name
Zone 3 Supply Node, !- Air Outlet Node Name
0.47; !- Maximum air flow rate {m3/s}
Example of Heat/Cool Unitary System Specification
Unitary
System Heat and Cool (AirLoopHVAC) Outputs[LINK]
HVAC,Average, Unitary System Fan Part Load Ratio
[]
HVAC,Average, Unitary System Compressor Part Load
Ratio
This output variable is the ratio of actual air mass flow
rate through the unitary system to the system’s design air
mass flow rate (i.e., design volumetric flow rate converted to
dry air mass flow rate). For continuous fan operation mode,
this variable is always 1.0 when the unitary system is
available (based on the availability schedule). For cycling
fan/cycling coil operation mode, the actual air mass flow rate
is calculated based on the ratio of the sensible heating (or
cooling) load to the steady-state unitary system heating (or
cooling) capacity. For the cycling fan mode, the runtime
fraction for the unitary system fan may be different from the
fan part-load ratio reported here due the part-load
performance of the system’s heating (or cooling) coil (delay
at start-up to reach steady-state output). In general, runtime
fractions are reported by individual components where
appropriate (e.g., Fan:OnOff).
Unitary
System Compressor Part Load Ratio [][LINK]
This output variable is the ratio of the sensible cooling
load to the steady-state cooling capacity of the unitary
system’s DX cooling coil. The runtime fraction for the DX
cooling coil compressor may be different from the compressor
part-load ratio reported here due the part-load performance of
the cooling coil (delay at start-up to reach steady-state
output). In general, runtime fractions are reported by
individual components where appropriate.
The unitary air-to-air heat pump is a “virtual” component
that consists of a fan component (OnOff or ConstantVolume), a
DX cooling coil component, a DX heating coil component, and a
Gas or Electric supplementary heating coil component as shown
in the Figure below.
Schematic of EnergyPlus Unitary
Air-to-Air Heat Pump (Blow Through Configuration) [fig:schematic-of-energyplus-unitary-air-to-air-heat-pump-blow-through-configuration]
Links to the fan, DX cooling coil, DX heating coil, and
supplementary heating coil specifications are provided in the
heat pump’s input data syntax. In addition the control zone
name and the system design operating conditions are specified
by the heat pump inputs.
This alpha field contains the schedule name (ref. Schedule
objects) that contains information on the availability of the
heat pump to operate. A schedule value greater than 0 (usually
1 is used) indicates that the unit can be on during the hour.
A value less than or equal to 0 (usually 0 is used) denotes
that the unit must be off for the hour. If this field is left
blank, the schedule has a value of 1 for all time periods.
This numeric field defines the supply air flow rate leaving
the heat pump in cubic meters per second when the DX cooling
coil is operating. Values must be greater than 0 or this field
is autosizable.
This numeric field defines the supply air flow rate leaving
the heat pump in cubic meters per second when the DX heating
coil and/or supplemental heater are operating. Values must be
greater than 0 or this field is autosizable.
This numeric field defines the supply air flow rate leaving
the heat pump in cubic meters per second when neither cooling
or heating is required (i.e., DX coils and supplemental heater
are off but the supply air fan operates). This field is only
used when the heat pump operating mode is specified as
continuous fan operation. Values must be greater than or equal
to zero, or this field is autosizable. If the heat pump
operating mode is specified as continuous fan operation and
this value is set to zero or this field is left blank, then
the model assumes that the supply air flow rate when no
cooling/heating is needed is equal to the supply air flow rate
when the compressor was last operating (for cooling operation
or heating operation).
Field:
Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where
the thermostat controlling the heat pump is located.
This alpha field contains the identifying type of supply
air fan specified for the heat pump. Fan type must be
Fan:OnOff
or Fan:ConstantVolume.
Fan:ConstantVolume
is used when the Supply Air Fan Operating Mode Schedule values
are never 0 and the fan operates continuously. Fan:OnOff
is used when the fan cycles on and off with the cooling or
heating coil (i.e. Supply Air Fan Operating Mode Schedule
values are at times 0).
This alpha field contains the identifying name given to the
heat pump supply air fan, and should match the name specified
in the corresponding fan object.
This alpha field contains the identifying name given to the
heat pump DX heating coil, and should match the name specified
in the corresponding DX heating coil object.
This alpha field contains the identifying name given to the
heat pump cooling coil, and should match the name specified in
the corresponding DX cooling coil object.
This alpha field contains the identifying type of
supplemental heating coil specified in the heat pump. The hot
water and steam heating coils require specifying plant loop,
branches, and connector objects to support the heating coils,
and are placed on the demand side of the plantloop. The hot
water flow modulation through the supplemental heating coil
does not require additional controller or Controller:WaterCoil
object. The parent object (Airloop Air to Air Heat Pump)
itself provides the “controller” function of modulating water
flow. Heating coil type must be:
This alpha field contains the identifying name given to the
heat pump supplemental heating coil, and should match the name
specified in the corresponding heating coil object.
Field:
Maximum Supply Air Temperature from Supplemental Heater[LINK]
This numeric field defines the maximum allowed supply air
temperature exiting the heat pump supplemental heating
coil.
Field:
Maximum Outdoor Dry-Bulb Temperature for Supplemental Heater
Operation[LINK]
This numeric field defines the outdoor air dry-bulb
temperature above which the heat pump supplemental heating
coil is disabled. The temperature for this input field must be
less than or equal to 21 C. If this input field is left blank,
the default value is 21 C.
This alpha field has two choices:
BlowThrough or DrawThrough.
The first choice represents a blow through system where the
supply air fan is before the DX cooling/heating coil and the
supplementary heating coil. The second choice represents a
draw through system where the supply air fan is between the DX
cooling/heating coil and the supplementary heating coil. If
this input field is left blank, the default is blow
through.
Field: Supply Air Fan Operating Mode Schedule
Name
This alpha field specifies the name of the supply air fan
operating mode schedule. The supply air fan operating mode may
vary during the simulation based on time-of-day or with a
change of season. Schedule values of 0 denote that the unitary
system supply air fan and the heating or cooling coil cycle on
and off together to meet the heating or cooling load (a.k.a.
AUTO fan). Schedule values other than 0 denote that the supply
fan runs continuously while the heating or cooling coil cycles
to meet the load.
As shown in the example below, correct specification of the
air-to-air heat pump requires specification of the following
objects in addition to the heat pump object:
1) Fan (Fan:OnOff or Fan:ConstantVolume)
2) Heating coil (Coil:Heating:DX:SingleSpeed)
3) Cooling coil (Coil:Cooling:DX:SingleSpeed or
CoilSystem:Cooling:DX:HeatExchangerAssisted)
4) Supplemental heating coil (Coil:Heating:Fuel or
Coil:Heating:Electric)
5) Direct air unit
(AirTerminal:SingleDuct:ConstantVolume:NoReheat)for each zone
served by the unitary system
This alpha input field contains the type of
dehumidification control. The following options are valid for
this field:
None - meet sensible load only, no
active dehumidification control
Multimode - activate enhanced
dehumidification mode as needed and meet sensible cooling
load. This option is used to model DX equipment with a
controllable heat exchanger assisting the DX cooling coil for
improved dehumidification. It is valid only with cooling coil
type = CoilSystem:Cooling:DX:HeatExchangerAssisted.
CoolReheat - cool beyond the dry-bulb
temperature set point as required to meet the high humidity
setpoint. The excess cooling beyond the cooling set point
temperature is offset by the supplemental heating coil. If
cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted,
then the heat exchanger is assumed to always transfer energy
between the cooling coil’s inlet and outlet airstreams when
the cooling coil is operating.
The default is None. For the other
dehumidification control modes, the maximum humidity setpoint
is required. This must be set using a ZoneControl:Humidistat
object. When extra dehumidification is required, the system
may not be able to meet the humidity setpoint if its full
capacity is not adequate. Supplemental heating coil
(supplemental heating coil type and name) is a required input
in AirToAir HeatPumps. The supplemental heating coil capacity
must be adequate enough to meet the heating coil load and
offset the excess cooling load due to extra dehumidification
required to meet the high relative humidity setpoint.
This input specifies the ratio of heat pump heating to
cooling capacity. The default value is 1.0.
Note: the air-to-air heat pump’s fan, cooling coil, heating
coil and supplementary heating coil must be connected in the
air loop according to the configuration shown above (Figure
118) for the blow-through fan configuration. The only other
valid configuration is with a draw-through fan placement,
where the fan is located between the DX heating coil and the
supplementary heating coil.
AirLoopHVAC:UnitaryHeatPump:AirToAir
Example Specification[LINK]
AirLoopHVAC:UnitaryHeatPump:AirToAir,
DXAC Heat Pump 1, !- Heat Pump name
FanAndCoilAvailSched, !- Heat Pump availability schedule
Mixed Air Node, !- Heat Pump air inlet node
Air Loop Outlet Node, !- Heat Pump air outlet node
1.3, !- Cooling Supply Air Flow Rate {m3/s}
1.3, !- Heating Supply Air Flow Rate {m3/s}
0.0, !- No Load Supply Air Flow Rate {m3/s}
East Zone, !- Controlling zone or thermostat location
Fan:OnOff, !- Supply air fan type
Supply Fan 1, !- Supply air fan name –- same name used in fan object
Coil:Heating:DX:SingleSpeed,!- Heating coil type
Heat Pump DX Heating Coil 1,!- Heating coil name –- same name used in DX heating coil object
Coil:Cooling:DX:SingleSpeed,!- Cooling coil type
Heat Pump ACDXCoil 1, !- Cooling coil name –- same name used in DX cooling coil object
Coil:Heating:Fuel, !- Supplemental heating coil type
Heat Pump DX Supp Heating Coil 1, !- Supplemental heating coil name–- same as in heating coil object
50, !- Maximum supply air temperature from supplemental heater [C]
21, !- Maximum outdoor dry-bulb temp for supplemental heating coil operation [C]
BlowThrough, !- Fan placement
CycFanSchedule, !- Supply air fan operating mode schedule name
CoolReheat; !- Dehumidification Control Type
Coil:Heating:DX:SingleSpeed,
Heat Pump DX Heating Coil 1,!- Name of heating coil
FanAndCoilAvailSched, !- Heating coil schedule
35000, !- Rated total heating capacity [W] (at 21.11C/8.33C)
2.75, !- Rated heating COP
1.7, !- Rated air flow rate [m3/s]
Heating Coil Air Inlet Node,!- Coil air inlet node
SuppHeating Coil Air Inlet Node, !- Coil air outlet node
HPACHeatCapFT, !- Heating capacity modifier curve (temperature,C)
HPACHeatCapFFF, !- Heating capacity modifier curve (flow fraction)
HPACHeatEIRFT, !- Energy input ratio modifier curve (temperature,C)
HPACHeatEIRFFF, !- Energy input ratio modifier curve (flow fraction)
HPACCoolPLFFPLR, !- Part load fraction modifier curve (function of part-load ratio)
, !- defrost EIR modifier curve (temp, C) not required for resistive defrost
CyclingFanAndCompressor, !- Operation mode (cycling fan, cycling compressor)
-5.0, !- Minimum OAT for heat pump compressor operation [C]
5.0, !- Maximum outdoor dry-bulb temp for defrost operation [C]
200.0, !- Crankcase heater capacity[W]
10.0, !- Maximum OAT for crankcase heater operation [C]
resistive, !- Defrost strategy (resistive or reverse-cycle)
timed, !- Defrost control (timed or on-demand)
0.166667, !- Defrost time period fraction (used for timed defrost control only)
20000; !- Resistive defrost heater capacity [W]
Coil:Cooling:DX:SingleSpeed,
Heat Pump ACDXCoil 1, !- Name of cooling coil
FanAndCoilAvailSched, !- Availability schedule
32000, !- Rated total cooling capacity [W]
0.75, !- Rated sensible heat ratio
3.0, !- Rated COP
1.7, !- Rated air flow rate [m3/s]
DX Cooling Coil Air Inlet Node, !- Coil air inlet node
Heating Coil Air Inlet Node,!- Coil air outlet node
HPACCoolCapFT, !- Cooling capacity modifier curve (temperature,C)
HPACCoolCapFFF, !- Cooling capacity modifier curve (flow fraction)
HPACCoolEIRFT, !- Energy input ratio modifier curve (temperature,C)
HPACCoolEIRFFF, !- Energy input ratio modifier curve (flow fraction)
HPACCoolPLFFPLR, !- Part load factor modifier curve (function of part-load ratio)
CyclingFanAndCompressor; !- Operation mode (cycling fan, cycling compressor)
Coil:Heating:Fuel,
Heat Pump DX Supp Heating Coil 1, !- Name of heating coil
FanAndCoilAvailSched, !- Availability schedule
NaturalGas, !- Fuel Type
0.8, !- Gas Burner Efficiency of the Coil
32000, !- Nominal Capacity of the Coil [W]
SuppHeating Coil Air Inlet Node, !- Supplementary heating coil air side inlet node
Air Loop Outlet Node; !- Supplementary heating coil air side outlet node
Fan:OnOff,
Supply Fan 1, !- Fan Name
FanAndCoilAvailSched, !- Fan Schedule
0.7, !- Fan Total Efficiency
300.0, !- Delta Pressure [N/M^2]
1.7, !- Max Vol Flow Rate [m^3/Sec]
0.9, !- motor efficiency
1.0, !- motor in air stream fraction
Mixed Air Node, !- fan inlet node
DX Cooling Coil Air Inlet Node; !- fan outlet node
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone1DirectAir, !- Name
, !- Availability Schedule Name
Zone 1 Terminal Inlet Node, !- Air Inlet Node Name
Zone 1 Supply Node, !- Air Outlet Node Name
0.612; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone2DirectAir, !- Name
, !- Availability Schedule Name
Zone 2 Terminal Inlet Node, !- Air Inlet Node Name
Zone 2 Supply Node, !- Air Outlet Node Name
0.476; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone3DirectAir, !- Name
, !- Availability Schedule Name
Zone 3 Terminal Inlet Node, !- Air Inlet Node Name
Zone 3 Supply Node, !- Air Outlet Node Name
0.612; !- Maximum air flow rate {m3/s}
This output variable is the ratio of actual air mass flow
rate through the heat pump to the heat pump’s design air mass
flow rate (i.e., design volumetric flow rate converted to dry
air mass flow rate). For continuous fan operation mode, this
variable is always 1.0 when the furnace is available (based on
the availability schedule). For cycling fan/cycling coil
operation mode, the actual air mass flow rate is calculated
based on the ratio of the sensible heating (or cooling) load
to the steady-state heat pump heating (or cooling) capacity.
For the cycling fan mode, the runtime fraction for the heat
pump fan may be different from the fan part-load ratio
reported here due the part-load performance of the heat pump’s
heating (or cooling) coil (delay at start-up to reach
steady-state output). In general, runtime fractions are
reported by individual components where appropriate (e.g.,
Fan:OnOff).
Unitary
System Compressor Part Load Ratio [][LINK]
This output variable is the ratio of the sensible load
(heating or cooling) to the steady-state capacity of the heat
pump’s DX heating or cooling coil. The runtime fraction for
the heat pump compressor may be different from the compressor
part-load ratio reported here due the part-load performance of
the heating/cooling coil (delay at start-up to reach
steady-state output). In general, runtime fractions are
reported by individual components where appropriate.
Unitary
System Dehumidification Induced Heating Demand Rate [W][LINK]
This output variable is the additional heating demand rate
of the supplemental heating coil of an Air-to-Air heat pumps
in Watts. This additional heating demand is induced when zone
air overshoots the heating setpoint due to extra
dehumidification requirement to meet the high humidity
setpoint. This value is always positive. This value is
calculated for each HVAC system timestep, and the results are
averaged for the timestep being reported.
The multispeed air-to-air heat pump is a “virtual”
component that consists of a fan component (On/Off or
ConstVolume), a DX multispeed cooling coil component, a DX
multispeed heating coil component, and a Gas or Electric
supplemental heating coil component. This system also includes
the option to use available waste energy to heat water. A
schematic diagram of the air-to-air multispeed heat pump is
shown below. The component connection sequence for the blow
through option (shown below) from inlet to outlet is fan,
cooling coil, heating coil, and supplemental heater. The
connection sequence for the draw through option is cooling
coil, heating coil, fan, and supplemental heater.
The main difference between this heat pump object and other
EnergyPlus heat pump objects is that this object allows from
two to four discrete compressor speeds for heating and cooling
operation (instead of a single speed for each mode). The
lowest speed is called Speed 1, and the highest speed is
called Speed n (2, 3 or 4 as specified in the input syntax).
This object allows a different number of speeds for cooling
and heating, and each speed has an associated airflow rate.
The airflow rates for the various heating speeds can be
different from the airflow rates for the cooling speeds. In
addition, the airflow rate when no cooling or heating is
needed can also be defined. The number of cooling and heating
speeds defined by the user in this heat pump object must equal
the number of speeds defined in the associated coils (child
objects). For example, the number of speeds for cooling
defined in this heat pump object must be equal to the number
of speeds defined in the associated cooling coil object.
Links to the fan, DX multispeed cooling coil, DX multispeed
heating coil, and supplementary heating coil specifications
are provided in the heat pump’s input data syntax. In
addition, the control zone name and airflow rates at the
corresponding compressor speeds are specified by the heat pump
syntax.
This alpha field contains the schedule name (ref. Schedule
objects) that contains information on the availability of the
heat pump to operate. A schedule value greater than 0 (usually
1 is used) indicates that the unit can be on during the time
period. A value less than or equal to 0 (usually 0 is used)
denotes that the unit must be off for the time period. If this
field is left blank, the schedule has a value of 1 for all
time periods.
This alpha field contains the identifying type of supply
air fan specified for the heat pump. Fan type must be Fan:OnOff
or Fan:ConstantVolume.Fan:ConstantVolume
can only be used when the supply air fan operating mode is
continuous (see field ’Supply air fan operating mode schedule
name).
This alpha field contains the identifying name given to the
heat pump supply air fan, and should match the name specified
in the corresponding fan object.
This alpha field has two choices:
BlowThrough or DrawThrough.
The first choice stands for “blow through fan”. This means
that the unit consists of a fan followed by a DX multispeed
cooling coil, DX multispeed heating coil, and a supplemental
heating coil. The fan “blows through” the cooling and heating
coils. The second choice stands for “draw through fan”. This
means that the unit consists of the DX cooling and heating
coils followed by a fan, with the supplemental heater located
at the outlet of the fan. The fan “draws” air through the DX
coils.
Note: the multispeed heat pump’s supply
air fan, cooling coil, heating coil and supplemental heating
coil must be connected according to the configuration shown
above (Figure 5)
for the ‘blow through’ fan configuration. For the ‘draw
through’ fan configuration the fan must be located between the
DX heating coil and the supplemental heater, whose outlet node
is the system outlet node. In addition, the DX cooling coil
and DX heating coil operation mode must be specified
consistently with the heat pump’s supply air fan operating
mode (e.g., with the heat pump’s supply air fan set to cycle
on and off with the cooling/heating load, the DX cooling and
heating coil operation mode must be CyclingFanAndCompressor).
If the operation modes in the parent (heat pump) and child
(coil) objects are specified differently, the operation mode
in the parent object prevails.
Field:
Supply Air Fan Operating Mode Schedule Name[LINK]
This alpha field contains the schedule name (ref. Schedule
objects) that contains information to control the supply air
fan. Schedule values of zero mean that the supply air fan will
cycle off if there is no cooling or heating load in the
control zone. Non-zero schedule values mean that the supply
air fan will operate continuously even if there is no cooling
or heating load in the control zone. If this field is left
blank, the supply air fan will operate continuously for the
entire simulation period.
This alpha field contains the identifying name given to the
DX heating coil, and should match the name specified in the
corresponding DX heating coil object.
This alpha field contains the identifying name given to the
heat pump cooling coil, and should match the name specified in
the corresponding DX cooling coil object.
This alpha field contains the identifying type of
supplemental heating coil specified in the heat pump. The hot
water and steam heating coils require specifying plant loop,
branches, and connectors objects to support the heating coils,
and are placed on the demand side of the plantloop. The hot
water flow modulation through the supplemental heating coil
does not require additional controller or Controller:WaterCoil
object. The parent object (Unitary MultiSpeed Air to Air Heat
Pump) itself provides the “controller” function of modulating
water flow. Heating coil type must be:
This alpha field contains the identifying name given to the
heat pump supplemental heating coil, and should match the name
specified in the corresponding heating coil object.
Field:
Maximum Supply Air Temperature from Supplemental Heater[LINK]
This numeric field defines the maximum allowed supply air
temperature (in degrees C) exiting the heat pump supplemental
heating coil. If the calculated supply air temperature exiting
the supplemental heater exceeds this value, then it is reset
to this maximum temperature. This field is autosizable.
Field:
Maximum Outdoor Dry-Bulb Temperature for Supplemental Heater
Operation[LINK]
This numeric field defines the outdoor air dry-bulb
temperature above which the heat pump supplemental heating
coil is disabled. The temperature for this input field must
be less than or equal to 21 C. If this input field is left
blank, the default value is 21 C.
This field defines auxiliary electrical power (W) consumed
during the on-cycle period (i.e., when the cooling or heating
coil is operating). The model assumes that this auxiliary
power does not contribute to heating the supply air. The
minimum value for this field is 0.0, and the default value is
also 0.0 if the field is left blank.
This field defines auxiliary electrical power (W) consumed
during the off-cycle period (i.e., when the cooling and
heating coil are not operating). The model assumes that this
auxiliary power does not contribute to heating the supply air.
The minimum value for this field is 0.0, and the default value
is also 0.0 if the field is left blank.
This optional input field defines the design water flow
rate used if the heat recovery option is being simulated. If
this value is greater than 0.0 then a heat recovery loop must
be specified and attached to the multispeed heat pump using
the next 2 node fields. To determine how the heat recovery
algorithm works, refer to the EnergyPlus Engineering Reference
in the AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed
with Heat Recovery section. The units for this input value are
cubic meters per second.
Field:
Maximum Temperature for Heat Recovery[LINK]
This field sets the maximum temperature (in degrees C) that
this heat pump can produce for heat recovery. The idea behind
this field is that the current models do not take temperatures
into account for availability and they just pass Q’s around
the loop without a temperature limit. This temperature limit
puts an upper bound on the recovered heat and limits the max
temperature leaving the component.
As temperatures in the loop approach the maximum
temperature, the temperature difference between the entering
water and the surfaces in the piece of equipment becomes
smaller. For the given heat recovery flow rate and that
temperature difference the amount of heat recovered will be
reduced, and eventually there will be no heat recovered when
the entering water temperature is equal to the maximum
temperature specified by the user in this field. The reduced
amount of heat recovered will diminish if the temperature of
the loop approach is the maximum temperature, and this will
show up in the reporting. This allows the user to set the
availability or the quality of the heat recovered for usage in
other parts of the system or to heat domestic hot water
supply.
This numeric field defines the supply air flow rate leaving
the heat pump in cubic meters per second when neither cooling
nor heating is required (i.e., DX coils and supplemental
heater are off but the supply air fan operates). This field is
only used when the heat pump supply air fan is scheduled to
operate continuously regardless of DX coil operation (ref.
field “Supply Air Fan Operating Mode Schedule). Values must be
greater than or equal to zero, or this field is autosizable.
If the heat pump supply air fan is scheduled to operate
continuously and the input value for this field is set to zero
or this field is left blank, then the model assumes that the
supply air flow rate when no cooling/heating is needed is
equal to the supply air flow rate when the compressor was last
operating (for cooling operation or heating operation).
This field defines the number of heating speeds for the
heat pump, and must match the number of heating speeds defined
in the associated heating coil. The value for this input field
defines the number of airflow rates that must be defined for
heating in the field below. The minimum value for this field
is one and the maximum value is four. If the Heating Coil
Object Type above are Coil:Heating:Water
or Coil:Heating:Steam,
then this field should be 1.
This field defines the number of cooling speeds for the
heat pump, and must match the number of cooling speeds defined
in the associated DX cooling coil. The value for this input
field defines the number of airflow rates that must be defined
for cooling in the field below. The minimum value for this
field is two and the maximum value is four.
This required numeric field defines the supply air flow
rate leaving the heat pump in cubic meters per second when the
DX heating coil and/or supplemental heater are operating at
Speed 1 (lowest speed). Values must be greater than 0 or this
field is autosizable.
This required numeric field defines the supply air flow
rate leaving the heat pump in cubic meters per second when the
DX heating coil and/or supplemental heater are operating at
Speed 2. Values must be greater than 0 or this field is
autosizable. If not autosized, the entered value must be
greater or equal to the flow rate specified for heating Speed
1.
This numeric field defines the supply air flow rate leaving
the heat pump in cubic meters per second when the DX heating
coil and/or supplemental heater are operating at Speed 3.
Values must be greater than 0 or this field is autosizable. If
not autosized, the entered value must be greater or equal to
the flow rate specified for heating Speed 2. If the ‘Number of
Speeds for Heating’ is less than 3, then this field can be
left blank.
This numeric field defines the supply air flow rate leaving
the heat pump in cubic meters per second when the DX heating
coil and/or supplemental heater are operating at Speed 4 (high
speed). Values must be greater than 0 or this field is
autosizable. If not autosized, the entered value must be
greater or equal to the flow rate specified for heating Speed
3. If the ‘Number of Speeds for Heating’ is less than 4, then
this field can be left blank.
Note: When autosizable is selected for any
of the supply air volumetric flow rate fields, all supply air
flow fields at the different speeds must be specified as
autosizable. Otherwise, a fatal error will be issued and the
simulation will terminate.
This required numeric field defines the supply air flow
rate leaving the heat pump in cubic meters per second when the
DX cooling coil is operating at Speed 1 (lowest speed). Values
must be greater than 0 or this field is autosizable.
This required numeric field defines the supply air flow
rate leaving the heat pump in cubic meters per second when the
DX cooling coil is operating at Speed 2. Values must be
greater than 0 or this field is autosizable. If not autosized,
the entered value must be greater or equal to the flow rate
specified for cooling Speed 1.
This numeric field defines the supply air flow rate leaving
the heat pump in cubic meters per second when the DX cooling
coil is operating at Speed 3. Values must be greater than 0 or
this field is autosizable. If not autosized, the entered value
must be greater or equal to the flow rate specified for
cooling Speed 2. If the ‘Number of Speeds for Cooling’ is less
than 3, then this field can be left blank.
This numeric field defines the supply air flow rate leaving
the heat pump in cubic meters per second when the DX cooling
coil is operating at Speed 4 (highest speed). Values must be
greater than 0 or this field is autosizable. If not autosized,
the entered value must be greater or equal to the flow rate
specified for cooling Speed 3. If the ‘Number of Speeds for
Cooling’ is less than 4, then this field can be left
blank.
Following is an example input for the object and its
associated components.
AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed,
DXAC Heat Pump 1, !- Name of multispeed heat pump
FanAndCoilAvailSched, !- Availability schedule
Mixed Air Node, !- Heat pump air inlet node name
Air Loop Outlet Node, !- Heat pump air outlet node name
East Zone, !- Controlling zone or thermostat location
Fan:OnOff, !- Supply air fan type
Supply Fan 1, !- Supply air fan name
BlowThrough, !- Supply air fan placement
FanModeSchedule, !- Supply air fan operating mode schedule name
Coil:Heating:DX:MultiSpeed, Heat Pump DX Heating Coil 1, !- Heating coil type & name
, !- DX Heating Coil Sizing Ratio
Coil:Cooling:DX:MultiSpeed, Heat Pump ACDXCoil 1, !- Cooling coil type & name
Coil:Heating:Fuel, !- Supplemental heating coil type
Supp Gas Heating Coil 1, !- Supplemental heating coil name
50.0, !- Maximum supply air temperature from supplemental heater
21, !- Maximum outdoor dry-bulb temperature for supplemental heater operation
0, !- Auxiliary On-Cycle Electric Power {W}
0, !- Auxiliary Off-Cycle Electric Power {W}
0.00, !- Design Heat Recovery Water Flow Rate {m3/s}
80.0,,, !- Maximum Temp for Heat Recovery {C} & Node names (none)
0.2, !- Supply air volumetric flow rate when no cooling or heating is needed
4, !- Number of speeds for heating
4, !- Number of speeds for cooling
0.4, !- Heating Speed 1 Supply Air Flow Rate
0.8, !- Heating Speed 2 Supply Air Flow Rate
1.2, !- Heating Speed 3 Supply Air Flow Rate
1.7, !- Heating Speed 4 Supply Air Flow Rate
0.4, !- Cooling Speed 1 Supply Air Flow Rate
0.8, !- Cooling Speed 2 Supply Air Flow Rate
1.2, !- Cooling Speed 3 Supply Air Flow Rate
1.7; !- Cooling Speed 4 Supply Air Flow Rate
Coil:Heating:DX:MultiSpeed,
Heat Pump DX Heating Coil 1,!- Name of heat pump heating coil
FanAndCoilAvailSched, !- Availability Schedule
Heating Coil Air Inlet Node,!- Coil Air Inlet Node
SuppHeating Coil Air Inlet Node, !- Coil Air Outlet Node
CyclingFanAndCompressor, !- Supply Air Fan Operation Mode
-8.0, !- Minimum Outdoor Dry-bulb Temperature for Compressor Operation {C}
200.0, !- Crankcase Heater Capacity {W}
10.0, !- Maximum Outdoor Dry-bulb Temperature for Crankcase Heater
!- Operation {C}
HPACDefrostCAPFT, !- Defrost energy input ratio modifier curve (temperature)
7.22, !- Maximum Outdoor Dry-bulb Temperature for Defrost Operation
reverse-cycle, !- Defrost Strategy
timed, !- Defrost Control
0.058333, !- Defrost Time Period Fraction
2000.0, !- Resistive Defrost Heater Capacity {W}
No, !- Apply Part Load Fraction to Speeds greater than 1
NaturalGas, !- Fuel type
4, !- Number of speeds
7500, !- Rated Total Heating Capacity, Speed 1 {W}
2.75, !- Rated COP, Speed 1
0.45, !- Rated Air Volume Flow Rate, Speed 1 {m3/s}
HPACHeatCapFT Speed 1, !- Total Heating Capacity Modifier Curve, Speed 1 (temperature)
HPACHeatCapFF Speed 1, !- Total Heating capacity modifier curve, Speed 1 (flow fraction)
HPACHeatEIRFT Speed 1, !- Energy input ratio modifier curve, Speed 1 (temperature)
HPACHeatEIRFF Speed 1, !- Energy input ratio modifier curve, Speed 1 (flow fraction)
HPACHeatPLFFPLR Speed 1, !- Part load fraction correlation, Speed 1 (part load ratio)
0.2, !- Rated waste heat fraction of power input, Speed 1
HAPCHeatWHFT Speed 1, !- Waste heat modifier curve, Speed 1 (temperature)
17500, !- Rated Total Heating Capacity, Speed 2 {W}
2.75, !- Rated COP, Speed 2
0.85, !- Rated Air Volume Flow Rate, Speed 2 {m3/s}
HPACHeatCapFT Speed 2, !- Total Heating Capacity Modifier Curve, Speed 2 (temperature)
HPACHeatCapFF Speed 2, !- Total Heating capacity modifier curve, Speed 2 (flow fraction)
HPACHeatEIRFT Speed 2, !- Energy input ratio modifier curve, Speed 2 (temperature)
HPACHeatEIRFF Speed 2, !- Energy input ratio modifier curve, Speed 2 (flow fraction)
HPACHeatPLFFPLR Speed 2, !- Part load fraction correlation, Speed 2 (part load ratio)
0.2, !- Rated waste heat fraction of power input, Speed 2
HAPCHeatWHFT Speed 2, !- Waste heat modifier curve, Speed 2 (temperature)
25500, !- Rated Total Heating Capacity, Speed 3 {W}
2.75, !- Rated COP, Speed 3
1.25, !- Rated Air Volume Flow Rate, Speed 3 {m3/s}
HPACHeatCapFT Speed 3, !- Total Heating Capacity Modifier Curve, Speed 3 (temperature)
HPACHeatCapFF Speed 3, !- Total Heating capacity modifier curve, Speed 3 (flow fraction)
HPACHeatEIRFT Speed 3, !- Energy input ratio modifier curve, Speed 3 (temperature)
HPACHeatEIRFF Speed 3, !- Energy input ratio modifier curve, Speed 3 (flow fraction)
HPACHeatPLFFPLR Speed 3, !- Part load fraction correlation, Speed 3 (part load ratio)
0.2, !- Rated waste heat fraction of power input, Speed 3
HAPCHeatWHFT Speed 3, !- Waste heat modifier curve, Speed 3 (temperature)
35500, !- Rated Total Heating Capacity, Speed 4 {W}
2.75, !- Rated COP, Speed 4
1.75, !- Rated Air Volume Flow Rate, Speed 4 {m3/s}
HPACHeatCapFT Speed 4, !- Total Heating Capacity Modifier Curve, Speed 4 (temperature)
HPACHeatCapFF Speed 4, !- Total Heating capacity modifier curve, Speed 4 (flow fraction)
HPACHeatEIRFT Speed 4, !- Energy input ratio modifier curve, Speed 4 (temperature)
HPACHeatEIRFF Speed 4, !- Energy input ratio modifier curve, Speed 4 (flow fraction)
HPACHeatPLFFPLR Speed 4, !- Part load fraction correlation, Speed 4 (part load ratio)
0.2, !- Rated waste heat fraction of power input, Speed 4
HAPCHeatWHFT Speed 4; !- Waste heat modifier curve, Speed 4 (temperature)
COIL:Cooling:DX:MultiSpeed,
Heat Pump ACDXCoil 1, !- Coil Name
FanAndCoilAvailSched, !- Availability Schedule
DX Cooling Coil Air Inlet Node, !- Coil Air Inlet Node
Heating Coil Air Inlet Node,!- Coil Air Outlet Node
CyclingFanAndCompressor, !- Supply Air Fan Operation Mode
Outdoor Condenser Air Node, !- Condenser Air Inlet Node Name
AirCooled, !- Condenser Type
, !- Name of Water Storage Tank for Supply
, !- Name of Water Storage Tank for Condensate Collection
No, !- Apply Part Load Fraction to Speeds greater than 1
No, !- Apply Latent Degradation to Speeds greater than 1
200.0, !- Crankcase Heater Capacity {W}
10.0, !- Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation {C}
NaturalGas, !- Fuel type
4, !- Number of speeds
7500, !- Rated Total Cooling Capacity, Speed 1 (gross) {W}
0.75, !- Rated SHR, Speed 1
3.0, !- Rated COP, Speed 1
0.40, !- Rated Air Volume Flow Rate, Speed 1 {m3/s}
HPACCoolCapFT Speed 1, !- Total Cooling Capacity Modifier Curve, Speed 1 (temperature)
HPACCoolCapFF Speed 1, !- Total Cooling Capacity Modifier Curve, Speed 1 (flow fraction)
HPACCOOLEIRFT Speed 1, !- Energy Input Ratio Modifier Curve, Speed 1 (temperature)
HPACCOOLEIRFF Speed 1, !- Energy Input Ratio Modifier Curve, Speed 1 (flow fraction)
HPACCOOLPLFFPLR Speed 1, !- Part Load Fraction Correlation, Speed 1 (part load ratio)
1000.0, !- Nominal Time for Condensate Removal to Begin, Speed 1 {s}
1.5, !- Ratio of Initial Moisture Evaporation Rate and Steady-state Latent Capacity, Speed 1 {dimensionless}
3.0, !- Maximum ON/OFF Cycling Rate, Speed 1 {cycles/hr}
45.0, !- Latent Capacity Time Constant, Speed 1 {s}
0.2, !- Rated waste heat fraction of power input, Speed 1 {dimensionless}
HAPCCoolWHFT Speed 1, !- Waste heat modifier curve, Speed 1 (temperature)
0.9, !- Evaporative Condenser Effectiveness, Speed 1 {dimensionless}
0.05, !- Evaporative Condenser Air Volume Flow Rate, Speed 1 {m3/s}
50, !- Evaporative Condenser Pump Rated Power Consumption, Speed 1 {W}
17500, !- Rated Total Cooling Capacity, Speed 2 (gross) {W}
0.75, !- Rated SHR, Speed 2
3.0, !- Rated COP, Speed 2
0.85, !- Rated Air Volume Flow Rate, Speed 2 {m3/s}
HPACCoolCapFT Speed 2, !- Total Cooling Capacity Modifier Curve, Speed 2 (temperature)
HPACCoolCapFF Speed 2, !- Total Cooling Capacity Modifier Curve, Speed 2 (flow fraction)
HPACCOOLEIRFT Speed 2, !- Energy Input Ratio Modifier Curve, Speed 2 (temperature)
HPACCOOLEIRFF Speed 2, !- Energy Input Ratio Modifier Curve, Speed 2 (flow fraction)
HPACCOOLPLFFPLR Speed 1, !- Part Load Fraction Correlation, Speed 2 (part load ratio)
1000.0, !- Nominal Time for Condensate Removal to Begin, Speed 2 {s}
1.5, !- Ratio of Initial Moisture Evaporation Rate and Steady-state Latent Capacity, Speed 2 {dimensionless}
3.0, !- Maximum ON/OFF Cycling Rate, Speed 2 {cycles/hr}
45.0, !- Latent Capacity Time Constant, Speed 2 {s}
0.2, !- Rated waste heat fraction of power input, Speed 2 {dimensionless}
HAPCCoolWHFT Speed 2, !- Waste heat modifier curve, Speed 2 (temperature)
0.9, !- Evaporative Condenser Effectiveness, Speed 2 {dimensionless}
0.1, !- Evaporative Condenser Air Volume Flow Rate, Speed 2 {m3/s}
60, !- Evaporative Condenser Pump Rated Power Consumption, Speed 2 {W}
25500, !- Rated Total Cooling Capacity, Speed 3 (gross) {W}
0.75, !- Rated SHR, Speed 3
3.0, !- Rated COP, Speed 3
1.25, !- Rated Air Volume Flow Rate, Speed 3 {m3/s}
HPACCoolCapFT Speed 3, !- Total Cooling Capacity Modifier Curve, Speed 3 (temperature)
HPACCoolCapFF Speed 3, !- Total Cooling Capacity Modifier Curve, Speed 3 (flow fraction)
HPACCOOLEIRFT Speed 3, !- Energy Input Ratio Modifier Curve, Speed 3 (temperature)
HPACCOOLEIRFF Speed 3, !- Energy Input Ratio Modifier Curve, Speed 3 (flow fraction)
HPACCOOLPLFFPLR Speed 1, !- Part Load Fraction Correlation, Speed 3 (part load ratio)
1000.0, !- Nominal Time for Condensate Removal to Begin, Speed 3 {s}
1.5, !- Ratio of Initial Moisture Evaporation Rate and Steady-state Latent Capacity, Speed 3 {dimensionless}
3.0, !- Maximum ON/OFF Cycling Rate, Speed 3 {cycles/hr}
45.0, !- Latent Capacity Time Constant, Speed 3 {s}
0.2, !- Rated waste heat fraction of power input, Speed 3 {dimensionless}
HAPCCoolWHFT Speed 3, !- Waste heat modifier curve, Speed 3 (temperature)
0.9, !- Evaporative Condenser Effectiveness, Speed 3 {dimensionless}
0.2, !- Evaporative Condenser Air Volume Flow Rate, Speed 3 {m3/s}
80, !- Evaporative Condenser Pump Rated Power Consumption, Speed 3 {W}
35500, !- Rated Total Cooling Capacity, Speed 4 (gross) {W}
0.75, !- Rated SHR, Speed 4
3.0, !- Rated COP, Speed 4
1.75, !- Rated Air Volume Flow Rate, Speed 4 {m3/s}
HPACCoolCapFT Speed 4, !- Total Cooling Capacity Modifier Curve, Speed 4 (temperature)
HPACCoolCapFF Speed 4, !- Total Cooling Capacity Modifier Curve, Speed 4 (flow fraction)
HPACCOOLEIRFT Speed 4, !- Energy Input Ratio Modifier Curve, Speed 4 (temperature)
HPACCOOLEIRFF Speed 4, !- Energy Input Ratio Modifier Curve, Speed 4 (flow fraction)
HPACCOOLPLFFPLR Speed 1, !- Part Load Fraction Correlation, Speed 4 (part load ratio)
1000.0, !- Nominal Time for Condensate Removal to Begin, Speed 4 {s}
1.5, !- Ratio of Initial Moisture Evaporation Rate and Steady-state Latent Capacity, Speed 4 {dimensionless}
3.0, !- Maximum ON/OFF Cycling Rate, Speed 4 {cycles/hr}
45.0, !- Latent Capacity Time Constant, Speed 4 {s}
0.2, !- Rated waste heat fraction of power input, Speed 4 {dimensionless}
HAPCCoolWHFT Speed 4, !- Waste heat modifier curve, Speed 4 (temperature)
0.9, !- Evaporative Condenser Effectiveness, Speed 4 {dimensionless}
0.3, !- Evaporative Condenser Air Volume Flow Rate, Speed 4 {m3/s}
100; !- Evaporative Condenser Pump Rated Power Consumption, Speed 4 {W}
Coil:Heating:Fuel,
Supp Gas Heating Coil 1, !- Coil Name
FanAndCoilAvailSched, !- Availability Schedule Name
NaturalGas, !- Fuel Type
0.8, !- Gas Burner Efficiency of the Coil
45000, !- Nominal Capacity of the Coil {W}
SuppHeating Coil Air Inlet Node, !- Coil\_Air\_Inlet\_Node
Air Loop Outlet Node; !- Coil\_Air\_Outlet\_Node
Fan:OnOff,
Supply Fan 1, !- Fan Name
FanAndCoilAvailSched, !- Availability Schedule Name
0.7, !- Fan Total Efficiency
300.0, !- Delta Pressure {Pa}
1.7, !- Max Flow Rate {m3/s}
0.9, !- Motor Efficiency
1.0, !- Motor In Airstream Fraction
Mixed Air Node, !- Fan\_Inlet\_Node
DX Cooling Coil Air Inlet Node; !- Fan\_Outlet\_Node
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone1DirectAir, !- Name
, !- Availability Schedule Name
Zone 1 Terminal Inlet Node, !- Air Inlet Node Name
Zone 1 Supply Node, !- Air Outlet Node Name
0.612; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone2DirectAir, !- Name
, !- Availability Schedule Name
Zone 2 Terminal Inlet Node, !- Air Inlet Node Name
Zone 2 Supply Node, !- Air Outlet Node Name
0.476; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone3DirectAir, !- Name
, !- Availability Schedule Name
Zone 3 Terminal Inlet Node, !- Air Inlet Node Name
Zone 3 Supply Node, !- Air Outlet Node Name
0.612; !- Maximum air flow rate {m3/s}
This output variable is the ratio of actual air mass flow
rate through the multispeed heat pump to the heat pump’s
design air mass flow rate (i.e., design volumetric flow rate
converted to dry air mass flow rate) at Speed 1. For
continuous fan operation mode, this variable is always 1.0
when the heat pump is available (based on the availability
schedule). For cycling fan/cycling coil operation mode, the
actual air mass flow rate is calculated based on the ratio of
the sensible heating (or cooling) load to the steady-state
heat pump heating (or cooling) capacity. For the cycling fan
mode, the runtime fraction for the heat pump fan may be
different from the fan part-load ratio reported here due the
part-load performance of the heat pump’s heating (or cooling)
coil (delay at start-up to reach steady-state output). In
general, runtime fractions are reported by individual
components where appropriate (e.g., Fan:OnOff). When the speed
number is greater than 1, the value is 1.0.
Unitary
System Compressor Part Load Ratio [][LINK]
This output variable is the ratio of the sensible load
(heating or cooling) to the steady-state capacity of the
multispeed heat pump’s DX heating or cooling coil at Speed 1.
The runtime fraction for the heat pump compressor may be
different from the compressor part-load ratio reported here
due the part-load performance of the heating/cooling coil
(delay at start-up to reach steady-state output). In general,
runtime fractions are reported by individual components where
appropriate. When the speed number is greater than 1, the
value is 1.0.
This output variable is the ratio of the sensible load
(heating or cooling) to the steady-state capacity of the
multispeed heat pump’s DX heating or cooling coil (Speed 1)
for the entire system timestep. The value is between 0.0 and
1.0 when the heat pump is cycling on and off its lowest speed
(Speed 1) and 1.0 when the multispeed heat pump operates at
speeds above 1.
When Single Mode Operation is specified, the value is
between 0.0 and 1.0 when the heat pump is cycling on at any
given speed.
This output variable is the ratio of time in a system
timestep that the compressor is at rated speed between two
consecutive speed numbers ( [Compressor Speed - Compressor
speed at Speed i-1] / [Compressor speed at Speed i -
Compressor speed at Speed i-1]). The compressor speed ratio
reports (1.0 is max, 0.0 is min) and any value in between as
it is averaged over the timestep. The value is 0.0 during
Speed 1 operation.
The physical meaning of the speed ratio is dependent on the
compressor configuration defined in the field of child coil
object: Apply Part Load Fraction to Speeds greater than 1. The
allowed choice is either Yes or No. When No is entered, one
compressor is assumed for all speeds. The speed ratio
represents how long the higher speed runs as a fraction of the
system timestep, and the lower speed runs in the rest of the
system timestep. When Yes is entered, multiple compressors are
assumed, and each compressor has associated speed. The speed
ratio represents how long the higher speed runs as a fraction
of the system timestep, and the low speed runs in a whole
system timestep.
When Single Mode Operation is specified, the speed ratio is
set to 0 at Speed 1, and 1 at Speed > 1
This output variable reports the maximum speed needed when
the heat pump operates to meet the sensible load (heating or
cooling) in a system timestep. When the value is 1, the heat
pump operates at Speed 1 (lowest speed). For this case the
cycling ratio is between 0.0 and 1.0, while the speed ratio is
0.0. When the speed number output variable is above one, such
as i, the heat pump operation is determined by the speed ratio
through linear interpolation. For example, when the speed
ratio is 0.4 and the speed number is 3, the heat pump operates
at Speed 3 for 40% of a system timestep and at Speed 2 for 60%
of a system timestep for a single compressor. For multiple
compressors, the heat pump operates at Speed 3 in the 40% of a
system timestep and at Speed 2 in the whole system
timestep.
This output field is the total (enthalpy) heat addition
rate of the multispeed heat pump to the zones it is serving in
Watts. This value is calculated using the enthalpy difference
of the heat pump outlet air and inlet air streams, and the air
mass flow rate through the heat pump. This value is calculated
for each HVAC system timestep being simulated, and the results
(enthalpy addition only) are averaged for the timestep being
reported.
This output field is the total (enthalpy) heat extraction
rate of the multispeed heat pump from the zones it is serving
in Watts. This value is calculated using the enthalpy
difference of the heat pump outlet air and inlet air streams,
and the air mass flow rate through the heat pump. This value
is calculated for each HVAC system timestep being simulated,
and the results (enthalpy extraction only) are averaged for
the timestep being reported.
This output field reports the sensible heat addition rate
of the multispeed heat pump to the zones it is serving in
Watts. This value is calculated using the enthalpy difference
of the heat pump outlet air and inlet air streams at a
constant humidity ratio, and the air mass flow rate through
the heat pump. This value is calculated for each HVAC system
timestep being simulated, and the results (heating only) are
averaged for the timestep being reported.
This output field reports the moist air sensible heat
extraction rate of the multispeed heat pump from the zones it
is serving in Watts. This value is calculated using the
enthalpy difference of the heat pump outlet air and inlet air
streams at a constant humidity ratio, and the air mass flow
rate through the heat pump. This value is calculated for each
HVAC system timestep being simulated, and the results (cooling
only) are averaged for the timestep being reported.
This output field is the latent heat addition
(humidification) rate of the multispeed heat pump in Watts.
This value is calculated as the difference between the total
energy rate and the sensible energy rate provided by the
multispeed heat pump. This value is calculated for each HVAC
system timestep being simulated, and the results (latent heat
addition only) are averaged for the timestep being
reported.
This output field is the latent heat extraction
(dehumidification) rate of the multispeed heat pump in Watts.
This value is calculated as the difference between the total
energy rate and the sensible energy rate provided by the
multispeed heat pump. This value is calculated for each HVAC
system timestep being simulated, and the results (latent heat
extraction only) are averaged for the timestep being
reported.
This output field is the electricity consumption rate of
the multispeed heat pump in Watts. The consumption includes
electricity used by the DX coils (including crankcase heater
if the fuel type is electricity), fans (indoor supply air fan
and the condenser fans associated with the DX coil[s]),
defrost mode operation (resistive or reverse-cycle), auxiliary
power during on and off period, and the supplemental heating
coil (if electric). This value is calculated for each HVAC
system timestep being simulated, and the results are averaged
for the timestep being reported. Any non-electric energy use
is not reported by the heat pump object but is reported in the
associated coil objects as appropriate.
This output field is the electricity consumption of the
multispeed heat pump in Joules for the timestep being
reported. The consumption includes electricity used by the DX
compressor (including crankcase heater if the fuel type is
electricity), fans (indoor supply air fan and the condenser
fans associated with the DX coil[s]), defrost mode operation
(resistive or reverse-cycle), auxiliary power during on and
off period, and the supplemental heating coil (if electric).
This value is calculated for each HVAC system timestep being
simulated, and the results are summed for the timestep being
reported. Any non-electric energy use is not reported by the
heat pump object but is reported in the associated coil
objects as appropriate.
Unitary
System Ancillary Electricity Rate [W][LINK]
This output field is the average auxiliary electricity
consumption rate (including both on-cycle and off-cycle) in
Watts for the timestep being reported.
Unitary
System Cooling Ancillary Electricity Energy [J][LINK]
This is the auxiliary electricity consumption in Joules for
the timestep being reported. This is the auxiliary electricity
consumption during periods when the heat pump is providing
cooling (DX cooling coil is operating). This output is also
added to a meter with Resource Type = Electricity, End Use Key
= Cooling, Group Key = System (ref. Output:Meter
objects).
Unitary
System Heating Ancillary Electricity Energy [J][LINK]
This is the auxiliary electricity consumption in Joules for
the timestep being reported. This is the auxiliary electricity
consumption during periods when the heat pump is providing
heating (DX heating coil is operating). This output is also
added to a meter with Resource Type = Electricity, End Use Key
= Heating, Group Key = System (ref. Output:Meter
objects).
Unitary
System Heat Recovery Inlet Temperature [C][LINK]
Unitary
System Heat Recovery Outlet Temperature [C][LINK]
Unitary
System Heat Recovery Fluid Mass Flow Rate [kg/s][LINK]
These outputs are the heat recovery inlet and outlet
temperatures and water mass flow rate for multispeed heat
pumps with heat recovery.
The EnergyPlus furnace is a “virtual” component that
consists of a fan component (OnOff or ConstantVolume) and a
Gas or Electric heating coil component. The blow through
furnace configuration is shown in the Figure below.
Schematic of Blow Through
Furnace Model [fig:schematic-of-blow-through-furnace-model]
Links to the fan and heating coil specifications are
provided in the furnace input data syntax. In addition the
control zone name and the furnace design operating conditions
are specified by the furnace inputs.
This alpha field contains the schedule name which contains
information on the availability of the furnace to operate. A
schedule value equal to 0 denotes that the furnace must be off
for that time period. A value greater than 0 denotes that the
furnace is available to operate during that time period. This
schedule may be used to completely disable the unitary system
as required. If this field is left blank, the schedule has a
value of 1 for all time periods.
This alpha field contains the furnace outlet node name.
Field: Supply Air Fan Operating Mode Schedule
Name
This alpha field specifies the name of the supply air fan
operating mode schedule. The supply air fan operating mode may
vary during the simulation based on time-of-day or with a
change of season. Schedule values of 0 denote that the furnace
supply air fan and the heating coil cycle on and off together
to meet the heating load (a.k.a. AUTO fan). Schedule values
other than 0 denote that the supply fan runs continuously
while the heating coil cycles to meet the load.
This numeric field contains the design operating furnace
air outlet temperature in degrees C when the furnace is
heating. If this input field is left blank, the default value
is 80 C.
This numeric field contains the design volumetric flow rate
of the furnace in cubic meters per second. This volumetric
flow rate should match the flow rate specified for the furnace
fan.
Field:
Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where
the thermostat controlling the furnace is located.
This alpha field contains the identifying type of supply
air fan specified for the furnace. Fan type must be Fan:OnOff
or Fan:ConstantVolume.
Fan:ConstantVolume
is used when the Supply Air Fan Operating Mode Schedule values
are never 0 and the fan operates continuously. Fan:OnOff
is used when the fan cycles on and off with the cooling or
heating coil (i.e. Supply Air Fan Operating Mode Schedule
values are at times 0).
This alpha field has two choices:
BlowThrough or DrawThrough.
The first choice stands for “blow through fan”. This means
that the unit consists of a fan followed by the heating coil.
The fan “blows through” the heating coil. The second choice
stands for “draw through fan”. This means that the unit
consists of the heating coil followed by a fan. The fan “draws
air through” the heating coil. If this field is left blank,
the default is blow through.
This alpha field contains the identifying type of heating
coil specified in the furnace. The hot water and steam heating
coils require specifying plant loop, branches, and connectors
objects to support the heating coils, and are placed on the
demand side of the plantloop. The hot water flow modulation
through the heating coil does not require additional
controller or Controller:WaterCoil
object. The parent object (Unitary Heat Only Furnace) itself
provides the “controller” function of modulating water flow.
Heating coil type must be:
This alpha field contains the identifying name given to the
furnace heating coil.
As shown in the example below, correct specification of the
furnace requires specification of the following objects in
addition to the furnace object:
1) fan (Fan:OnOff or Fan:ConstantVolume)
2) heating coil (Coil:Heating:Fuel or
Coil:Heating:Electric)
3) direct air unit
(AirTerminal:SingleDuct:ConstantVolume:NoReheat) for each zone
served by the furnace
Note: the furnace’s fan and heating coil must be connected
in the air loop according to the configuration shown above
(Figure 6)
when a blow through fan configuration is specified. If a draw
through fan is used, the fan is located down stream of the
heating coil. In addition, the volumetric air flow rate
specified in the direct air unit for the controlling zone
should properly reflect the fractional volumetric air flow
rate specified in the furnace object.
AirLoopHVAC:Unitary:Furnace:HeatOnly,
Gas Furnace 1, !- Name
FanAndCoilAvailSched, !- Availability Schedule Name
Air Loop Inlet Node, !- Furnace Air Inlet Node Name
Air Loop Outlet Node, !- Furnace Air Outlet Node Name
CycFanSchedule, !- Supply Air Fan Operating Mode Schedule Name
80, !- Maximum Supply Air Temperature {C}
1.3, !- Heating Supply Air Flow Rate {m3/s}
East Zone, !- Controlling Zone or Thermostat Location
Fan:OnOff, !- Supply Fan Object Type
Supply Fan 1, !- Supply Fan Fame
BlowThrough, !- Fan Placement
Coil:Heating:Fuel, !- Heating Coil Object Type
Furnace Coil; !- Heating Coil Name
Coil:Heating:Fuel,
Furnace Coil, !- Coil Name
FanAndCoilAvailSched, !- Availability Schedule Name
NaturalGas, !- Fuel Type
0.8, !- Gas Burner Efficiency of the Coil
20000, !- Nominal Capacity of the Coil {W}
Heating Coil Air Inlet Node,!- Coil_Air_Inlet_Node
Air Loop Outlet Node, !- Coil_Air_Outlet_Node
, !- Coil_Temp_Setpoint_Node
100, !- On Cycle Parasitic Electric Load {W}
PLFCurveforGasFurnace, !- Part load fraction correlation (function of part load ratio)
10; !- Off Cycle Parasitic Fuel Load {W}
Curve:Cubic,
PLFCurveforGasFurnace, !- Name
0.8, !- Coefficient1 Constant
0.2, !- Coefficient2 x
0.0, !- Coefficient3 x**2
0.0, !- Coefficient4 x**3
0, !- Minimum Value of x
1; !- Maximum Value of x
Fan:OnOff,
Supply Fan 1, !- Fan Name
FanAndCoilAvailSched, !- Availability Schedule Name
0.7, !- Fan Total Efficiency
600.0, !- Delta Pressure {Pa}
1.3, !- Max Flow Rate {m3/s}
0.9, !- Motor Efficiency
1.0, !- Motor In Airstream Fraction
Air Loop Inlet Node, !- Fan_Inlet_Node
Heating Coil Air Inlet Node;!- Fan_Outlet_Node
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone1DirectAir, !- Name
, !- Availability Schedule Name
Zone 1 Terminal Inlet Node, !- Air Inlet Node Name
Zone 1 Supply Node, !- Air Outlet Node Name
0.47; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone2DirectAir, !- Name
, !- Availability Schedule Name
Zone 2 Terminal Inlet Node, !- Air Inlet Node Name
Zone 2 Supply Node, !- Air Outlet Node Name
0.36; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone3DirectAir, !- Name
, !- Availability Schedule Name
Zone 3 Terminal Inlet Node, !- Air Inlet Node Name
Zone 3 Supply Node, !- Air Outlet Node Name
0.47; !- Maximum air flow rate {m3/s}
This output variable is the ratio of actual air mass flow
rate through the furnace to the furnace’s design air mass flow
rate (i.e., design volumetric flow rate converted to dry air
mass flow rate). For continuous fan operation mode, this
variable is always 1.0 when the furnace is available (based on
the availability schedule). For cycling fan/cycling coil
operation mode, the actual air mass flow rate is calculated
based on the ratio of the sensible heating load to the furnace
heating capacity. For the cycling fan mode, the runtime
fraction for the furnace fan may be different from the fan
part-load ratio reported here due the part-load performance of
the furnace’s heating coil (delay at start-up to reach
steady-state heating output). In general, runtime fractions
are reported by individual components where appropriate (e.g.,
Fan:OnOff).
The AirLoopHVAC:UnitaryHeatOnly
is identical to the AirLoopHVAC:Unitary:Furnace:HeatOnly
model. The heat-only unitary system is a “virtual” component
that consists of a fan component (OnOff or ConstantVolume) and
a Gas or Electric heating coil component. The blow through
unitary system configuration is shown in the Figure below.
Schematic of Blow Through
Heat-Only Unitary System [fig:schematic-of-blow-through-heat-only-unitary]
Links to the fan and heating coil specifications are
provided in the unitary system input data syntax. In addition,
the control zone name and the unitary system design operating
conditions are specified by the unitary system syntax.
This alpha field contains the schedule name which contains
information on the availability of the unitary system to
operate. A schedule value equal to 0 denotes that the unitary
system must be off for that time period. A value greater than
0 denotes that the unitary system is available to operate
during that time period. This schedule may be used to
completely disable the unitary system as required. If this
field is left blank, the schedule has a value of 1 for all
time periods.
This alpha field contains the unitary system outlet node
name.
Field: Supply Air Fan Operating Mode Schedule
Name
This alpha field specifies the name of the supply air fan
operating mode schedule. The supply air fan operating mode may
vary during the simulation based on time-of-day or with a
change of season. Schedule values of 0 denote that the furnace
supply air fan and the heating coil cycle on and off together
to meet the heating load (a.k.a. AUTO fan). Schedule values
other than 0 denote that the supply fan runs continuously
while the heating coil cycles to meet the load.
This numeric field contains the design air outlet
temperature in degrees C when the unitary system is heating.
If this input field is left blank, the default value is 80
C.
This numeric field contains the design volumetric flow rate
of the unitary system in cubic meters per second. This
volumetric flow rate should match the flow rate specified for
the unitary system fan.
Field:
Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where
the thermostat controlling the unitary system is located.
This alpha field contains the identifying type of supply
air fan specified for the unitary system. Fan type must be
Fan:OnOff
or Fan:ConstantVolume.
Fan:ConstantVolume
is used when the Supply Air Fan Operating Mode Schedule values
are never 0 and the fan operates continuously. Fan:OnOff
is used when the fan cycles on and off with the cooling or
heating coil (i.e. Supply Air Fan Operating Mode Schedule
values are at times 0).
This alpha field has two choices:
BlowThrough or DrawThrough.
The first choice stands for “blow through fan”. This means
that the unit consists of a fan followed by the heating coil.
The fan “blows through” the heating coil. The second choice
stands for “draw through fan”. This means that the unit
consists of the heating coil followed by a fan. The fan “draws
air through” the heating coil. If this field is left blank,
the default is blow through.
This alpha field contains the identifying type of heating
coil specified in the unitary system. The hot water and steam
heating coils require specifying plant loop, branches, and
connectors objects to support the heating coils, and are
placed on the demand side of the plantloop. The hot water flow
modulation through the heating coil does not require
additional controller or Controller:WaterCoil
object. The parent object (Unitary Heat Only) itself provides
the “controller” function of modulating water flow. Heating
coil type must be:
This alpha field contains the identifying name given to the
unitary system heating coil.
As shown in the example below, correct specification of the
heat-only unitary system requires specification of the
following objects in addition to the unitary system
object:
1) fan (Fan:OnOff or Fan:ConstantVolume)
2) heating coil (Coil:Heating:Fuel or
Coil:Heating:Electric)
3) direct air unit
(AirTerminal:SingleDuct:ConstantVolume:NoReheat) for each zone
served by the furnace
Note: the unitary system’s fan and heating coil must be
connected in the air loop according to the configuration shown
above (Figure 7)
when a blow through fan configuration is specified. If a draw
through fan is used, the fan is located down stream of the
heating coil. In addition, the volumetric air flow rate
specified in the direct air unit for the controlling zone
should properly reflect the fractional volumetric air flow
rate specified in the unitary system object.
AirLoopHVAC:UnitaryHeatOnly,
Gas Unitary System 1, !- Name
FanAndCoilAvailSched, !- Availability Schedule Name
Air Loop Inlet Node, !- Unitary System Air Inlet Node Name
Air Loop Outlet Node, !- Unitary System Air Outlet Node Name
CycFanSchedule, !- Supply Air Fan Operating Mode Schedule Name
80, !- Maximum Supply Air Temperature {C}
1.3, !- Heating Supply Air Flow Rate {m3/s}
East Zone, !- Controlling Zone or Thermostat Location
Fan:OnOff, !- Supply Fan Object Type
Supply Fan 1, !- Supply Fan Name
BlowThrough, !- Fan Placement
Coil:Heating:Fuel, !- Heating Coil Object Type
Unitary System Heating Coil;!- Heating Coil Name
Coil:Heating:Fuel,
Unitary System Heating Coil,!- Coil Name
FanAndCoilAvailSched, !- Availability Schedule Name
NaturalGas, !- Fuel Type
0.8, !- Gas Burner Efficiency of the Coil
20000, !- Nominal Capacity of the Coil {W}
Heating Coil Air Inlet Node,!- Coil_Air_Inlet_Node
Air Loop Outlet Node, !- Coil_Air_Outlet_Node
, !- Coil_Temp_Setpoint_Node
100, !- On Cycle Parasitic Electric Load {W}
PLFCurveforUnitarySystem, !- Part load fraction correlation (function of part load ratio)
10; !- Off Cycle Parasitic Fuel Load {W}
Curve:Cubic,
PLFCurveforUnitarySystem, !- Name
0.8, !- Coefficient1 Constant
0.2, !- Coefficient2 x
0.0, !- Coefficient3 x**2
0.0, !- Coefficient4 x**3
0, !- Minimum Value of x
1; !- Maximum Value of x
Fan:OnOff,
Supply Fan 1, !- Fan Name
FanAndCoilAvailSched, !- Availability Schedule Name
0.7, !- Fan Total Efficiency
600.0, !- Delta Pressure {Pa}
1.3, !- Max Flow Rate {m3/s}
0.9, !- Motor Efficiency
1.0, !- Motor In Airstream Fraction
Air Loop Inlet Node, !- Fan_Inlet_Node
Heating Coil Air Inlet Node;!- Fan_Outlet_Node
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone1DirectAir, !- Name
, !- Availability Schedule Name
Zone 1 Terminal Inlet Node, !- Air Inlet Node Name
Zone 1 Supply Node, !- Air Outlet Node Name
0.47; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone2DirectAir, !- Name
, !- Availability Schedule Name
Zone 2 Terminal Inlet Node, !- Air Inlet Node Name
Zone 2 Supply Node, !- Air Outlet Node Name
0.36; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone3DirectAir, !- Name
, !- Availability Schedule Name
Zone 3 Terminal Inlet Node, !- Air Inlet Node Name
Zone 3 Supply Node, !- Air Outlet Node Name
0.47; !- Maximum air flow rate {m3/s}
This output variable is the ratio of actual air mass flow
rate through the unitary system to the unitary system’s design
air mass flow rate (i.e., design volumetric flow rate
converted to dry air mass flow rate). For continuous fan
operation mode, this variable is always 1.0 when the unitary
system is available (based on the availability schedule). For
cycling fan/cycling coil operation mode, the actual air mass
flow rate is calculated based on the ratio of the sensible
heating load to the unitary system heating capacity. For the
cycling fan mode, the runtime fraction for the unitary system
fan may be different from the fan part-load ratio reported
here due the part-load performance of the unitary system’s
heating coil (delay at start-up to reach steady-state heating
output). In general, runtime fractions are reported by
individual components where appropriate (e.g., Fan:OnOff).
The unitary water-to-air heat pump is similar to the
unitary air-to-air heat pump except water is used on the
source side. Links to the fan, WaterToAirHeatPump cooling
coil, WaterToAirHeatPump heating coil, and supplementary
heating coil specifications are provided in the heat pump’s
input data syntax. The heat pump switches between cooling and
heating depending on the zone’s demand. The load side (air) of
the unitary water-to-air heat pump consists of an On/Off fan
component, a WaterToAirHeatPump cooling coil component, a
WaterToAirHeatPump heating coil component, and a Gas,
Electric, Steam, or Hot Water supplemental heating coil
component. The source side (water) of the heat pump is
connected to a condenser loop with a heat exchanger (ground
heat exchanger or other type) or a plant loop with a heating
source such as a boiler and a cooling source such as a chiller
or cooling tower. The diagram below shows the setup and
connection of the heat pump for the source side and load side
for a ground heat exchanger configuration. Note that on the
load side, the WaterToAirHeatPump cooling coil must always be
placed before the WaterToAirHeatPump heating coil.
There are three type of WaterToAirHeatPump coil models
available:
This alpha field contains the schedule name (ref. Schedule
objects) that contains information on the availability of the
heat pump to operate. A schedule value greater than 0 (usually
1 is used) indicates that the unit can be on during the time
period. A value less than or equal to 0 (usually 0 is used)
denotes that the unit must be off for the time period. If this
field is left blank, the schedule has a value of 1 for all
time periods.
This numeric field contains the design volumetric flow rate
through the heat pump in cubic meters per second. This volume
flow rate is only used when the cooling and heating coil
object type is Coil:*:WaterToAirHeatPump:ParameterEstimation.
Although a value greater than 0 is required (input cannot be
blank or 0), this input is not used for the EquationFit model.
Instead, the supply air flow rate is determined by the input
in the corresponding Coil:*:WaterToAirHeatPump:EquationFit
objects.
Field:
Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where
the thermostat controlling the heat pump is located.
This alpha field contains the identifying name given to the
heat pump supply air fan, and should match the name specified
in the corresponding fan object.
This alpha field contains the identifying name given to the
WaterToAirHeatPump heating coil, and should match the name
specified in the corresponding WaterToAirHeatPump heating coil
object.
This numeric value allows the user to determine how close
the air side has to be controlled. Lower the value of
convergence better the control of air side conditions and less
the zone temperature fluctuations. However in a poorly
designed system, a lower convergence might result in warning
errors which are caused due to the iteration limit for run
time fraction calculation is limited to 20.
This alpha field contains the identifying name given to the
WaterToAirHeatPump cooling coil, and should match the name
specified in the corresponding WaterToAirHeatPump cooling coil
object.
This numeric value allows the user to determine how close
the air side has to be controlled. Lower the value of
convergence better the control of air side conditions and less
the zone temperature fluctuations. However in a poorly
designed system, a lower convergence might result in warning
errors which are caused due to the iteration limit for run
time fraction calculation is limited to 20.
This is the object type of the supplemental heating coil.
The hot water and steam heating coils require specifying plant
loop, branches, and connectors objects to support the heating
coils, and are placed on the demand side of the plantloop. The
hot water flow modulation through the supplemental heating
coil does not require additional controller or Controller:WaterCoil
object. The parent object (AirLoop Unitary Water to Air Heat
Pump) itself provides the “controller” function of modulating
water flow. The valid choices are:
This alpha field contains the identifying name given to the
supplemental heating coil, and should match the name specified
in the corresponding supplemental heating coil object.
Field:
Maximum Supply Air Temperature from Supplemental Heater[LINK]
This numeric field defines the maximum allowed supply air
temperature exiting the heat pump supplemental heating coil in
degrees Celsius.
Field:
Maximum Outdoor Dry-Bulb Temperature for Supplemental Heater
Operation[LINK]
This numeric field defines the outdoor air dry-bulb
temperature in degrees Celsius above which the heat pump
supplemental heating coil is disabled. The temperature for
this input field must be less than or equal to 21°C. If this
input field is left blank, the default value is 21°C.
Field:
Outdoor Dry-Bulb Temperature Sensor Node Name[LINK]
This alpha field specifies the name of the outdoor node
which controls the operation of the supplemental heating coil.
If this field is left blank, the outdoor temperature is based
solely on the weather data. If this field is not blank, the
node name specified must also be listed in an OutdoorAir:Node
object where the height of the node is taken into
consideration when calculating outdoor temperature from the
weather data. Alternately, the node name must be specified in
an OutdoorAir:NodeList
object where the outdoor temperature is taken directly from
the weather data.
This alpha field has two choices:
BlowThrough or DrawThrough.
The first choice represents a blow through system where the
supply air fan is before the WaterToAirHeatPump
cooling/heating coil and the supplementary heating coil. The
second choice represents a draw through system where the
supply fan is between the WaterToAirHeatPump cooling/heating
coil and the supplementary heating coil. If this input field
is left blank, the default is blow through.
Field:
Supply Air Fan Operating Mode Schedule Name[LINK]
This alpha field specifies the name of the supply air fan
operating mode schedule. The supply air fan operating mode may
vary during the simulation based on time-of-day or with a
change of season. Schedule values of 0 denote that the supply
air fan and the heating/cooling coil cycle on and off together
to meet the heating or cooling load (a.k.a. AUTO fan).
Schedule values other than 0 denote that the supply air fan
runs continuously while the heating or cooling coil cycles to
meet the load. If this field is left blank, the model assumes
the supply air fan cycles with the heating or cooling coil
throughout the simulation period.
As shown in the example below, correct specification of the
water-to-air heat pump requires specification of the following
objects in addition to the AirLoopHVAC:UnitaryHeatPump:WaterToAir
object:
On/Off fan
WaterToAirHeatPump cooling coil
WaterToAirHeatPump heating coil
Supplementary heating coil
Direct air unit for each zone served by the heat
pump
Condenser demand branches
It should be noted that the volumetric air flow rate
specified in the direct air unit for the controlling zone
should properly reflect the fractional volumetric air flow
rate specified in the heat pump object.
This alpha input field contains the type of
dehumidification control. The following options are valid for
this field:
None - meet sensible load only, no active
dehumidification control
CoolReheat - cool beyond the dry-bulb
temperature set point as required to meet the high humidity
setpoint. The excess cooling beyond the cooling set point
temperature is offset by the supplemental heating coil.
The default is None. For
CoolReheat dehumidification control modes,
the maximum humidity setpoint is required. This must be set
using a ZoneControl:Humidistat
object. When extra dehumidification is required, the system
may not be able to meet the humidity setpoint if its full
capacity is not adequate. Supplemental heating coil
(supplemental heating coil type and name) is a required input
in WaterToAir HeatPumps. When dehumidification control is
active the heating and the reheat load due to extra
dehumidification are met with supplemental heating coil. The
supplemental heating coil capacity must be adequate enough to
meet the heating coil load and offset the excess cooling load
due to extra dehumidification. The dehumidification control
type CoolReheat works only with Coil:Cooling:WaterToAirHeatPump:EquationFit
cooling coil type.
This field specifies the way in which water flow through
the heat pump coils will be modeled. This field is only used
when WatertoAirHeatPump:EquationFit coils are used. There are
three options:
Cycling
Constant
CyclingOnDemand
Cycling varies water flow through the coil
based on the heat pump Part Load Ratio. This control method
is appropriate for modeling heat pumps that are outfitted with
a solenoid valve which allows water to flow through the coil
only when the compressor is active. This is the default for
EnergyPlus V8 and later.
Constant provides a constant water flow
regardless of heat pump operation. Remember that EnergyPlus
has two coils (a heating coil and a cooling coil) to
approximate the operation of one coil that can operate in
either heating mode or cooling mode. Therefore, when the
water flow mode is constant, there will be full flow through
either the heating coil or the cooling coil, but not both at
the same time.
ConstantOnDemand provides full flow
through the coil whenever there is a load. When there is no
load, there is zero flow through the coil. This control
strategy represents the way EnergyPlus modeled heat pump water
flow prior to Version
8.
This input specifies the ratio of heat pump heating to
cooling capacity. The default value is 1.0.
Following is an example of IDF usage:
AirLoopHVAC:UnitaryHeatPump:WaterToAir,
DXAC Heat Pump 1, !- Name
FanAndCoilAvailSched, !- Availability Schedule Name
Mixed Air Node, !- Air Inlet Node Name
Air Loop Outlet Node, !- Air Outlet Node Name
2, !- Supply Air Flow Fate {m3/s}
East Zone, !- Controlling Zone or Thermostat Location
Fan:OnOff, !- Supply Air Fan Object Type
Supply Fan 1, !- Supply Air Fan Name
Coil:Heating:WaterToAirHeatPump:ParameterEstimation, !- Heating Coil Object Type
Heat Pump Heating Mode, !- Heating Coil Name
0.001, !- Heating Convergence
Coil:Cooling:WaterToAirHeatPump:ParameterEstimation, !- Cooling Coil Object Type
Heat Pump Cooling Mode, !- Cooling Coil Name
0.001, !- Cooling Convergence
Coil:Heating:Fuel, !- Supplemental Heating Coil Object Type
Heat Pump DX Supp Heating Coil 1, !- Supplemental Heating Coil Name
50, !- Maximum Supply Air Temperature from Supplemental Heater {C}
21, !- Maximum Outdoor Dry-Bulb Temperature for Supplemental Heater Operation {C}
Outside Air Inlet Node, !- Outdoor Dry-Bulb Temperature Sensor Node Name
BlowThrough, !- Fan Placement
CyclingFanSch, !- Supply Air Fan Operating Mode Schedule Name
CoolReheat; !- Dehumidification Control Type
Schedule:Compact,
CyclingFanSch, !- Name
Fraction, !- Schedule Type Limits Name
Through: 12/31, !- Field 1
For: AllDays, !- Field 2
Until: 24:00, !- Field 3
0.0; !- Field 4
Coil:Cooling:WaterToAirHeatPump:ParameterEstimation,
Heat Pump Cooling Mode, !- Name
Scroll, !- Compressor Type
R22, !- Refrigerant Type
0.0015, !- Design Source Side Flow Rate {m3/s}
38000, !- Nominal Cooling Coil Capacity {W)
0, !- Nominal Time for Condensate Removal to Begin {s}
0, !- Ratio of Initial Moisture Evaporation Rate and Steady State Latent Capacity
3000000, !- High Pressure CutOff {Pa}
0, !- Low Pressure CutOff {Pa}
Water to Air Heat Pump Source Side1 Inlet Node, !- Water Inlet Node Name
Water to Air Heat Pump Source Side1 Outlet Node, !- Water Outlet Node Name
Cooling Coil Air Inlet Node,!- Air Inlet Node Name
Heating Coil Air Inlet Node,!- Air Outlet Node Name
3.78019E+03, !- Parameter 1 {W/K}
2.80303E+03, !- Parameter 2 {W/K}
7.93591E-01, !- Parameter 3 {C}
1.91029E+03, !- Parameter 4 {W}
2.66127E+00, !- Parameter 5
1.06009E-02, !- Parameter 6
1.65103E+00, !- Parameter 7
9.73887E-03, !- Parameter 8
1.04563E+03; !- Parameter 9
Coil:Heating:WaterToAirHeatPump:ParameterEstimation,
Heat Pump HEATING Mode, !- Name
Scroll, !- Compressor Type
R22, !- Refrigerant Type
0.0015, !- Design Source Side Flow Rate {m3/s}
38000, !- Nominal Heating Coil Capacity {W}
3000000, !- High Pressure CutOff
0, !- Low Pressure CutOff {Pa}
Water to Air Heat Pump Source Side2 Inlet Node, !- Water Inlet Node Name
Water to Air Heat Pump Source Side2 Outlet Node, !- Water Outlet Node Name
Heating Coil Air Inlet Node,!- Air Inlet Node Name
SuppHeating Coil Air Inlet Node, !- Air Outlet Node Name
3.91379E+03, !- Parameter 1 {W/K}
5.94753E-01, !- Parameter 2 {C}
2.49945E+03, !- Parameter 3 {W}
8.68734E-01, !- Parameter 4
7.23595E-03, !- Parameter 5
3.69126E+00, !- Parameter 6
1.75701E-05, !- Parameter 7
3.65348E+03; !- Parameter 8
Coil:Heating:Fuel,
Heat Pump DX Supp Heating Coil 1, !- Name
FanAndCoilAvailSched, !- Availability Schedule Name
NaturalGas, !- Fuel Type
0.8, !- Gas Burner Efficiency
32000, !- Nominal Capacity {W}
SuppHeating Coil Air Inlet Node, !- Air Inlet Node Name
Air Loop Outlet Node; !- Air Outlet Node Name
BRANCH,
Gshp Cooling Condenser Branch, !- Name
, !- Pressure Drop Curve Name
Coil:Cooling:WaterToAirHeatPump:ParameterEstimation, !- Component 1 Object Type
Heat Pump Cooling Mode, !- Component 1 Name
Water to Air Heat Pump Source Side1 Inlet Node, !- Component 1 Inlet Node Name
Water to Air Heat Pump Source Side1 Outlet Node; !- Component 1 Outlet Node Name
BRANCH,
Gshp Heating Condenser Branch, !- Name
, !- Pressure Drop Curve Name
Coil:Heating:WaterToAirHeatPump:ParameterEstimation, !- Component 1 Object Type
Heat Pump Heating Mode, !- Component 1 Name
Water to Air Heat Pump Source Side2 Inlet Node, !- Component 1 Inlet Node Name
Water to Air Heat Pump Source Side2 Outlet Node; !- Component 1 Outlet Node Name
Fan:OnOff,
Supply Fan 1, !- Name
FanAndCoilAvailSched, !- Availability Schedule Name
0.7, !- FanTotal Efficiency
300.0, !- – Pressure Rise {Pa}
2.0, !- Maximum Flow Rate {m3/s}
0.9, !- Motor Efficiency
1.0, !- Motor In Airstream Fraction
Mixed Air Node, !- Air Inlet_Node Name
Cooling Coil Air Inlet Node;!- Air Outlet Node Name
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone1DirectAir, !- Name
, !- Availability Schedule Name
Zone 1 Terminal Inlet Node, !- Air Inlet Node Name
Zone 1 Supply Node, !- Air Outlet Node Name
0.7; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone2DirectAir, !- Name
, !- Availability Schedule Name
Zone 2 Terminal Inlet Node, !- Air Inlet Node Name
Zone 2 Supply Node, !- Air Outlet Node Name
0.6; !- Maximum air flow rate {m3/s}
AirTerminal:SingleDuct:ConstantVolume:NoReheat,
Zone3DirectAir, !- Name
, !- Availability Schedule Name
Zone 3 Terminal Inlet Node, !- Air Inlet Node Name
Zone 3 Supply Node, !- Air Outlet Node Name
0.7; !- Maximum air flow rate {m3/s}
The heat pump demand as well as the compressor and
fan part-load ratios may be obtained with the output variables
shown below.
HVAC,Average, Unitary System Requested Sensible Cooling
Rate [W]
HVAC,Average, Unitary System Requested Latent Cooling
Rate [W]
HVAC,Average, Unitary System Requested Heating Rate
[W]
HVAC,Average, Unitary System Compressor Part Load Ratio
[]
HVAC,Average, Unitary System Fan Part Load
Ratio
HVAC,Average, Unitary System Dehumidification Induced
Heating Demand Rate [W]
Unitary
System Requested Sensible Cooling Rate [W][LINK]
This output variable is the sensible cooling requested from
the zone thermostat in watts. This value is calculated using
the unitary heat pump outlet air and zone conditions, the
specific heat of the zone air, and the supply air mass flow
rate entering/leaving the system. This value is calculated for
each HVAC system timestep being simulated, and the results are
averaged for the timestep being reported.
Unitary
System Requested Latent Cooling Rate [W][LINK]
This output variable is the latent cooling requested from
the zone humidistat in watts. This value is calculated using
the unitary heat pump outlet air and zone conditions, the heat
of vaporization of water at the current zone conditions, and
the supply air mass flow rate entering/leaving the system.
This value is calculated for each HVAC system timestep being
simulated, and the results are averaged for the timestep being
reported.
This output variable is the sensible heating requested from
the zone thermostat in watts. This value is calculated using
the unitary heat pump outlet air and zone conditions, the
specific heat of the zone air, and the supply air mass flow
rate entering/leaving the system. This value is calculated for
each HVAC system timestep being simulated, and the results are
averaged for the timestep being reported.
Unitary
System Compressor Part Load Ratio [][LINK]
This output variable is the ratio of actual load on the
unitary system to the unitary system’s steady state output.
This ratio is based on the nominal capacity of the unit.
This output variable is the ratio of actual air mass flow
rate through the unitary system to the unitary system’s design
air mass flow rate (i.e., design volumetric flow rate
converted to dry air mass flow rate). For continuous fan
operation mode, this variable is always 1.0 when the unitary
system is available (based on the availability schedule).
Unitary
System Dehumidification Induced Heating Demand Rate [W][LINK]
This output variable is the additional heating demand rate
of the supplemental heating coil of a Water-to-Air heat pumps
in Watts. This additional heating demand is induced when zone
air overshoots the heating setpoint due to extra
dehumidification requirement to meet the high humidity
setpoint. This value is always positive. This value is
calculated for each HVAC system timestep, and the results are
averaged for the timestep being reported.
The changeover-bypass variable air volume (CBVAV) unitary
system is a compound object made up of other components. Each
CBVAV system consists of an outdoor air mixer, direct
expansion (DX) cooling coil, heating coil, and a supply air
fan as shown in the figures below. Zone
thermostats and terminal units are required in each zone
served by this system. The terminal units are specific to this
system type and are either AirTerminal:SingleDuct:VAV:HeatAndCool:Reheat
or AirTerminal:SingleDuct:VAV:HeatAndCool:NoReheat.
A zone humidistat and single zone max humidity set point
manager may also be specified to help control high humidity
levels. These individual components are described elsewhere in
this document. The system may also be connected to an inlet
node of either the AirLoopHVAC:ZoneMixer
or AirLoopHVAC:ReturnPlenum
to more accurately model the AirLoopHVAC:OutdoorAirSystem.
The CBVAV unitary system object coordinates the operation of
these components and is modeled as a type of air loop
equipment (Ref. AirLoopHVAC).
Schematic of a CBVAV unitary
system (draw through fan placement) [fig:schematic-of-a-cbvav-unitary-system-draw]Schematic of a CBVAV unitary
system (blow through fan placement) [fig:schematic-of-a-cbvav-unitary-system-blow]Schematic of a CBVAV unitary
system used with outdoor air system [fig:schematic-of-a-cbvav-unitary-system-used-with-outdoor-air-system]
Links to the CBVAV system’s supply air fan, coils, and
outdoor air mixer specifications are provided in the object’s
input syntax. Additional inputs include system and outdoor air
flow rates during heating and cooling operation, the priority
control mode, and dehumidification control type. A description
of each input field for the CBVAV unitary system compound
object is provided below.
This alpha field defines a unique user-assigned name for an
instance of a changeover-bypass VAV system. Any reference to
this system by another object will use this name.
This alpha field defines the name of the schedule (ref:
Schedule) that denotes whether the system operates during a
given time period. A schedule value equal to 0 denotes that
the system must be off for that time period, and a schedule
value greater than 0 denotes that the system is available to
operate during that time period. This schedule may be used to
completely disable the system (all of its coils and the supply
air fan) as required. If this field is left blank, the
schedule has a value of 1 for all time periods.
This numeric field defines the air flow rate through the
system (i.e., through the fan and heating/cooling coils) in
cubic meters per second when the DX cooling coil is operating.
Values must be greater than 0, or this field is
autosizable.
This numeric field defines the air flow rate through the
system (i.e., through the fan and heating/cooling coils) in
cubic meters per second when the heating coil is operating.
Values must be greater than 0, or this field is
autosizable.
This numeric field defines the air flow rate through the
system (i.e., through the fan and heating/cooling coils) in
cubic meters per second when neither cooling nor heating is
required (i.e., the DX cooling coil and heating coil are off
but the supply air fan operates). Values must be greater than
or equal to zero, or this field is autosizable. This field is
only used when the unitary system’s supply air fan operating
mode is specified as continuous fan operation (Ref. Field:
Supply air fan operating mode schedule name). If the system’s
supply air fan operating mode is specified as continuous fan
operation and this value is set to zero or the field is left
blank, then the model assumes that the system air flow rate
when no heating/cooling is needed is equal to the system air
flow rate when the coils were last operating (for cooling
operation or heating operation).
This numeric field defines the outdoor air flow rate
through the system (i.e., through the Outdoor air Mixer’s
Outside_Air_Stream_Node) in cubic meters per second when the
DX cooling coil is operating. Values must be greater than or
equal to 0, or this field is autosizable. Note that the
Cooling Outdoor Air Flow Rate can be changed during the
simulation using a multiplier schedule (Ref. Field: Outdoor
air volumetric flow rate multiplier schedule name). For any
simulation timestep, the Cooling Outdoor Air Flow Rate cannot
exceed the system air volumetric flow rate during cooling
operation.
This numeric field defines the outdoor air flow rate
through the system (i.e., through the Outdoor air Mixer’s
Outside_Air_Stream_Node) in cubic meters per second when the
heating coil is operating. Values must be greater than or
equal to 0, or this field is autosizable. Note that the
Heating Outdoor Air Flow Rate can be changed during the
simulation using a multiplier schedule (Ref. Field: Outdoor
air volumetric flow rate multiplier schedule name). For any
simulation timestep, the Heating Outdoor Air Flow Rate cannot
exceed the system air volumetric flow rate during heating
operation.
Field:
No Load Outdoor Air Flow Rate When No Cooling or Heating is
Needed[LINK]
This numeric field defines the outdoor air flow rate
through the system (i.e., through the Outdoor air Mixer’s
Outside_Air_Stream_Node) in cubic meters per second when
neither cooling nor heating is required (i.e., the DX cooling
coil and heating coil are off but the supply air fan
operates). Values must be greater than or equal to 0, or this
field is autosizable. Note that the no load outdoor air flow
rate can be changed during the simulation using a multiplier
schedule (Ref. Field: Outdoor air volumetric flow rate
multiplier schedule name). For any simulation timestep, the no
load outdoor air flow rate cannot exceed the no load supply
air flow rate. This field is only used when the unitary
system’s supply air fan operating mode is specified as
continuous fan operation (Ref. Field: Supply air fan operating
mode schedule name). If the system’s supply air fan operating
mode is specified as continuous fan operation and this value
is set to zero or the field is left blank, then the model
assumes that the no load outdoor air flow rate is equal to the
outdoor air flow rate when the coils were last operating (for
cooling operation [i.e. Cooling outdoor air flow rate] or
heating operation [i.e. Heating outdoor air flow rate]) and
this field is not used.
Field:
Outdoor Air Flow Rate Multiplier Schedule Name[LINK]
This alpha field defines the name of a schedule (ref:
Schedule) that contains multipliers for the outdoor air volume
flow rates (heating, cooling, no heating/cooling). Schedule
values must be from zero to 1. If this field is left blank,
then the model assumes that the outdoor air multiplier is 1
for the entire simulation period.
This alpha field defines the name of the HVAC system node
where the bypass air mixes with the unitary system’s inlet
air. This name should match the name of the Return Air Stream
Node Name for the OutdoorAir:Mixer
associated with this system. This node name must be different
from the system’s air inlet node name.
This alpha field defines the name of the HVAC system node
where the conditioned air is split into bypass air and supply
air leaving the system (e.g., delivered to the terminal
units). This splitter air node name should match the outlet
node name for the last component (furthest downstream) in this
unitary system. For blow through fan placement, the splitter
air node is the outlet node of the heating coil. For draw
through fan placement, the splitter node is the outlet node of
the supply air fan.
This field specifies the type of outdoor air mixer used by
this CBVAV unitary system. The outdoor air mixer component is
part of the CBVAV unitary compound object. The only available
outdoor air mixer type is:
This alpha field defines the name of an outdoor air mixer
component that composes part of the CBVAV system. The name of
the outdoor air mixer’s Return_Air_Stream_Node should match
the bypass duct mixer node name, and be different from the
CBVAV system’s air inlet node name. The Mixed Air Node Name of
the outdoor air mixer should be the same as the CBVAV system’s
supply fan inlet air node (for blow through fan placement) or
the system’s DX cooling coil inlet node (for draw through fan
placement).
This alpha field defines the type of fan used by this
unitary system. The only valid choices are Fan:SystemModel,
Fan:OnOff,
and Fan:ConstantVolume.
The input requirements for these fan objects are described
elsewhere in this document.
This alpha field defines the name of the fan component that
composes part of this unitary system. Note that the fan
component’s maximum flow rate should be greater than or equal
to the largest system air volumetric flow rate specified for
this unitary system (heating, cooling, and no
heating/cooling). In addition, the fan’s inlet air node should
be the same as the outdoor air mixer’s Mixed Air Node (for
blow through fan placement) or the heating coil’s outlet node
(for draw through fan placement). The fan outlet air node
should be the same as the DX cooling coil’s air inlet node
(for blow through fan placement) or the system’s bypass duct
splitter node (for draw through fan placement).
This alpha field defines the placement of the supply air
fan within this unitary system. The only valid choices are
BlowThrough and DrawThrough.
With blow through placement, the supply air fan is located
immediately upstream of the system’s cooling coil. With draw
through placement, the supply air fan is located immediately
downstream of the heating coil.
Field:
Supply Air Fan Operating Mode Schedule Name[LINK]
This alpha field defines the name of a schedule that
specifies the supply air fan operating mode during the
simulation. A schedule value of 0 denotes the fan cycles off
when no cooling or heating is required, and any other value
denotes that the fan runs continuously regardless of the need
for heating or cooling. If this field is left blank, the model
assumes continuous supply air fan operation for the entire
simulation period.
This alpha field defines the name of the cooling coil used
by this unitary system, and this name should match the name
specified in the corresponding cooling coil object.
This alpha field defines the type of heating coil used by
this unitary system. The hot water and steam heating coils
require specifying plant loop, branches, and connector objects
to support the heating coils, and are placed on the demand
side of the plantloop. The hot water flow modulation through
the heating coil does not require additional controller or Controller:WaterCoil
object. The parent object (CBVAV Unitary System) itself
provides the “controller” function of modulating water flow.
The valid choices are:
This alpha field defines the name of the heating coil used
by this unitary system, and this name should match the name
specified in the corresponding heating coil object.
This choice field defines the cooling or heating priority
control mode for the unitary system. Valid choices are:
CoolingPriority
HeatingPriority
ZonePriority
LoadPriority
If CoolingPriority is selected, the system operates to meet
the cooling load if any zone served by this system (air loop)
requires cooling. If no zones require cooling, then the system
operates in heating mode if needed. If HeatingPriority is
selected, the system operates to meet the heating load if any
zone requires heating. If no zones require heating, then the
system operates in cooling mode if needed. If ZonePriority is
selected, the system operates based on the maximum number of
zones requiring either heating or cooling. If the number of
zones requiring cooling is greater than the number of zones
requiring heating, then the system operates in cooling mode.
If the number of zones requiring heating is greater than the
number of zones requiring cooling, then the system operates in
heating mode. If the number of zones requiring cooling equals
the number of zones requiring heating, then the largest
combined load (i.e., the sum of the cooling loads for zones
requiring cooling compared to the sum of the heating loads for
zones that require heating) sets the cooling or heating
operating mode for the system during that simulation timestep.
If LoadPriority is selected, the system operates based on the
largest combined load (i.e., the sum of the cooling loads for
zones requiring cooling compared to the sum of the heating
loads for zones that require heating). If the total load for
zones requiring cooling is greater than the total load for
zones requiring heating, then the system operates in cooling
mode. Similar logic is used for heating mode selection. If the
total cooling load equals the total heating load, then cooling
or heating operation reverts to the total number of zones
requiring cooling or heating (and if equal reverts to cooling
mode if the cooling load is non-zero, otherwise, heating
mode.
Field:
Minimum Outlet Air Temperature During Cooling Operation[LINK]
This numeric field defines the minimum outlet air
temperature leaving the system when the unit is operating to
provide cooling. Values are specified in degrees Celsius and
must be greater than 0. The default value is 8°C. This value
must be less than or equal to the maximum outlet air
temperature during heating operation.
Field:
Maximum Outlet Air Temperature During Heating Operation[LINK]
This numeric field defines the maximum outlet air
temperature leaving the system when the unit is operating to
provide heating. Values are specified in degrees Celsius and
must be greater than 0. The default value is 50°C. This value
must be greater than or equal to the minimum outlet air
temperature during cooling operation.
This alpha field contains the type of dehumidification
control. The following options are valid for this field:
None - meet sensible load only, no active
dehumidification control
Multimode - activate enhanced
dehumidification mode as needed and meet sensible load. This
option is used to model DX equipment with a controllable heat
exchanger assisting the DX cooling coil for improved
dehumidification. It is valid only with cooling coil type = Coil:Cooling:DX:TwoStageWithHumidityControlMode.
CoolReheat - cool beyond the dry-bulb
temperature set point as required to meet the high humidity
setpoint. It is valid only with cooling coil type = Coil:Cooling:DX:TwoStageWithHumidityControlMode.
The default is None. For the other
dehumidification control modes, the maximum humidity setpoint
on the CBVAV system’s air outlet node is used. This must be
set using a ZoneControl:Humidistat
and one of:
This alpha field defines the name of the HVAC system node
where the bypass air enters the zone mixer or return plenum.
This node name must be different from the system’s Air
Outlet Node Name and Bypass Duct
Splitter Node Name. This name should match the name
of the inlet node in the AirLoopHVAC:ZoneMixer
or AirLoopHVAC:ReturnPlenum
associated with this system.
Field:
Minimum Runtime Before Operating Mode Change[LINK]
This numeric field defines the amount of time, in hours,
the HVAC system operates before a mode change is allowed. The
value entered must be greater than or equal to 0. The default
value is 0.25 hours if this input is present and blank. If
this field is not present the minimum runtime is 0 hours
(i.e., immediate change over as needed).
As shown in the example below, correct specification of the
CBVAV unitary system requires specification of the following
objects in addition to the AirLoopHVAC:UnitaryHeatCool:VAVChangeoverBypass
object:
1) outdoor air mixer (OutdoorAir:Mixer)
2) fan (Fan:SystemModel, Fan:OnOff,
or Fan:ConstantVolume)
4) heating coil (Coil:Heating:Fuel, Coil:Heating:Electric,
or Coil:Heating:DX:SingleSpeed)
5) terminal unit for each zone being served by this
system (AirTerminal:SingleDuct:VAV:HeatAndCool:Reheat or
AirTerminal:SingleDuct:VAV:HeatAndCool:NoReheat)
6) When the Plenum or Mixer Inlet Node Name is specified,
this node name must connect to either the AirLoopHVAC:ZoneMixer
or AirLoopHVAC:ReturnPlenum
and the AirLoopHVAC:OutdoorAirSystem
may then be used to control the outdoor air flow rates. When
using the AirloopHVAC:OutdoorAirSystem it is recommended that
the Cooling, Heating and No Load Outdoor Air Flow Rate inputs
are set to 0, otherwise the amount of outdoor air is increased
and the coils may not autosize properly.
Note: The fan, heating coil, cooling coil, and outdoor air
mixer must be connected in the air loop according to the
configurations shown above (Figure 9,
Figure 10
or Figure 11).
AirLoopHVAC:UnitaryHeatCool:VAVChangeoverBypass,
GasHeat CBVAV System, !- Name of unitary system
FanAndCoilAvailSched, !- Availability schedule name
1.8, !- Cooling Supply Air Flow Rate {m3/s}
1.7, !- Heating Supply Air Flow Rate {m3/s}
1.6, !- No Load Supply Air Flow Rate {m3/s}
0.32, !- Cooling Outdoor Air Flow Rate {m3/s}
0.3, !- Heating Outdoor Air Flow Rate {m3/s}
0.27, !- No Load Outdoor Air Flow Rate {m3/s}
Outdoor Air Multiplier Schedule, !- Outdoor air volumetric flow rate multiplier schedule name
Air Loop Inlet Node, !- Air inlet node name
Mixer Inlet Node, !- Bypass duct mixer node name
Heating Coil Air Outlet Node, !- Bypass duct splitter node name
Air Loop Outlet Node, !- Air outlet node name
OutdoorAir:Mixer, !- Outdoor Air Mixer Object Type
Outdoor air Mixer, !- Outdoor air mixer name
Fan:OnOff, !- Supply air fan type
Supply Fan 1, !- Supply air fan name
BlowThrough, !- Supply air fan placement
Fan OpMode Schedule, !- Supply air fan operating mode schedule name
Coil:Cooling:DX:TwoStageWithHumidityControlMode, !- Cooling coil type
ACDXCoil 2, !- Cooling coil name
Coil:Heating:Fuel, !- Heating coil type
Furnace Heating Coil 1, !- Heating coil name
CoolingPriority, !- Priority control mode
10.0, !- Minimum outlet air temperature during cooling operation {C}
50.0, !- Maximum outlet air temperature during heating operation {C}
None; !- Dehumidification control type
OutdoorAir:Mixer,
Outdoor air Mixer, !- Name
Mixed Air Node, !- Mixed Air Node Name
Outdoor air Inlet Node, !- Outdoor Air Stream Node
Relief Air Outlet Node, !- Relief Air Stream Node Name
Mixer Inlet Node; !- Return Air Stream Node Name
Fan:OnOff,
Supply Fan 1, !- Fan Name
FanAndCoilAvailSched, !- Availability Schedule Name
0.7, !- Fan Total Efficiency
600.0, !- Delta Pressure {Pa}
1.8, !- Max Flow Rate {m3/s}
0.9, !- Motor Efficiency
1.0, !- Motor In Airstream Fraction
Mixed Air Node, !- Fan\_Inlet\_Node
DX Cooling Coil Air Inlet Node; !- Fan\_Outlet\_Node
Coil:Cooling:DX:TwoStageWithHumidityControlMode,
ACDXCoil 2, !- Coil Name
FanAndCoilAvailSched, !- Availability Schedule
DX Cooling Coil Air Inlet Node, !- Coil Air Inlet Node
Heating Coil Air Inlet Node,!- Coil Air Outlet Node
, !- Crankcase Heater Capacity {W}
, !- Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation {C}
2, !- Number of Capacity Stages
0, !- Number of Enhanced Dehumidification Modes
CoilPerformance:DX:Cooling, !- Normal Mode Stage 1 Coil Performance Object Type
ACDXCoil 2 Standard Mode-Stage 1, !- Normal Mode Stage 1 Coil Performance Object Name
CoilPerformance:DX:Cooling, !- Normal Mode Stage 1+2 Coil Performance Object Type
ACDXCoil 2 Standard Mode-Stage 1&2; !- Normal Mode Stage 1+2 Coil Performance Object Name
Coil:Heating:Fuel,
Furnace Heating Coil 1, !- Coil Name
FanAndCoilAvailSched, !- Availability Schedule Name
NaturalGas, !- Fuel Type
0.8, !- Gas Burner Efficiency of the Coil
35000, !- Nominal Capacity of the Coil {W}
Heating Coil Air Inlet Node,!- Coil\_Air\_Inlet\_Node
Heating Coil Air Outlet Node; !- Coil\_Air\_Outlet\_Node
AirTerminal:SingleDuct:VAV:HeatAndCool:Reheat,
Zone 1 VAV System, !- Name of System
FanAndCoilAvailSched, !- System Availability schedule
Zone 1 Reheat Air Inlet Node, !- DAMPER Air Outlet Node
Zone 1 VAV Inlet Node, !- UNIT Air Inlet Node
0.583, !- Maximum air flow rate {m3/s}
0.25, !- Zone Minimum Air Flow Fraction
, !- Control node
Coil:Heating:Electric, !- Reheat Component Object
Reheat Coil Zone 1, !- Name of Reheat Component
0.0, !- Max Reheat Water Flow {m3/s}
0.0, !- Min Reheat Water Flow {m3/s}
Zone 1 Reheat Air Outlet Node, !- UNIT Air Outlet Node
0.001; !- Convergence Tolerance
AirTerminal:SingleDuct:VAV:HeatAndCool:Reheat,
Zone 2 VAV System, !- Name of System
FanAndCoilAvailSched, !- System Availability schedule
Zone 2 Reheat Air Inlet Node, !- DAMPER Air Outlet Node
Zone 2 VAV Inlet Node, !- UNIT Air Inlet Node
0.583, !- Maximum air flow rate {m3/s}
0.25, !- Zone Minimum Air Flow Fraction
, !- Control node
Coil:Heating:Electric, !- Reheat Component Object
Reheat Coil Zone 2, !- Name of Reheat Component
0.0, !- Max Reheat Water Flow {m3/s}
0.0, !- Min Reheat Water Flow {m3/s}
Zone 2 Reheat Air Outlet Node, !- UNIT Air Outlet Node
0.001; !- Convergence Tolerance
AirTerminal:SingleDuct:VAV:HeatAndCool:NoReheat,
Zone 3 VAV System, !- Name of System
FanAndCoilAvailSched, !- System Availability schedule
Zone 3 Reheat Air Outlet Node, !- UNIT Air Outlet Node
Zone 3 VAV Inlet Node, !- UNIT Air Inlet Node
0.584, !- Maximum air flow rate {m3/s}
0.25; !- Zone Minimum Air Flow Fraction
This output field is the total (enthalpy) heat addition
rate of the CBVAV system in Watts. This value is calculated
using the enthalpy difference of the outlet air and inlet air
streams, and the supply air mass flow rate entering/leaving
the system. This value is calculated for each HVAC system
timestep being simulated, and the results (enthalpy addition
only) are averaged for the timestep being reported.
This output field is the total (enthalpy) heat addition of
the CBVAV system in Joules over the timestep being reported.
This value is calculated using the enthalpy difference of the
outlet air and inlet air streams, the supply air mass flow
rate entering/leaving the system, and the HVAC simulation
timestep. This value is calculated for each HVAC system
timestep being simulated, and the results (enthalpy addition
only) are summed for the timestep being reported.
This output field is the total (enthalpy) heat extraction
rate of the CBVAV system in Watts. This value is calculated
using the enthalpy difference of the outlet air and inlet air
streams, and the supply air mass flow rate entering/leaving
the system. This value is calculated for each HVAC system
timestep being simulated, and the results (enthalpy extraction
only) are averaged for the timestep being reported.
This output field is the total (enthalpy) heat extraction
of the CBVAV system in Joules over the timestep being
reported. This value is calculated using the enthalpy
difference of the outlet air and inlet air streams, the supply
air mass flow rate entering/leaving the system, and the HVAC
simulation timestep. This value is calculated for each HVAC
system timestep being simulated, and the results (enthalpy
extraction only) are summed for the timestep being
reported.
This output field is the sensible heat addition rate of the
CBVAV system in Watts. This value is calculated using the
enthalpy difference of the outlet air and inlet air streams at
a constant humidity ratio, and the supply air mass flow rate
entering/leaving the system. This value is calculated for each
HVAC system timestep being simulated, and the results (heating
only) are averaged for the timestep being reported.
This output field is the sensible heat addition of the
CBVAV system in Joules over the timestep being reported. This
value is calculated using the enthalpy difference of the
outlet air and inlet air streams at a constant humidity ratio,
the supply air mass flow rate entering/leaving the system, and
the HVAC simulation timestep. This value is calculated for
each HVAC system timestep being simulated, and the results
(heating only) are summed for the timestep being reported.
This output field reports the moist air sensible heat
extraction rate of the CBVAV system in Watts. This value is
calculated using the enthalpy difference of the outlet air and
inlet air streams at a constant humidity ratio, and the supply
air mass flow rate entering/leaving the system. This value is
calculated for each HVAC system timestep being simulated, and
the results (cooling only) are averaged for the timestep being
reported.
This output field reports the moist air sensible heat
extraction of the CBVAV system in Joules over the timestep
being reported. This value is calculated using the enthalpy
difference of the outlet air and inlet air streams at a
constant humidity ratio, the supply air mass flow rate
entering/leaving the system, and the HVAC simulation timestep.
This value is calculated for each HVAC system timestep being
simulated, and the results (cooling only) are summed for the
timestep being reported.
This output field is the latent heat addition
(humidification) rate of the CBVAV system in Watts. This value
is calculated as the difference between the total energy rate
and the sensible energy rate provided by the system. This
value is calculated for each HVAC system timestep being
simulated, and the results (latent heat addition only) are
averaged for the timestep being reported.
This output field is the latent heat addition
(humidification) of the CBVAV system in Joules over the
timestep being reported. This value is calculated as the
difference between the total energy and the sensible energy
delivered by the system. This value is calculated for each
HVAC system timestep being simulated, and the results (latent
heat addition only) are summed for the timestep being
reported.
This output field is the latent heat extraction
(dehumidification) rate of the CBVAV system in Watts. This
value is calculated as the difference between the total energy
rate and the sensible energy rate provided by the system. This
value is calculated for each HVAC system timestep being
simulated, and the results (latent heat extraction only) are
averaged for the timestep being reported.
This output field is the latent heat extraction
(dehumidification) of the CBVAV system in Joules over the
timestep being reported. This value is calculated as the
difference between the total energy and the sensible energy
delivered by the system. This value is calculated for each
HVAC system timestep being simulated, and the results (latent
heat extraction only) are summed for the timestep being
reported.
This output field is the electricity consumption rate of
the CBVAV system in Watts. The consumption includes
electricity used by the DX compressor (including crankcase
heater), fans (indoor supply air fan and the condenser fans
associated with the DX coil[s]), defrost mode operation
(resistive or reverse-cycle), and the heating coil (if
electric). This value is calculated for each HVAC system
timestep being simulated, and the results are averaged for the
timestep being reported.
This output field is the electricity consumption of the
CBVAV system in Joules for the time period being reported. The
consumption includes electricity used by the DX compressor
(including crankcase heater), fans (indoor supply air fan and
the condenser fans associated with the DX coil[s]), defrost
mode operation (resistive or reverse-cycle), and the heating
coil (if electric). This value is calculated for each HVAC
system timestep being simulated, and the results are summed
for the timestep being reported.
This output field is the part-load ratio of the supply air
fan, which will be either zero or 1 for each simulation
timestep. For this system, the fan will operate continuously
for the simulation timestep if the system is available (ref.
Field: Availability schedule name) and there is a cooling or
heating load to be met (i.e., fan part-load ratio will equal
1). When the system is available but there is no cooling or
heating load to be met, the fan will either be off for the
entire timestep or on for the entire timestep depending on the
supply air fan operating mode schedule (ref. Field: Supply Air
Fan Operating Mode Schedule Name). This value is set for each
HVAC system timestep being simulated, and the results are
averaged for the timestep being reported.
Unitary
System Compressor Part Load Ratio [][LINK]
This output field is the part-load ratio of the compressor
used by the DX coils (cooling and heating). The compressor
part-load ratio is defined as the total coil load divided by
the coil steady-state capacity (steady-state capacity of first
stage for multi-mode coils). This value is calculated for each
HVAC system timestep being simulated, and the results are
averaged for the timestep being reported.
Unitary
System Bypass Air Mass Flow Rate [kg/s][LINK]
This output field is the mass flow rate of air, in kg/s,
being bypassed from the supply air path and blended with the
air entering the CBVAV system. This value is calculated for
each HVAC system timestep being simulated, and the results are
averaged for the timestep being reported.
Unitary
System Air Outlet Setpoint Temperature [C][LINK]
This output field is the dry-bulb set point temperature in
degrees Celsius. This set point temperature is calculated by
the model based on the zone cooling/heating loads calculated
by EnergyPlus, and the priority control mode and the
dehumidification control type specified for this unitary
system. The CBVAV system attempts to achieve the outlet air
set point temperature to the extent possible.
This output field is the current operating mode, either
cooling, heating or no cooling or heating. A value of 0
represents no cooling or heating is required, a value of 1
represents cooling and a value of 2 represents heating. These
specific values can be seen using the detailed time step
reporting frequency. If longer reporting frequencies are used
(e.g., timestep, hourly, etc.) then this output is averaged
over the reporting interval and the result is dependent on the
value selected for Minimum Runtime Before Operating Mode
Change.
Group – Unitary Equipment[LINK]
Furnace and Unitary Systems[LINK]
The components
AirLoopHVAC:UnitarySystem
AirLoopHVAC:Unitary:Furnace:HeatOnly
AirLoopHVAC:Unitary:Furnace:HeatCool
AirLoopHVAC:UnitaryHeatOnly
AirLoopHVAC:UnitaryHeatCool
AirLoopHVAC:UnitaryHeatPump:AirToAir
AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed
are compound components usually placed in the primary air loop as the sole component. On the zone equipment side they are usually connected to one or more zones through uncontrolled terminal units (i.e., AirTerminal:SingleDuct:ConstantVolume:NoReheat objects). The maximum or design air flow rate through the furnace or unitary system should usually be set equal to the sum of the maximum air flow rates through the terminal unit objects. However, the simulation program can usually account for unequal air flows if the user wishes to model this scenario.
The following HVAC equipment types are allowed in the air loop. The component matrix shows which coils and fans are allowed with which equipment models.
AirLoopHVAC:UnitarySystem[LINK]
The AirloopHVAC:UnitarySystem object is intended to replace all other air loop equipment, although other system types are still available. This system is unique in that it can accommodate all fan and coil types whereas other system types are specific to the type of fan and coil available for simulation. Additionally, although the AirloopHVAC:UnitarySystem is intended for use in the primary airloop, this object can be modeled as zone equipment (i.e., listed in a ZoneHVAC:EquipmentList) or as an outside air system component (i.e., listed in a AirLoopHVAC:OutdoorAirSystem:EquipmentList). Water coil controllers are not required when these coil types are used with the AirloopHVAC:UnitarySystem object (i.e., leave the controller list name blank in the AirLoopHVAC object if water coils are used exclusively within the Unitary System).
The AirLoopHVAC:UnitarySystem object is a “virtual” component that consists of a fan component (OnOff, ConstantVolume, VariableVolume, or ComponentModel), a cooling coil component, a heating coil component, and a reheat coil as shown in Figure 1. When a draw through configuration is desired, the fan is placed directly after the heating coil. If dehumidification control is selected, a reheat coil component is also required. If the reheat coil is present and the dehumidification control type input is not specified as CoolReheat, the reheat coil will not be active. All of the fan and coil components are optional which allows the AirLoopHVAC:UnitarySystem object to be configured for fan-only, heating-only, cooling-only, or both heating and cooling. It may also be applied without a fan, controlling one or more coils, similar to the function of CoilSystem:Cooling:DX.
When the AirloopHVAC:UnitarySystem object is modeled as an equipment on an air loop with an economizer, and when the system is using either a Coil:Cooling:DX:Multispeed, Coil:Cooling:DX:VariableSpeed, or a Coil:Cooling:DX object, two types of economizer staging operation are available, see the Economizer Operation Staging input of the hyperref[controlleroutdoorair]Controller:OutdoorAir object.
Links to the fan, cooling coil, heating coil and reheat coil specifications are provided in the unitary system input data syntax. In addition, the control zone name and the system design operating conditions are specified by the unitary system inputs.
Schedules And Availability Manager[LINK]
For unitary systems, don’t use the night cycle manager. Use a scheduled availability manager and let the system be always on. Then use the Supply Air Fan Operating Mode Schedule Name in the unitary system to switch between continuous fan (for ventilation) during occupied periods and switch to cycling fan for unoccupied. The system will cycle on as the thermostat requests, and this way it will run just enough to meet the load - no need for a minimum cycle time.
Multi-speed fan chilled and hot water coils Air Handling Unit (AHU) can be modeled using Airloop Unitary System HVAC object (AirloopHVAC:UnitarySystem). AHU with chilled and hot water coils is setup by specifying Fan:OnOff and DesignSpecificationPerformance:MultiSpeed objects in Unitary System. The design specification performance object allows running the chilled and hot water coils capacity control using a multi-speed supply air fan. The multi-speed fan capacity control for chilled and hot water coil AHU is performed by modulating the supply air flow rate while maintaining a constant water flow rate. The chilled or hot water flow rates is set at maximum fixed flow rate when there is cooling or heating load and the water flow rate is set to zero when there is no load. Such control strategy is called two-position cooling or heating coil control. The fan speed selection depends on the current load, at lower load the fan is operated at minimum speed (Speed = 1) and the fan speed level increases progressively as the load increases until it reaches the maximum speed level specified. The multi-speed fan operation is modulated between the speeds to meet the current load. When the supply air fan is cycling between consecutive speeds levels, the speed ratio is calculated that indicates what fraction of the time step that the system run at the higher of the two speeds. At lower load, the fan may cycle on-off or run continuously depending the fan operating schedule specified. When the fan is cycling a part-load ratio is calculated to reflect the proportion of the system timestep the fan and coils were operating. In continuous fan operating mode only the coil cycles on-off and the part-load ratio applies to the coil only. Multi-speed fan capacity control is allowed with load based control type only.
Inputs[LINK]
Field: Name[LINK]
This alpha field contains the identifying name for the unitary system.
Field: Control Type[LINK]
This alpha field contains control type i.e. load based or setpoint based for the unitary system. Valid choices are Load, SetPoint and SingleZoneVAV. Load and SingleZoneVAV control requires a Controlling Zone name. SetPoint control requires set points at each coil outlet node. A single set point at the outlet of the system is allowed but not recommended. If setpoint control is used and the system represents a heat pump (i.e., cooling and heating coils are both DX coils) then only one of these coils may operate at a time. SingleZoneVAV requires two distinct fan flow rates, namely the Cooling and Heating Supply Air Flow Rate and a lower No Load Supply Air Flow Rate which is used during times of reduced cooling or heating loads. SingleZoneVAV allows load control at low speed fan until the load exceeds available capacity or the outlet air temperature exceeds the specified limits where the fan speed is then increased. For the SingleZoneVAV control type, temperature limits are identified in the input fields for Minimum and Maximum Supply Air Temperature. Additionally, specific coil types are required for the SingleZoneVAV control type. The cooling coil types are Coil:Cooling:Water, Coil:Cooling:Water:DetailedGeometry, Coil:Cooling:DX:SingleSpeed, and Coil:Cooling:DX:VariableSpeed while the heating coil types are Coil:Heating:Water, Coil:Heating:Fuel, Coil:Heating:Electric, Coil:Heating:DX:SingleSpeed, and Coil:Heating:DX:VariableSpeed. If alternate coil types are used they are modeled using the load based control method.
Field: Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where the thermostat controlling the unitary system is located. This field is required when Load or SingleZoneVAV control type is selected.
Field: Dehumidification Control Type[LINK]
This alpha field contains the type of dehumidification control. The following options are valid for this field:
None - meet sensible load only, no active dehumidification control. None is required when Control Type = SingleZoneVAV.
Multimode - activate enhanced dehumidification mode as needed and meet sensible load. This option is used to model DX equipment with a controllable heat exchanger assisting the DX cooling coil for improved dehumidification. It is valid only with cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted.
CoolReheat - cool beyond the dry-bulb temperature set point as required to meet the high humidity setpoint. If cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted, then the heat exchanger is assumed to always transfer energy between the cooling coil’s inlet and outlet airstreams when the cooling coil is operating.
The default is None. For the other dehumidification control modes, the maximum humidity setpoint is used. This must be set using a ZoneControl:Humidistat object. When extra dehumidification is required, the system may not be able to meet the humidity setpoint if its full capacity is not adequate. If the dehumidification control type is specified as CoolReheat, then two additional inputs (reheat coil type and name) are also required as shown below. Although the reheat coil is required only when CoolReheat is selected, the optional reheat coil may be present for any of the allowed Dehumidification Control Types. If the reheat coil is present and the dehumidification control type is not specified as CoolReheat, the reheat coil will not be active,
Field: Availability Schedule Name[LINK]
This alpha field contains the schedule name which contains information on the availability of the unitary system to operate. A schedule value equal to 0 denotes that the unitary system must be off for that time period. A value greater than 0 denotes that the unitary system is available to operate during that time period. This schedule may be used to completely disable the unitary system as required. If this field is left blank, the schedule has a value of 1 for all time periods.
Field: Unitary System Air Inlet Node Name[LINK]
This alpha field contains the unitary system air inlet node name.
When the UnitarySystem is used to serve a zone as a zone equipment unit, this node name must be either the name of a zone air exhaust node (Ref. ZoneHVAC:EquipmentConnections) to draw air from a zone directly or an induced air outlet node (Ref. AirLoopHVAC:ReturnPlenum) to draw air from a return plenum, when the zone return node is connected to a return plenum.
Field: Unitary System Air Outlet Node Name[LINK]
This alpha field contains the unitary system air outlet node name.
Field: Supply Fan Object Type[LINK]
This alpha field contains the identifying type of supply air fan specified for the unitary system. Fan type must be Fan:OnOff, Fan:ConstantVolume, Fan:VariableVolume, or Fan:ComponentModel. Fan:ConstantVolume is used when the Supply Air Fan Operating Mode Schedule values are never 0 and the fan operates continuously. Fan:OnOff is used when the fan cycles on and off with the cooling or heating coil (i.e. Supply Air Fan Operating Mode Schedule values are at times 0). Fan:VariableVolume is used for variable air volume systems or multi- or variable-speed coils. The Fan:ComponentModel may be used in place of the ConstantVolume or VariableVolume fan types to more accurately represent fan performance.
Field: Supply Fan Name[LINK]
This alpha field contains the unique identifying name given to the unitary system fan.
Field: Fan Placement[LINK]
This alpha field has two choices: BlowThrough or DrawThrough. The first choice stands for “blow through fan”. This means that the unit consists of a fan followed by the main cooling and heating coils and supplemental heating coil. The fan “blows through” the cooling and heating coils. The second choice stands for “draw through fan”. This means that the unit consists of the main cooling/heating coil(s) followed by a fan, with the supplemental heater located at the outlet of the fan. The fan “draws air through” the cooling/heating coil(s). If this field is left blank, the default is blow through.
Field: Supply Air Fan Operating Mode Schedule Name[LINK]
This alpha field specifies the name of the supply air fan operating mode schedule. The supply air fan operating mode may vary during the simulation based on time-of-day or with a change of season. Schedule values of 0 denote that the unitary system supply air fan and the heating or cooling coil cycle on and off together to meet the heating or cooling load (a.k.a. AUTO fan). Schedule values other than 0 denote that the supply fan runs continuously while the heating or cooling coil cycles to meet the load. The SingleZoneVAV control type is only active when the supply air fan runs continuously (i.e., during cycling fan operation the Control Type = Load model is used).
Field: Heating Coil Object Type[LINK]
This alpha field contains the identifying type of heating coil specified in the unitary system. The hot water and steam heating coils require specifying plant loop, branches, and connector objects to support the heating coils, and are placed on the demand side of the plantloop. Only specific coil types are allowed when Control Type = SingleZoneVAV as noted. Allowable coil types are:
Coil:Heating:DX:SingleSpeed
Coil:Heating:DX:TwoSpeed
Coil:Heating:DX:MultiSpeed
Coil:Heating:DX:VariableSpeed
Coil:Heating:WaterToAirHeatPump:ParameterEstimation
Coil:Heating:WaterToAirHeatPump:EquationFit
Coil:Heating:WaterToAirHeatPump:VariableSpeedEquationFit
Coil:Heating:Fuel
Coil:Heating:Gas:MultiStage
Coil:Heating:Electric
Coil:Heating:Electric:MultiStage
Coil:Heating:Water
Coil:Heating:Steam
Coil:Heating:Desuperheater
Coil:UserDefined
Field: Heating Coil Name[LINK]
This alpha field contains the identifying name given to the unitary system heating coil.
Field: DX Heating Coil Sizing Ratio[LINK]
This numeric field is used to adjust heat pump heating capacity with respect to DX cooling capacity. It is used only for DX heat pump configurations (i.e., a DX cooling and heating coil is used).
Field: Cooling Coil Object Type[LINK]
This alpha field contains the identifying type of cooling coil specified in the unitary system. Allowable coil types are:
Coil:Cooling:DX:SingleSpeed
Coil:Cooling:DX:SingleSpeed:ThermalStorage
Coil:Cooling:DX:TwoSpeed
Coil:Cooling:DX:MultiSpeed
Coil:Cooling:DX:VariableSpeed
Coil:Cooling:DX:TwoStageWithHumidityControlMode
CoilSystem:Cooling:DX:HeatExchangerAssisted
Coil:Cooling:WaterToAirHeatPump:ParameterEstimation
Coil:Cooling:WaterToAirHeatPump:EquationFit
Coil:Cooling:WaterToAirHeatPump:VariableSpeedEquationFit
Coil:Cooling:Water
Coil:Cooling:Water:DetailedGeometry
CoilSystem:Cooling:Water:HeatExchangerAssisted
Coil:UserDefined
Field: Cooling Coil Name[LINK]
This alpha field contains the identifying name given to the unitary system cooling coil.
Field: Use DOAS DX Cooling Coil[LINK]
This input field enables DX Cooling coils to be used for 100% outdoor air dedicated outdoor air system applications. There are two choices Yes or No. If Yes, the DX coil is used as 100% outdoor DX coil. If No, the DX coil is used as regular DX coil. This input field is optional and the default is No. No should be specified when selecting the SingleZoneVAV control type.
Field: Minimum Supply Air Temperature[LINK]
When Use DOAS DX Cooling Coil is specified as Yes, this input field is the DX Cooling coils leaving minimum air temperature for frost control. The DX cooling coil leaving air temperature is not allowed to exceed this minimum air temperature. The DX cooling coil frost controller adjusts or limits the desired coil outlet air setpoint temperature when the coil outlet temperature exceeds this minimum temperature limit specified. The minimum and maximum values of this input field are 0.0\(^{o}\)C and 7.5\(^{o}\)C, and the default value is 2.0\(^{o}\)C. This field is not autosizable when the input for Use DOAS DX Cooling Coil = Yes. When Control Type = SingleZoneVAV, enter the minimum air temperature limit for reduced fan speed in cooling mode. For SingleZoneVAV, the maximum limit for the minimum supply air temperature is 20.0\(^{o}\)C. Additionally, for the SingleZoneVAV model this input does not limit the minimum supply air temperature resulting from cooling coil operation at high fan speed.
Field: Latent Load Control[LINK]
This alpha field defines the latent load control method. Available choices are SensibleOnlyLoadControl, LatentOnlyLoadControl, LatentWithSensibleLoadControl, or LatentOrSensibleLoadControl. The default choice is SensibleOnlyLoadControl. The SensibleOnlyLoadControl choice will operate to meet only a sensible load and is also required when SingleZoneVAV control is selected. The LatentOnlyLoadConrol will operate to meet only a latent load. The LatentWithSensibleLoadControl will operate to meet the latent load only if there is a sensible load. The LatentOrSensibleLoadControl will operate to meet either a latent or sensible load.
Field: Supplemental Heating Coil Object Type[LINK]
This alpha field contains the identifying type of supplemental heating coil specified in the unitary system. The hot water and steam heating coils require specifying plant loop, branches, and connector objects to support the heating coils, and are placed on the demand side of the plant loop. The Coil:UserDefined object must be configured as a heating coil. Supplemental heating type must be one of:
Coil:Heating:Electric
Coil:Heating:Fuel
Coil:Heating:Desuperheater
Coil:Heating:Water
Coil:Heating:Steam
Coil:UserDefined
Field: Supplemental Heating Coil Name[LINK]
This alpha field contains the identifying name given to the unitary system supplemental or reheat coil object. This coil provides supplemental heat during heating mode operation, or reheats the supply air during dehumidification mode operation. For set point based control, all coils will control to their respective outlet air temperature set point.
Field: Cooling Supply Air Flow Rate Method[LINK]
This alpha field defines the supply air flow method during cooling operation. Available choices are SupplyAirFlowRate, FlowPerFloorArea, FractionOfAutosizedCoolingValue, FlowPerCoolingCapacity. For each of the choices, a corresponding air flow rate for cooling must be specified. If the system does not have a cooling coil a 0 may be entered for cooling air flow rate and/or no load supply air flow rate to turn the fan off when cooling is not required.
Field: Cooling Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the unitary system in cubic meters per second when the cooling coil is operating. Values must be greater than 0 if the cooling coil is present or this field is autosizable. Required field when Cooling Supply Air Flow Rate Method is SupplyAirFlowRate.
Field: Cooling Supply Air Flow Rate Per Floor Area[LINK]
This numeric field defines the supply air flow rate per floor area leaving the unitary system in meters per second when the cooling coil is operating. Values must be greater than 0 if the cooling coil is present or this field is autosizable. Required field when Cooling Supply Air Flow Rate Method is FlowPerFloorArea.
Field: Cooling Fraction of Autosized Design Cooling Supply Air Flow Rate[LINK]
This numeric field defines the fraction of autosized supply air flow rate leaving the unitary system when the cooling coil is operating. Values must be greater than 0 if the cooling coil is present or this field is autosizable. Required field when Cooling Supply Air Flow Rate Method is FractionOfAutosizedCoolingValue.
Field: Cooling Supply Air Flow Rate Per Unit of Capacity[LINK]
This numeric field defines the supply air flow rate per unit of capacity leaving the unitary system when the cooling coil is operating. Values must be greater than 0 if the cooling coil is present or this field is autosizable. Required field when Cooling Supply Air Flow Rate Method is FlowPerCoolingCapacity.
Field: Heating Supply Air Flow Rate Method[LINK]
This alpha field defines the supply air flow method during heating operation. Available choices are SupplyAirFlowRate, FlowPerFloorArea, FractionOfAutosizedHeatingValue, FlowPerHeatingCapacity. For each of the choices, a corresponding air flow rate for heating must be specified. If the system does not have a heating coil a 0 may be entered for heating air flow rate and/or no load supply air flow rate to turn the fan off when heating is not required.
Field: Heating Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the unitary system in cubic meters per second when the heating coil is operating. Values must be greater than 0 if the heating coil is present or this field is autosizable. Required field when Heating Supply Air Flow Rate Method is SupplyAirFlowRate.
Field: Heating Supply Air Flow Rate Per Floor Area[LINK]
This numeric field defines the supply air flow rate per floor area leaving the unitary system in meters per second when the heating coil is operating. Values must be greater than 0 if the heating coil is present or this field is autosizable. Required field when Heating Supply Air Flow Rate Method is FlowPerFloorArea.
Field: Heating Fraction of Autosized Design Heating Supply Air Flow Rate[LINK]
This numeric field defines the fraction of autosized supply air flow rate leaving the unitary system when the heating coil is operating. Values must be greater than 0 if the heating coil is present or this field is autosizable. Required field when Heating Supply Air Flow Rate Method is FractionOfAutosizedHeatingValue.
Field: Heating Supply Air Flow Rate Per Unit of Capacity[LINK]
This numeric field defines the supply air flow rate per unit of capacity leaving the unitary system when the heating coil is operating. Values must be greater than 0 if the heating coil is present or this field is autosizable. Required field when Heating Supply Air Flow Rate Method is FlowPerHeatingCapacity.
Field: No Load Supply Air Flow Rate Method[LINK]
This alpha field defines the supply air flow method when neither cooling or heating is required. Available choices are SupplyAirFlowRate, FlowPerFloorArea, FractionOfAutosizedCoolingValue, FractionOfAutosizedHeatingValue, FlowPerCoolingCapacity, FlowPerHeatingCapacity. For each of the choices, a corresponding air flow rate must be specified. The following fields are also used to specify the lower air flow rate for the SingleZoneVAV control method with recommendations of greater than or equal to 67% of the Cooling or Heating Supply Air Flow Rate when any DX coil is used and 50% for other coil types.
Field: No Load Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the unitary system in cubic meters per second when neither cooling or heating is required (i.e., main cooling/heating coils and supplemental heater are off but the supply air fan operates). This field is only used when the unitary system operating mode is specified as continuous fan operation or when the Control Type is specified as SingleZoneVAV. Values must be greater than or equal to 0, or this field is autosizable. If this field is autosized, then it is sized to the minimum of the heating and cooling lowest speed supply air flow rate. If the Control Type is specified as SingleZoneVAV and this field is autosized, then the no load supply air flow rate is set equal to 0.5 or 0.667 times the maximum flow rate for water or coils, respectively. If the unitary system operating mode is specified as continuous fan operation and this value is set to zero or this field is left blank, then the model assumes that the supply air flow rate when no cooling/heating is needed is equal to the supply air flow rate when the compressor was last operating (for cooling operation or heating operation). This field should not be set to 0 when Control Type is specified as SingleZoneVAV.
Field: No Load Supply Air Flow Rate Per Floor Area[LINK]
This numeric field defines the supply air flow rate per floor area leaving the unitary system in meters per second when neither cooling or heating coil is operating. Values must be greater than or equal to 0 or this field is autosizable. Required field when No Load Supply Air Flow Rate Method During is FlowPerFloorArea.
Field: No Load Fraction of Autosized Cooling Supply Air Flow Rate[LINK]
This numeric field defines the fraction of autosized supply air flow rate leaving the unitary system when neither cooling or heating coil is operating. Values must be greater than or equal to 0 or this field is autosizable. Required field when No Load Supply Air Flow Rate Method is FractionOfAutosizedCoolingValue.
Field: No Load Fraction of Autosized Heating Supply Air Flow Rate[LINK]
This numeric field defines the fraction of autosized supply air flow rate leaving the unitary system when the neither cooling or heating coil is operating. Values must be greater than or equal to 0 or this field is autosizable. Required field when No Load Supply Air Flow Rate Method is FractionOfAutosizedHeatingValue.
Field: No Load Supply Air Flow Rate Per Unit of Capacity During Cooling Operation[LINK]
This numeric field defines the supply air flow rate per unit of capacity leaving the unitary system when neither cooling or heating is operating. Values must be greater than or equal to 0 or this field is autosizable. Required field when No Load Supply Air Flow Rate Method is FlowPerCoolingCapacity.
Field: No Load Supply Air Flow Rate Per Unit of Capacity During Heating Operation[LINK]
This numeric field defines the supply air flow rate per unit of capacity leaving the unitary system when neither cooling or heating is operating. Values must be greater than or equal to 0 or this field is autosizable. Required field when No Load Supply Air Flow Rate Method is FlowPerHeatingCapacity.
Field: No Load Supply Air Flow Rate Control Set To Low Speed[LINK]
This alpha field defines whether the supply air flow rate leaving the air conditioner in cubic meters per second when neither cooling nor heating is required is set to the coil high speed or low speed air flow rate. The valid choices are Yes or No. The default value is Yes. If the coil type does not have multiple air flow rates or if Design Specification Multispeed Object Type = UnitarySystemPerformance:Multispeed then this field is not used. If Yes is selected and the coil air flow rate is autosized the No Load Supply Air Flow Rate is proportional to the number of speeds.
Field: Maximum Supply Air Temperature[LINK]
This numeric field contains the design operating air outlet temperature in degrees C when the unitary system is heating. If this input field is left blank, the default value is 80 C. When Control Type = SingleZoneVAV, enter the maximum air temperature limit for reduced fan speed in heating model. For the SingleZoneVAV model this input does not limit the maximum supply air temperature resulting from heating or supplemental heating coil operation at high fan speed. This field is autosizable.
Field: Maximum Outdoor Dry-Bulb Temperature for Supplemental Heater Operation[LINK]
This numeric field defines the outdoor air dry-bulb temperature above which the heat pump supplemental heating coil is disabled. The temperature for this input field must be less than or equal to 21 C. If this input field is left blank, the default value is 21 C.
Field: Outdoor Dry-Bulb Temperature Sensor Node Name[LINK]
This alpha field specifies the name of the outdoor node which controls the operation of the supplemental heating coil. If this field is left blank, the outdoor temperature is based solely on the weather data. If this field is not blank, the node name specified must also be listed in an OutdoorAir:Node object where the height of the node is taken into consideration when calculating outdoor temperature from the weather data. Alternately, the node name must be specified in an OutdoorAir:NodeList object where the outdoor temperature is taken directly from the weather data.
Field: Ancillary On-Cycle Electric Power[LINK]
This field defines ancillary electrical power (W) consumed during the on-cycle period (i.e., when the cooling or heating coil is operating). The model assumes that this ancillary power does not contribute to heating the supply air. The minimum value for this field is 0.0, and the default value is also 0.0 if the field is left blank.
Field: Ancillary Off-Cycle Electric Power[LINK]
This field defines ancillary electrical power (W) consumed during the off-cycle period (i.e., when the cooling and heating coil are not operating). The model assumes that this ancillary power does not contribute to heating the supply air. The minimum value for this field is 0.0, and the default value is also 0.0 if the field is left blank.
Field: Design Heat Recovery Water Flow Rate[LINK]
This optional input field defines the design water flow rate used if the heat recovery option is being simulated. If this value is greater than 0.0 then a heat recovery loop must be specified and attached to the multispeed heat pump using the next 2 node fields. To determine how the heat recovery algorithm works, refer to the EnergyPlus Engineering Reference in the AirLoopHVAC:UnitarySystem with Heat Recovery section. The units for this input value are cubic meters per second.
Field: Maximum Temperature for Heat Recovery[LINK]
This field sets the maximum temperature (in degrees C) that this heat pump can produce for heat recovery. The idea behind this field is that the current models do not take temperatures into account for availability and they just pass Q’s around the loop without a temperature limit. This temperature limit puts an upper bound on the recovered heat and limits the max temperature leaving the component.
As temperatures in the loop approach the maximum temperature, the temperature difference between the entering water and the surfaces in the piece of equipment becomes smaller. For the given heat recovery flow rate and that temperature difference the amount of heat recovered will be reduced, and eventually there will be no heat recovered when the entering water temperature is equal to the maximum temperature specified by the user in this field. The reduced amount of heat recovered will diminish if the temperature of the loop approach is the maximum temperature, and this will show up in the reporting. This allows the user to set the availability or the quality of the heat recovered for usage in other parts of the system or to heat domestic hot water supply.
Field: Heat Recovery Water Inlet Node Name[LINK]
This alpha field contains the identifying name for the heat recovery side inlet node.
Field: Heat Recovery Water Outlet Node Name[LINK]
This alpha field contains the identifying name for the heat recovery side outlet node.
Field: Design Specification Multispeed Object Type[LINK]
This alpha field contains the identifying type for the design specification multispeed object. This field is only needed when multispeed cooling or heating coil is specified.
Field: Design Specification Multispeed Object Name[LINK]
This alpha field contains the identifying name for the design specification multispeed object. This field is only needed when multispeed cooling or heating coil is specified.
As shown in the example below, correct specification of the heat/cool unitary system requires specification of the following objects in addition to the unitary system object:
Fan (Fan:OnOff or Fan:ConstantVolume)
Cooling coil
Heating coil
Reheat coil
Direct air unit (AirTerminal:SingleDuct:ConstantVolume:NoReheat) for each zone served by the unitary system when used in an air loop
Outputs[LINK]
HVAC,Average, Unitary System Fan Part Load Ratio []
HVAC,Average, Unitary System Compressor Part Load Ratio
HVAC,Average,Unitary System Total Cooling Rate [W]
HVAC,Average,Unitary System Total Heating Rate [W]
HVAC,Average,Unitary System Sensible Cooling Rate [W]
HVAC,Average,Unitary System Sensible Heating Rate [W]
HVAC,Average,Unitary System Latent Cooling Rate [W]
HVAC,Average,Unitary System Latent Heating Rate [W]
HVAC,Average,Unitary System Electricity Rate [W]
HVAC,Sum,Unitary System Electricity Energy [J]
HVAC,Average,Unitary System Ancillary Electricity Rate [W]
HVAC,Sum,Unitary System Cooling Ancillary Electricity Energy [J]
HVAC,Sum,Unitary System Heating Ancillary Electricity Energy [J]
Load based and SingleZoneVAV control outputs
HVAC,Average,Unitary System Predicted Sensible Load to Setpoint Heat Transfer Rate [W]
HVAC,Average,Unitary System Predicted Moisture Load to Setpoint Heat Transfer Rate [W]
Two speed coil outputs
HVAC,Average,Unitary System Cycling Ratio []
HVAC,Average,Unitary System Compressor Speed Ratio []
Multi speed coil outputs
HVAC,Average,Unitary System DX Coil Cycling Ratio []
HVAC,Average,Unitary System DX Coil Speed Ratio []
HVAC,Average,Unitary System DX Coil Speed Level []
Multi speed coil outputs(If heat recovery is specified)
HVAC,Average, Unitary System Heat Recovery Rate [W]
HVAC,Average, Unitary System Heat Recovery Inlet Temperature [C]
HVAC,Average, Unitary System Heat Recovery Outlet Temperature [C]
HVAC,Average, Unitary System Heat Recovery Fluid Mass Flow Rate [kg/s]
HVAC,Sum, Unitary System Heat Recovery Energy [J]
Variable speed coils
HVAC,Average, Unitary System Requested Sensible Cooling Rate [W]
HVAC,Average, Unitary System Requested Latent Cooling Rate [W]
Water to air heat pump outputs
HVAC,Average, Unitary System Requested Sensible Cooling Rate [W]
HVAC,Average, Unitary System Requested Latent Cooling Rate [W]
HVAC,Average, Unitary System Requested Heating Rate [W]
HVAC,Average, Unitary System Water Coil Cycling Ratio []
HVAC,Average, Unitary System Water Coil Speed Ratio []
HVAC,Average, Unitary System Water Coil Speed Level []
Subcool reheat coil outputs under Coil:Cooling:DX
HVAC,Average, Unitary System Zone Load Sensible Heat Ratio []
HVAC,Average, Unitary System Cooling Coil Load Sensible Heat Ratio []
Unitary System Fan Part Load Ratio [][LINK]
This output variable is the ratio of actual air mass flow rate through the unitary system to the unitary system’s design air mass flow rate (i.e., design volumetric flow rate converted to dry air mass flow rate). For continuous fan operation mode, this variable is always 1.0 when the unitary system is available (based on the availability schedule). For cycling fan/cycling coil operation mode, the actual air mass flow rate is calculated based on the ratio of the sensible heating (or cooling) load to the steady-state unitary system heating (or cooling) capacity. For the cycling fan mode, the runtime fraction for the unitary system fan may be different from the fan part-load ratio reported here due the part-load performance of the unitary system’s heating (or cooling) coil (delay at start-up to reach steady-state output). In general, runtime fractions are reported by individual components where appropriate (e.g., Fan:OnOff). When the speed number is greater than 1, the value is 1.0.
Unitary System Compressor Part Load Ratio [][LINK]
This output variable is the ratio of the sensible load (heating or cooling) to the steady-state capacity of the unitary system’s DX heating or cooling coil at Speed 1. The runtime fraction for the unitary system compressor may be different from the compressor part-load ratio reported here due the part-load performance of the heating/cooling coil (delay at start-up to reach steady-state output). In general, runtime fractions are reported by individual components where appropriate. When the speed number is greater than 1, the value is 1.0.
Unitary System DX Coil Cycling Ratio [][LINK]
This output variable is the ratio of the sensible load (heating or cooling) to the steady-state capacity of the unitary system’s DX heating or cooling coil (Speed 1) for the entire system timestep. The value is between 0.0 and 1.0 when the unitary system is cycling on and off its lowest speed (Speed 1) and 1.0 when the unitary system operates at speeds above 1.
When Single Mode Operation is specified, the value is between 0.0 and 1.0 when the heat pump is cycling on at any given speed.
Unitary System DX Coil Speed Ratio [][LINK]
This output variable is the ratio of time in a system timestep that the compressor is at rated speed between two consecutive speed numbers ( [Compressor Speed - Compressor speed at Speed i-1] / [Compressor speed at Speed i - Compressor speed at Speed i-1]). The compressor speed ratio reports (1.0 is max, 0.0 is min) and any value in between as it is averaged over the timestep. The value is 0.0 during Speed 1 operation.
The physical meaning of the speed ratio is dependent on the compressor configuration defined in the field of child coil object: Apply Part Load Fraction to Speeds greater than 1. The allowed choice is either Yes or No. When No is entered, one compressor is assumed for all speeds. The speed ratio represents how long the higher speed runs as a fraction of the system timestep, and the lower speed runs in the rest of the system timestep. When Yes is entered, multiple compressors are assumed, and each compressor has associated speed. The speed ratio represents how long the higher speed runs as a fraction of the system timestep, and the low speed runs in a whole system timestep.
When Single Mode Operation is specified, the speed ratio is set to 0 at Speed 1 and 1 at Speed > 1.
Unitary System DX Coil Speed Level [][LINK]
This output variable reports the maximum speed needed when the unitary system operates to meet the sensible load (heating or cooling) in a system timestep. When the value is 1, the unitary system operates at Speed 1 (lowest speed). For this case the cycling ratio is between 0.0 and 1.0, while the speed ratio is 0.0. When the speed number output variable is above one, such as i, the unitary system operation is determined by the speed ratio through linear interpolation. For example, when the speed ratio is 0.4 and the speed number is 3, the unitary system operates at Speed 3 for 40% of a system timestep and at Speed 2 for 60% of a system timestep for a single compressor. For multiple compressors, the unitary system operates at Speed 3 in the 40% of a system timestep and at Speed 2 in the whole system timestep.
Unitary System Total Heating Rate [W][LINK]
This output field is the total (enthalpy) heat addition rate of the unitary system to the zones it is serving in Watts. For set point control, this value is calculated using the enthalpy difference of the unitary system outlet air and inlet air streams, and the air mass flow rate through the unitary system. This value is calculated for each HVAC system timestep being simulated, and the results (enthalpy addition only) are averaged for the timestep being reported. For load or single zone VAV control this value is calculated using the outlet air and zone air conditions.
Unitary System Total Cooling Rate [W][LINK]
This output field is the total (enthalpy) heat extraction rate of the unitary system from the zones it is serving in Watts. For set point control, this value is calculated using the enthalpy difference of the unitary system outlet air and inlet air streams, and the air mass flow rate through the unitary system. This value is calculated for each HVAC system timestep being simulated, and the results (enthalpy extraction only) are averaged for the timestep being reported. For load or single zone VAV control this value is calculated using the outlet air and zone air conditions.
Unitary System Sensible Heating Rate [W][LINK]
This output field reports the sensible heat addition rate of the unitary system to the zones it is serving in Watts. For set point control, this value is calculated using the enthalpy difference of the unitary system outlet air and inlet air streams at a constant humidity ratio, and the air mass flow rate through the unitary system. This value is calculated for each HVAC system timestep being simulated, and the results (heating only) are averaged for the timestep being reported. For load or single zone VAV control this value is calculated using the outlet air and zone air conditions.
Unitary System Sensible Cooling Rate [W][LINK]
This output field reports the moist air sensible heat extraction rate of the unitary system from the zones it is serving in Watts. For set point control, this value is calculated using the enthalpy difference of the unitary system outlet air and inlet air streams at a constant humidity ratio, and the air mass flow rate through the unitary system. This value is calculated for each HVAC system timestep being simulated, and the results (cooling only) are averaged for the timestep being reported. For load or single zone VAV control this value is calculated using the outlet air and zone air conditions.
Unitary System Latent Heating Rate [W][LINK]
This output field is the latent heat addition (humidification) rate of the unitary system in Watts. This value is calculated as the difference between the total energy rate and the sensible energy rate provided by the unitary system. This value is calculated for each HVAC system timestep being simulated, and the results (latent heat addition only) are averaged for the timestep being reported.
Unitary System Latent Cooling Rate [W][LINK]
This output field is the latent heat extraction (dehumidification) rate of the unitary system in Watts. This value is calculated as the difference between the total energy rate and the sensible energy rate provided by the unitary system. This value is calculated for each HVAC system timestep being simulated, and the results (latent heat extraction only) are averaged for the timestep being reported.
Unitary System Electricity Rate [W][LINK]
This output field is the electricity consumption rate of the unitary system in Watts. The consumption includes electricity used by the DX coils (including crankcase heater if the fuel type is electricity), fans (indoor supply air fan and the condenser fans associated with the DX coil[s]), defrost mode operation (resistive or reverse-cycle), auxiliary power during on and off period, and the supplemental heating coil (if electric). This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported. Any non-electric energy use is not reported by the unitary system object but is reported in the associated coil objects as appropriate.
Unitary System Electricity Energy [J][LINK]
This output field is the electricity consumption of the unitary system in Joules for the timestep being reported. The consumption includes electricity used by the DX compressor (including crankcase heater if the fuel type is electricity), fans (indoor supply air fan and the condenser fans associated with the DX coil[s]), defrost mode operation (resistive or reverse-cycle), auxiliary power during on and off period, and the supplemental heating coil (if electric). This value is calculated for each HVAC system timestep being simulated, and the results are summed for the timestep being reported. Any non-electric energy use is not reported by the unitary system object but is reported in the associated coil objects as appropriate.
Unitary System Ancillary Electricity Rate [W][LINK]
This output field is the average auxiliary electricity consumption rate (including both on-cycle and off-cycle) in Watts for the timestep being reported.
Unitary System Cooling Ancillary Electricity Energy [J][LINK]
This is the auxiliary electricity consumption in Joules for the timestep being reported. This is the auxiliary electricity consumption during periods when the unitary system is providing cooling (DX cooling coil is operating). This output is also added to a meter with Resource Type = Electricity, End Use Key = Cooling, Group Key = System (ref. Output:Meter objects).
Unitary System Heating Ancillary Electricity Energy [J][LINK]
This is the auxiliary electricity consumption in Joules for the timestep being reported. This is the auxiliary electricity consumption during periods when the unitary system is providing heating (DX heating coil is operating). This output is also added to a meter with Resource Type = Electricity, End Use Key = Heating, Group Key = System (ref. Output:Meter objects).
Unitary System Predicted Sensible Load to Setpoint Heat Transfer Rate [W][LINK]
This output variable is available only for load based and single zone VAV control and is the adjusted sensible load requested from the zone thermostat in watts. This value is calculated by adjusting the zone predicted sensible load to setpoint heat transfer rate based on the controlling zone air flow fraction and the impact of fan heat and outdoor air so that the thermostat setpoints are met. This value is used for control purposes within the Unitary System model. Positive values denote a heating load while negative valued denote a cooling load. Positive and negative values do not necessarily represent which coil type is active (e.g., a positive heating load does not necessarily mean the heating coil will turn on). This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Unitary System Predicted Moisture Load to Setpoint Heat Transfer Rate [W][LINK]
This output variable is available only for load based control and is the adjusted moisture load requested from the zone humidistat in watts. This value is calculated by adjusting the zone predicted moisture load to setpoint heat transfer rate based on the heat of vaporization of water, controlling zone air flow fraction and the dehumidification control type (i.e., the moisture load is set to 0 for non-dehumidification systems). When this value is non-zero and dehumidification is requested, the Unitary System Predicted Moisture Load to Setpoint Heat Transfer Rate is compared to the result of sensible only control and if the coil does not provide sufficient dehumidification the coil capacity is increased to meet this moisture load. This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Unitary System Heat Recovery Inlet Temperature [C][LINK]
Unitary System Heat Recovery Outlet Temperature [C][LINK]
Unitary System Heat Recovery Fluid Mass Flow Rate [kg/s][LINK]
These outputs are the heat recovery inlet and outlet temperatures and water mass flow rate for unitary systems with heat recovery.
Unitary System Heat Recovery Rate [W][LINK]
Unitary System Heat Recovery Energy [J][LINK]
For multispeed unitary systems with heat recovery, these outputs are the recoverable energy rate (in Watts) and energy (in Joules).
Unitary System Requested Sensible Cooling Rate [W][LINK]
This output variable is the sensible cooling requested from the zone thermostat in watts. This value is calculated using the unitary system outlet air and zone conditions, the specific heat of the zone air, and the supply air mass flow rate entering/leaving the system. This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Unitary System Requested Latent Cooling Rate [W][LINK]
This output variable is the latent cooling requested from the zone humidistat in watts. This value is calculated using the unitary system outlet air and zone conditions, the heat of vaporization of water at the current zone conditions, and the supply air mass flow rate entering/leaving the system. This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Unitary System Requested Heating Rate [W][LINK]
This output variable is the sensible heating requested from the zone thermostat in watts. This value is calculated using the unitary system outlet air and zone conditions, the specific heat of the zone air, and the supply air mass flow rate entering/leaving the system. This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Unitary System Water Coil Cycling Ratio [][LINK]
This output variable is the ratio of the sensible load (heating or cooling) to the steady-state capacity of the multispeed fan chilled water or hot water coil for the entire system timestep. The value is between 0.0 and 1.0 when the AHU is cycling on and off its lowest speed (fan speed 1) and 1.0 when the multispeed fan chilled water or hot water AHU operates at speed levels above 1.
Unitary System Water Coil Speed Ratio [][LINK]
This output variable is the ratio of time in a system timestep that the AHU fan is at rated speed between two consecutive speed levels ( [System Load – Capacity at Fan Speed i-1] / [Capacity at Fan Speed i – Capacity at Fan Speed i-1]). The fan speed ratio reports (1.0 is max, 0.0 is min) and any value in between as it is averaged over the timestep. The value is 0.0 during Speed 1 operation. AHU speed ratio depends on the system load and the supply air fan speed. The speed ratio represents how long the higher speed runs as a fraction of the system timestep, and the lower speed runs in the rest of the system timestep.
Unitary System Water Coil Speed Level [][LINK]
This output variable reports the maximum speed needed when the system operates to meet the sensible load (heating or cooling) in a system timestep. When the value is 1, the AHU operates at Speed 1 (lowest speed). For this case the cycling ratio is between 0.0 and 1.0, while the speed ratio is 0.0. When the speed level is above the minimum (speed = 1), the system operation is determined by the speed ratio. For example, when the speed ratio is 0.4 and the speed lever is 3, then the supply air fan and water coil operate at Speed 3 for 40% of a system timestep and at Speed 2 for 60% of a system timestep.
Unitary System Zone Load Sensible Heat Ratio [][LINK]
This output variable reports the load sensible heat ratio, defined as sensible load / (sensible load + latent load) for a subcool reheat coil. The value is used to determine required coil output sensible heat ratio.
Unitary System Cooling Coil Load Sensible Heat Ratio [][LINK]
This output variable reports the cooling coil load sensible heat ratio, defined as sensible output / (sensible output + latent output) for a subcool reheat coil. The value is used to determine mode ratio between coil normal operation mode and subcool or reheat operation mode.
UnitarySystemPerformance:Multispeed[LINK]
Inputs[LINK]
Field: Name[LINK]
This alpha field contains the identifying name for the multispeed performance specification.
Field: Number of Speeds for Heating[LINK]
This field defines the number of heating speeds for the heat pump, and must match the number of heating speeds defined in the associated heating coil. The value for this input field defines the number of airflow rate ratios that must be defined for heating in the fields below. The minimum value for this field is one and the maximum value is the number specified in the coil object. If the heating coil type used in the unitary system object is not a multispeed coil type, then this field should be 1.
Field: Number of Speeds for Cooling[LINK]
This field defines the number of cooling speeds for the heat pump, and must match the number of cooling speeds defined in the associated DX cooling coil. The value for this input field defines the number of airflow rate ratios that must be defined for cooling in the fields below. The minimum value for this field is one and the maximum value is the number specified in the coil object. If the cooling coil type used in the unitary system object is not a multispeed coil type, then this field should be 1.
Field: Single Mode Operation[LINK]
This field specifies the coil operation mode for multiple speed DX cooling and heating coils during each HVAC timestep. The allowed choice is Yes or No. The No choice allows a coil works between two adjacent speeds when a system load is greater than the coil capacity at speed 1. The Yes choice allows a coil works with a single capacity at a different speed. The speed number is determined by a system load.
The allowed cooling and heating coil types are restricted to the following combinations:
Coil:Cooling:DX:MultiSpeed and Coil:Heating:DX:MultiSpeed or Coil:Cooling:DX:MultiSpeed and Coil:Heating:Fuel.
Field: No Load Supply Air Flow Rate Ratio[LINK]
This field defines the no load operating air flow rate when the system fan is specified to operate continuously. The allowed fractions are between 0 and 1 with a default value of 1. This fraction is usually set to the minimum of heating and cooling operation lowest speed supply air flow fraction. The no load air flow rate will be calculated as this fraction multiplied by the minimum of the cooling and heating high speed supply air flow rate. If the cooling or heating coil is not present, this fraction is multiplied by the operating supply air flow rate.
Field Group: Heating and Cooling Speeds 1 to 10[LINK]
The air flow through a multispeed coil system is specified as a group of two air flow ratio inputs, one each for heating and cooling. If the number of speeds for heating and cooling are different, inputs for both heating and cooling are still required for a given speed yet one input may be blank. The maximum of the inputs for Number of Speeds for Cooling and Number of Speeds for Heating specified above determines how many groups of heating and cooling supply air flow ratio inputs are required. Both inputs for Speed 1 are required and specify the air flow ratio for the lowest speed, followed by the inputs for Speed 2, Speed 3, etc. up to a maximum of 10 speeds. These inputs are applicable only to multispeed or variable speed coils.
Field: Heating Speed <x> Supply Air Flow Ratio[LINK]
This numeric field defines the ratio of supply air flow rate leaving the unitary system to the maximum air flow rate specified in the coil object at maximum speed when the heating coil is operating at Speed <x>. Values must be greater than 0. The entered value must be greater or equal to the flow rate ratio specified for the previous heating speed. If the ‘Number of Speeds for Heating’ is less than <x>, then this field can be left blank.
Field: Cooling Speed <x> Supply Air Flow Ratio {#field-cooling-speed-x-supply-[LINK]
air-flow-ratio}
This numeric field defines the ratio of supply air flow rate leaving the unitary system to the maximum air flow rate specified in the coil object at maximum speed when the cooling coil is operating at Speed <x>. Values must be greater than 0. The entered value must be greater or equal to the flow rate ratio specified for the previous cooling speed. If the ‘Number of Speeds for Cooling’ is less than <x>, then this field can be left blank.
AirLoopHVAC:Unitary:Furnace:HeatCool[LINK]
The heat/cool furnace is a “virtual” component that consists of a fan component (OnOff or ConstantVolume), a DX cooling coil component, and a Gas or Electric heating coil component. The blow through furnace configuration is shown in Figure 2 below. When a draw through furnace configuration is desired, the fan is placed directly after the heating coil. If the dehumidification control type is specified as CoolReheat, a reheat coil component is also required. If the reheat coil is present and the dehumidification control type input is not specified as CoolReheat, the reheat coil will not be active,
Note: the coil order shown here has been revised from previous versions (prior to V4.0) of Energyplus to configure the cooling coil upstream of the heating coil. This configuration provides uniformity with all unitary equipment. However, for unitary HeatCool systems that do not use a reheat coil, the heating coil can also be placed upstream of the cooling coil. This optional coil placement is retained to allow compatibility with previous versions of Energyplus. For input files developed using previous versions of Energyplus, it is recommended that the coil order be revised according to the figure above.
Links to the fan, heating coil, DX cooling coil and optional reheat coil specifications are provided in the furnace input data syntax. In addition, the control zone name and the furnace design operating conditions are specified by the furnace inputs.
Inputs[LINK]
Field: Name[LINK]
This alpha field contains the identifying name for the unit.
Field: Availability Schedule Name[LINK]
This alpha field contains the schedule name which contains information on the availability of the furnace to operate. A schedule value equal to 0 denotes that the furnace must be off for that time period. A value greater than 0 denotes that the furnace is available to operate during that time period. This schedule may be used to completely disable the furnace as required. If this field is left blank, the schedule has a value of 1 for all time periods.
Field: Furnace Air Inlet Node Name[LINK]
This alpha field contains the furnace inlet node name.
Field: Furnace Air Outlet Node Name[LINK]
This alpha field contains the furnace outlet node name.
Field: Supply Air Fan Operating Mode Schedule Name[LINK]
This alpha field specifies the name of the supply air fan operating mode schedule. The supply air fan operating mode may vary during the simulation based on time-of-day or with a change of season. Schedule values of 0 denote that the furnace supply air fan and the heating or cooling coil cycle on and off together to meet the heating or cooling load (a.k.a. AUTO fan). Schedule values other than 0 denote that the supply fan runs continuously while the heating or cooling coil cycles to meet the load.
Field: Maximum Supply Air Temperature[LINK]
This numeric field contains the design operating furnace air outlet temperature in degrees C when the furnace is heating. If this input field is left blank, the default value is 80 C.
Field: Cooling Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the furnace in cubic meters per second when the DX cooling coil is operating. Values must be greater than 0 or this field is autosizable.
Field: Heating Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the furnace in cubic meters per second when the DX heating coil and/or supplemental heater are operating. Values must be greater than 0 or this field is autosizable.
Field: No Load Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the furnace in cubic meters per second when neither cooling or heating is required (i.e., DX coils and supplemental heater are off but the supply air fan operates). This field is only used when the furnace operating mode is specified as continuous fan operation. Values must be greater than or equal to zero, or this field is autosizable. If the furnace operating mode is specified as continuous fan operation and this value is set to zero or this field is left blank, then the model assumes that the supply air flow rate when no cooling/heating is needed is equal to the supply air flow rate when the compressor was last operating (for cooling operation or heating operation).
Field: Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where the thermostat controlling the furnace is located.
Field: Supply Fan Object Type[LINK]
This alpha field contains the identifying type of supply air fan specified for the furnace. Fan type must be Fan:OnOff or Fan:ConstantVolume. Fan:ConstantVolume is used when the Supply Air Fan Operating Mode Schedule values are never 0 and the fan operates continuously. Fan:OnOff is used when the fan cycles on and off with the cooling or heating coil (i.e. Supply Air Fan Operating Mode Schedule values are at times 0).
Field: Supply Fan Name[LINK]
This alpha field contains the identifying name given to the furnace fan.
Field: Fan Placement[LINK]
This alpha field has two choices: BlowThrough or DrawThrough. The first choice stands for “blow through fan”. This means that the unit consists of a fan followed by the DX coils and supplemental heating coil. The fan “blows through” the cooling and heating coils. The second choice stands for “draw through fan”. This means that the unit consists of the DX coil(s) followed by a fan, with the supplemental heater located at the outlet of the fan. The fan “draws air through” the DX coil(s). If this field is left blank, the default is blow through.
Field: Heating Coil Object Type[LINK]
This alpha field contains the identifying type of heating coil specified in the furnace. The hot water and steam heating coils require specifying plant loop, branches, and connector objects to support the heating coils, and are placed on the demand side of the plantloop. The hot water flow modulation through the heating coil does not require additional controller or Controller:WaterCoil object. The parent object (Unitary Heat and Cool Furnace) itself provides the “controller” function of modulating water flow. Allowable coil types are:
Coil:Heating:Electric
Coil:Heating:Fuel
Coil:Heating:Water
Coil:Heating:Steam
Field: Heating Coil Name[LINK]
This alpha field contains the identifying name given to the furnace heating coil.
Field: Cooling Coil Object Type[LINK]
This alpha field contains the identifying type of cooling coil specified in the furnace. Only allowable coil types are:
Coil:Cooling:DX:SingleSpeed
CoilSystem:Cooling:DX:HeatExchangerAssisted
Coil:Cooling:DX:VariableSpeed
Field: Cooling Coil Name[LINK]
This alpha field contains the identifying name given to the furnace cooling coil.
Field: Dehumidification Control Type[LINK]
This alpha field contains the type of dehumidification control. The following options are valid for this field:
None - meet sensible load only, no active dehumidification control
Multimode - activate enhanced dehumidification mode as needed and meet sensible load. This option is used to model DX equipment with a controllable heat exchanger assisting the DX cooling coil for improved dehumidification. It is valid only with cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted.
CoolReheat - cool beyond the dry-bulb temperature set point as required to meet the high humidity setpoint. If cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted, then the heat exchanger is assumed to always transfer energy between the cooling coil’s inlet and outlet airstreams when the cooling coil is operating.
The default is None. For the other dehumidification control modes, the maximum humidity setpoint is used. This must be set using a ZoneControl:Humidistat object. When extra dehumidification is required, the system may not be able to meet the humidity setpoint if its full capacity is not adequate. If the dehumidification control type is specified as CoolReheat, then two additional inputs (reheat coil type and name) are also required as shown below. Although the reheat coil is required only when CoolRheat is selected, the optional reheat coil may be present for any of the allowed Dehumidification Control Types. If the reheat coil is present and the dehumidification control type is not specified as CoolReheat, the reheat coil will not be active,
Field: Reheat Coil Object Type[LINK]
This alpha field contains the identifying type of reheat coil specified in the furnace. The hot water and steam heating coils require specifying plant loop, branches, and connector objects to support the heating coils, and are placed on the demand side of the plantloop. The hot water flow modulation through the reheat coil does not require additional controller or Controller:WaterCoil object. The parent object (Unitary Heat and Cool Furnace) itself provides the “controller” function of modulating water flow. Reheat coil type must be one of:
Coil:Heating:Electric
Coil:Heating:Fuel
Coil:Heating:Desuperheater
Coil:Heating:Water
Coil:Heating:Steam
Field: Reheat Coil Name[LINK]
This alpha field contains the identifying name given to the furnace reheat coil.
As shown in the example below, correct specification of the heat/cool furnace requires specification of the following objects in addition to the furnace object:
fan (Fan:OnOff or Fan:ConstantVolume)
cooling coil (Coil:Cooling:DX:SingleSpeed or CoilSystem:Cooling:DX:HeatExchangerAssisted)
heating coil (Coil:Heating:Fuel or Coil:Heating:Electric)
reheat coil (optional, Coil:Heating:Fuel, Coil:Heating:Electric, or Coil:Heating:Desuperheater)
terminal unit (AirTerminal:SingleDuct:ConstantVolume:NoReheat) for each zone served by the furnace
Note: the furnace’s fan, cooling coil, heating coil and optional reheat coil must be connected in the air loop according to the configuration shown above (Figure 2) when CoolReheat is selected as the dehumidification control type. In addition, the volumetric air flow rate specified in the terminal air unit for the controlling zone should properly reflect the fractional volumetric air flow rate specified in the furnace object.
Example of Heat/Cool Furnace Specification
Outputs[LINK]
HVAC,Average,Unitary System Fan Part Load Ratio []
HVAC,Average,Unitary System Compressor Part Load Ratio []
Unitary System Fan Part Load Ratio[LINK]
This output variable is the ratio of actual air mass flow rate through the furnace to the furnace’s design air mass flow rate (i.e., design volumetric flow rate converted to dry air mass flow rate). For continuous fan operation mode, this variable is always 1.0 when the furnace is available (based on the availability schedule). For cycling fan/cycling coil operation mode, the actual air mass flow rate is calculated based on the ratio of the sensible heating (or cooling) load to the steady-state furnace heating (or cooling) capacity. For the cycling fan mode, the runtime fraction for the furnace fan may be different from the fan part-load ratio reported here due the part-load performance of the furnace’s heating (or cooling) coil (delay at start-up to reach steady-state output). In general, runtime fractions are reported by individual components where appropriate (e.g., Fan:OnOff).
Unitary System Compressor Part Load Ratio []
AirLoopHVAC:UnitaryHeatCool[LINK]
The AirLoopHVAC:UnitaryHeatCool object is the identical model to the AirLoopHAVC:Unitary:Furnace:HeatCool object. The heat/cool unitary system is a “virtual” component that consists of a fan component (OnOff or ConstantVolume), a DX cooling coil component and a Gas or Electric heating coil component as shown in Figure 3. When a draw through configuration is desired, the fan is placed directly after the heating coil. If dehumidification control is selected, a reheat coil component is also required. If the reheat coil is present and the dehumidification control type input is not specified as CoolReheat, the reheat coil will not be active,
Note: the coil order shown here has been revised from previous versions (prior to V4.0) of Energyplus to configure the cooling coil upstream of the heating coil. This configuration provides uniformity with all unitary equipment. However, for unitary HeatCool systems that do not use a reheat coil, the heating coil can also be placed upstream of the cooling coil. This optional coil placement is retained to allow compatibility with previous versions of Energyplus. For input files developed using previous versions of Energyplus, it is recommended that the coil order be revised according to the figure above.
Links to the fan, DX cooling coil, heating coil and optional reheat coil specifications are provided in the unitary system input data syntax. In addition, the control zone name and the system design operating conditions are specified by the unitary system inputs.
Field: Name[LINK]
This alpha field contains the identifying name for the unitary system.
Field: Availability Schedule Name[LINK]
This alpha field contains the schedule name which contains information on the availability of the unitary system to operate. A schedule value equal to 0 denotes that the unitary system must be off for that time period. A value greater than 0 denotes that the unitary system is available to operate during that time period. This schedule may be used to completely disable the unitary system as required. If this field is left blank, the schedule has a value of 1 for all time periods.
Field: Unitary System Air Inlet Node Name[LINK]
This alpha field contains the unitary system inlet node name.
Field: Unitary System Air Outlet Node Name[LINK]
This alpha field contains the unitary system outlet node name.
Field: Supply Air Fan Operating Mode Schedule Name[LINK]
This alpha field specifies the name of the supply air fan operating mode schedule. The supply air fan operating mode may vary during the simulation based on time-of-day or with a change of season. Schedule values of 0 denote that the unitary system supply air fan and the heating or cooling coil cycle on and off together to meet the heating or cooling load (a.k.a. AUTO fan). Schedule values other than 0 denote that the supply fan runs continuously while the heating or cooling coil cycles to meet the load.
Field: Maximum Supply Air Temperature[LINK]
This numeric field contains the design operating air outlet temperature in degrees C when the unitary system is heating. If this input field is left blank, the default value is 80 C.
Field: Cooling Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the unitary system in cubic meters per second when the DX cooling coil is operating. Values must be greater than 0 or this field is autosizable.
Field: Heating Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the unitary system in cubic meters per second when the DX heating coil and/or supplemental heater are operating. Values must be greater than 0 or this field is autosizable.
Field: No Load Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the unitary system in cubic meters per second when neither cooling or heating is required (i.e., DX coils and supplemental heater are off but the supply air fan operates). This field is only used when the unitary system operating mode is specified as continuous fan operation. Values must be greater than or equal to zero, or this field is autosizable. If the unitary system operating mode is specified as continuous fan operation and this value is set to zero or this field is left blank, then the model assumes that the supply air flow rate when no cooling/heating is needed is equal to the supply air flow rate when the compressor was last operating (for cooling operation or heating operation).
Field: Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where the thermostat controlling the unitary system is located.
Field: Supply Fan Object Type[LINK]
This alpha field contains the identifying type of supply air fan specified for the unitary system. Fan type must be Fan:OnOff or Fan:ConstantVolume. Fan:ConstantVolume is used when the Supply Air Fan Operating Mode Schedule values are never 0 and the fan operates continuously. Fan:OnOff is used when the fan cycles on and off with the cooling or heating coil (i.e. Supply Air Fan Operating Mode Schedule values are at times 0).
Field: Supply Fan Name[LINK]
This alpha field contains the identifying name given to the unitary system fan.
Field: Fan Placement[LINK]
This alpha field has two choices: BlowThrough or DrawThrough. The first choice stands for “blow through fan”. This means that the unit consists of a fan followed by the DX coils and supplemental heating coil. The fan “blows through” the cooling and heating coils. The second choice stands for “draw through fan”. This means that the unit consists of the DX coil(s) followed by a fan, with the supplemental heater located at the outlet of the fan. The fan “draws air through” the DX coil(s). If this field is left blank, the default is blow through.
Field: Heating Coil Object Type[LINK]
This alpha field contains the identifying type of heating coil specified in the unitary system. The hot water and steam heating coils require specifying plant loop, branches, and connector objects to support the heating coils, and are placed on the demand side of the plantloop. The hot water flow modulation through the heating coil does not require additional controller or Controller:WaterCoil object. The parent object (Unitary Heat and Cool System) itself provides the “controller” function of modulating water flow. Allowable coil types are:
Coil:Heating:Electric
Coil:Heating:Fuel
Coil:Heating:Water
Coil:Heating:Steam
Field: Heating Coil Name[LINK]
This alpha field contains the identifying name given to the unitary system heating coil.
Field: Cooling Coil Object Type[LINK]
This alpha field contains the identifying type of cooling coil specified in the unitary system. Only allowable coil types are:
Coil:Cooling:DX:SingleSpeed
CoilSystem:Cooling:DX:HeatExchangerAssisted
Coil:Cooling:DX:VariableSpeed
Field: Cooling Coil Name[LINK]
This alpha field contains the identifying name given to the unitary system cooling coil.
Field: Dehumidification Control Type[LINK]
This alpha field contains the type of dehumidification control. The following options are valid for this field:
None - meet sensible load only, no active dehumidification control
Multimode - activate enhanced dehumidification mode as needed and meet sensible load. This option is used to model DX equipment with a controllable heat exchanger assisting the DX cooling coil for improved dehumidification. It is valid only with cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted.
CoolReheat - cool beyond the dry-bulb temperature set point as required to meet the high humidity setpoint. If cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted, then the heat exchanger is assumed to always transfer energy between the cooling coil’s inlet and outlet airstreams when the cooling coil is operating.
The default is None. For the other dehumidification control modes, the maximum humidity setpoint is used. This must be set using a ZoneControl:Humidistat object. When extra dehumidification is required, the system may not be able to meet the humidity setpoint if its full capacity is not adequate. If the dehumidification control type is specified as CoolReheat, then two additional inputs (reheat coil type and name) are also required as shown below. Although the reheat coil is required only when CoolReheat is selected, the optional reheat coil may be present for any of the allowed Dehumidification Control Types. If the reheat coil is present and the dehumidification control type is not specified as CoolReheat, the reheat coil will not be active,
Field: Reheat Coil Object Type[LINK]
This alpha field contains the identifying type of reheat coil specified in the unitary system. The hot water and steam heating coils require specifying plant loop, branches, and connector objects to support the heating coils, and are placed on the demand side of the plantloop. The hot water flow modulation through the reheat coil does not require additional controller or Controller:WaterCoil object. The parent object (Unitary Heat and Cool System) itself provides the “controller” function of modulating water flow. Reheat coil type must be one of:
Coil:Heating:Electric
Coil:Heating:Fuel
Coil:Heating:Desuperheater
Coil:Heating:Water
Coil:Heating:Steam
Field: Reheat Coil Name[LINK]
This alpha field contains the identifying name given to the unitary system reheat coil.
As shown in the example below, correct specification of the heat/cool unitary system requires specification of the following objects in addition to the unitary system object:
1) Fan (Fan:OnOff or Fan:ConstantVolume)
2) Cooling coil (Coil:Cooling:DX:SingleSpeed or CoilSystem:Cooling:DX:HeatExchangerAssisted)
3) Heating coil (Coil:Heating:Fuel or Coil:Heating:Electric)
4) Reheat coil (optional, Coil:Heating:Fuel, Coil:Heating:Electric, or Coil:Heating:Desuperheater)
5) Direct air unit (AirTerminal:SingleDuct:ConstantVolume:NoReheat) for each zone served by the unitary system
Note: the unitary system’s fan, cooling coil, heating coil and optional reheat coil must be connected in the air loop according to the configuration shown above (Figure 3). In addition, the volumetric air flow rate specified in the direct air unit for the controlling zone should properly reflect the fractional volumetric air flow rate specified in the unitary system object.
Example of Heat/Cool Unitary System Specification
Unitary System Heat and Cool (AirLoopHVAC) Outputs[LINK]
HVAC,Average, Unitary System Fan Part Load Ratio []
HVAC,Average, Unitary System Compressor Part Load Ratio
Unitary System Fan Part Load Ratio [][LINK]
This output variable is the ratio of actual air mass flow rate through the unitary system to the system’s design air mass flow rate (i.e., design volumetric flow rate converted to dry air mass flow rate). For continuous fan operation mode, this variable is always 1.0 when the unitary system is available (based on the availability schedule). For cycling fan/cycling coil operation mode, the actual air mass flow rate is calculated based on the ratio of the sensible heating (or cooling) load to the steady-state unitary system heating (or cooling) capacity. For the cycling fan mode, the runtime fraction for the unitary system fan may be different from the fan part-load ratio reported here due the part-load performance of the system’s heating (or cooling) coil (delay at start-up to reach steady-state output). In general, runtime fractions are reported by individual components where appropriate (e.g., Fan:OnOff).
Unitary System Compressor Part Load Ratio [][LINK]
This output variable is the ratio of the sensible cooling load to the steady-state cooling capacity of the unitary system’s DX cooling coil. The runtime fraction for the DX cooling coil compressor may be different from the compressor part-load ratio reported here due the part-load performance of the cooling coil (delay at start-up to reach steady-state output). In general, runtime fractions are reported by individual components where appropriate.
AirLoopHVAC:UnitaryHeatPump:AirToAir[LINK]
The unitary air-to-air heat pump is a “virtual” component that consists of a fan component (OnOff or ConstantVolume), a DX cooling coil component, a DX heating coil component, and a Gas or Electric supplementary heating coil component as shown in the Figure below.
Links to the fan, DX cooling coil, DX heating coil, and supplementary heating coil specifications are provided in the heat pump’s input data syntax. In addition the control zone name and the system design operating conditions are specified by the heat pump inputs.
Inputs[LINK]
Field: Name[LINK]
This alpha field contains the identifying name for the unitary system heat pump.
Field: Availability Schedule Name[LINK]
This alpha field contains the schedule name (ref. Schedule objects) that contains information on the availability of the heat pump to operate. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the hour. A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off for the hour. If this field is left blank, the schedule has a value of 1 for all time periods.
Field: Air Inlet Node Name[LINK]
This alpha field contains the name of the HVAC system node from which the heat pump draws its inlet air.
Field: Air Outlet Node Name[LINK]
This alpha field contains the name of the HVAC system node to which the heat pump sends its outlet air.
Field: Cooling Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the heat pump in cubic meters per second when the DX cooling coil is operating. Values must be greater than 0 or this field is autosizable.
Field: Heating Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the heat pump in cubic meters per second when the DX heating coil and/or supplemental heater are operating. Values must be greater than 0 or this field is autosizable.
Field: No Load Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the heat pump in cubic meters per second when neither cooling or heating is required (i.e., DX coils and supplemental heater are off but the supply air fan operates). This field is only used when the heat pump operating mode is specified as continuous fan operation. Values must be greater than or equal to zero, or this field is autosizable. If the heat pump operating mode is specified as continuous fan operation and this value is set to zero or this field is left blank, then the model assumes that the supply air flow rate when no cooling/heating is needed is equal to the supply air flow rate when the compressor was last operating (for cooling operation or heating operation).
Field: Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where the thermostat controlling the heat pump is located.
Field: Supply Air Fan Object Type[LINK]
This alpha field contains the identifying type of supply air fan specified for the heat pump. Fan type must be Fan:OnOff or Fan:ConstantVolume. Fan:ConstantVolume is used when the Supply Air Fan Operating Mode Schedule values are never 0 and the fan operates continuously. Fan:OnOff is used when the fan cycles on and off with the cooling or heating coil (i.e. Supply Air Fan Operating Mode Schedule values are at times 0).
Field: Supply Air Fan Name[LINK]
This alpha field contains the identifying name given to the heat pump supply air fan, and should match the name specified in the corresponding fan object.
Field: Heating Coil Object Type[LINK]
This alpha field contains the identifying type of heating coil specified in the heat pump. Heating coil type must be either Coil:Heating:DX:SingleSpeed or Coil:Heating:DX:VariableSpeed.
Field: Heating Coil Name[LINK]
This alpha field contains the identifying name given to the heat pump DX heating coil, and should match the name specified in the corresponding DX heating coil object.
Field: Cooling Coil Object Type[LINK]
This alpha field contains the identifying type of cooling coil specified in the heat pump. There are three valid choices for this field:
Coil:Cooling:DX:SingleSpeed
CoilSystem:Cooling:DX:HeatExchangerAssisted
Coil:Cooling:DX:VariableSpeed
Field: Cooling Coil Name[LINK]
This alpha field contains the identifying name given to the heat pump cooling coil, and should match the name specified in the corresponding DX cooling coil object.
Field: Supplemental Heating Coil Object Type[LINK]
This alpha field contains the identifying type of supplemental heating coil specified in the heat pump. The hot water and steam heating coils require specifying plant loop, branches, and connector objects to support the heating coils, and are placed on the demand side of the plantloop. The hot water flow modulation through the supplemental heating coil does not require additional controller or Controller:WaterCoil object. The parent object (Airloop Air to Air Heat Pump) itself provides the “controller” function of modulating water flow. Heating coil type must be:
Coil:Heating:Electric
Coil:Heating:Fuel
Coil:Heating:Water
Coil:Heating:Steam
Field: Supplemental Heating Coil Name[LINK]
This alpha field contains the identifying name given to the heat pump supplemental heating coil, and should match the name specified in the corresponding heating coil object.
Field: Maximum Supply Air Temperature from Supplemental Heater[LINK]
This numeric field defines the maximum allowed supply air temperature exiting the heat pump supplemental heating coil.
Field: Maximum Outdoor Dry-Bulb Temperature for Supplemental Heater Operation[LINK]
This numeric field defines the outdoor air dry-bulb temperature above which the heat pump supplemental heating coil is disabled. The temperature for this input field must be less than or equal to 21 C. If this input field is left blank, the default value is 21 C.
Field: Fan Placement[LINK]
This alpha field has two choices: BlowThrough or DrawThrough. The first choice represents a blow through system where the supply air fan is before the DX cooling/heating coil and the supplementary heating coil. The second choice represents a draw through system where the supply air fan is between the DX cooling/heating coil and the supplementary heating coil. If this input field is left blank, the default is blow through.
Field: Supply Air Fan Operating Mode Schedule Name
This alpha field specifies the name of the supply air fan operating mode schedule. The supply air fan operating mode may vary during the simulation based on time-of-day or with a change of season. Schedule values of 0 denote that the unitary system supply air fan and the heating or cooling coil cycle on and off together to meet the heating or cooling load (a.k.a. AUTO fan). Schedule values other than 0 denote that the supply fan runs continuously while the heating or cooling coil cycles to meet the load.
As shown in the example below, correct specification of the air-to-air heat pump requires specification of the following objects in addition to the heat pump object:
1) Fan (Fan:OnOff or Fan:ConstantVolume)
2) Heating coil (Coil:Heating:DX:SingleSpeed)
3) Cooling coil (Coil:Cooling:DX:SingleSpeed or CoilSystem:Cooling:DX:HeatExchangerAssisted)
4) Supplemental heating coil (Coil:Heating:Fuel or Coil:Heating:Electric)
5) Direct air unit (AirTerminal:SingleDuct:ConstantVolume:NoReheat)for each zone served by the unitary system
Field: Dehumidification Control Type[LINK]
This alpha input field contains the type of dehumidification control. The following options are valid for this field:
None - meet sensible load only, no active dehumidification control
Multimode - activate enhanced dehumidification mode as needed and meet sensible cooling load. This option is used to model DX equipment with a controllable heat exchanger assisting the DX cooling coil for improved dehumidification. It is valid only with cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted.
CoolReheat - cool beyond the dry-bulb temperature set point as required to meet the high humidity setpoint. The excess cooling beyond the cooling set point temperature is offset by the supplemental heating coil. If cooling coil type = CoilSystem:Cooling:DX:HeatExchangerAssisted, then the heat exchanger is assumed to always transfer energy between the cooling coil’s inlet and outlet airstreams when the cooling coil is operating.
The default is None. For the other dehumidification control modes, the maximum humidity setpoint is required. This must be set using a ZoneControl:Humidistat object. When extra dehumidification is required, the system may not be able to meet the humidity setpoint if its full capacity is not adequate. Supplemental heating coil (supplemental heating coil type and name) is a required input in AirToAir HeatPumps. The supplemental heating coil capacity must be adequate enough to meet the heating coil load and offset the excess cooling load due to extra dehumidification required to meet the high relative humidity setpoint.
Field: DX Heating Coil Sizing Ratio[LINK]
This input specifies the ratio of heat pump heating to cooling capacity. The default value is 1.0.
Note: the air-to-air heat pump’s fan, cooling coil, heating coil and supplementary heating coil must be connected in the air loop according to the configuration shown above (Figure 118) for the blow-through fan configuration. The only other valid configuration is with a draw-through fan placement, where the fan is located between the DX heating coil and the supplementary heating coil.
AirLoopHVAC:UnitaryHeatPump:AirToAir Example Specification[LINK]
Outputs[LINK]
HVAC, Average, Unitary System Fan Part Load Ratio []
HVAC, Average, Unitary System Compressor Part Load Ratio []
HVAC, Average, Unitary System Dehumidification Induced Heating Demand Rate [W]
Unitary System Fan Part Load Ratio [][LINK]
This output variable is the ratio of actual air mass flow rate through the heat pump to the heat pump’s design air mass flow rate (i.e., design volumetric flow rate converted to dry air mass flow rate). For continuous fan operation mode, this variable is always 1.0 when the furnace is available (based on the availability schedule). For cycling fan/cycling coil operation mode, the actual air mass flow rate is calculated based on the ratio of the sensible heating (or cooling) load to the steady-state heat pump heating (or cooling) capacity. For the cycling fan mode, the runtime fraction for the heat pump fan may be different from the fan part-load ratio reported here due the part-load performance of the heat pump’s heating (or cooling) coil (delay at start-up to reach steady-state output). In general, runtime fractions are reported by individual components where appropriate (e.g., Fan:OnOff).
Unitary System Compressor Part Load Ratio [][LINK]
This output variable is the ratio of the sensible load (heating or cooling) to the steady-state capacity of the heat pump’s DX heating or cooling coil. The runtime fraction for the heat pump compressor may be different from the compressor part-load ratio reported here due the part-load performance of the heating/cooling coil (delay at start-up to reach steady-state output). In general, runtime fractions are reported by individual components where appropriate.
Unitary System Dehumidification Induced Heating Demand Rate [W][LINK]
This output variable is the additional heating demand rate of the supplemental heating coil of an Air-to-Air heat pumps in Watts. This additional heating demand is induced when zone air overshoots the heating setpoint due to extra dehumidification requirement to meet the high humidity setpoint. This value is always positive. This value is calculated for each HVAC system timestep, and the results are averaged for the timestep being reported.
AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed[LINK]
The multispeed air-to-air heat pump is a “virtual” component that consists of a fan component (On/Off or ConstVolume), a DX multispeed cooling coil component, a DX multispeed heating coil component, and a Gas or Electric supplemental heating coil component. This system also includes the option to use available waste energy to heat water. A schematic diagram of the air-to-air multispeed heat pump is shown below. The component connection sequence for the blow through option (shown below) from inlet to outlet is fan, cooling coil, heating coil, and supplemental heater. The connection sequence for the draw through option is cooling coil, heating coil, fan, and supplemental heater.
The main difference between this heat pump object and other EnergyPlus heat pump objects is that this object allows from two to four discrete compressor speeds for heating and cooling operation (instead of a single speed for each mode). The lowest speed is called Speed 1, and the highest speed is called Speed n (2, 3 or 4 as specified in the input syntax). This object allows a different number of speeds for cooling and heating, and each speed has an associated airflow rate. The airflow rates for the various heating speeds can be different from the airflow rates for the cooling speeds. In addition, the airflow rate when no cooling or heating is needed can also be defined. The number of cooling and heating speeds defined by the user in this heat pump object must equal the number of speeds defined in the associated coils (child objects). For example, the number of speeds for cooling defined in this heat pump object must be equal to the number of speeds defined in the associated cooling coil object.
Links to the fan, DX multispeed cooling coil, DX multispeed heating coil, and supplementary heating coil specifications are provided in the heat pump’s input data syntax. In addition, the control zone name and airflow rates at the corresponding compressor speeds are specified by the heat pump syntax.
If the ZoneControl:Thermostat:StagedDualSetpoint object and other zone control thermostat and humidistat are assigned to the same controlled zone in the Controlling Zone or Thermostat Location field, the ZoneControl:Thermostat:StagedDualSetpoint object takes precedence and the stage number provided by the the ZoneControl:Thermostat:StagedDualSetpoint object is used to set the speed number.
Inputs[LINK]
Field: Name[LINK]
This alpha field contains the identifying name for the multispeed heat pump.
Field: Availability Schedule Name[LINK]
This alpha field contains the schedule name (ref. Schedule objects) that contains information on the availability of the heat pump to operate. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off for the time period. If this field is left blank, the schedule has a value of 1 for all time periods.
Field: Air Inlet Node Name[LINK]
This alpha field contains the name of the HVAC system node from which the heat pump draws its inlet air.
Field: Air Outlet Node Name[LINK]
This alpha field contains the name of the HVAC system node to which the heat pump sends its outlet air.
Field: Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where the thermostat controlling the multispeed heat pump is located.
Field: Supply Air Fan Object Type[LINK]
This alpha field contains the identifying type of supply air fan specified for the heat pump. Fan type must be Fan:OnOff or Fan:ConstantVolume. Fan:ConstantVolume can only be used when the supply air fan operating mode is continuous (see field ’Supply air fan operating mode schedule name).
Field: Supply Air Fan Name[LINK]
This alpha field contains the identifying name given to the heat pump supply air fan, and should match the name specified in the corresponding fan object.
Field: Supply Air Fan Placement[LINK]
This alpha field has two choices: BlowThrough or DrawThrough. The first choice stands for “blow through fan”. This means that the unit consists of a fan followed by a DX multispeed cooling coil, DX multispeed heating coil, and a supplemental heating coil. The fan “blows through” the cooling and heating coils. The second choice stands for “draw through fan”. This means that the unit consists of the DX cooling and heating coils followed by a fan, with the supplemental heater located at the outlet of the fan. The fan “draws” air through the DX coils.
Note: the multispeed heat pump’s supply air fan, cooling coil, heating coil and supplemental heating coil must be connected according to the configuration shown above (Figure 5) for the ‘blow through’ fan configuration. For the ‘draw through’ fan configuration the fan must be located between the DX heating coil and the supplemental heater, whose outlet node is the system outlet node. In addition, the DX cooling coil and DX heating coil operation mode must be specified consistently with the heat pump’s supply air fan operating mode (e.g., with the heat pump’s supply air fan set to cycle on and off with the cooling/heating load, the DX cooling and heating coil operation mode must be CyclingFanAndCompressor). If the operation modes in the parent (heat pump) and child (coil) objects are specified differently, the operation mode in the parent object prevails.
Field: Supply Air Fan Operating Mode Schedule Name[LINK]
This alpha field contains the schedule name (ref. Schedule objects) that contains information to control the supply air fan. Schedule values of zero mean that the supply air fan will cycle off if there is no cooling or heating load in the control zone. Non-zero schedule values mean that the supply air fan will operate continuously even if there is no cooling or heating load in the control zone. If this field is left blank, the supply air fan will operate continuously for the entire simulation period.
Field: Heating Coil Object Type[LINK]
This alpha field contains the identifying type of heating coil specified in the heat pump. Allowable choices for Heating coil type are Coil:Heating:DX:MultiSpeed, Coil:Heating:Electric:MultiStage, Coil:Heating:Gas:MultiStage, Coil:Heating:Water, and Coil:Heating:Steam.
Field: Heating Coil Name[LINK]
This alpha field contains the identifying name given to the DX heating coil, and should match the name specified in the corresponding DX heating coil object.
Field: DX Heating Coil Sizing Ratio[LINK]
This input specifies the ratio of heat pump heating to cooling capacity. The default value is 1.0.
Field: Cooling Coil Object Type[LINK]
This alpha field contains the identifying type of cooling coil specified in the heat pump. Cooling coil type must be Coil:Cooling:DX:MultiSpeed.
Field: Cooling Coil Name[LINK]
This alpha field contains the identifying name given to the heat pump cooling coil, and should match the name specified in the corresponding DX cooling coil object.
Field: Supplemental Heating Coil Object Type[LINK]
This alpha field contains the identifying type of supplemental heating coil specified in the heat pump. The hot water and steam heating coils require specifying plant loop, branches, and connectors objects to support the heating coils, and are placed on the demand side of the plantloop. The hot water flow modulation through the supplemental heating coil does not require additional controller or Controller:WaterCoil object. The parent object (Unitary MultiSpeed Air to Air Heat Pump) itself provides the “controller” function of modulating water flow. Heating coil type must be:
Coil:Heating:Electric
Coil:Heating:Fuel
Coil:Heating:Water
Coil:Heating:Steam
Field: Supplemental Heating Coil Name[LINK]
This alpha field contains the identifying name given to the heat pump supplemental heating coil, and should match the name specified in the corresponding heating coil object.
Field: Maximum Supply Air Temperature from Supplemental Heater[LINK]
This numeric field defines the maximum allowed supply air temperature (in degrees C) exiting the heat pump supplemental heating coil. If the calculated supply air temperature exiting the supplemental heater exceeds this value, then it is reset to this maximum temperature. This field is autosizable.
Field: Maximum Outdoor Dry-Bulb Temperature for Supplemental Heater Operation[LINK]
This numeric field defines the outdoor air dry-bulb temperature above which the heat pump supplemental heating coil is disabled. The temperature for this input field must be less than or equal to 21 C. If this input field is left blank, the default value is 21 C.
Field: Auxiliary On-Cycle Electric Power[LINK]
This field defines auxiliary electrical power (W) consumed during the on-cycle period (i.e., when the cooling or heating coil is operating). The model assumes that this auxiliary power does not contribute to heating the supply air. The minimum value for this field is 0.0, and the default value is also 0.0 if the field is left blank.
Field: Auxiliary Off-Cycle Electric Power[LINK]
This field defines auxiliary electrical power (W) consumed during the off-cycle period (i.e., when the cooling and heating coil are not operating). The model assumes that this auxiliary power does not contribute to heating the supply air. The minimum value for this field is 0.0, and the default value is also 0.0 if the field is left blank.
Field: Design Heat Recovery Water Flow Rate[LINK]
This optional input field defines the design water flow rate used if the heat recovery option is being simulated. If this value is greater than 0.0 then a heat recovery loop must be specified and attached to the multispeed heat pump using the next 2 node fields. To determine how the heat recovery algorithm works, refer to the EnergyPlus Engineering Reference in the AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed with Heat Recovery section. The units for this input value are cubic meters per second.
Field: Maximum Temperature for Heat Recovery[LINK]
This field sets the maximum temperature (in degrees C) that this heat pump can produce for heat recovery. The idea behind this field is that the current models do not take temperatures into account for availability and they just pass Q’s around the loop without a temperature limit. This temperature limit puts an upper bound on the recovered heat and limits the max temperature leaving the component.
As temperatures in the loop approach the maximum temperature, the temperature difference between the entering water and the surfaces in the piece of equipment becomes smaller. For the given heat recovery flow rate and that temperature difference the amount of heat recovered will be reduced, and eventually there will be no heat recovered when the entering water temperature is equal to the maximum temperature specified by the user in this field. The reduced amount of heat recovered will diminish if the temperature of the loop approach is the maximum temperature, and this will show up in the reporting. This allows the user to set the availability or the quality of the heat recovered for usage in other parts of the system or to heat domestic hot water supply.
Field: Heat Recovery Water Inlet Node Name[LINK]
This alpha field contains the identifying name for the heat recovery side inlet node.
Field: Heat Recovery Water Outlet Node Name[LINK]
This alpha field contains the identifying name for the heat recovery side outlet node.
Field: No Load Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the heat pump in cubic meters per second when neither cooling nor heating is required (i.e., DX coils and supplemental heater are off but the supply air fan operates). This field is only used when the heat pump supply air fan is scheduled to operate continuously regardless of DX coil operation (ref. field “Supply Air Fan Operating Mode Schedule). Values must be greater than or equal to zero, or this field is autosizable. If the heat pump supply air fan is scheduled to operate continuously and the input value for this field is set to zero or this field is left blank, then the model assumes that the supply air flow rate when no cooling/heating is needed is equal to the supply air flow rate when the compressor was last operating (for cooling operation or heating operation).
Field: Number of Speeds for Heating[LINK]
This field defines the number of heating speeds for the heat pump, and must match the number of heating speeds defined in the associated heating coil. The value for this input field defines the number of airflow rates that must be defined for heating in the field below. The minimum value for this field is one and the maximum value is four. If the Heating Coil Object Type above are Coil:Heating:Water or Coil:Heating:Steam, then this field should be 1.
Field: Number of Speeds for Cooling[LINK]
This field defines the number of cooling speeds for the heat pump, and must match the number of cooling speeds defined in the associated DX cooling coil. The value for this input field defines the number of airflow rates that must be defined for cooling in the field below. The minimum value for this field is two and the maximum value is four.
Field: Heating Speed 1 Supply Air Flow Rate[LINK]
This required numeric field defines the supply air flow rate leaving the heat pump in cubic meters per second when the DX heating coil and/or supplemental heater are operating at Speed 1 (lowest speed). Values must be greater than 0 or this field is autosizable.
Field: Heating Speed 2 Supply Air Flow Rate[LINK]
This required numeric field defines the supply air flow rate leaving the heat pump in cubic meters per second when the DX heating coil and/or supplemental heater are operating at Speed 2. Values must be greater than 0 or this field is autosizable. If not autosized, the entered value must be greater or equal to the flow rate specified for heating Speed 1.
Field: Heating Speed 3 Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the heat pump in cubic meters per second when the DX heating coil and/or supplemental heater are operating at Speed 3. Values must be greater than 0 or this field is autosizable. If not autosized, the entered value must be greater or equal to the flow rate specified for heating Speed 2. If the ‘Number of Speeds for Heating’ is less than 3, then this field can be left blank.
Field: Heating Speed 4 Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the heat pump in cubic meters per second when the DX heating coil and/or supplemental heater are operating at Speed 4 (high speed). Values must be greater than 0 or this field is autosizable. If not autosized, the entered value must be greater or equal to the flow rate specified for heating Speed 3. If the ‘Number of Speeds for Heating’ is less than 4, then this field can be left blank.
Note: When autosizable is selected for any of the supply air volumetric flow rate fields, all supply air flow fields at the different speeds must be specified as autosizable. Otherwise, a fatal error will be issued and the simulation will terminate.
Field: Cooling Speed 1 Supply Air Flow Rate[LINK]
This required numeric field defines the supply air flow rate leaving the heat pump in cubic meters per second when the DX cooling coil is operating at Speed 1 (lowest speed). Values must be greater than 0 or this field is autosizable.
Field: Cooling Speed 2 Supply Air Flow Rate[LINK]
This required numeric field defines the supply air flow rate leaving the heat pump in cubic meters per second when the DX cooling coil is operating at Speed 2. Values must be greater than 0 or this field is autosizable. If not autosized, the entered value must be greater or equal to the flow rate specified for cooling Speed 1.
Field: Cooling Speed 3 Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the heat pump in cubic meters per second when the DX cooling coil is operating at Speed 3. Values must be greater than 0 or this field is autosizable. If not autosized, the entered value must be greater or equal to the flow rate specified for cooling Speed 2. If the ‘Number of Speeds for Cooling’ is less than 3, then this field can be left blank.
Field: Cooling Speed 4 Supply Air Flow Rate[LINK]
This numeric field defines the supply air flow rate leaving the heat pump in cubic meters per second when the DX cooling coil is operating at Speed 4 (highest speed). Values must be greater than 0 or this field is autosizable. If not autosized, the entered value must be greater or equal to the flow rate specified for cooling Speed 3. If the ‘Number of Speeds for Cooling’ is less than 4, then this field can be left blank.
Following is an example input for the object and its associated components.
Outputs[LINK]
HVAC,Average,Unitary System Fan Part Load Ratio []
HVAC,Average,Unitary System Compressor Part Load Ratio []
HVAC,Average,Unitary System DX Coil Cycling Ratio []
HVAC,Average,Unitary System DX Coil Speed Ratio []
HVAC,Average,Unitary System DX Coil Speed Level []
HVAC,Average,Unitary System Electricity Rate [W]
HVAC,Sum,Unitary System Electricity Energy [J]
HVAC,Average,Unitary System Total Cooling Rate [W]
HVAC,Average,Unitary System Total Heating Rate [W]
HVAC,Average,Unitary System Sensible Cooling Rate [W]
HVAC,Average,Unitary System Sensible Heating Rate [W]
HVAC,Average,Unitary System Latent Cooling Rate [W]
HVAC,Average,Unitary System Latent Heating Rate [W]
HVAC,Average,Unitary System Ancillary Electricity Rate [W]
HVAC,Sum,Unitary System Cooling Ancillary Electricity Energy [J]
HVAC,Sum,Unitary System Heating Ancillary Electricity Energy [J]
If heat recovery is specified:
HVAC,Average, Unitary System Heat Recovery Rate [W]
HVAC,Average, Unitary System Heat Recovery Inlet Temperature [C]
HVAC,Average, Unitary System Heat Recovery Outlet Temperature [C]
HVAC,Average, Unitary System Heat Recovery Fluid Mass Flow Rate [kg/s]
HVAC,Sum, Unitary System Heat Recovery Energy [J]
Unitary System Fan Part Load Ratio [][LINK]
This output variable is the ratio of actual air mass flow rate through the multispeed heat pump to the heat pump’s design air mass flow rate (i.e., design volumetric flow rate converted to dry air mass flow rate) at Speed 1. For continuous fan operation mode, this variable is always 1.0 when the heat pump is available (based on the availability schedule). For cycling fan/cycling coil operation mode, the actual air mass flow rate is calculated based on the ratio of the sensible heating (or cooling) load to the steady-state heat pump heating (or cooling) capacity. For the cycling fan mode, the runtime fraction for the heat pump fan may be different from the fan part-load ratio reported here due the part-load performance of the heat pump’s heating (or cooling) coil (delay at start-up to reach steady-state output). In general, runtime fractions are reported by individual components where appropriate (e.g., Fan:OnOff). When the speed number is greater than 1, the value is 1.0.
Unitary System Compressor Part Load Ratio [][LINK]
This output variable is the ratio of the sensible load (heating or cooling) to the steady-state capacity of the multispeed heat pump’s DX heating or cooling coil at Speed 1. The runtime fraction for the heat pump compressor may be different from the compressor part-load ratio reported here due the part-load performance of the heating/cooling coil (delay at start-up to reach steady-state output). In general, runtime fractions are reported by individual components where appropriate. When the speed number is greater than 1, the value is 1.0.
Unitary System DX Coil Cycling Ratio [][LINK]
This output variable is the ratio of the sensible load (heating or cooling) to the steady-state capacity of the multispeed heat pump’s DX heating or cooling coil (Speed 1) for the entire system timestep. The value is between 0.0 and 1.0 when the heat pump is cycling on and off its lowest speed (Speed 1) and 1.0 when the multispeed heat pump operates at speeds above 1.
When Single Mode Operation is specified, the value is between 0.0 and 1.0 when the heat pump is cycling on at any given speed.
Unitary System DX Coil Speed Ratio [][LINK]
This output variable is the ratio of time in a system timestep that the compressor is at rated speed between two consecutive speed numbers ( [Compressor Speed - Compressor speed at Speed i-1] / [Compressor speed at Speed i - Compressor speed at Speed i-1]). The compressor speed ratio reports (1.0 is max, 0.0 is min) and any value in between as it is averaged over the timestep. The value is 0.0 during Speed 1 operation.
The physical meaning of the speed ratio is dependent on the compressor configuration defined in the field of child coil object: Apply Part Load Fraction to Speeds greater than 1. The allowed choice is either Yes or No. When No is entered, one compressor is assumed for all speeds. The speed ratio represents how long the higher speed runs as a fraction of the system timestep, and the lower speed runs in the rest of the system timestep. When Yes is entered, multiple compressors are assumed, and each compressor has associated speed. The speed ratio represents how long the higher speed runs as a fraction of the system timestep, and the low speed runs in a whole system timestep.
When Single Mode Operation is specified, the speed ratio is set to 0 at Speed 1, and 1 at Speed > 1
Unitary System DX Coil Speed Level [][LINK]
This output variable reports the maximum speed needed when the heat pump operates to meet the sensible load (heating or cooling) in a system timestep. When the value is 1, the heat pump operates at Speed 1 (lowest speed). For this case the cycling ratio is between 0.0 and 1.0, while the speed ratio is 0.0. When the speed number output variable is above one, such as i, the heat pump operation is determined by the speed ratio through linear interpolation. For example, when the speed ratio is 0.4 and the speed number is 3, the heat pump operates at Speed 3 for 40% of a system timestep and at Speed 2 for 60% of a system timestep for a single compressor. For multiple compressors, the heat pump operates at Speed 3 in the 40% of a system timestep and at Speed 2 in the whole system timestep.
Unitary System Total Heating Rate [W][LINK]
This output field is the total (enthalpy) heat addition rate of the multispeed heat pump to the zones it is serving in Watts. This value is calculated using the enthalpy difference of the heat pump outlet air and inlet air streams, and the air mass flow rate through the heat pump. This value is calculated for each HVAC system timestep being simulated, and the results (enthalpy addition only) are averaged for the timestep being reported.
Unitary System Total Cooling Rate [W][LINK]
This output field is the total (enthalpy) heat extraction rate of the multispeed heat pump from the zones it is serving in Watts. This value is calculated using the enthalpy difference of the heat pump outlet air and inlet air streams, and the air mass flow rate through the heat pump. This value is calculated for each HVAC system timestep being simulated, and the results (enthalpy extraction only) are averaged for the timestep being reported.
Unitary System Sensible Heating Rate [W][LINK]
This output field reports the sensible heat addition rate of the multispeed heat pump to the zones it is serving in Watts. This value is calculated using the enthalpy difference of the heat pump outlet air and inlet air streams at a constant humidity ratio, and the air mass flow rate through the heat pump. This value is calculated for each HVAC system timestep being simulated, and the results (heating only) are averaged for the timestep being reported.
Unitary System Sensible Cooling Rate [W][LINK]
This output field reports the moist air sensible heat extraction rate of the multispeed heat pump from the zones it is serving in Watts. This value is calculated using the enthalpy difference of the heat pump outlet air and inlet air streams at a constant humidity ratio, and the air mass flow rate through the heat pump. This value is calculated for each HVAC system timestep being simulated, and the results (cooling only) are averaged for the timestep being reported.
Unitary System Latent Heating Rate [W][LINK]
This output field is the latent heat addition (humidification) rate of the multispeed heat pump in Watts. This value is calculated as the difference between the total energy rate and the sensible energy rate provided by the multispeed heat pump. This value is calculated for each HVAC system timestep being simulated, and the results (latent heat addition only) are averaged for the timestep being reported.
Unitary System Latent Cooling Rate [W][LINK]
This output field is the latent heat extraction (dehumidification) rate of the multispeed heat pump in Watts. This value is calculated as the difference between the total energy rate and the sensible energy rate provided by the multispeed heat pump. This value is calculated for each HVAC system timestep being simulated, and the results (latent heat extraction only) are averaged for the timestep being reported.
Unitary System Electricity Rate [W][LINK]
This output field is the electricity consumption rate of the multispeed heat pump in Watts. The consumption includes electricity used by the DX coils (including crankcase heater if the fuel type is electricity), fans (indoor supply air fan and the condenser fans associated with the DX coil[s]), defrost mode operation (resistive or reverse-cycle), auxiliary power during on and off period, and the supplemental heating coil (if electric). This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported. Any non-electric energy use is not reported by the heat pump object but is reported in the associated coil objects as appropriate.
Unitary System Electricity Energy [J][LINK]
This output field is the electricity consumption of the multispeed heat pump in Joules for the timestep being reported. The consumption includes electricity used by the DX compressor (including crankcase heater if the fuel type is electricity), fans (indoor supply air fan and the condenser fans associated with the DX coil[s]), defrost mode operation (resistive or reverse-cycle), auxiliary power during on and off period, and the supplemental heating coil (if electric). This value is calculated for each HVAC system timestep being simulated, and the results are summed for the timestep being reported. Any non-electric energy use is not reported by the heat pump object but is reported in the associated coil objects as appropriate.
Unitary System Ancillary Electricity Rate [W][LINK]
This output field is the average auxiliary electricity consumption rate (including both on-cycle and off-cycle) in Watts for the timestep being reported.
Unitary System Cooling Ancillary Electricity Energy [J][LINK]
This is the auxiliary electricity consumption in Joules for the timestep being reported. This is the auxiliary electricity consumption during periods when the heat pump is providing cooling (DX cooling coil is operating). This output is also added to a meter with Resource Type = Electricity, End Use Key = Cooling, Group Key = System (ref. Output:Meter objects).
Unitary System Heating Ancillary Electricity Energy [J][LINK]
This is the auxiliary electricity consumption in Joules for the timestep being reported. This is the auxiliary electricity consumption during periods when the heat pump is providing heating (DX heating coil is operating). This output is also added to a meter with Resource Type = Electricity, End Use Key = Heating, Group Key = System (ref. Output:Meter objects).
Unitary System Heat Recovery Inlet Temperature [C][LINK]
Unitary System Heat Recovery Outlet Temperature [C][LINK]
Unitary System Heat Recovery Fluid Mass Flow Rate [kg/s][LINK]
These outputs are the heat recovery inlet and outlet temperatures and water mass flow rate for multispeed heat pumps with heat recovery.
Unitary System Heat Recovery Rate [W][LINK]
Unitary System Heat Recovery Energy [J][LINK]
For multispeed heat pumps with heat recovery, these outputs are the recoverable energy rate (in Watts) and energy (in Joules).
AirLoopHVAC:Unitary:Furnace:HeatOnly[LINK]
The EnergyPlus furnace is a “virtual” component that consists of a fan component (OnOff or ConstantVolume) and a Gas or Electric heating coil component. The blow through furnace configuration is shown in the Figure below.
Links to the fan and heating coil specifications are provided in the furnace input data syntax. In addition the control zone name and the furnace design operating conditions are specified by the furnace inputs.
Inputs[LINK]
Field: Name[LINK]
This alpha field contains the identifying name for the furnace.
Field: Availability Schedule Name[LINK]
This alpha field contains the schedule name which contains information on the availability of the furnace to operate. A schedule value equal to 0 denotes that the furnace must be off for that time period. A value greater than 0 denotes that the furnace is available to operate during that time period. This schedule may be used to completely disable the unitary system as required. If this field is left blank, the schedule has a value of 1 for all time periods.
Field: Furnace Inlet Node Name[LINK]
This alpha field contains the furnace inlet node name.
Field: Furnace Outlet Node Name[LINK]
This alpha field contains the furnace outlet node name.
Field: Supply Air Fan Operating Mode Schedule Name
This alpha field specifies the name of the supply air fan operating mode schedule. The supply air fan operating mode may vary during the simulation based on time-of-day or with a change of season. Schedule values of 0 denote that the furnace supply air fan and the heating coil cycle on and off together to meet the heating load (a.k.a. AUTO fan). Schedule values other than 0 denote that the supply fan runs continuously while the heating coil cycles to meet the load.
Field: Maximum Supply Air Temperature[LINK]
This numeric field contains the design operating furnace air outlet temperature in degrees C when the furnace is heating. If this input field is left blank, the default value is 80 C.
Field: Heating Supply Air Flow Rate[LINK]
This numeric field contains the design volumetric flow rate of the furnace in cubic meters per second. This volumetric flow rate should match the flow rate specified for the furnace fan.
Field: Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where the thermostat controlling the furnace is located.
Field: Supply Fan Object Type[LINK]
This alpha field contains the identifying type of supply air fan specified for the furnace. Fan type must be Fan:OnOff or Fan:ConstantVolume. Fan:ConstantVolume is used when the Supply Air Fan Operating Mode Schedule values are never 0 and the fan operates continuously. Fan:OnOff is used when the fan cycles on and off with the cooling or heating coil (i.e. Supply Air Fan Operating Mode Schedule values are at times 0).
Field: Supply Fan Name[LINK]
This alpha field contains the identifying name given to the furnace fan.
Field: Fan Placement[LINK]
This alpha field has two choices: BlowThrough or DrawThrough. The first choice stands for “blow through fan”. This means that the unit consists of a fan followed by the heating coil. The fan “blows through” the heating coil. The second choice stands for “draw through fan”. This means that the unit consists of the heating coil followed by a fan. The fan “draws air through” the heating coil. If this field is left blank, the default is blow through.
Field: Heating Coil Object Type[LINK]
This alpha field contains the identifying type of heating coil specified in the furnace. The hot water and steam heating coils require specifying plant loop, branches, and connectors objects to support the heating coils, and are placed on the demand side of the plantloop. The hot water flow modulation through the heating coil does not require additional controller or Controller:WaterCoil object. The parent object (Unitary Heat Only Furnace) itself provides the “controller” function of modulating water flow. Heating coil type must be:
Coil:Heating:Electric
Coil:Heating:Fuel
Coil:Heating:Water
Coil:Heating:Steam
Field: Heating Coil Name[LINK]
This alpha field contains the identifying name given to the furnace heating coil.
As shown in the example below, correct specification of the furnace requires specification of the following objects in addition to the furnace object:
1) fan (Fan:OnOff or Fan:ConstantVolume)
2) heating coil (Coil:Heating:Fuel or Coil:Heating:Electric)
3) direct air unit (AirTerminal:SingleDuct:ConstantVolume:NoReheat) for each zone served by the furnace
Note: the furnace’s fan and heating coil must be connected in the air loop according to the configuration shown above (Figure 6) when a blow through fan configuration is specified. If a draw through fan is used, the fan is located down stream of the heating coil. In addition, the volumetric air flow rate specified in the direct air unit for the controlling zone should properly reflect the fractional volumetric air flow rate specified in the furnace object.
Example of Heat-Only Furnace Specification
Outputs[LINK]
Unitary System Fan Part Load Ratio [][LINK]
This output variable is the ratio of actual air mass flow rate through the furnace to the furnace’s design air mass flow rate (i.e., design volumetric flow rate converted to dry air mass flow rate). For continuous fan operation mode, this variable is always 1.0 when the furnace is available (based on the availability schedule). For cycling fan/cycling coil operation mode, the actual air mass flow rate is calculated based on the ratio of the sensible heating load to the furnace heating capacity. For the cycling fan mode, the runtime fraction for the furnace fan may be different from the fan part-load ratio reported here due the part-load performance of the furnace’s heating coil (delay at start-up to reach steady-state heating output). In general, runtime fractions are reported by individual components where appropriate (e.g., Fan:OnOff).
AirLoopHVAC:UnitaryHeatOnly[LINK]
The AirLoopHVAC:UnitaryHeatOnly is identical to the AirLoopHVAC:Unitary:Furnace:HeatOnly model. The heat-only unitary system is a “virtual” component that consists of a fan component (OnOff or ConstantVolume) and a Gas or Electric heating coil component. The blow through unitary system configuration is shown in the Figure below.
Links to the fan and heating coil specifications are provided in the unitary system input data syntax. In addition, the control zone name and the unitary system design operating conditions are specified by the unitary system syntax.
Inputs[LINK]
Field: Name[LINK]
This alpha field contains the identifying name for the unitary system.
Field: Availability Schedule Name[LINK]
This alpha field contains the schedule name which contains information on the availability of the unitary system to operate. A schedule value equal to 0 denotes that the unitary system must be off for that time period. A value greater than 0 denotes that the unitary system is available to operate during that time period. This schedule may be used to completely disable the unitary system as required. If this field is left blank, the schedule has a value of 1 for all time periods.
Field: Unitary System Air Inlet Node Name[LINK]
This alpha field contains the unitary system inlet node name.
Field: Unitary System Air Outlet Node Name[LINK]
This alpha field contains the unitary system outlet node name.
Field: Supply Air Fan Operating Mode Schedule Name
This alpha field specifies the name of the supply air fan operating mode schedule. The supply air fan operating mode may vary during the simulation based on time-of-day or with a change of season. Schedule values of 0 denote that the furnace supply air fan and the heating coil cycle on and off together to meet the heating load (a.k.a. AUTO fan). Schedule values other than 0 denote that the supply fan runs continuously while the heating coil cycles to meet the load.
Field: Maximum Supply Air Temperature[LINK]
This numeric field contains the design air outlet temperature in degrees C when the unitary system is heating. If this input field is left blank, the default value is 80 C.
Field: Heating Supply Air Flow Rate[LINK]
This numeric field contains the design volumetric flow rate of the unitary system in cubic meters per second. This volumetric flow rate should match the flow rate specified for the unitary system fan.
Field: Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where the thermostat controlling the unitary system is located.
Field: Supply Fan Object Type[LINK]
This alpha field contains the identifying type of supply air fan specified for the unitary system. Fan type must be Fan:OnOff or Fan:ConstantVolume. Fan:ConstantVolume is used when the Supply Air Fan Operating Mode Schedule values are never 0 and the fan operates continuously. Fan:OnOff is used when the fan cycles on and off with the cooling or heating coil (i.e. Supply Air Fan Operating Mode Schedule values are at times 0).
Field: Supply Fan Name[LINK]
This alpha field contains the identifying name given to the unitary system fan.
Field: Fan Placement[LINK]
This alpha field has two choices: BlowThrough or DrawThrough. The first choice stands for “blow through fan”. This means that the unit consists of a fan followed by the heating coil. The fan “blows through” the heating coil. The second choice stands for “draw through fan”. This means that the unit consists of the heating coil followed by a fan. The fan “draws air through” the heating coil. If this field is left blank, the default is blow through.
Field: Heating Coil Object Type[LINK]
This alpha field contains the identifying type of heating coil specified in the unitary system. The hot water and steam heating coils require specifying plant loop, branches, and connectors objects to support the heating coils, and are placed on the demand side of the plantloop. The hot water flow modulation through the heating coil does not require additional controller or Controller:WaterCoil object. The parent object (Unitary Heat Only) itself provides the “controller” function of modulating water flow. Heating coil type must be:
Coil:Heating:Electric
Coil:Heating:Fuel
Coil:Heating:Water
Coil:Heating:Steam
Field: Heating Coil Name[LINK]
This alpha field contains the identifying name given to the unitary system heating coil.
As shown in the example below, correct specification of the heat-only unitary system requires specification of the following objects in addition to the unitary system object:
1) fan (Fan:OnOff or Fan:ConstantVolume)
2) heating coil (Coil:Heating:Fuel or Coil:Heating:Electric)
3) direct air unit (AirTerminal:SingleDuct:ConstantVolume:NoReheat) for each zone served by the furnace
Note: the unitary system’s fan and heating coil must be connected in the air loop according to the configuration shown above (Figure 7) when a blow through fan configuration is specified. If a draw through fan is used, the fan is located down stream of the heating coil. In addition, the volumetric air flow rate specified in the direct air unit for the controlling zone should properly reflect the fractional volumetric air flow rate specified in the unitary system object.
Example of Heat-Only Unitary System Specification
Outputs[LINK]
Unitary System Fan Part Load Ratio [][LINK]
This output variable is the ratio of actual air mass flow rate through the unitary system to the unitary system’s design air mass flow rate (i.e., design volumetric flow rate converted to dry air mass flow rate). For continuous fan operation mode, this variable is always 1.0 when the unitary system is available (based on the availability schedule). For cycling fan/cycling coil operation mode, the actual air mass flow rate is calculated based on the ratio of the sensible heating load to the unitary system heating capacity. For the cycling fan mode, the runtime fraction for the unitary system fan may be different from the fan part-load ratio reported here due the part-load performance of the unitary system’s heating coil (delay at start-up to reach steady-state heating output). In general, runtime fractions are reported by individual components where appropriate (e.g., Fan:OnOff).
AirLoopHVAC:UnitaryHeatPump:WaterToAir[LINK]
The unitary water-to-air heat pump is similar to the unitary air-to-air heat pump except water is used on the source side. Links to the fan, WaterToAirHeatPump cooling coil, WaterToAirHeatPump heating coil, and supplementary heating coil specifications are provided in the heat pump’s input data syntax. The heat pump switches between cooling and heating depending on the zone’s demand. The load side (air) of the unitary water-to-air heat pump consists of an On/Off fan component, a WaterToAirHeatPump cooling coil component, a WaterToAirHeatPump heating coil component, and a Gas, Electric, Steam, or Hot Water supplemental heating coil component. The source side (water) of the heat pump is connected to a condenser loop with a heat exchanger (ground heat exchanger or other type) or a plant loop with a heating source such as a boiler and a cooling source such as a chiller or cooling tower. The diagram below shows the setup and connection of the heat pump for the source side and load side for a ground heat exchanger configuration. Note that on the load side, the WaterToAirHeatPump cooling coil must always be placed before the WaterToAirHeatPump heating coil.
There are three type of WaterToAirHeatPump coil models available:
Coil:Cooling:WaterToAirHeatPump:ParameterEstimation
Coil:Heating:WaterToAirHeatPump:ParameterEstimation
Coil:Cooling:WaterToAirHeatPump:EquationFit
Coil:Heating:WaterToAirHeatPump:EquationFit
Coil:Cooling:WatertoAirHeatPump:VariableSpeedEquationFit
Coil:Heating:WatertoAirHeatPump:VariableSpeedEquationFit
In addition, the control zone name and the system design operating conditions are specified by the heat pump inputs.
Inputs[LINK]
Field: Name[LINK]
This alpha field contains the identifying name for the unitary system heat pump.
Field: Availability Schedule Name[LINK]
This alpha field contains the schedule name (ref. Schedule objects) that contains information on the availability of the heat pump to operate. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off for the time period. If this field is left blank, the schedule has a value of 1 for all time periods.
Field: Air Inlet Node Name[LINK]
This alpha field contains the name of the HVAC system node from which the heat pump draws its inlet air.
Field: Air Outlet Node Name[LINK]
This alpha field contains the name of the HVAC system node to which the heat pump sends its outlet air.
Field: Supply Air Flow Rate[LINK]
This numeric field contains the design volumetric flow rate through the heat pump in cubic meters per second. This volume flow rate is only used when the cooling and heating coil object type is Coil:*:WaterToAirHeatPump:ParameterEstimation. Although a value greater than 0 is required (input cannot be blank or 0), this input is not used for the EquationFit model. Instead, the supply air flow rate is determined by the input in the corresponding Coil:*:WaterToAirHeatPump:EquationFit objects.
Field: Controlling Zone or Thermostat Location[LINK]
This alpha field contains the identifying zone name where the thermostat controlling the heat pump is located.
Field: Supply Air Fan Object Type[LINK]
This alpha field contains the identifying type of supply air fan specified in the heat pump. Fan type must be Fan:OnOff.
Field: Supply Air Fan Name[LINK]
This alpha field contains the identifying name given to the heat pump supply air fan, and should match the name specified in the corresponding fan object.
Field: Heating Coil Object Type[LINK]
This alpha field contains the identifying type of heating coil specified in the heat pump. Heating coil types are:
Coil:Heating:WaterToAirHeatPump:ParameterEstimation
Coil:Heating:WaterToAirHeatPump:EquationFit
Coil:Heating:WaterToAirHeatPump:VariableSpeedEquationFit
Field: Heating Coil Name[LINK]
This alpha field contains the identifying name given to the WaterToAirHeatPump heating coil, and should match the name specified in the corresponding WaterToAirHeatPump heating coil object.
Field: Heating Convergence[LINK]
This numeric value allows the user to determine how close the air side has to be controlled. Lower the value of convergence better the control of air side conditions and less the zone temperature fluctuations. However in a poorly designed system, a lower convergence might result in warning errors which are caused due to the iteration limit for run time fraction calculation is limited to 20.
Field: Cooling Coil Object Type[LINK]
This alpha field contains the identifying type of cooling coil specified in the heat pump. Cooling coil types are:
Coil:Cooling:WaterToAirHeatPump:ParameterEstimation
Coil:Cooling:WaterToAirHeatPump:EquationFit
Coil:Cooling:WaterToAirHeatPump:VariableSpeedEquationFit
Field: Cooling Coil Name[LINK]
This alpha field contains the identifying name given to the WaterToAirHeatPump cooling coil, and should match the name specified in the corresponding WaterToAirHeatPump cooling coil object.
Field: Cooling Convergence[LINK]
This numeric value allows the user to determine how close the air side has to be controlled. Lower the value of convergence better the control of air side conditions and less the zone temperature fluctuations. However in a poorly designed system, a lower convergence might result in warning errors which are caused due to the iteration limit for run time fraction calculation is limited to 20.
Field: Supplemental Heating Coil Object Type[LINK]
This is the object type of the supplemental heating coil. The hot water and steam heating coils require specifying plant loop, branches, and connectors objects to support the heating coils, and are placed on the demand side of the plantloop. The hot water flow modulation through the supplemental heating coil does not require additional controller or Controller:WaterCoil object. The parent object (AirLoop Unitary Water to Air Heat Pump) itself provides the “controller” function of modulating water flow. The valid choices are:
Coil:Heating:Electric
Coil:Heating:Fuel
Coil:Heating:Water
Coil:Heating:Steam
Field: Supplemental Heating Coil Name[LINK]
This alpha field contains the identifying name given to the supplemental heating coil, and should match the name specified in the corresponding supplemental heating coil object.
Field: Maximum Supply Air Temperature from Supplemental Heater[LINK]
This numeric field defines the maximum allowed supply air temperature exiting the heat pump supplemental heating coil in degrees Celsius.
Field: Maximum Outdoor Dry-Bulb Temperature for Supplemental Heater Operation[LINK]
This numeric field defines the outdoor air dry-bulb temperature in degrees Celsius above which the heat pump supplemental heating coil is disabled. The temperature for this input field must be less than or equal to 21°C. If this input field is left blank, the default value is 21°C.
Field: Outdoor Dry-Bulb Temperature Sensor Node Name[LINK]
This alpha field specifies the name of the outdoor node which controls the operation of the supplemental heating coil. If this field is left blank, the outdoor temperature is based solely on the weather data. If this field is not blank, the node name specified must also be listed in an OutdoorAir:Node object where the height of the node is taken into consideration when calculating outdoor temperature from the weather data. Alternately, the node name must be specified in an OutdoorAir:NodeList object where the outdoor temperature is taken directly from the weather data.
Field: Fan Placement[LINK]
This alpha field has two choices: BlowThrough or DrawThrough. The first choice represents a blow through system where the supply air fan is before the WaterToAirHeatPump cooling/heating coil and the supplementary heating coil. The second choice represents a draw through system where the supply fan is between the WaterToAirHeatPump cooling/heating coil and the supplementary heating coil. If this input field is left blank, the default is blow through.
Field: Supply Air Fan Operating Mode Schedule Name[LINK]
This alpha field specifies the name of the supply air fan operating mode schedule. The supply air fan operating mode may vary during the simulation based on time-of-day or with a change of season. Schedule values of 0 denote that the supply air fan and the heating/cooling coil cycle on and off together to meet the heating or cooling load (a.k.a. AUTO fan). Schedule values other than 0 denote that the supply air fan runs continuously while the heating or cooling coil cycles to meet the load. If this field is left blank, the model assumes the supply air fan cycles with the heating or cooling coil throughout the simulation period.
As shown in the example below, correct specification of the water-to-air heat pump requires specification of the following objects in addition to the AirLoopHVAC:UnitaryHeatPump:WaterToAir object:
On/Off fan
WaterToAirHeatPump cooling coil
WaterToAirHeatPump heating coil
Supplementary heating coil
Direct air unit for each zone served by the heat pump
Condenser demand branches
It should be noted that the volumetric air flow rate specified in the direct air unit for the controlling zone should properly reflect the fractional volumetric air flow rate specified in the heat pump object.
Field: Dehumidification Control Type[LINK]
This alpha input field contains the type of dehumidification control. The following options are valid for this field:
None - meet sensible load only, no active dehumidification control
CoolReheat - cool beyond the dry-bulb temperature set point as required to meet the high humidity setpoint. The excess cooling beyond the cooling set point temperature is offset by the supplemental heating coil.
The default is None. For CoolReheat dehumidification control modes, the maximum humidity setpoint is required. This must be set using a ZoneControl:Humidistat object. When extra dehumidification is required, the system may not be able to meet the humidity setpoint if its full capacity is not adequate. Supplemental heating coil (supplemental heating coil type and name) is a required input in WaterToAir HeatPumps. When dehumidification control is active the heating and the reheat load due to extra dehumidification are met with supplemental heating coil. The supplemental heating coil capacity must be adequate enough to meet the heating coil load and offset the excess cooling load due to extra dehumidification. The dehumidification control type CoolReheat works only with Coil:Cooling:WaterToAirHeatPump:EquationFit cooling coil type.
Field: Heat Pump Coil Water Flow Mode[LINK]
This field specifies the way in which water flow through the heat pump coils will be modeled. This field is only used when WatertoAirHeatPump:EquationFit coils are used. There are three options:
Cycling
Constant
CyclingOnDemand
Cycling varies water flow through the coil based on the heat pump Part Load Ratio. This control method is appropriate for modeling heat pumps that are outfitted with a solenoid valve which allows water to flow through the coil only when the compressor is active. This is the default for EnergyPlus V8 and later.
Constant provides a constant water flow regardless of heat pump operation. Remember that EnergyPlus has two coils (a heating coil and a cooling coil) to approximate the operation of one coil that can operate in either heating mode or cooling mode. Therefore, when the water flow mode is constant, there will be full flow through either the heating coil or the cooling coil, but not both at the same time.
ConstantOnDemand provides full flow through the coil whenever there is a load. When there is no load, there is zero flow through the coil. This control strategy represents the way EnergyPlus modeled heat pump water flow prior to Version 8.
Field: DX Heating Coil Sizing Ratio[LINK]
This input specifies the ratio of heat pump heating to cooling capacity. The default value is 1.0.
Following is an example of IDF usage:
Outputs[LINK]
Energy use reporting for the water-to-air heat pump is documented under the heat pump coil object types:
Coil:Cooling:WaterToAirHeatPump:ParameterEstimation
Coil:Heating:WaterToAirHeatPump:ParameterEstimation
Coil:Cooling:WaterToAirHeatPump:EquationFit
Coil:Heating:WaterToAirHeatPump:EquationFit
The heat pump demand as well as the compressor and fan part-load ratios may be obtained with the output variables shown below.
HVAC,Average, Unitary System Requested Sensible Cooling Rate [W]
HVAC,Average, Unitary System Requested Latent Cooling Rate [W]
HVAC,Average, Unitary System Requested Heating Rate [W]
HVAC,Average, Unitary System Compressor Part Load Ratio []
HVAC,Average, Unitary System Fan Part Load Ratio
HVAC,Average, Unitary System Dehumidification Induced Heating Demand Rate [W]
Unitary System Requested Sensible Cooling Rate [W][LINK]
This output variable is the sensible cooling requested from the zone thermostat in watts. This value is calculated using the unitary heat pump outlet air and zone conditions, the specific heat of the zone air, and the supply air mass flow rate entering/leaving the system. This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Unitary System Requested Latent Cooling Rate [W][LINK]
This output variable is the latent cooling requested from the zone humidistat in watts. This value is calculated using the unitary heat pump outlet air and zone conditions, the heat of vaporization of water at the current zone conditions, and the supply air mass flow rate entering/leaving the system. This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Unitary System Requested Heating Rate [W][LINK]
This output variable is the sensible heating requested from the zone thermostat in watts. This value is calculated using the unitary heat pump outlet air and zone conditions, the specific heat of the zone air, and the supply air mass flow rate entering/leaving the system. This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Unitary System Compressor Part Load Ratio [][LINK]
This output variable is the ratio of actual load on the unitary system to the unitary system’s steady state output. This ratio is based on the nominal capacity of the unit.
Unitary System Fan Part Load Ratio [][LINK]
This output variable is the ratio of actual air mass flow rate through the unitary system to the unitary system’s design air mass flow rate (i.e., design volumetric flow rate converted to dry air mass flow rate). For continuous fan operation mode, this variable is always 1.0 when the unitary system is available (based on the availability schedule).
Unitary System Dehumidification Induced Heating Demand Rate [W][LINK]
This output variable is the additional heating demand rate of the supplemental heating coil of a Water-to-Air heat pumps in Watts. This additional heating demand is induced when zone air overshoots the heating setpoint due to extra dehumidification requirement to meet the high humidity setpoint. This value is always positive. This value is calculated for each HVAC system timestep, and the results are averaged for the timestep being reported.
AirLoopHVAC:UnitaryHeatCool:VAVChangeoverBypass[LINK]
The changeover-bypass variable air volume (CBVAV) unitary system is a compound object made up of other components. Each CBVAV system consists of an outdoor air mixer, direct expansion (DX) cooling coil, heating coil, and a supply air fan as shown in the figures below. Zone thermostats and terminal units are required in each zone served by this system. The terminal units are specific to this system type and are either AirTerminal:SingleDuct:VAV:HeatAndCool:Reheat or AirTerminal:SingleDuct:VAV:HeatAndCool:NoReheat. A zone humidistat and single zone max humidity set point manager may also be specified to help control high humidity levels. These individual components are described elsewhere in this document. The system may also be connected to an inlet node of either the AirLoopHVAC:ZoneMixer or AirLoopHVAC:ReturnPlenum to more accurately model the AirLoopHVAC:OutdoorAirSystem. The CBVAV unitary system object coordinates the operation of these components and is modeled as a type of air loop equipment (Ref. AirLoopHVAC).
Links to the CBVAV system’s supply air fan, coils, and outdoor air mixer specifications are provided in the object’s input syntax. Additional inputs include system and outdoor air flow rates during heating and cooling operation, the priority control mode, and dehumidification control type. A description of each input field for the CBVAV unitary system compound object is provided below.
Inputs[LINK]
Field: Name[LINK]
This alpha field defines a unique user-assigned name for an instance of a changeover-bypass VAV system. Any reference to this system by another object will use this name.
Field: Availability Schedule Name[LINK]
This alpha field defines the name of the schedule (ref: Schedule) that denotes whether the system operates during a given time period. A schedule value equal to 0 denotes that the system must be off for that time period, and a schedule value greater than 0 denotes that the system is available to operate during that time period. This schedule may be used to completely disable the system (all of its coils and the supply air fan) as required. If this field is left blank, the schedule has a value of 1 for all time periods.
Field: Cooling Supply Air Flow Rate[LINK]
This numeric field defines the air flow rate through the system (i.e., through the fan and heating/cooling coils) in cubic meters per second when the DX cooling coil is operating. Values must be greater than 0, or this field is autosizable.
Field: Heating Supply Air Flow Rate[LINK]
This numeric field defines the air flow rate through the system (i.e., through the fan and heating/cooling coils) in cubic meters per second when the heating coil is operating. Values must be greater than 0, or this field is autosizable.
Field: No Load Supply Air Flow Rate[LINK]
This numeric field defines the air flow rate through the system (i.e., through the fan and heating/cooling coils) in cubic meters per second when neither cooling nor heating is required (i.e., the DX cooling coil and heating coil are off but the supply air fan operates). Values must be greater than or equal to zero, or this field is autosizable. This field is only used when the unitary system’s supply air fan operating mode is specified as continuous fan operation (Ref. Field: Supply air fan operating mode schedule name). If the system’s supply air fan operating mode is specified as continuous fan operation and this value is set to zero or the field is left blank, then the model assumes that the system air flow rate when no heating/cooling is needed is equal to the system air flow rate when the coils were last operating (for cooling operation or heating operation).
Field: Cooling Outdoor Air Flow Rate[LINK]
This numeric field defines the outdoor air flow rate through the system (i.e., through the Outdoor air Mixer’s Outside_Air_Stream_Node) in cubic meters per second when the DX cooling coil is operating. Values must be greater than or equal to 0, or this field is autosizable. Note that the Cooling Outdoor Air Flow Rate can be changed during the simulation using a multiplier schedule (Ref. Field: Outdoor air volumetric flow rate multiplier schedule name). For any simulation timestep, the Cooling Outdoor Air Flow Rate cannot exceed the system air volumetric flow rate during cooling operation.
Field: Heating Outdoor Air Flow Rate[LINK]
This numeric field defines the outdoor air flow rate through the system (i.e., through the Outdoor air Mixer’s Outside_Air_Stream_Node) in cubic meters per second when the heating coil is operating. Values must be greater than or equal to 0, or this field is autosizable. Note that the Heating Outdoor Air Flow Rate can be changed during the simulation using a multiplier schedule (Ref. Field: Outdoor air volumetric flow rate multiplier schedule name). For any simulation timestep, the Heating Outdoor Air Flow Rate cannot exceed the system air volumetric flow rate during heating operation.
Field: No Load Outdoor Air Flow Rate When No Cooling or Heating is Needed[LINK]
This numeric field defines the outdoor air flow rate through the system (i.e., through the Outdoor air Mixer’s Outside_Air_Stream_Node) in cubic meters per second when neither cooling nor heating is required (i.e., the DX cooling coil and heating coil are off but the supply air fan operates). Values must be greater than or equal to 0, or this field is autosizable. Note that the no load outdoor air flow rate can be changed during the simulation using a multiplier schedule (Ref. Field: Outdoor air volumetric flow rate multiplier schedule name). For any simulation timestep, the no load outdoor air flow rate cannot exceed the no load supply air flow rate. This field is only used when the unitary system’s supply air fan operating mode is specified as continuous fan operation (Ref. Field: Supply air fan operating mode schedule name). If the system’s supply air fan operating mode is specified as continuous fan operation and this value is set to zero or the field is left blank, then the model assumes that the no load outdoor air flow rate is equal to the outdoor air flow rate when the coils were last operating (for cooling operation [i.e. Cooling outdoor air flow rate] or heating operation [i.e. Heating outdoor air flow rate]) and this field is not used.
Field: Outdoor Air Flow Rate Multiplier Schedule Name[LINK]
This alpha field defines the name of a schedule (ref: Schedule) that contains multipliers for the outdoor air volume flow rates (heating, cooling, no heating/cooling). Schedule values must be from zero to 1. If this field is left blank, then the model assumes that the outdoor air multiplier is 1 for the entire simulation period.
Field: Air Inlet Node Name[LINK]
This alpha field defines the name of the HVAC system node from which the system draws its inlet air.
Field: Bypass Duct Mixer Node Name[LINK]
This alpha field defines the name of the HVAC system node where the bypass air mixes with the unitary system’s inlet air. This name should match the name of the Return Air Stream Node Name for the OutdoorAir:Mixer associated with this system. This node name must be different from the system’s air inlet node name.
Field: Bypass Duct Splitter Node Name[LINK]
This alpha field defines the name of the HVAC system node where the conditioned air is split into bypass air and supply air leaving the system (e.g., delivered to the terminal units). This splitter air node name should match the outlet node name for the last component (furthest downstream) in this unitary system. For blow through fan placement, the splitter air node is the outlet node of the heating coil. For draw through fan placement, the splitter node is the outlet node of the supply air fan.
Field: Air Outlet Node Name[LINK]
This alpha field defines the name of the HVAC system node to which the system sends its outlet air.
Field: Outdoor Air Mixer Object Type[LINK]
This field specifies the type of outdoor air mixer used by this CBVAV unitary system. The outdoor air mixer component is part of the CBVAV unitary compound object. The only available outdoor air mixer type is:
Field: Outdoor Air Mixer Name[LINK]
This alpha field defines the name of an outdoor air mixer component that composes part of the CBVAV system. The name of the outdoor air mixer’s Return_Air_Stream_Node should match the bypass duct mixer node name, and be different from the CBVAV system’s air inlet node name. The Mixed Air Node Name of the outdoor air mixer should be the same as the CBVAV system’s supply fan inlet air node (for blow through fan placement) or the system’s DX cooling coil inlet node (for draw through fan placement).
Field: Supply Air Fan Object Type[LINK]
This alpha field defines the type of fan used by this unitary system. The only valid choices are Fan:SystemModel, Fan:OnOff, and Fan:ConstantVolume. The input requirements for these fan objects are described elsewhere in this document.
Field: Supply Air Fan Name[LINK]
This alpha field defines the name of the fan component that composes part of this unitary system. Note that the fan component’s maximum flow rate should be greater than or equal to the largest system air volumetric flow rate specified for this unitary system (heating, cooling, and no heating/cooling). In addition, the fan’s inlet air node should be the same as the outdoor air mixer’s Mixed Air Node (for blow through fan placement) or the heating coil’s outlet node (for draw through fan placement). The fan outlet air node should be the same as the DX cooling coil’s air inlet node (for blow through fan placement) or the system’s bypass duct splitter node (for draw through fan placement).
Field: Supply Air Fan Placement[LINK]
This alpha field defines the placement of the supply air fan within this unitary system. The only valid choices are BlowThrough and DrawThrough. With blow through placement, the supply air fan is located immediately upstream of the system’s cooling coil. With draw through placement, the supply air fan is located immediately downstream of the heating coil.
Field: Supply Air Fan Operating Mode Schedule Name[LINK]
This alpha field defines the name of a schedule that specifies the supply air fan operating mode during the simulation. A schedule value of 0 denotes the fan cycles off when no cooling or heating is required, and any other value denotes that the fan runs continuously regardless of the need for heating or cooling. If this field is left blank, the model assumes continuous supply air fan operation for the entire simulation period.
Field: Cooling Coil Object Type[LINK]
This alpha field defines the type of cooling coil used by this unitary system. There are three valid choices for this field:
Coil:Cooling:DX:SingleSpeed
Coil:Cooling:DX:VariableSpeed
CoilSystem:Cooling:DX:HeatExchangerAssisted
Coil:Cooling:DX:TwoStageWithHumidityControlMode
The input requirements for these cooling coil objects are described elsewhere in this document.
Field: Cooling Coil Name[LINK]
This alpha field defines the name of the cooling coil used by this unitary system, and this name should match the name specified in the corresponding cooling coil object.
Field: Heating Coil Object Type[LINK]
This alpha field defines the type of heating coil used by this unitary system. The hot water and steam heating coils require specifying plant loop, branches, and connector objects to support the heating coils, and are placed on the demand side of the plantloop. The hot water flow modulation through the heating coil does not require additional controller or Controller:WaterCoil object. The parent object (CBVAV Unitary System) itself provides the “controller” function of modulating water flow. The valid choices are:
Coil:Heating:Electric
Coil:Heating:Fuel
Coil:Heating:DX:SingleSpeed
Coil:Heating:DX:VariableSpeed
Coil:Heating:Water
Coil:Heating:Steam
The input requirements for these heating coil objects are described elsewhere in this document.
Field: Heating Coil Name[LINK]
This alpha field defines the name of the heating coil used by this unitary system, and this name should match the name specified in the corresponding heating coil object.
Field: Priority Control Mode[LINK]
This choice field defines the cooling or heating priority control mode for the unitary system. Valid choices are:
CoolingPriority
HeatingPriority
ZonePriority
LoadPriority
If CoolingPriority is selected, the system operates to meet the cooling load if any zone served by this system (air loop) requires cooling. If no zones require cooling, then the system operates in heating mode if needed. If HeatingPriority is selected, the system operates to meet the heating load if any zone requires heating. If no zones require heating, then the system operates in cooling mode if needed. If ZonePriority is selected, the system operates based on the maximum number of zones requiring either heating or cooling. If the number of zones requiring cooling is greater than the number of zones requiring heating, then the system operates in cooling mode. If the number of zones requiring heating is greater than the number of zones requiring cooling, then the system operates in heating mode. If the number of zones requiring cooling equals the number of zones requiring heating, then the largest combined load (i.e., the sum of the cooling loads for zones requiring cooling compared to the sum of the heating loads for zones that require heating) sets the cooling or heating operating mode for the system during that simulation timestep. If LoadPriority is selected, the system operates based on the largest combined load (i.e., the sum of the cooling loads for zones requiring cooling compared to the sum of the heating loads for zones that require heating). If the total load for zones requiring cooling is greater than the total load for zones requiring heating, then the system operates in cooling mode. Similar logic is used for heating mode selection. If the total cooling load equals the total heating load, then cooling or heating operation reverts to the total number of zones requiring cooling or heating (and if equal reverts to cooling mode if the cooling load is non-zero, otherwise, heating mode.
Field: Minimum Outlet Air Temperature During Cooling Operation[LINK]
This numeric field defines the minimum outlet air temperature leaving the system when the unit is operating to provide cooling. Values are specified in degrees Celsius and must be greater than 0. The default value is 8°C. This value must be less than or equal to the maximum outlet air temperature during heating operation.
Field: Maximum Outlet Air Temperature During Heating Operation[LINK]
This numeric field defines the maximum outlet air temperature leaving the system when the unit is operating to provide heating. Values are specified in degrees Celsius and must be greater than 0. The default value is 50°C. This value must be greater than or equal to the minimum outlet air temperature during cooling operation.
Field: Dehumidification Control Type[LINK]
This alpha field contains the type of dehumidification control. The following options are valid for this field:
None - meet sensible load only, no active dehumidification control
Multimode - activate enhanced dehumidification mode as needed and meet sensible load. This option is used to model DX equipment with a controllable heat exchanger assisting the DX cooling coil for improved dehumidification. It is valid only with cooling coil type = Coil:Cooling:DX:TwoStageWithHumidityControlMode.
CoolReheat - cool beyond the dry-bulb temperature set point as required to meet the high humidity setpoint. It is valid only with cooling coil type = Coil:Cooling:DX:TwoStageWithHumidityControlMode.
The default is None. For the other dehumidification control modes, the maximum humidity setpoint on the CBVAV system’s air outlet node is used. This must be set using a ZoneControl:Humidistat and one of:
SetpointManager:SingleZone:Humidity:Maximum
SetpointManager:MultiZone:Humidity:Maximum
SetpointManager:MultiZone:MaximumHumidity:Average
objects. When extra dehumidification is required, the system may not be able to meet the humidity setpoint if its full capacity is not adequate.
Field: Plenum or Mixer Inlet Node Name[LINK]
This alpha field defines the name of the HVAC system node where the bypass air enters the zone mixer or return plenum. This node name must be different from the system’s Air Outlet Node Name and Bypass Duct Splitter Node Name. This name should match the name of the inlet node in the AirLoopHVAC:ZoneMixer or AirLoopHVAC:ReturnPlenum associated with this system.
Field: Minimum Runtime Before Operating Mode Change[LINK]
This numeric field defines the amount of time, in hours, the HVAC system operates before a mode change is allowed. The value entered must be greater than or equal to 0. The default value is 0.25 hours if this input is present and blank. If this field is not present the minimum runtime is 0 hours (i.e., immediate change over as needed).
As shown in the example below, correct specification of the CBVAV unitary system requires specification of the following objects in addition to the AirLoopHVAC:UnitaryHeatCool:VAVChangeoverBypass object:
1) outdoor air mixer (OutdoorAir:Mixer)
2) fan (Fan:SystemModel, Fan:OnOff, or Fan:ConstantVolume)
3) cooling coil (Coil:Cooling:DX:SingleSpeed, CoilSystem:Cooling:DX:HeatExchangerAssisted, or Coil:Cooling:DX:TwoStageWithHumidityControlMode)
4) heating coil (Coil:Heating:Fuel, Coil:Heating:Electric, or Coil:Heating:DX:SingleSpeed)
5) terminal unit for each zone being served by this system (AirTerminal:SingleDuct:VAV:HeatAndCool:Reheat or AirTerminal:SingleDuct:VAV:HeatAndCool:NoReheat)
6) When the Plenum or Mixer Inlet Node Name is specified, this node name must connect to either the AirLoopHVAC:ZoneMixer or AirLoopHVAC:ReturnPlenum and the AirLoopHVAC:OutdoorAirSystem may then be used to control the outdoor air flow rates. When using the AirloopHVAC:OutdoorAirSystem it is recommended that the Cooling, Heating and No Load Outdoor Air Flow Rate inputs are set to 0, otherwise the amount of outdoor air is increased and the coils may not autosize properly.
Note: The fan, heating coil, cooling coil, and outdoor air mixer must be connected in the air loop according to the configurations shown above (Figure 9, Figure 10 or Figure 11).
Outputs[LINK]
HVAC,Average,Unitary System Total Heating Rate [W]
HVAC,Sum,Unitary System Total Heating Energy [J]
HVAC,Average,Unitary System Total Cooling Rate [W]
HVAC,Sum,Unitary System Total Cooling Energy [J]
HVAC,Average,Unitary System Sensible Heating Rate [W]
HVAC,Sum,Unitary System Sensible Heating Energy [J]
HVAC,Average,Unitary System Sensible Cooling Rate [W]
HVAC,Sum,Unitary System Sensible Cooling Energy [J]
HVAC,Average,Unitary System Latent Heating Rate [W]
HVAC,Sum,Unitary System Latent Heating Energy [J]
HVAC,Average,Unitary System Latent Cooling Rate [W]
HVAC,Sum,Unitary System Latent Cooling Energy [J]
HVAC,Average,Unitary System Electricity Rate [W]
HVAC,Sum,Unitary System Electricity Energy [J]
HVAC,Average,Unitary System Fan Part Load Ratio []
HVAC,Average,Unitary System Compressor Part Load Ratio []
HVAC,Average,Unitary System Bypass Air Mass Flow Rate [kg/s]
HVAC,Average,Unitary System Air Outlet Setpoint Temperature [C]
HVAC,Average,Unitary System Operating Mode Index []
Unitary System Total Heating Rate [W][LINK]
This output field is the total (enthalpy) heat addition rate of the CBVAV system in Watts. This value is calculated using the enthalpy difference of the outlet air and inlet air streams, and the supply air mass flow rate entering/leaving the system. This value is calculated for each HVAC system timestep being simulated, and the results (enthalpy addition only) are averaged for the timestep being reported.
Unitary System Total Heating Energy [J][LINK]
This output field is the total (enthalpy) heat addition of the CBVAV system in Joules over the timestep being reported. This value is calculated using the enthalpy difference of the outlet air and inlet air streams, the supply air mass flow rate entering/leaving the system, and the HVAC simulation timestep. This value is calculated for each HVAC system timestep being simulated, and the results (enthalpy addition only) are summed for the timestep being reported.
Unitary System Total Cooling Rate [W][LINK]
This output field is the total (enthalpy) heat extraction rate of the CBVAV system in Watts. This value is calculated using the enthalpy difference of the outlet air and inlet air streams, and the supply air mass flow rate entering/leaving the system. This value is calculated for each HVAC system timestep being simulated, and the results (enthalpy extraction only) are averaged for the timestep being reported.
Unitary System Total Cooling Energy [J][LINK]
This output field is the total (enthalpy) heat extraction of the CBVAV system in Joules over the timestep being reported. This value is calculated using the enthalpy difference of the outlet air and inlet air streams, the supply air mass flow rate entering/leaving the system, and the HVAC simulation timestep. This value is calculated for each HVAC system timestep being simulated, and the results (enthalpy extraction only) are summed for the timestep being reported.
Unitary System Sensible Heating Rate [W][LINK]
This output field is the sensible heat addition rate of the CBVAV system in Watts. This value is calculated using the enthalpy difference of the outlet air and inlet air streams at a constant humidity ratio, and the supply air mass flow rate entering/leaving the system. This value is calculated for each HVAC system timestep being simulated, and the results (heating only) are averaged for the timestep being reported.
Unitary System Sensible Heating Energy [J][LINK]
This output field is the sensible heat addition of the CBVAV system in Joules over the timestep being reported. This value is calculated using the enthalpy difference of the outlet air and inlet air streams at a constant humidity ratio, the supply air mass flow rate entering/leaving the system, and the HVAC simulation timestep. This value is calculated for each HVAC system timestep being simulated, and the results (heating only) are summed for the timestep being reported.
Unitary System Sensible Cooling Rate [W][LINK]
This output field reports the moist air sensible heat extraction rate of the CBVAV system in Watts. This value is calculated using the enthalpy difference of the outlet air and inlet air streams at a constant humidity ratio, and the supply air mass flow rate entering/leaving the system. This value is calculated for each HVAC system timestep being simulated, and the results (cooling only) are averaged for the timestep being reported.
Unitary System Sensible Cooling Energy [J][LINK]
This output field reports the moist air sensible heat extraction of the CBVAV system in Joules over the timestep being reported. This value is calculated using the enthalpy difference of the outlet air and inlet air streams at a constant humidity ratio, the supply air mass flow rate entering/leaving the system, and the HVAC simulation timestep. This value is calculated for each HVAC system timestep being simulated, and the results (cooling only) are summed for the timestep being reported.
Unitary System Latent Heating Rate [W][LINK]
This output field is the latent heat addition (humidification) rate of the CBVAV system in Watts. This value is calculated as the difference between the total energy rate and the sensible energy rate provided by the system. This value is calculated for each HVAC system timestep being simulated, and the results (latent heat addition only) are averaged for the timestep being reported.
Unitary System Latent Heating Energy [J][LINK]
This output field is the latent heat addition (humidification) of the CBVAV system in Joules over the timestep being reported. This value is calculated as the difference between the total energy and the sensible energy delivered by the system. This value is calculated for each HVAC system timestep being simulated, and the results (latent heat addition only) are summed for the timestep being reported.
Unitary System Latent Cooling Rate [W][LINK]
This output field is the latent heat extraction (dehumidification) rate of the CBVAV system in Watts. This value is calculated as the difference between the total energy rate and the sensible energy rate provided by the system. This value is calculated for each HVAC system timestep being simulated, and the results (latent heat extraction only) are averaged for the timestep being reported.
Unitary System Latent Cooling Energy [J][LINK]
This output field is the latent heat extraction (dehumidification) of the CBVAV system in Joules over the timestep being reported. This value is calculated as the difference between the total energy and the sensible energy delivered by the system. This value is calculated for each HVAC system timestep being simulated, and the results (latent heat extraction only) are summed for the timestep being reported.
Unitary System Electricity Rate [W][LINK]
This output field is the electricity consumption rate of the CBVAV system in Watts. The consumption includes electricity used by the DX compressor (including crankcase heater), fans (indoor supply air fan and the condenser fans associated with the DX coil[s]), defrost mode operation (resistive or reverse-cycle), and the heating coil (if electric). This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Unitary System Electricity Energy [J][LINK]
This output field is the electricity consumption of the CBVAV system in Joules for the time period being reported. The consumption includes electricity used by the DX compressor (including crankcase heater), fans (indoor supply air fan and the condenser fans associated with the DX coil[s]), defrost mode operation (resistive or reverse-cycle), and the heating coil (if electric). This value is calculated for each HVAC system timestep being simulated, and the results are summed for the timestep being reported.
Unitary System Fan Part Load Ratio [][LINK]
This output field is the part-load ratio of the supply air fan, which will be either zero or 1 for each simulation timestep. For this system, the fan will operate continuously for the simulation timestep if the system is available (ref. Field: Availability schedule name) and there is a cooling or heating load to be met (i.e., fan part-load ratio will equal 1). When the system is available but there is no cooling or heating load to be met, the fan will either be off for the entire timestep or on for the entire timestep depending on the supply air fan operating mode schedule (ref. Field: Supply Air Fan Operating Mode Schedule Name). This value is set for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Unitary System Compressor Part Load Ratio [][LINK]
This output field is the part-load ratio of the compressor used by the DX coils (cooling and heating). The compressor part-load ratio is defined as the total coil load divided by the coil steady-state capacity (steady-state capacity of first stage for multi-mode coils). This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Unitary System Bypass Air Mass Flow Rate [kg/s][LINK]
This output field is the mass flow rate of air, in kg/s, being bypassed from the supply air path and blended with the air entering the CBVAV system. This value is calculated for each HVAC system timestep being simulated, and the results are averaged for the timestep being reported.
Unitary System Air Outlet Setpoint Temperature [C][LINK]
This output field is the dry-bulb set point temperature in degrees Celsius. This set point temperature is calculated by the model based on the zone cooling/heating loads calculated by EnergyPlus, and the priority control mode and the dehumidification control type specified for this unitary system. The CBVAV system attempts to achieve the outlet air set point temperature to the extent possible.
Unitary System Operating Mode Index [][LINK]
This output field is the current operating mode, either cooling, heating or no cooling or heating. A value of 0 represents no cooling or heating is required, a value of 1 represents cooling and a value of 2 represents heating. These specific values can be seen using the detailed time step reporting frequency. If longer reporting frequencies are used (e.g., timestep, hourly, etc.) then this output is averaged over the reporting interval and the result is dependent on the value selected for Minimum Runtime Before Operating Mode Change.
Documentation content copyright © 1996-2026 The Board of Trustees of the University of Illinois and the Regents of the University of California through the Ernest Orlando Lawrence Berkeley National Laboratory. All rights reserved. EnergyPlus is a trademark of the US Department of Energy.
This documentation is made available under the EnergyPlus Open Source License v1.0.