In order for EnergyPlus to successfully calculate zone
design heating and cooling loads and air flow rates and for
the program to use these results to automatically size the
HVAC components a number of input objects must be present and
certain object input fields must be entered.
The input file should contain a SimulationControl
object. The 1\(^{st}\) field
Do Zone
Sizing Calculation should be entered as Yes.
This will cause a zone sizing simulation to be done using all
the sizing periods in the input file as weather. If there are
no air or water loops in the HVAC input fields 2 and 3 can be
set to No. If there are one or more air loops (i.e.,
there is at least one AirLoopHVAC
object in the input file) then the 2\(^{nd}\) field Do System
Sizing Calculation should be entered as Yes. If
there are one or more water loops (Plant Loop objects) then
the 3\(^{rd}\) field Do
Plant Sizing Calculation should be set to Yes.
Finally either the 4\(^{th}\)
field (Run Simulation for Sizing Periods) or the
5\(^{th}\) field (Run
Simulation for Weather File Run Periods) should be set to
Yes in order to autosize the components and do a real
simulation using the autosized components. The component
autosizing calculations are done on the first pass through the
HVAC system in the real simulation.
There must be at least 2 (up to any number)
SizingPeriod objects present. Normally one will be for summer
conditions and one for winter. The summer day should normally
have the field Day Type set to
SummerDesignDay. The winter design day should
normally have Day Type set to
WinterDesignDay.
To apply a global sizing factor include the Sizing:Parameters
object.
For each controlled zone in the input file there should
be a corresponding Sizing:Zone
object. Similarly for each AirLoopHVAC
there should be a Sizing:System
object. And for each Plant or Condenser Loop there should be a
Sizing:Plant
object. Note however that if a controlled zone has no
corresponding Zone
Sizing object the data from the first Zone
Sizing object will be used. Thus if all the zone sizing
information is the same only one Zone
Sizing object need be entered.
Only controlled zones are included in the zone and
system sizing calculations. Thus for a design air flow rate to
be calculated for a zone, it must contain a thermostat
even though it might not need or have a thermostat in the
full simulation. An illustration would be a three zone
building with a packaged single zone system and a thermostat
in one of the zones. In order for the two slave zones to be
included in the design air flow calculations they must be
treated as if they have a thermostat: there must be a ZoneControl:Thermostat
for each of the slave zones.
Some attention should be paid to schedules. In a weekly
schedule object the 9\(^{th}\) and 10\(^{th}\) day schedules are for
summer and winter design days respectively. This means that if
a SizingPeriod object has field Day Type set to
SummerDesignDay the day schedule for summer sizing
periods will be in effect. Similarly if a SizingPeriod object
has field Day Type set to WinterDesignDay
the day schedule for winter sizing periods will be in effect.
Some possible applications of this capability are:
1) setting internal loads (lights, equipment, occupancy)
to maximum all day for cooling and to zero all day for
heating;
2) setting heating and cooling thermostat set points to
constant values (no set up or set back);
3) setting heating and cooling equipment to be always
on.
None of these applications are necessarily recommended but
these and other uses of the special summer/winter design day
schedules may prove useful for specific situations.
Other than zone thermostat setpoints, the sizing
calculations generally know nothing about the system control
inputs such as setpoints and availability schedules. The user
must coordinate sizing inputs with the actual simulation
control inputs.
The sizing calculations only recognize the presence of
central heating and cooling coils, preheat and precool coils
and reheat coils. These are assumed to deliver the various
supply temperatures specified in the Sizing:System
and Sizing:Zone
objects. The impact of other components such as heat recovery,
dehumidifiers, and pumps are not accounted for in the sizing
calculations. Central supply and return fan temperature rise
is taken into account in sizing the central cooling
coils.
For autosizing to occur at the component level the user
must enter the special value autosize in the numeric
fields for which autosizing is available. Those fields can be
found by looking at the Energy+.idd data dictionary file or
under individual object details in this document. Fields that
can be autosized are denoted with the comment
\autosizable. The components and fields that are
autosizable are listed in the following table. Note that
spaces may be inserted in object names to facilitate
readability.
Details of Autosizable Objects/Fields
Component / Object Name
Autosizable Fields
AirConditioner:VariableRefrigerantFlow
Gross Rated Total Cooling
Capacity
Gross Rated Heating
Capacity
Resistive Defrost Heater
Capacity
Water Condenser Volume Flow
Rate
Evaporative Condenser Air Flow
Rate
Evaporative Condenser Pump Rated
Power Consumption
AirLoopHVAC
Design Supply Air Flow Rate
AirLoopHVAC:Unitary:Furnace:HeatCool
Maximum Supply Air
Temperature
Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Load Supply Air Flow
Rate
AirLoopHVAC:Unitary:Furnace:HeatOnly
Maximum Supply Air
Temperature
Supply Air Flow Rate
AirLoopHVAC:UnitaryHeatCool
Maximum Supply Air
Temperature
Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Load Supply Air Flow
Rate
AirLoopHVAC:UnitaryHeatCool:VAVChangeoverBypass
Cooling System Air Flow
Rate
Heating System Air Flow
Rate
No Load System Air Flow
Rate
Cooling Outdoor Air Flow
Rate
Heating Outdoor Air Flow
Rate
No Load Outdoor Air Flow
Rate
AirLoopHVAC:UnitaryHeatOnly
Maximum Supply Air
Temperature
Supply Air Flow Rate
AirLoopHVAC:UnitaryHeatPump:AirToAir
Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Load Supply Air Flow
Rate
Maximum Supply Air Temperature
from Supplemental Heater
AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed
Maximum Supply Air Temperature
from Supplemental Heater
No Load Supply Air Flow
Rate
Heating Speed 1 Supply Air Flow
Rate
Heating Speed 2 Supply Air Flow
Rate
Heating Speed 3 Supply Air Flow
Rate
Heating Speed 4 Supply Air Flow
Rate
Cooling Speed 1 Supply Air Flow
Rate
Cooling Speed 2 Supply Air Flow
Rate
Cooling Speed 3 Supply Air Flow
Rate
Cooling Speed 4 Supply Air Flow
Rate
AirLoopHVAC:UnitaryHeatPump:WaterToAir
Supply Air Flow Rate
Maximum Supply Air Temperature
from Supplemental Heater
Rated Heating Capacity At
Selected Nominal Speed Level
Rated Air Flow Rate At Selected
Nominal Speed Level
Rated Water Flow Rate At
Selected Nominal Speed Level
CoilPerformance:DX:Cooling
Gross Rated Total Cooling
Capacity
Gross Rated Sensible Heat
Ratio
Rated Air Flow Rate
Evaporative Condenser Air Flow
Rate
Evaporative Condenser Pump Rated
Power Consumption
CondenserLoop
Maximum Loop Flow Rate
Controller:OutdoorAir
Minimum Outdoor Air Flow
Rate
Maximum Outdoor Air Flow
Rate
Controller:WaterCoil
Controller Convergence
Tolerance
Maximum Actuated Flow
CoolingTower:SingleSpeed
Design Water Flow Rate
Design Air Flow Rate
Design Fan Power
Design U-Factor Times Area
Value
CoolingTower:TwoSpeed
Design Water Flow Rate
High Fan Speed Air Flow
Rate
High Fan Speed Fan Power
High Fan Speed U-Factor Times
Area Value
CoolingTower:VariableSpeed
Design Water Flow Rate
Design Air Flow Rate
Design Fan Power
CoolingTower:VariableSpeed:Merkel
Nominal Capacity
Design Water Flow Rate
Design Air Flow Rate U-Factor
Times Area Value
EvaporativeCooler:Indirect:ResearchSpecial
Secondary Fan Flow Rate
EvaporativeFluidCooler:SingleSpeed
Design Air Flow Rate
Design Air Flow Rate Fan
Power
Design Air Flow Rate U-factor
Times Area Value
Design Water Flow Rate
EvaporativeFluidCooler:TwoSpeed
High Fan Speed Air Flow
Rate
High Fan Speed Fan Power
High Fan Speed U-factor Times
Area Value
Design Water Flow Rate
Fan:ComponentModel
Maximum Flow Rate
Minimum Flow Rate
Motor Fan Pulley Ratio
Belt Maximum Torque
Maximum Motor Output Power
Maximum VFD Output Power
Fan:ConstantVolume
Maximum Flow Rate
Fan:OnOff
Maximum Flow Rate
FanPerformance:NightVentilation
Maximum Flow Rate
Fan:VariableVolume
Maximum Flow Rate
FluidCooler:SingleSpeed
Design Air Flow Rate U-factor
Times Area Value
Design Water Flow Rate
Design Air Flow Rate
Design Air Flow Rate Fan
Power
FluidCooler:TwoSpeed
High Fan Speed U-factor Times
Area Value
Design Water Flow Rate
High Fan Speed Air Flow
Rate
High Fan Speed Fan Power
HeaderedPumps:ConstantSpeed
Total Rated Flow Rate
Rated Power Consumption
HeaderedPumps:VariableSpeed
Total Rated Flow Rate
Rated Power Consumption
HeatExchanger:AirToAir:SensibleAndLatent
Nominal Supply Air Flow
Rate
HeatExchanger:FluidToFluid
Loop Demand Side Design Flow
Rate
Loop Supply Side Design Flow
Rate
Heat Exchanger U-Factor Times
Area Value
Humidifier:Steam:Electric
Rated Power
HVACTemplate:Plant:Boiler
Capacity
HVACTemplate:Plant:Chiller
Capacity
HVACTemplate:Plant:Tower
High Speed Nominal Capacity
High Speed Fan Power
Low Speed Nominal Capacity
Low Speed Fan Power
Free Convection Capacity
HVACTemplate:System:ConstantVolume
Supply Fan Maximum Flow
Rate
Heating Coil Capacity
Maximum Outdoor Air Flow
Rate
Minimum Outdoor Air Flow
Rate
Humidifier Rated Electric
Power
HVACTemplate:System:DedicatedOutdoorAir
Supply Fan Flow Rate
DX Cooling Coil Gross Rated
Total Capacity
DX Cooling Coil Gross Rated
Sensible Heat Ratio
Humidifier Rated Electric
Power
HVACTemplate:System:DualDuct
Main Supply Fan Maximum Flow
Rate
Cold Duct Supply Fan Maximum
Flow Rate
Hot Duct Supply Fan Maximum Flow
Rate
Heating Coil Capacity
Maximum Outdoor Air Flow
Rate
Minimum Outdoor Air Flow
Rate
Humidifier Rated Electric
Power
HVACTemplate:System:PackagedVAV
Supply Fan Maximum Flow
Rate
Supply Fan Minimum Flow
Rate
Cooling Coil Gross Rated Total
Capacity
Cooling Coil Gross Rated
Sensible Heat Ratio
Heating Coil Capacity
Maximum Outdoor Air Flow
Rate
Minimum Outdoor Air Flow
Rate
Humidifier Rated Electric
Power
HVACTemplate:System:Unitary
Supply Fan Maximum Flow
Rate
Cooling Coil Gross Rated Total
Capacity
Cooling Coil Gross Rated
Sensible Heat Ratio
Heating Coil Capacity
Maximum Outdoor Air Flow
Rate
Minimum Outdoor Air Flow
Rate
Humidifier Rated Electric
Power
HVACTemplate:System:UnitaryHeatPump:AirToAir
Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Load Supply Air Flow
Rate
Cooling Coil Gross Rated Total
Capacity
Cooling Coil Gross Rated
Sensible Heat Ratio
Heat Pump Heating Coil Gross
Rated Capacity
Supplemental Heating Coil
Capacity
Maximum Outdoor Air Flow
Rate
Minimum Outdoor Air Flow
Rate
Humidifier Rated Electric
Power
HVACTemplate:System:UnitarySystem
Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Load Supply Air Flow
Rate
DX Cooling Coil Gross Rated
Total Capacity
DX Cooling Coil Gross Rated
Sensible Heat Ratio
Heating Coil Gross Rated
Capacity
Supplemental Heating or Reheat
Coil Capacity
Maximum Outdoor Air Flow
Rate
Minimum Outdoor Air Flow
Rate
Humidifier Rated Electric
Power
HVACTemplate:System:VAV
Supply Fan Maximum Flow
Rate
Supply Fan Minimum Flow
Rate
Maximum Outdoor Air Flow
Rate
Minimum Outdoor Air Flow
Rate
Humidifier Rated Electric
Power
HVACTemplate:System:VRF
Gross Rated Total Cooling
Capacity
Gross Rated Heating
Capacity
Resistive Defrost Heater
Capacity
Water Condenser Volume Flow
Rate
Evaporative Condenser Air Flow
Rate
Evaporative Condenser Pump Rated
Power Consumption
HVACTemplate:Zone:BaseboardHeat
Baseboard Heating Capacity
HVACTemplate:Zone:ConstantVolume
Supply Air Maximum Flow
Rate
Baseboard Heating Capacity
HVACTemplate:Zone:DualDuct
Supply Air Maximum Flow
Rate
Baseboard Heating Capacity
HVACTemplate:Zone:FanCoil
Supply Air Maximum Flow
Rate
Baseboard Heating Capacity
HVACTemplate:Zone:IdealLoadsAirSystem
Maximum Heating Air Flow
Rate
Maximum Sensible Heating
Capacity
Maximum Cooling Air Flow
Rate
Maximum Total Cooling
Capacity
HVACTemplate:Zone:PTAC
Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Load Supply Air Flow
Rate
Cooling Coil Gross Rated Total
Capacity
Cooling Coil Gross Rated
Sensible Heat Ratio
Heating Coil Capacity
Baseboard Heating Capacity
HVACTemplate:Zone:PTHP
Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Load Supply Air Flow
Rate
Cooling Coil Gross Rated Total
Capacity
Cooling Coil Gross Rated
Sensible Heat Ratio
Heat Pump Heating Coil Gross
Rated Capacity
Supplemental Heating Coil
Capacity
Baseboard Heating Capacity
HVACTemplate:Zone:Unitary
Supply Air Maximum Flow
Rate
Baseboard Heating Capacity
HVACTemplate:Zone:VAV
Supply Air Maximum Flow
Rate
Baseboard Heating Capacity
HVACTemplate:Zone:VAV:FanPowered
Primary Supply Air Maximum Flow
Rate
Primary Supply Air Minimum Flow
Fraction
Secondary Supply Air Maximum
Flow Rate
Parallel Fan On Flow
Fraction
Baseboard Heating Capacity
HVACTemplate:Zone:VAV:HeatAndCool
Supply Air Maximum Flow
Rate
Baseboard Heating Capacity
HVACTemplate:Zone:VRF
Cooling Supply Air Flow
Rate
No Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Heating Supply Air Flow
Rate
Cooling Outdoor Air Flow
Rate
Heating Outdoor Air Flow
Rate
No Load Outdoor Air Flow
Rate
Cooling Coil Gross Rated Total
Capacity
Cooling Coil Gross Rated
Sensible Heat Ratio
Heat Pump Heating Coil Gross
Rated Capacity
Baseboard Heating Capacity
HVACTemplate:Zone:WaterToAirHeatPump
Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Load Supply Air Flow
Rate
Cooling Coil Gross Rated Total
Capacity
Cooling Coil Gross Rated
Sensible Heat Ratio
Heat Pump Heating Coil Gross
Rated Capacity
Supplemental Heating Coil
Capacity
Baseboard Heating Capacity
PlantComponent:TemperatureSource
Design Volume Flow Rate
PlantEquipmentOperation:ComponentSetpoint
Component 1 Flow Rate
Component 2 Flow Rate
Component 3 Flow Rate
Component 4 Flow Rate
Component 5 Flow Rate
Component 6 Flow Rate
Component 7 Flow Rate
Component 8 Flow Rate
Component 9 Flow Rate
Component 10 Flow Rate
PlantLoop
Maximum Loop Flow Rate
Pump:ConstantSpeed
Rated Flow Rate
Rated Power Consumption
Pump:VariableSpeed
Rated Flow Rate
Rated Power Consumption
Pump:VariableSpeed:Condensate
Rated Flow Rate
Rated Power Consumption
Sizing:System
Design Outdoor Air Flow
Rate
SolarCollector:FlatPlate:PhotovoltaicThermal
Design Flow Rate
ThermalStorage:ChilledWater:Mixed
Use Side Design Flow Rate
Source Side Design Flow
Rate
ThermalStorage:ChilledWater:Stratified
Use Side Design Flow Rate
Source Side Design Flow
Rate
UnitarySystemPerformance:HeatPump:Multispeed
Heating Speed 1 Supply Air Flow
Ratio
Cooling Speed 1 Supply Air Flow
Ratio
Heating Speed 2 Supply Air Flow
Ratio
Cooling Speed 2 Supply Air Flow
Ratio
Heating Speed 3 Supply Air Flow
Ratio
Cooling Speed 3 Supply Air Flow
Ratio
Heating Speed 4 Supply Air Flow
Ratio
Cooling Speed 4 Supply Air Flow
Ratio
WaterHeater:Mixed
Tank Volume
Heater Maximum Capacity
Use Side Design Flow Rate
Source Side Design Flow
Rate
WaterHeater:Stratified
Tank Volume
Tank Height
Heater 1 Capacity
Use Side Design Flow Rate
Source Side Design Flow
Rate
ZoneHVAC:Baseboard:Convective:Electric
Nominal Capacity
ZoneHVAC:Baseboard:Convective:Water
U-Factor Times Area Value
Maximum Water Flow Rate
ZoneHVAC:Baseboard:RadiantConvective:Electric
Nominal Capacity
ZoneHVAC:Baseboard:RadiantConvective:Steam
Maximum Steam Flow Rate
ZoneHVAC:Baseboard:RadiantConvective:Water
Rated Capacity
Maximum Water Flow Rate
ZoneHVAC:EnergyRecoveryVentilator
Supply Air Flow Rate
Exhaust Air Flow Rate
ZoneHVAC:EvaporativeCoolerUnit
Design Supply Air Flow Rate
ZoneHVAC:FourPipeFanCoil
Maximum Supply Air Flow
Rate
Maximum Outdoor Air Flow
Rate
Maximum Cold Water Flow
Rate
Maximum Hot Water Flow Rate
ZoneHVAC:HighTemperatureRadiant
Maximum Power Input
ZoneHVAC:IdealLoadsAirSystem
Maximum Heating Air Flow
Rate
Maximum Sensible Heating
Capacity
Maximum Cooling Air Flow
Rate
Maximum Total Cooling
Capacity
ZoneHVAC:LowTemperatureRadiant:Electric
Maximum Electrical Power to
Panel
ZoneHVAC:LowTemperatureRadiant:VariableFlow
Hydronic Tubing Length
Maximum Hot Water Flow
Maximum Cold Water Flow
ZoneHVAC:OutdoorAirUnit
Outdoor Air Flow Rate
Exhaust Air Flow Rate
ZoneHVAC:PackagedTerminalAirConditioner
Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Load Supply Air Flow
Rate
Cooling Outdoor Air Flow
Rate
Heating Outdoor Air Flow
Rate
No Load Outdoor Air Flow
Rate
ZoneHVAC:PackagedTerminalHeatPump
Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Load Supply Air Flow
Rate
Cooling Outdoor Air Flow
Rate
Heating Outdoor Air Flow
Rate
No Load Outdoor Air Flow
Rate
Maximum Supply Air Temperature
from Supplemental Heater
ZoneHVAC:TerminalUnit:VariableRefrigerantFlow
Cooling Supply Air Flow
Rate
No Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Heating Supply Air Flow
Rate
Cooling Outdoor Air Flow
Rate
Heating Outdoor Air Flow
Rate
No Load Outdoor Air Flow
Rate
ZoneHVAC:UnitHeater
Maximum Supply Air Flow
Rate
Maximum Hot Water or Steam Flow
Rate
ZoneHVAC:UnitVentilator
Maximum Supply Air Flow
Rate
Minimum Outdoor Air Flow
Rate
Maximum Outdoor Air Flow
Rate
ZoneHVAC:VentilatedSlab
Maximum Air Flow Rate
Minimum Outdoor Air Flow
Rate
Maximum Outdoor Air Flow
Rate
ZoneHVAC:WaterToAirHeatPump
Cooling Supply Air Flow
Rate
Heating Supply Air Flow
Rate
No Load Supply Air Flow
Rate
Cooling Outdoor Air Flow
Rate
Heating Outdoor Air Flow
Rate
No Load Outdoor Air Flow
Rate
Maximum Supply Air Temperature
from Supplemental Heater
ZoneHVAC:WindowAirConditioner
Maximum Supply Air Flow
Rate
Maximum Outdoor Air Flow
Rate
There are 3 places in the input where the user can impose
sizing factors.
1. In Sizing Parameters (object: Sizing:Parameters), the
user can specify an over-all sizing factor. This factor is
applied to all the zone design loads and air flow rates
resulting from the zone sizing calculations.
2. In Zone
Sizing (object: Sizing:Zone), the user can specify a sizing
factor for a specific zone. The factor is applied to the
calculated zone design loads and air flow rates for the zone
named in the Sizing:Zone
object. This sizing factor overrides the global sizing factor.
That is, a zone sizing factor, if specified, replaces the
global sizing factor for the named zone.
3. For some plant components (basically all central
chillers, boilers and cooling towers) the user can specify a
sizing factor that modifies the autosized component capacity
and flow rates. These factors are applied after the
application of global or zone sizing factors. They are
primarily used to split the design load between multiple
components. These sizing factors can change the autosizing of
the associated loops and pumps. The following rules are
followed the effect of plant component sizing factors on loops
and pumps.
a. For supply side branches, the sizing factors of all
components in series on the branch are summed and the result
becomes the branch sizing factor. If there is a branch pump
its autosized design flow rate is multiplied by the branch
sizing factor.
b. For each loop, if the average of the branch sizing
factors is less than 1, the loop sizing factor is set equal to
the sum of the branch sizing factors. If the average is
greater than 1, the loop sizing factor is set equal to the
maximum of the branch sizing factors. The loop sizing factor
is applied to the loop design flow rate (if autosized) and to
the loop pump flow rate (if autosized).
Mixed user-specified and autosized inputs can be
successfully used if the following points and suggestions are
followed.
1. Each component is autosized independently. Thus user
input for a flow rate in one component will have no effect on
other components’ autosized flow rates. For instance,
specifying the chilled water loop pump’s rated flow rate will
have no effect on the autosizing of the chiller’s design
evaporator flow rate or on the plant loop’s autosized maximum
loop flow rate.
2. Within a component it is best to autosize all inputs
are enter specified values for all inputs. For example, in a
chiller, if only the nominal capaciity is user-specified, the
autosized chilled water flow rate may not be consistent with
the specified capacity.
3. Sizing information flows only from the sizing objects
to the components. The sizing calculations have no knowledge
of user-specified values in a component. The only exception to
this rule is that plant loop sizing will collect all component
design water flow rates whether autosized or
user-specified.
4. If the user wants to specify a zone or system air
flow rate it should be done using the Sizing:Zone
and Sizing:System objects rather than done in the individual
components.
5. The plant loop flow rates are sized from the total
design demand of the components connected to each loop. The
components demanding water need not be autosized for the plant
loop autosizing to work successfully. So the user could
specify all the air side components and autosize all the plant
loops and plant components. Or specify the chilled water loop
flow rate, chilled water pump inputs and chiller inputs and
let the condenser loop and tower autosize.
The results of the component autosizing calculations are
reported on the eplusout.eio file. For each component
field that has been autosized the object type, object name,
field description with unit, and value are printed out as
comma separated data on a line beginning with Component
Sizing. Examples of this are shown in the Output Details
and Examples document.
The complete list of objects that have autosized fields is
shown in the following table. Note that spaces may be inserted
in object names to facilitate readability.
User or
External Zone Design Flow Rate Inputs[LINK]
In EnergyPlus the autosizing calculations start with a
calculation of the zone design air flow rates using zone by
zone design day simulations. The resulting zone design air
flow rates and daily air flow sequences are used in the
subsequent HVAC and central plant air and fluid flow design
calculations and in the component autosizing calculations. The
user can override or change the calculated zone design air
flow rates in several ways.
1) The user can enter a value for Sizing Factor
in the Sizing:Parameters
object (see description below).
2) The user can specify a zone level Zone
Sizing Factor in each Sizing:Zone
object.
3) For each zone the user can input a Cooling Design
Air Flow Rate and/or a Heating Design Air Flow
Rate (and specify Cooling Design Air Flow Method =
Flow/Zone and Heating Design Air Flow Method =
Flow/Zone). These user inputs override the calculated
values. The program divides the user input cooling or heating
design air flow rate by the calculated values and uses the
result as a zone sizing factor to multiply all the elements in
the design heating and cooling air flow and load sequences.
From this point the design calculations proceed as usual.
User
or External System Design Flow Rate Inputs[LINK]
Using the results of the zone design air flow rate
calculation (including any user input or altered flow rates)
EnergyPlus proceeds to calculate central air system flow rates
and cooling and heating loads. The results of this calculation
can be overridden in the following way.
For each system (AirLoopHVAC), in the corresponding Sizing:System
object, specify Cooling Design Air Flow Method to be
Flow/System and input a value for Cooling Design
Air Flow Rate. Similarly for heating specify Heating
Design Air Flow Method to be Flow/System and
input a value for Heating Design Air Flow Rate.
This object allows for the outdoor air requirements to be
defined in a common location for use by other objects. This
object may be referenced by name from other objects (e.g., VAV
terminal units, AirTerminal:SingleDuct:Uncontrolled,
and AirTerminal:SingleDuct:Mixer) as required to identify an
outdoor air quantity for use by that object. Note that a zone
name Is not included as an input to this zone outdoor air
definition and the number of people in a zone, zone floor
area, and zone volume can only be determined after this object
has been referenced by another. A single zone outdoor air
definition may be referenced by multiple objects to specify
that the same outdoor air requirements are used by those
objects or multiple zone outdoor air objects may be
defined and referenced by other objects as needed. If multiple
zone outdoor air definitions are used, each outdoor air
definition must have a unique name.
The input must be either Flow/Person,
Flow/Area, Flow/Zone, AirChanges/Hour,
Sum, Maximum,
IndoorAirQualityProcedure,
ProportionalControlBasedOnDesignOccupancy, or
ProportionalControlBasedonOccupancySchedule. The
default is Flow/Person.
Flow/Person means the program will use the
input from the field Outdoor Air Flow per Person and
the actual zone occupancy to calculate a zone outdoor air flow
rate.
Flow/Area means that the program will use the
input from the field Outdoor Air Flow per Zone
Floor Area and the actual zone floor area as the zone
outdoor air flow rate.
Flow/Zone means that the program will use the
input of the field Outdoor Air Flow per Zone
as the zone outdoor air flow rate.
AirChanges/Hour means that the program will
use the input from the field Air Changes per Hour and
the actual zone volume (divided by 3600 seconds per hour) as
the zone outdoor air flow rate.
Sum means that the flows calculated from the
fields Outdoor Air Flow per Person,Outdoor Air
Flow per Area, Outdoor Air Flow per Zone,
and Air Changes per Hour (using the associated
conversions to m\(^{3}\)/s
for each field) will be added to obtain the zone outdoor air
flow rate.
Maximum means that the maximum flow derived
from Outdoor Air Flow per Person,Outdoor Air
Flow per Area, Outdoor Air Flow per Zone,
and Air Changes per Hour (using the associated
conversions to m\(^{3}\)/s
for each field) will be used as the zone outdoor air flow
rate.
IndoorAirQualityProcedure means that the
program will use the other procedure defined in ASHRAE
Standard 62.1-2007 to calculate the amount of outdoor air
necessary in order to maintain the levels of indoor air carbon
dioxide at or below the setpoint defined in the ZoneControl:ContaminantController
object. Appendix A of the ASHRAE 62.1-2010 user’s manual
discusses another method for implementing CO2-based DCV in a
single zone system. The last two methods of Proportional
Control calculate the required outdoor air flow rate which
varies in proportion to the percentage of the CO2 signal range
and has two choices to calculate occupancy-based outdoor air
rate.
ProportionalControlBasedonOccupancySchedule
uses the real occupancy at the current time step to calculate
outdoor air rate.
ProportionalControlBasedonDesignOccupancy uses
the design occupancy level to calculate outdoor air rate. The
former choice is a good approach to estimate outdoor air rate.
However, for practical applications, the zone controller
usually does not have the real time occupancy information, and
the design occupancy level is assumed. The latter choice is
used in the design stage.
The design outdoor air volume flow rate per person for this
zone in cubic meters per second per person. The default is
0.00944 (20 cfm per person). An outdoor air flow rate is
calculated based on the total number of people for all People
statements assigned to the zone. Occupancy schedule values
are not applied during sizing calculations and
are applied during the remainder of the simulation.
This input is used if Outdoor Air Method is one of
Outdoor Air Flow per Person, Sum, or
Maximum.
The design outdoor air volume flow rate per square meter of
floor area (units are m\(^{3}\)/s-m\(^{2}\)). This input is used if
Outdoor Air Method is Flow/Area, Sum or
Maximum. The default value for this field is 0.
The design outdoor air flow rate for this zone in cubic
meters per second. This input field is used if Outdoor Air
Method is Flow/Zone, Sum or Maximum.
The default value for this field is 0.
The design outdoor air volume flow rate in air changes per
hour. This factor is used along with the Zone
Volume and converted to cubic meters per second. This input
field is used if Outdoor Air Method is
AirChanges/Hour, Sum or Maximum. The default
value for this field is 0.
This field is the name of schedule that defines how outdoor
air requirements change over time. The field is optional. If
left blank, the schedule defaults to 1.0. If used, then the
schedule values are multiplied by the outdoor air flow rate
defined by the previous fields. The schedule values must be
between 0 and 1, inclusive.
If this DesignSpecification:OutdoorAir
object is referenced by a Controller:MechanicalVentilation
object (either directly or indirectly through Sizing:Zone),
the schedule will be applied to all types of outdoor air
calculations for the corresponding zone, regardless of the
System Outdoor Air Method selected. If the schedule value is
zero, then the zone will be completely removed from the system
outdoor air calculations.
Field:
Proportional Control Minimum Outdoor Air Flow Rate Schedule
Name[LINK]
This field is the name of schedule that defines how minimum
outdoor air requirements change over time. The field is
optional. If left blank, the schedule defaults to 1.0. If used
when the field System Outdoor Air Method =
ProportionalControlBasedOnDesignOARate in Controller:MechanicalVentilation,
then the schedule values are multiplied by the outdoor air
flow rate.
An IDF example:
DesignSpecification:OutdoorAir
ZoneOAData, !- Name
Sum, !- Outdoor Air Method
0.00944, !- Outdoor Air Flow per Person {m3/s}
0.00305, !- Outdoor Air Flow per Zone Floor Area {m3/s-m2}
, !- Outdoor Air Flow per Zone {m3/s}
, !- Outdoor Air Flow Air Changes per Hour
OARequirements Sched; !- Outdoor Air Schedule Name
Schedule:Compact,
OARequirements Sched, !- Name
Any Number, !- Schedule Type Limits Name
Through: 12/31, !- Field 1
For: Weekdays SummerDesignDay WinterDesignDay, !- Field 2
Until: 24:00, 1.0, !- Field 4
For: AllOtherDays, !- Field 5
Until: 24:00, 0.5; !- Field 7
This object is used to describe the air distribution
effectiveness and fraction of secondary recirculation air
(return air not directly mixed with outdoor air) of a zone. It
is referenced by the Sizing:Zone
and Controller:MechanicalVentilation
objects.
The unique user assigned name for an instance of this
object. Any other object referencing this object will use this
name.
Field:
Zone Air Distribution Effectiveness in Cooling Mode[LINK]
The positive numeric input for this field is the zone air
distribution effectiveness when the zone is in cooling mode.
Default value of this field is 1.0. ASHRAE Standard 62.1-2010
provides typical values.
Field:
Zone Air Distribution Effectiveness in Heating Mode[LINK]
The positive numeric input for this field is the zone air
distribution effectiveness when the zone is in heating mode.
Default value of this field is 1.0. ASHRAE Standard 62.1-2010
provides typical values as follows:
Zone Air Distribution
Effectiveness (Source: ASHRAE Standard 62.1-2010) [fig:zone-air-distribution-effectiveness-source]
Field:
Zone Air Distribution Effectiveness Schedule Name[LINK]
This optional field input points to a schedule with values
of zone air distribution effectiveness. It provides a more
flexible way of specifying zone air distribution effectiveness
if it changes with time and/or system operating status and
controls. If the schedule is specified, the zone air
distribution effectiveness in cooling mode and heating mode
will be ignored.
Field:
Zone Secondary Recirculation Fraction[LINK]
The non-negative numeric input for this field is the
fraction of a zone’s recirculation air that does not directly
mix with the outdoor air. The zone secondary recirculation
fraction Er is determined by the designer based on system
configuration. For plenum return systems with secondary
recirculation (e.g., fan-powered VAV with plenum return) Er is
usually less than 1.0, although values may range from 0.1 to
1.2 depending upon the location of the ventilation zone
relative to other zones and the air handler. For ducted return
systems with secondary recirculation (e.g., fan-powered VAV
with ducted return), Er is typically 0.0, while for those with
system-level recirculation (e.g, dual-fan dual-duct systems
with ducted return) Er is typically 1.0. For other system
types, Er is typically 0.75. Minimum is 0.0, and default is
0.0 for single-path systems (also to maintain backward
compatibility). For parallel fan-powered VAV systems, the
secondary ventilation path only functions (Er > 0.0) when
the fans in the VAV boxes operate, which is during heating.
The local ventilation path and the benefits of secondary
recirculation disappear during cooling, when the local
parallel fans are off (Er = 0.0).
This optional input sets a minimum on the ventilation
efficiency for the zone. It is only used with the Ventilation
Rate Procedure (VRP), single-path method. VRP should be chosen
in Sizing System, System Outdoor Air Method =
VentilationRateProcedure. Single-path method is indicated by
leaving the previous input (Zone Secondary Recirculation
Fraction) blank or setting it to 0.0. If the calculated value
of ventilation efficiency for a zone is less than this value,
it is raised to this minimum by raising the zone minimum air
flow rate. This new value for zone minimum air flow rate then
overrides other defaults and inputs in Sizing:Zone.
An example of this in an IDF context is shown:
DesignSpecification:ZoneAirDistribution,
CM DSZAD ZN_1_FLR_1_SEC_1, !- Name
1, !- Zone Air Distribution Effectiveness in Cooling Mode {dimensionless}
1, !- Zone Air Distribution Effectiveness in Heating Mode {dimensionless}
; !- Zone Air Distribution Effectiveness Schedule Name
This object allows the user to specify global heating and
cooling sizing ratios. These ratios will be applied at the
zone level to all of the zone heating and cooling loads and
air flow rates. These new loads and air flow rates are then
used to calculate the system level flow rates and capacities
and are used in all component sizing calculations.
The user can also specify the width (in load timesteps) of
a moving average window which can be used to smooth the
calculated zone design flow sequences. The use of this
parameter is described below.
The number of load timesteps in the zone design flow
sequence averaging window. The default is 1, in which case the
calculated zone design flow rates are averaged over the load
timestep.
The zone design air flow rate calculation is performed
assuming a potentially infinite supply of heating or cooling
air at a fixed temperature. Thus the calculated design air
flow rate will always be able to meet any load or change in
load no matter how large or abrupt. In reality air flow rates
are limited by duct sizes and fan capacities. The idealized
zone design flow calculation may result in unrealistically
large flow rates, especially if the user is performing the
sizing calculations using thermostat schedules with night
setup or setback. The calculated zone design flow rates are
always averaged over the load timestep. The user may want to
perform a broader average to mitigate the effect of thermostat
setup and setback and prevent the warm up or cool down flow
rates from dominating the design flow rate calculation..
Specifying the width of the averaging window allows the user
to do this.
For example, if the load calculation timestep is 15 minutes
and the user specifies the Timesteps in Averaging Window
to be 4, the zone design air flows will be averaged over a
time period of 1 hour. Specifying 8 would result in averaging
over a 2 hour period.
As described early in the document (see: EnergyPlus Output
Processing), the user may select the “style” for the sizing
result files (epluszsz.<ext>, eplusssz.<ext>).
This object applies to all sizing output files.
OutputControl:Sizing:Style,
\memo default style for the Sizing output files is comma -- this works well for
\memo importing into spreadsheet programs such as Excel(tm) but not so well for word
\memo processing progams -- there tab may be a better choice. fixed puts spaces between
\memo the "columns"
\unique-object
A1; \field Column Separator
\required-field
\type choice
\key Comma
\key Tab
\key Fixed
For this field, the desired separator for columns is
entered. “Comma” creates comma separated fields/columns in the
outputs (eplus<sizing type>.csv files are created).
“Tab” creates tab separated fields/columns in the outputs
(eplus<sizing type>.tab files are created). “Fixed”
creates space separated fields/columns in the outputs
(eplus<sizing type>.txt files are created) but these are
not necessarily lined up for easy printing.
Note that both tab and comma separated files easily import
into Excel™ or other spreadsheet programs. The tab delimited
files can also be viewed by text editors, word processing
programs and easily converted to “tables” within those
programs.
The Sizing:Zone
object provides the data needed to perform a zone design air
flow calculation for a single zone. This calculation assumes a
variable amount of supply air at a fixed temperature and
humidity. The information needed consists of the zone inlet
supply air conditions: temperature and humidity ratio for
heating and cooling. The calculation is done for every design
day included in the input. The maximum cooling load and air
flow and the maximum heating load and air flow are then saved
for the system level design calculations and for the component
automatic sizing calculations.
The Sizing:Zone
object is also the place where the user can specify the design
outdoor air flow rate by referencing the name of a design
specification outdoor air object. This can be specified in a
number of ways (ref. DesignSpecification:OutdoorAir).This data
is saved for use in the system sizing calculation or for
sizing zone components that use outdoor air.
The user can also place limits on the heating and design
cooling air flow rates. See Heating Design Air Flow
Method and Cooling Design Air Flow Method below
and the explanations of the various heating and cooling flow
input fields.
The user can ask the zone design calculation to take into
account the effect of a Dedicated Outdoor Air System on the
zone design loads and airflow rates. The design calculation
will calculate the heat addition rate to the zone of an
idealized SOA system and add or subtract the result from the
total zone loads and flow rates.
The name of the Zone
corresponding to this Sizing:Zone
object. This is the zone for which the design air flow
calculation will be made using the input data of this Sizing:Zone
Object.
Field:
Zone Cooling Design Supply Air Temperature Input Method[LINK]
The input must be either SupplyAirTemperature or
TemperatureDifference. SupplyAirTemperature
means that the user inputs from the fields of Zone
Cooling Design Supply Air Temperature will be used to
determine the zone cooling design air flow rates.
TemperatureDifference means that the user inputs from
the fields of Zone
Cooling Design Supply Air Temperature Difference will be used
to determine the zone cooling design air flow rates.
Field:
Zone Cooling Design Supply Air Temperature[LINK]
The supply air temperature in degrees Celsius for the zone
cooling design air flow rate calculation. Air is supplied to
the zone at this temperature during the cooling design day
simulation, The zone load is met by varying the zone air flow
rate. The maximum zone flow rate is saved as the zone cooling
design air flow rate. This field is only used when Zone
Cooling Design Supply Air Temperature Input Method =
SupplyAirTemperature.
Field:
Zone Cooling Design Supply Air Temperature Difference[LINK]
The temperature difference between cooling design supply
air temperature and room air temperature in degrees Celsius
for the zone cooling design air flow rate calculation. Air is
supplied to the zone at this temperature during the cooling
design day simulation. The zone load is met by varying the
zone air flow rate. The maximum zone flow rate is saved as the
zone cooling design air flow rate. This field is only used
when Zone
Cooling Design Supply Air Temperature Input Method =
TemperatureDifference.
Field:
Zone Heating Design Supply Air Temperature Input Method[LINK]
The input must be either SupplyAirTemperature or
TemperatureDifference. SupplyAirTemperature
means that the user inputs from the fields of Zone
Heating Design Supply Air Temperature will be used to
determine the zone heating design air flow rates.
TemperatureDifference means that the user inputs from
the fields of Zone
Heating Design Supply Air Temperature Difference will be used
to determine the zone heating design air flow rates.
Field:
Zone Heating Design Supply Air Temperature[LINK]
The supply air temperature in degrees Celsius for the zone
heating design air flow rate calculation. Air is supplied to
the zone at this temperature during the heating design day
simulation, The zone load is met by varying the zone air flow
rate. The maximum zone flow rate is saved as the zone heating
design air flow rate. This field is only used when Zone
Heating Design Supply Air Temperature Input Method =
SupplyAirTemperature.
Field:
Zone Heating Design Supply Air Temperature Difference[LINK]
The temperature difference between heating design supply
air temperature and room air temperature in degrees Celsius
for the zone heating design air flow rate calculation. Air is
supplied to the zone at this temperature during the heating
design day simulation. The zone load is met by varying the
zone air flow rate. The maximum zone flow rate is saved as the
zone heating design air flow rate. This field is only used
when Zone
Heating Design Supply Air Temperature Input Method =
TemperatureDifference.
Field:
Zone Cooling Design Supply Air Humidity Ratio[LINK]
The humidity ratio in kilograms of water per kilogram of
dry air of the supply air in the zone cooling design air flow
rate calculation.
Field:
Zone Heating Design Supply Air Humidity Ratio[LINK]
The humidity ratio in kilograms of water per kilogram of
dry air of the supply air in the zone heating design air flow
rate calculation.
Field:
Design Specification Outdoor Air Object Name[LINK]
This alpha field specifies the name of a DesignSpecification:OutdoorAir
object which specifies the design outdoor air flow rate for
the zone.
When a choice of IndoorAirQualityProcedure is entered in
the Outdoor Air Method field of the DesignSpecification:OutdoorAir
object, the design outdoor airflow rate is calculated based on
the choice of Sum in the same field.
When a choice of ProportionalControlBasedOnDesignOccupancy
or ProportionalControlBasedonOccupancySchedule is entered, the
design outdoor airflow rate is calculated based on equations
specified in the "Proportional Control" section in the
Engineering Reference.
This input is a zone level heating sizing ratio. The zone
design heating air flow rates and loads will be multiplied by
the number input in this field. This input overrides the
building level sizing factor input in the Sizing:Parameters
object. And, of course, if this field is blank or zero, the
global heating sizing factor from the Sizing:Parameters
object is used.
This input is a zone level cooling sizing ratio. The zone
design cooling air flow rates and loads will be multiplied by
the number input in this field. This input overrides the
building level sizing factor input in the Sizing:Parameters
object. And, of course, if this field is blank or zero, the
global cooling sizing factor from the Sizing:Parameters
object is used.
The input must be either Flow/Zone, DesignDay, or
DesignDayWithLimit. Flow/Zone means that the
program will use the input of the field Cooling Design Air
Flow Rate as the zone design cooling air flow rate.
DesignDay means the program will calculate the zone
design cooling air flow rate using the Sizing:Zone
input data and a design day simulation without imposing any
limits other than those set by the minimum outside air
requirements. DesignDayWithLimit means that the
maximum from Cooling Minimum Air Flow per Zone
Floor Area and Cooling Minimum Air Flow will set
a lower limit on the design maximum cooling air flow rate. The
default method is DesignDay: i.e., the program uses
the calculated design values subject to ventilation
requirements.
The design zone cooling air flow rate in cubic meters per
second. This input is used if Cooling Design Air Flow
Method is specified as Flow/Zone. This value
will be multiplied by the global or zone sizing factor and by
zone multipliers.
Field:
Cooling Minimum Air Flow per Zone Floor Area[LINK]
The minimum zone cooling volumetric flow rate per square
meter (units are m\(^{3}\)/s-m\(^{2}\)). This field is used when
Cooling Design Air Flow Method is specified as
DesignDayWithLimit. In this case it sets a lower
bound on the zone design cooling air flow rate. In all cases
the maximum flow derived from Cooling Minimum Air Flow per
Zone
Floor Area, Cooling Minimum Air Flow,
Cooling Minimum Air Flow Fraction and the design
outdoor air flow rate (including VRP adjustments) is used to
set a minimum supply air flow rate for the zone for VAV
systems. The default is 0.000762, corresponding to 0.15
cfm/ft\(^{2}\). The
applicable sizing factor is not applied to this value.
The minimum zone cooling volumetric flow rate in m\(^{3}\)/s. This field is used when
Cooling Design Air Flow Method is specified as
DesignDayWithLimit. In this case it sets a lower
bound on the zone design cooling air flow rate. In all cases
the maximum flow derived from Cooling Minimum Air Flow per
Zone
Floor Area, Cooling Minimum Air Flow,
Cooling Minimum Air Flow Fraction and the design
outdoor air flow rate (including VRP adjustments) is used to
set a minimum supply air flow rate for the zone for VAV
systems. The default is zero. The applicable sizing factor is
not applied to this value.
The minimum zone design cooling volumetric flow rate
expressed as a fraction of the zone design cooling volumetric
flow rate. In all cases the maximum flow derived from
Cooling Minimum Air Flow per Zone
Floor Area, Cooling Minimum Air Flow,
Cooling Minimum Air Flow Fraction and the design
outdoor air flow rate (including VRP adjustments) is used to
set a minimum supply air flow rate for the zone for VAV
systems. The default is 0.2. This input is currently used in
sizing the VAV air terminal unit and fan minimum flow rate. It
does not currently affect other component autosizing.
The input must be either Flow/Zone, DesignDay, or
DesignDayWithLimit. Flow/Zone means that the
program will use the input of the field Heating Design Air
Flow Rate as the zone design heating air flow rate.
DesignDay means the program will calculate the zone
design heating air flow rate using the Sizing:Zone
input data and a design day simulation without imposing any
limits other than those set by the minimum outside air
requirements. DesignDayWithLimit means that the
maximum from Heating Maximum Air Flow per Zone
Floor Area and Heating Maximum Air Flow will set
a lower limit on the design maximum heating air flow rate. The
default method is DesignDay: i.e., the program uses
the calculated design values subject to ventilation
requirements.
The design zone heating air flow rate in cubic meters per
second. This input is used if Heating Design Air Flow
Method is specified as Flow/Zone. This value
will be multiplied by the global or zone sizing factor and by
zone multipliers.
Field:
Heating Maximum Air Flow per Zone Floor Area[LINK]
The maximum zone heating volumetric flow rate per square
meter (units are m\(^{3}\)/s-m\(^{2}\)). This field is used when
Heating Design Air Flow Method is specified as
DesignDayWithLimit. In this case it sets an upper
bound on the zone design heating air flow rate. For this and
the next two input fields, the maximum flow derived from
Heating Maximum Air Flow per Zone
Floor Area, Heating Maximum Air Flow, and
Heating Maximum Air Flow Fraction is used to set a
maximum heating supply air flow rate for the zone for VAV
systems. The default is 0.002032, corresponding to 0.40
cfm/ft\(^{2}\). If the
maximum heating design flow rate calculated using these input
fields is greater than the design heating flow rate calculated
during sizing, these input fields have no impact on sizing. It
may be more appropriate to select only one of these three
fields to calculate the maximum heating design flow rate
(i.e., if one ore more of these three fields is 0, it will not
be used in calculating the maximum heating design flow
rate).
The maximum zone heating volumetric flow rate in m\(^{3}\)/s. This field is used when
Heating Design Air Flow Method is specified as
DesignDayWithLimit. In this case it sets an upper
bound on the zone design heating air flow rate. For this field
and the two input fields just prior to and after this
field,,the maximum flow derived from Heating Maximum Air
Flow per Zone
Floor Area, Heating Maximum Air Flow, and
Heating Maximum Air Flow Fraction is used to set a
maximum heating supply air flow rate for the zone for VAV
systems. The default is 0.1415762, corresponding to 300 cfm.
If the maximum heating design flow rate calculated using these
input fields is greater than the design heating flow rate
calculated during sizing, these input fields have no impact on
sizing. It may be more appropriate to select only one of these
three fields to calculate the maximum heating design flow rate
(i.e., if one ore more of these three fields is 0, it will not
be used in calculating the maximum heating design flow
rate).
The maximum zone design heating volumetric flow rate
expressed as a fraction of the zone design cooling volumetric
flow rate. For this and the previous two input fields, the
maximum flow derived from Heating Maximum Air Flow per Zone
Floor Area, Heating Maximum Air Flow, and
Heating Maximum Air Flow Fraction is used to set a
maximum heating supply air flow rate for the zone for VAV
systems. The default is 0.3. If the maximum heating design
flow rate calculated using these input fields is greater than
the design heating flow rate calculated during sizing, these
input fields have no impact on sizing. It may be more
appropriate to select only one of these three fields to
calculate the maximum heating design flow rate (i.e., if one
ore more of these three fields is 0, it will not be used in
calculating the maximum heating design flow rate).
Field:
Design Specification Zone Air Distribution Object Name[LINK]
Field:
Account for Dedicated Outdoor Air System[LINK]
This is a choice field with choices Yes or
No. The default is No. Choosing Yes
means that the zone sizing calculation will use the subsequent
inputs to calculate the heat gain or loss (heat gains are
positive, heat loss is negative) imposed on the zone by a
Dedicated Outdoor Air System (DOAS). This heat gain is then
added to the zone design heat gain for the zone and the zone
design air flow rate is adjusted to meet the DOAS heat gain
plus the zone design heat gain.
Field:
Dedicated Outdoor Air System Control Strategy[LINK]
This is a choice field with a choice of three ideal control
strategies for the DOA system. The choices are
NeutralSupplyAir,
NeutralDehumidifiedSupplyAir, or
ColdSupplyAir. The default is
NeutralSupplyAir.
NeutralSupplyAir implies that the ventilation air
supplied to the zone will cause little heating or cooling. The
air will be heated or cooled to keep it between the low and
high temperature setpoints specified in the subsequent two
fields. A good choice for these fields might be 21.1 and 23.9
degrees C.
NeutralDehumidifiedSupplyAir means that the
ventilation air will be cooled and dehumidified and then
reheated to a neutral temperature. The ventilation air is
cooled to the lower setpoint temperature (if necessary) and
reheated to the upper setpoint temperature. A good choice for
the setpoints would be 14.4 and 22.2 degrees C.
ColdSupplyAir means that the ventilation air will
be used to supply cooling to the zone. Cold outside air is
heated to the upper setpoint; warm outside air is cooled to
the lower setpoint. A good choice for the setpoints would be
12.2 and 14.4 degrees C.
Field:
Dedicated Outdoor Air Low Temperatue Setpoint for Design[LINK]
The lower setpoint temperature to be used with the DOAS
design control strategy. The units are degrees C. The default
is autosized to the values given above for the three design
control strategies.
Field:
Dedicated Outdoor Air High Temperature Setpoint for
Design[LINK]
The higher setpoint temperature to be used with the DOAS
design control strategy. The units are degrees C. The default
is autosized to the values given above for the three design
control strategies.
An IDF example:
Sizing:Zone,
SPACE5-1, !- Name of a zone
14., !- Zone cooling design supply air temperature {C}
50., !- Zone heating design supply air temperature {C}
0.009, !- Zone cooling design supply air humidity ratio {kg-H2O/kg-air}
0.004, !- Zone heating design supply air humidity ratio {kg-H2O/kg-air}
DSOA1, !- Design Specification Outdoor Air Object Name
0.0, !- zone heating sizing factor
0.0, !- zone cooling sizing factor
designdaywithlimit, !- Cooling Design Air Flow Method
, !- cooling design air flow rate {m3/s}
, !- Cooling Minimum Air Flow per zone area {m3/s-m2}
, !- Cooling Minimum Air Flow {m3/s}
, !- fraction of the cooling design air flow rate
designday, !- Heating Design Air Flow Method
, !- heating design air flow rate {m3/s}
, !- heating max air flow per zone area {m3/s-m2}
, !- heating max air flow {m3/s}
, !- fraction of the cooling design air flow rate
DSZADO1, !- Design Specification Zone Air Distribution Object Name
Yes, !- Account for Dedicated Outside Air System
ColdSupplyAir, !- Dedicated Outside Air System Control Strategy
12.2, !- Dedicated Outside Air Low Setpoint for Design
14.4; !- Dedicated Outside Air High Setpoint for Design
DesignSpecification:OutdoorAir,
DSOA1, !- Name
SUM, !- Outdoor Air Method
0.00236, !- Outdoor Air Flow per Person
0.000305, !- Outdoor Air Flow per Zone Floor Area
0.0, !- Outdoor Air Flow per Zone
0.0, !- Outdoor Air Flow Air Changes per Hour
; !- Outdoor Air Flow Rate Fraction Schedule Name
DesignSpecification:ZoneAirDistribution,
DSZADO1, !- Name
1.0, !- Zone Air Distribution Effectiveness in Cooling Mode
1.0, !- Zone Air Distribution Effectiveness in Heating Mode
, !- Zone Air Distribution Effectiveness Schedule Name
0.3; !- Zone Secondary Recirculation Fraction
The zone design air flow rates and loads are output onto
the local file “epluszsz.<ext>” where <ext> is the
extension from the sizing style object (default is csv – a
comma separated file epluszsz.csv). The columns are
clearly labeled. It will easily import into Excel or other
spreadsheet program that accepts delimited files. All of these
values are design air flow rates and loads calculated by
the program. No sizing factors have been applied.
The calculated zone design air flow rates and the user
input or altered zone design air flow rates are also reported
on the eplusout.eio file. The values are printed out
for each zone as comma separated records beginning with Zone
Sizing. Items output on the eio file are: zone
name, load type (heating or cooling), design load, calculated
design air flow rate, user design air flow rate, design day
name, time of peak, outside temperature at peak, outside
humidity ratio at peak.
This object is used to describe general sizing and scalable
sizing methods which are referenced by zone HVAC equipment
objects. It is optional input field in zone HVAC objects. If a
name of this optional input is not specified or is blank then
the sizing method or input specified in the parent object is
used. If the name of this object is entered, then the values
or method specified overrides the sizing method in the parent
zone HVAC objects. This object is meant to provide scalable
sizing method to users. The name of this object is an optional
input field in the zoneHVAC objects. When this name in not
specified in the zone HVAC object the sizing method or the
value specified in the zone HVAC object will be used.
List of zoneHVAC objects than can reference this object
include:
The sizing methods input fields available in this objects
are for supply air flow and capacity for heating and cooling
operating modes. Some zone HVAC equipment has single supply
air flow rate input field that serves both cooling and heating
operating modes. So entering either of the cooling or heating
scalable sizing input field is sufficient. When there are
separate input fields for cooling, heating, no-cooling, and
no-heating operating modes, the corresponding input fields are
specified. The child components supply air flow rate are also
sized using scalable sizing methods specified in the parent
objects. The methods allow users to enter a fixed or hard
sized values, autosizable, or scalable sizing methods.
Methods allowed for sizing supply air flow rates include:
SupplyAirFlowRate,
FractionOfAutosizedCoolingAirflow,
FractionOfAutosizedHeatingAirflow,
FlowPerFloorArea, FlowPerCoolingCapacity, and
FlowPerHeatingCapacity. The different sizing options
are defined as follows:
SupplyAirFlowRate: entered when it is
intended that the user specified either hard value or the
simulation engine autosize the supply air flow rates for
cooling, heating, and no-cooling or no-heating operating
modes.
FlowPerFloorArea: entered when it is
intended that the simulation engine determine the supply air
flow rates from the user specified supply air flow rates
per unit floor area and the zone floor area of the zone
served by the zone HVAC equipment.
FractionOfAutosizedCoolingAirflow:
entered when it is intended that the simulation engine
determines the supply air flow rates from the user specified
flow fraction and autosized cooling design supply
air flow rate.
FractionOfAutosizedHeatingAirflow:
entered when it is intended that the simulation engine
determines the supply air flow rates from the user specified
flow fraction and autosized heating design supply
air flow rate.
FlowPerCoolingCapacity: entered when
it is intended t that he simulation engine determines the
supply air flow rates from the user specified supply air
flow per cooling capacity value and autosized cooling
design capacity.
FlowPerHeatingCapacity: entered when
it is intended that the simulation engine determines the
supply air flow rates from the user specified supply air
flow per heating capacity value and autosized heating
design capacity.
The Design Specification ZoneHVAC Sizing object also has
input fields for sizing or scalable sizing of cooling and
heating capacity. However, most of the parent zone HVAC
objects do not have input fields for sizing capacities. So,
the capacity scalable sizing fields in the parent objects are
used for sizing child components capacity sizings. The
scalable capacity sizing may be indirectly impacted by the
scalable supply air flow rates sizing values. Moreover, the
autosized cold water, hot water and steam flow rates in the
parent zone HVAC objects (e.g. FanCoils, UnitHeaters,
UnitVentilators, and VentilatedSlabs) and capacity in child
components are determined using the scalable sizing methods.
Sizing methods allowed for cooling and heating capacity
include: CoolingDesignCapacity,
HeatingDesignCapacity, CapacityPerFloorArea,
FractionOfAutosizedCoolingCapacity,
FractionOfAutosizedHeatingCapacity.
CoolingDesignCapacity: entered when it
is intended that user specifies either a hard sized cooling
capacity value or the simulation engine autosizes cooling
capacity value for the cooling design capacity.
HeatingDesignCapacity: entered when it
is intended that user specifies either a hard sized heating
capacity value or the simulation engine autosized heating
capacity value for the heating design capacity.
CapacityPerFloorArea: is entered when
it is intended that the simulation engine determines the
cooling or heating capacity from user specified capacity per
floor area value and the floor area of the zone served by the
zone HVAC equipment.
FractionOfAutosizedCoolingCapacity:
entered when it is intended that the simulation engine sizes
the cooling capacity from the user specified capacity
fraction and autosized cooling design capacity
value.
FractionOfAutosizedHeatingCapacity:
entered when it is intended that the simulation engine sizes
the heating capacity from the user specified capacity
fraction and autosized heating design capacity
value.
Unique identifier name of the DesignSpecification:ZoneHVAC:Sizing
object. This sizing specification object referenced by a zone
HVAC equipment whose design calculation will be made using the
input data of this object.
The input of this field must be the method used to
determine the cooling supply air volume flow rate. Input
allowed is either None, SupplyAirFlowRate,
FlowPerFloorArea,
FractionOfAutosizedCoolingAirflow, or
FlowPerCoolingCapacity. None means cooling coil is
not included in the zone HVAC equipment or this field may be
left blank. SupplyAirFlowRate means the user
specifies the magnitude of supply air flow rate or the program
calculates the design cooling supply air volume flow rate if
autosize is specified. FlowPerFloorArea means the
program calculates the cooling supply air volume flow rate
from zone floor area served by the zone HVAC unit and user
specified Flow Per Floor Area value.
FractionOfAutosizedCoolingAirflow means the program
calculates the cooling supply air volume flow rate from user
specified fraction and the autosized design cooling supply air
volume flow rate value determined by the simulation.
FlowPerCoolingCapacity means the supply air volume is
calculated from user specified flow per cooling capacity and
design cooling capacity determined by the simulation. The
default method is SupplyAirFlowRate.
Field:
Cooling Design Supply Air Flow Rate {m3/s}[LINK]
Enter the magnitude of the cooling supply air volume flow
rate in m3/s. This input is an alternative to using the
program auto-calculated value. This input is a required field
when the Cooling Design air Flow Method is
SupplyAirFlowRate. This field may be left blank if a
cooling coil is not included in the zone HVAC equipment. This
input field is also autosizable.
Field:
Cooling Design Supply Air Flow Rate Per Floor Area
{m3/s-m2}[LINK]
Enter the cooling supply air volume flow rate per zone
conditioned floor area in m3/s-m2. This field is required
field when the Cooling Design air Flow Method is
FlowPerFloorArea. This field may be left blank if a
cooling coil is not included in the zone HVAC equipment or the
Cooling Design Air Flow Method is not
FlowPerFloorArea. The program calculates the cooling
supply air volume flow rate from the zone conditioned floor
area served by the zone HVAC equipment and the flow per unit
area value specified by the user. Zone
sizing object (Sizing:Zone) is not required.
Field:
Fraction of Autosized Cooling Design Supply Air Flow Rate[LINK]
Enter the cooling supply air volume flow rate as a fraction
of the autosized cooling supply air flow rate. This input
field is required when the Cooling Design air Flow Method is
FractionOfAutosizedCoolingAirflow. This input field
may be left blank if a cooling coil is not included in the
zone HVAC equipment or the Cooling Design air Flow Method is
not FractionOfAutosizedCoolingAirflow. The program
calculates the cooling supply air volume flow rate from the
design autosized cooling supply air flow rate and user
specified fraction. Zone
sizing object (Sizing:Zone) is required.
Field:
Cooling Design Supply Air Flow Rate Per Unit Cooling Capacity
{m3/s-W}[LINK]
Enter the cooling supply air volume flow rate per unit
cooling capacity in m3/s-W. This input field is required when
the Cooling Design air Flow Method is
FlowPerCoolingCapacity. This field may be left blank
if a cooling coil is not included in the zone HVAC equipment
or the Cooling Design air Flow Method is not
FlowPerCoolingCapacity. The program calculates the
cooling supply air volume flow rate from the design autosized
cooling capacity and user specified flow per cooling capacity
value. Zone
sizing object (Sizing:Zone) is required.
Field:
Supply Air Flow Rate Method When No Cooling or Heating is
Required[LINK]
Enter the method used to determine the supply air volume
flow rate when No Cooling or Heating is required. Inputs
allowed are None, SupplyAirFlowRate,
FlowPerFloorArea,
FractionOfAutosizedCoolingAirflow, and
FractionOfAutosizedHeatingAirflow.None is
used when a cooling or heating coil is not included in the
zone HVAC equipment or this field may be left blank.
SupplyAirFlowRate means user specifies the magnitude
of supply air flow rate or the program calculates the design
supply air volume flow rate if autosize is specified.
FlowPerFloorArea means the program calculates the
supply air volume flow rate from the zone floor area served by
the zone HVAC unit and Flow Per Floor Area value specified by
user. FractionOfAutosizedCoolingAirflow means the
program calculates the supply air volume flow rate from user
specified fraction and autosized design cooling supply air
volume flow rate value determined by the program.
FractionOfAutosizedHeatingAirflow means the program calculates
the supply air volume flow rate from user specified fraction
and autosized heating supply air flow rate value determined by
the program. The default method is
SupplyAirFlowRate.
Field:
Supply Air Flow Rate When No Cooling or Heating is Required
{m3/s}[LINK]
Enter the magnitude of the supply air volume flow rate when
no cooling or heating is required in m3/s. This input is an
alternative to using the program auto-calculated value. This
input is a required field when the Supply Air Flow Rate Method
When No Cooling or Heating is Required is
SupplyAirFlowRate. This field may be left blank if a
cooling coil is not included in the zone HVAC equipment. This
input field is also autosizable.
Field:
Supply Air Flow Rate Per Floor Area When No Clg or Htg is
Required {m3/s-m2}[LINK]
Enter the magnitude of supply air volume flow rate per zone
floor area in m3/s-m2. This input is a required field when
Supply Air Flow Rate Method When No Cooling or Heating is
Required is FlowPerFloorArea. The program calculates
the supply air flow rate when no cooling or heating is
required from user specified flow per floor area and the zone
area served by current zoneHVAC equipment.
Field:
Fraction of Design Cooling Supply Air Flow Rate When No Clg or
Htg Required[LINK]
Enter the fraction of supply air volume flow rate as a
fraction of the autosized cooling supply air flow rate. This
input field is required field when Supply Air Flow Rate Method
When No Cooling or Heating is Required is
FractionOfAutosizedCoolingAirflow. The program
calculates the supply air flow rate when no cooling or heating
is required from user specified fraction and the design
cooling autosized supply air flow rate.
Field:
Fraction of Design Heating Supply Air Flow Rate When No Clg or
Htg Required[LINK]
Enter the fraction of supply air volume flow rate as a
fraction of the autosized cooling supply air flow rate. This
input field is required field when Supply Air Flow Rate Method
When No Cooling or Heating is Required is
FractionOfAutosizedHeatingAirflow. The program
calculates the supply air flow rate when no cooling or heating
is required from user specified fraction and the design
heating autosized supply air flow rate.
The input of this field must be the method used to
determine the heating supply air volume flow rate. Input
allowed is either None, SupplyAirFlowRate,
FlowPerFloorArea,
FractionOfAutosizedCoolingAirflow, or
FlowPerCoolingCapacity. None means heating
coil is not included in the zone HVAC equipment or this field
may be left blank. SupplyAirFlowRate means the user
specifies the magnitude of supply air flow rate or the program
calculates the design heating supply air volume flow rate if
autosize is specified. FlowPerFloorArea means the
program calculates the heating supply air volume flow rate
from zone floor area served by the zone HVAC unit and user
specified Flow Per Floor Area value.
FractionOfAutosizedHeatingAirflow means the program
calculates the heating supply air volume flow rate from user
specified fraction and the autosized design heating supply air
volume flow rate value determined by the simulation.
FlowPerHeatingCapacity means the supply air volume is
calculated from user specified flow per heating capacity and
design heating capacity determined by the simulation. The
default method is SupplyAirFlowRate.
Field:
Heating Design Supply Air Flow Rate {m3/s}[LINK]
Enter the magnitude of the heating supply air volume flow
rate in m3/s. This input is an alternative to using the
program auto-calculated value. This input is a required field
when the Heating Design air Flow Method is
SupplyAirFlowRate. This field may be left blank if a
heating coil is not included in the zone HVAC equipment. This
input field is also autosizable.
Field:
Heating Design Supply Air Flow Rate Per Floor Area
{m3/s-m2}[LINK]
Enter the heating supply air volume flow rate per zone
conditioned floor area in m3/s-m2. This field is required
field when the Heating Design air Flow Method is
FlowPerFloorArea. This field may be left blank if a
heating coil is not included in the zone HVAC equipment or the
Heating Design Air Flow Method is not
FlowPerFloorArea. The program calculates the heating
supply air volume flow rate from the zone conditioned floor
area served by the zone HVAC equipment and the flow per unit
area value specified by the user.
Field:
Fraction of Autosized Heating Design Supply Air Flow Rate[LINK]
Enter the heating supply air volume flow rate as a fraction
of the autosized heating supply air flow rate. This input
field is required when the Heating Design air Flow Method is
FractionOfAutosizedHeatingAirflow. This input field
may be left blank if a heating coil is not included in the
zone HVAC equipment or the Heating Design air Flow Method is
not FractionOfAutosizedHeatingAirflow. The program
calculates the heating supply air volume flow rate from the
design autosized heating supply air flow rate and user
specified fraction.
Field:
Heating Design Supply Air Flow Rate Per Unit Heating Capacity
{m3/s-W}[LINK]
Enter the heating supply air volume flow rate per unit
heating capacity in m3/s-W. This input field is required when
the Heating Design air Flow Method is
FlowPerHeatingCapacity. This field may be left blank
if a cooling coil is not included in the zone HVAC equipment
or the Heating Design air Flow Method is not
FlowPerHeatingCapacity. The program calculates the
heating supply air volume flow rate from the design autosized
heating capacity and user specified flow per unit heating
capacity value.
Enter the method used to determine the cooling design
capacity for scalable sizing. Input allowed is either
None, CoolingDesignCapacity,
CapacityPerFloorArea, and
FractionOfAutosizedCoolingCapacity. None is used when
a cooling coil is not included in the Zone
HVAC equipment or this field may be left blank. If this input
field is left blank, then the design cooling capacity is set
to zero. CoolingDesignCapacity means user specifies
the magnitude of cooling capacity or the program calculates
the design cooling capacity if autosize is specified.
CapacityPerFloorArea means the program calculates the
design cooling capacity from user specified cooling capacity
per floor area and floor area of the zone served by the HVAC
unit. FractionOfAutosizedCoolingCapacity means the
program calculates the design cooling capacity from user
specified fraction and the auto-sized design cooling capacity.
The default method is CoolingDesignCapacity.
Enter the magnitude of the cooling capacity in Watts. This
input is an alternative to using the program auto-calculated
cooling capacity value. This input is a required field when
the Cooling Design Capacity Method is
CoolingDesignCapacity. This field may be left blank
if a cooling coil is not included in the zone HVAC equipment
or alternative method is specified. This input field is
autosizable. Design day sizing run must be specified.
Field:
Cooling Design Capacity Per Floor Area {W/m2}[LINK]
Enter the cooling capacity per unit floor area in m3/s-m2.
This field is required field when the Cooling Design Capacity
Method is CapacityPerFloorArea. This field may be
left blank if a cooling coil is not included in the zone HVAC
equipment or the Cooling Design Capacity Method is not
CapacityPerFloorArea. The program calculates the
cooling capacity from floor area of the zone served by the
zone HVAC equipment and the cooling capacity per unit floor
area value specified by the user.
Field:
Fraction of Autosized Cooling Design Capacity[LINK]
Enter the cooling capacity as a fraction of the autosized
cooling capacity. This input field is required when the
Cooling Design Capacity Method is
FractionOfAutosizedCoolingCapacity. This input field
may be left blank if a cooling coil is not included in the
zone HVAC equipment or the Cooling Design Capacity Method is
not FractionOfAutosizedCoolingCapacity. The program
calculates the cooling capacity from the design autosized
cooling capacity and user specified fraction. Design day
sizing run must be specified.
Enter the method used to determine the heating design
capacity for scalable sizing. Input allowed is either
None, HeatingDesignCapacity,
CapacityPerFloorArea, and
FractionOfAutosizedHeatingCapacity. None is used when
a heating coil is not included in the Zone
HVAC equipment or this field may be left blank. If this input
field is left blank, then the design heating capacity is set
to zero. HeatingDesignCapacity means user specifies
the magnitude of heating capacity or the program calculates
the design heating capacity if autosize is specified.
CapacityPerFloorArea means the program calculates the
design heating capacity from user specified heating capacity
per floor area and floor area of the zone served by the HVAC
unit. FractionOfAutosizedHeatingCapacity means the
program calculates the design heating capacity from user
specified fraction and the auto-sized design heating capacity.
The default method is HeatingDesignCapacity.
Enter the magnitude of the heating capacity in Watts. This
input is an alternative to using the program auto-calculated
heating capacity value. This input is a required field when
the Heating Design Capacity Method is
HeatingDesignCapacity. This field may be left blank
if a heating coil is not included in the zone HVAC equipment
or alternative method is specified. This input field is
autosizable. Design day sizing run must be specified.
Field:
Heating Design Capacity Per Floor Area {W/m2}[LINK]
Enter the heating capacity per unit floor area in m3/s-m2.
This field is required field when the Heating Design Capacity
Method is CapacityPerFloorArea. This field may be
left blank if a heating coil is not included in the zone HVAC
equipment or the Heating Design Capacity Method is not
CapacityPerFloorArea. The program calculates the
heating capacity from floor area of the zone served by the
zone HVAC equipment and the heating capacity per unit floor
area value specified by the user.
Field:
Fraction of Autosized Heating Design Capacity[LINK]
Enter the heating capacity as a fraction of the autosized
heating capacity. This input field is required when the
Heating Design Capacity Method is
FractionOfAutosizedHeatingCapacity. This input field
may be left blank if a heating coil is not included in the
zone HVAC equipment or the Heating Design Capacity Method is
not FractionOfAutosizedHeatingCapacity. The program
calculates the heating capacity from the design autosized
cooling capacity and user specified fraction. Design day
sizing run must be specified.
DesignSpecification:ZoneHVAC:Sizing,
VRFDesignSpec1, !- Name
SupplyAirFlowRate, !- Cooling Design Air Flow Method
autosize, !- Cooling Design Supply Air Flow Rate
, !- Cooling Design Supply Air Flow Rate Per Floor Area
, !- Fraction of Autosized Cooling Design Supply Air Flow Rate
, !- Cooling Design Supply Air Flow Rate Per Unit of Capacity {m3/s-W}
SupplyAirFlowRate, !- Supply Air Flow Rate Method When No Cooling or Heating is Required
autosize, !- Supply Air Flow Rate When No Cooling or Heating is Required
, !- Supply Air Flow Rate Per Floor Area When No Clg or Htg is Required
, !- Fraction of Autosized Design Cooling Supply Air Flow Rate When No Clg or Htg
, !- Fraction of Autosized Design Heating Supply Air Flow Rate When No Clg or Htg
SupplyAirFlowRate, !- Heating Design Air Flow Method
autosize, !- Heating Design Supply Air Flow Rate
, !- Heating Design Supply Air Flow Rate Per Floor Area
, !- Fraction of Autosized Heating Design Supply Air Flow Rate
, !- Heating Design Supply Air Flow Rate Per Unit of Heating Capacity
CoolingDesignCapacity, !- Cooling Design Capacity Method
autosize, !- Cooling Design Capacity {W}
, !- Cooling Design Capacity Per Floor Area {W/m2}
, !- Fraction of Autosized Cooling Design Capacity {-}
HeatingDesignCapacity, !- Heating Design Capacity Method
autosize, !- Heating Design Capacity {W}
, !- Heating Design Capacity Per Floor Area {W/m2}
; !- Fraction of Autosized Cooling Design Capacity {-}
DesignSpecification:ZoneHVAC:Sizing,
VRFDesignSpec2, !- Name
FlowPerFloorArea, !- Cooling Design Air Flow Method
, !- Cooling Design Supply Air Flow Rate
3.6311418E-03, !- Cooling Design Supply Air Flow Rate Per Floor Area
, !- Fraction of Autosized Cooling Design Supply Air Flow Rate
, !- Cooling Design Supply Air Flow Rate Per Unit of Capacity {m3/s-W}
FlowPerFloorArea, !- Supply Air Flow Rate Method When No Cooling or Heating is Required
, !- Supply Air Flow Rate When No Cooling or Heating is Required
3.6311418E-03, !- Supply Air Flow Rate Per Floor Area When No Clg or Htg is Required
, !- Fraction of Autosized Design Cooling Supply Air Flow Rate When No Clg or Htg
, !- Fraction of Autosized Design Heating Supply Air Flow Rate When No Clg or Htg
FlowPerFloorArea, !- Heating Design Air Flow Method
, !- Heating Design Supply Air Flow Rate
3.6311418E-03, !- Heating Design Supply Air Flow Rate Per Floor Area
, !- Fraction of Autosized Heating Design Supply Air Flow Rate
, !- Heating Design Supply Air Flow Rate Per Unit of Heating Capacity
CoolingDesignCapacity, !- Cooling Design Capacity Method
autosize, !- Cooling Design Capacity {W}
, !- Cooling Design Capacity Per Floor Area {W/m2}
, !- Fraction of Autosized Cooling Design Capacity {-}
HeatingDesignCapacity, !- Heating Design Capacity Method
autosize, !- Heating Design Capacity {W}
, !- Heating Design Capacity Per Floor Area {W/m2}
; !- Fraction of Autosized Cooling Design Capacity {-}
DesignSpecification:ZoneHVAC:Sizing,
VRFDesignSpec3, !- Name
FractionOfAutosizedCoolingAirflow, !- Cooling Design Air Flow Method
, !- Cooling Design Supply Air Flow Rate
, !- Cooling Design Supply Air Flow Rate Per Floor Area
0.5, !- Fraction of Autosized Cooling Design Supply Air Flow Rate
, !- Cooling Design Supply Air Flow Rate Per Unit of Capacity {m3/s-W}
FractionOfAutosizedCoolingAirflow, !- Supply Air Flow Rate Method When No Cooling or Heating is Required
, !- Supply Air Flow Rate When No Cooling or Heating is Required
, !- Supply Air Flow Rate Per Floor Area When No Clg or Htg is Required
0.5, !- Fraction of Autosized Design Cooling Supply Air Flow Rate When No Clg or Htg
, !- Fraction of Autosized Design Heating Supply Air Flow Rate When No Clg or Htg
FractionOfAutosizedHeatingAirflow, !- Heating Design Air Flow Method
, !- Heating Design Supply Air Flow Rate
, !- Heating Design Supply Air Flow Rate Per Floor Area
0.5, !- Fraction of Autosized Heating Design Supply Air Flow Rate
, !- Heating Design Supply Air Flow Rate Per Unit of Heating Capacity
CoolingDesignCapacity, !- Cooling Design Capacity Method
autosize, !- Cooling Design Capacity {W}
, !- Cooling Design Capacity Per Floor Area {W/m2}
, !- Fraction of Autosized Cooling Design Capacity {-}
HeatingDesignCapacity, !- Heating Design Capacity Method
autosize, !- Heating Design Capacity {W}
, !- Heating Design Capacity Per Floor Area {W/m2}
; !- Fraction of Autosized Cooling Design Capacity {-}
DesignSpecification:ZoneHVAC:Sizing,
VRFDesignSpec4, !- Name
FlowPerCoolingCapacity, !- Cooling Design Air Flow Method
, !- Cooling Design Supply Air Flow Rate
, !- Cooling Design Supply Air Flow Rate Per Floor Area
, !- Fraction of Autosized Cooling Design Supply Air Flow Rate
2.9541628E-05, !- Cooling Design Supply Air Flow Rate Per Unit of Capacity {m3/s-W}
FractionOfAutosizedHeatingAirflow, !- Supply Air Flow Rate Method When No Cooling or Heating is Required
, !- Supply Air Flow Rate When No Cooling or Heating is Required
, !- Supply Air Flow Rate Per Floor Area When No Clg or Htg is Required
, !- Fraction of Autosized Design Cooling Supply Air Flow Rate When No Clg or Htg
0.413231177, !- Fraction of Autosized Design Heating Supply Air Flow Rate When No Clg or Htg
FlowPerHeatingCapacity, !- Heating Design Air Flow Method
, !- Heating Design Supply Air Flow Rate
, !- Heating Design Supply Air Flow Rate Per Floor Area
, !- Fraction of Autosized Heating Design Supply Air Flow Rate
2.9541628E-05, !- Heating Design Supply Air Flow Rate Per Unit of Heating Capacity
CoolingDesignCapacity, !- Cooling Design Capacity Method
autosize, !- Cooling Design Capacity {W}
, !- Cooling Design Capacity Per Floor Area {W/m2}
, !- Fraction of Autosized Cooling Design Capacity {-}
HeatingDesignCapacity, !- Heating Design Capacity Method
autosize, !- Heating Design Capacity {W}
, !- Heating Design Capacity Per Floor Area {W/m2}
; !- Fraction of Autosized Cooling Design Capacity {-}
Field:
Fraction of Design Sensible Cooling Load[LINK]
The fraction of the design sensible cooling load to be met
by this terminal unit. This fraction is applied after the Zone
Cooling Sizing Factor (see Sizing:Zone).
Field:
Cooling Design Supply Air Temperature Difference Ratio[LINK]
This ratio adjusts the supply air temperature difference
used to calculate the cooling design supply air flow rate for
this terminal unit.
Field:
Fraction of Design Sensible Heating Load[LINK]
The fraction of the design sensible heating load to be met
by this terminal unit. This fraction is applied after the Zone
Heating Sizing Factor (see Sizing:Zone).
Field:
Heating Design Supply Air Temperature Difference Ratio[LINK]
This ratio adjusts the supply air temperature difference
used to calculate the heating design supply air flow rate for
this terminal unit.
The fraction of the zone minimum outdoor air requirement to
be met by this terminal unit.
An IDF example:
DesignSpecification:AirTerminal:Sizing,
Recirculation System A Terminal Sizing, !- Name
0.6, !- Fraction of Design Cooling Load
0.8, !- Cooling Design Supply Air Temperature Difference Ratio
1.0, !- Fraction of Design Heating Load
1.0, !- Heating Design Supply Air Temperature Difference Ratio
0.0; !- Fraction of Minimum Outdoor Air Flow
The Sizing:System
object contains the input needed to perform a central forced
air system design air flow, heating capacity, and cooling
capacity calculation for a system serving one or more zones.
The information needed consists of the outside environmental
conditions and the design supply air temperatures, outdoor air
flow rate, and minimum system air flow ratio.
The outside conditions come from the design days in the
input. A system sizing calculation is performed for every
design day in the input file and the resulting maximum heating
and cooling air flow rates and capacities are saved for use in
the component sizing calculations.
Supply air conditions are specified by inputting a supply
air temperature for cooling, a supply air temperature for
heating, and a preheat temperature.
The system sizing calculation sums the zone design air flow
rates to obtain a system supply air flow rate. The design
conditions and the outdoor air flow rate are used to calculate
a design mixed air temperature. The temperature plus the
design supply air temperatures allows the calculation of
system design heating and cooling capacities.
The name of the AirLoopHVAC
corresponding to this Sizing:System
object. This is the air system for which the design
calculation will be made using the input data of this Sizing:System
Object.
The user specified type of load on which to size the
central system. The choices are Sensible,
Total and VentilationRequirement.
Sensible and Total mean that the central
system supply air flow rate will be determined by combining
the zone design air flow rates, which have been calculated to
meet the zone sensible loads from the design days.
VentilationRequirement means that the central system
supply air flow rate will be determined by the system
ventilation requirement. In addition Sensible tells
the program to size the central cooling coil using entering
air flow rate and air conditions at the sensible load peak;
Total indicates that the program should size the
central cooling coil at the air flow rate and conditions at
the total load peak. The central heating coil is always sized
at the conditions at the peak sensible heating load.
The design outdoor air flow rate in cubic meters per
second. Generally this should be the minimum outdoor air flow.
It is used for both heating and cooling design calculations.
The assumption for cooling is that any outdoor air economizer
will be closed. If Autosize is input the outdoor air
flow rate will be taken from the sum of the zone outdoor air
flow rates or calculated based on the System Outdoor Air
Method selection (field below).
Field:
Central Heating Maximum System Air Flow Ratio[LINK]
The ratio of the maximum system air flow rate for heating
to the maximum system air flow rate. The value must be between
0 and 1. For constant volume systems the ratio should be set
to 1. This ratio should be set to reflect what the user
expects the system flow rate to be when maximum heating demand
occurs. This ratio is used in calculating the central system
heating capacity. Thus if the system is VAV with the zone VAV
dampers held at minimum flow when there is a zone heating
demand, this ratio should be set to the minimum flow ratio. If
the zone VAV dampers are reverse action and can open to full
flow to meet heating demand, this ratio should be set to 1.
The default is set to 0.5, reflecting the fact that VAV
dampers are typically not allowed to fully open during
heating.
This field can be set to AutoSize. When
automatically calculated, the ratio is determined from the
system heating design flow rate divided by the main (which is
usually the max of heating and cooling design flow rates)
design flow rate. The design flow rates are also adjusted to
be more accurate by examining each of the air terminals
attached to the air system and summing the heating and maximum
flow rates.
The design humidity ratio exiting the precooling coil (if
any) in kilograms of water per kilogram of dry air.
(kgWater/kgDryAir)
Field:
Central Cooling Design Supply Air Temperature[LINK]
The design supply air temperature for cooling in degrees
Celsius. This should be the temperature of the air exiting the
central cooling coil.
Field:
Central Heating Design Supply Air Temperature[LINK]
The design supply air temperature for heating in degrees
Celsius. This can be either the reset temperature for a single
duct system or the actual hot duct supply air temperature for
dual duct systems. It should be the temperature at the exit of
the main heating coil. This value is also used for the sizing
of zone equipment (e.g., reheat coil) for the system embedded
with central heating coils, but it is not used if there is no
central heating coil in the system.
If the input is coincident the central system air
flow rate will be sized on the sum of the coincident zone air
flow rates. If the input is noncoincident the central
system air flow rate will be sized on the sum of the
noncoincident zone air flow rates. The default is
noncoincident.
Entering Yes means the system will be sized for
cooling using 100% outdoor air. Entering No means the
system will be sized for cooling using minimum outside air
(the default).
Entering Yes means the system will be sized for
heating using 100% outdoor air. Entering No means the
system will be sized for heating using minimum outside air
(the default).
Field:
Central Cooling Design Supply Air Humidity Ratio[LINK]
The design humidity ratio in kilograms of water per
kilogram of dry air at the exit of the central cooling coil.
The default is 0.008 (kgWater/kgDryAir).
Field:
Central Heating Design Supply Air Humidity Ratio[LINK]
The design humidity ratio in kilograms of water per
kilogram of dry air at the exit of the central heating coil.
This value is also used for the sizing of zone equipment
(e.g., reheat coil) for the system embedded with central
heating coils, but it is not used if there is no central
heating coil in the system. The default is 0.008
(kgWater/kgDryAir).
The input of this field must be the method used to
determine the airloop cooling supply air volume flow rate. The
input must be either, DesignDay,
Flow/System,FlowPerFloorArea,
FractionOfAutosizedCoolingAirflow, or
FlowPerCoolingCapacity. DesignDay means the
program will calculate the system design cooling supply air
volume flow rate using the System Sizing input data and a
design day simulation. Flow/System means that the
program will use the input of the field Cooling Design Air
Flow Rate as the system design cooling supply air volume
flow rate. FlowPerFloorArea means the program
calculates the cooling supply air volume flow rate from zone
floor area served by the airloop and user specified Flow
Per Floor Area value.
FractionOfAutosizedCoolingAirflow means the program
calculates the cooling supply air volume flow rate from user
specified fraction and the autosized design cooling supply air
volume flow rate value determined by the simulation.
FlowPerCoolingCapacity means the supply air volume is
calculated from user specified flow per cooling capacity and
design cooling capacity determined by the simulation. The
default method is DesignDay: i.e., the program uses
the calculated design values.
The design system cooling air flow rate in cubic meters per
second. This input is an alternative to using the program
autocalculated value. This input is used if Coolingi Supply
Air Flow Rate Method is Flow/System. This value will
not be multiplied by any sizing factor or by zone
multipliers. If using zone multipliers, this value must be
large enough to serve the multiplied zones.
Field:
Cooling Supply Air Flow Rate Per Floor Area {m3/s-m2}[LINK]
Enter the cooling supply air volume flow rate per zone
conditioned floor area in m3/s-m2. This field is required
field when the Cooling Supply Air Flow Rate Method is
FlowPerFloorArea. This field may be left blank if a
cooling coil is not included in the airloop or the Cooling
Supply Air Flow Rate Method is not FlowPerFloorArea.
The program calculates the cooling supply air volume flow rate
from the cooled floor area served by the air loop and the
Flow Per Unit Area value specified by the user.
Field:
Cooling Fraction of Autosized Cooling Design Supply Air Flow
Rate[LINK]
Enter the cooling supply air volume flow rate as a fraction
of the airloop autosized cooling supply air flow rate. This
input field is required when the Cooling Supply Air Flow Rate
Method is FractionOfAutosizedCoolingAirflow. This
input field may be left blank if a cooling coil is not
included in the airloop or the Cooling Supply Air Flow Rate
Method is not FractionOfAutosizedCoolingAirflow. The
program calculates the cooling supply air volume flow rate
from the design autosized cooling supply air flow rate and
user specified fraction.
Field:
Cooling Supply Air Flow Rate Per Unit Cooling Capacity
{m3/s-W}[LINK]
Enter the cooling supply air volume flow rate per unit
cooling capacity in m3/s-W. This input field is required when
the Cooling Supply Air Flow Rate Method is
FlowPerCoolingCapacity. This field may be left blank
if a cooling coil is not included in the airloop or the
Cooling Supply Air Flow Rate Method is not
FlowPerCoolingCapacity. The program calculates the
airloop cooling supply air volume flow rate from the design
autosized cooling capacity and user specified Flow Per
Cooling Capacity value.
The input of this field must be the method used to
determine the airloop heating supply air volume flow rate. The
input must be either, DesignDay,
Flow/System,FlowPerFloorArea,
FractionOfAutosizedHeatingAirflow,
FractionOfAutosizedCoolingAirflow or
FlowPerHeatingCapacity. DesignDay means the
program will calculate the system design heating supply air
volume flow rate using the System Sizing input data and a
design day simulation. Flow/System means that the
program will use the input of the field Heating Design Air
Flow Rate as the system design heating supply air volume
flow rate. FlowPerFloorArea means the program
calculates the system heating supply air volume flow rate from
zone floor area served by the airloop and user specified
Flow Per Floor Area value.
FractionOfAutosizedHeatingAirflow means the program
calculates the system heating supply air volume flow rate from
user specified fraction and the autosized system design
heating supply air volume flow rate value determined by the
simulation. FractionOfAutosizedCoolingAirflow means
the program calculates the system heating supply air volume
flow rate from user specified fraction and the autosized
system design cooling supply air volume flow rate value
determined by the simulation. FlowPerHeatingCapacity
means the system heating supply air volume is calculated from
user specified flow per heating capacity and design heating
capacity determined by the simulation. The default method is
DesignDay: i.e., the program uses the calculated
design values.
The design system heating air flow rate in cubic meters per
second. This input is an alternative to using the program
autocalculated value. This input is used if Heating Supply Air
Flow Rate Method is Flow/System. This value will not
be multiplied by any sizing factor or by zone multipliers. If
using zone multipliers, this value must be large enough to
serve the multiplied zones.
Field:
Heating Supply Air Flow Rate Per Floor Area {m3/s-m2}[LINK]
Enter the heating supply air volume flow rate per zone
conditioned floor area in m3/s-m2. This field is required
field when the Heating Supply Air Flow Rate Method is
FlowPerFloorArea. This field may be left blank if a
heating coil is not included in the airloop or the Heating
Supply Air Flow Rate Method is not FlowPerFloorArea.
The program calculates the heating supply air volume flow rate
from the heated or cooled floor area served by the air loop
and the Flow Per Unit Area value specified by the
user.
Field:
Heating Fraction of Autosized Heating Supply Air Flow
Rate[LINK]
Enter the heating supply air volume flow rate as a fraction
of the airloop autosized heating supply air flow rate. This
input field is required when the Heating Supply Air Flow Rate
Method is FractionOfAutosizedHeatingAirflow. This
input field may be left blank if heating coil is not included
in the airloop or the Heating Supply Air Flow Rate Method is
not FractionOfAutosizedHeatingAirflow. The program
calculates the heating supply air volume flow rate from the
design autosized heating supply air flow rate and user
specified fraction.
Field:
Heating Fraction of Autosized Cooling Supply Air Flow
Rate[LINK]
Enter the heating supply air volume flow rate as a fraction
of the airloop autosized cooling supply air flow rate. This
input field is required when the Heating Supply Air Flow Rate
Method is FractionOfAutosizedCoolingAirflow. This
input field may be left blank if heating coil is not included
in the airloop or the Heating Supply Air Flow Rate Method is
not FractionOfAutosizedCoolingAirflow. The program
calculates the heating supply air volume flow rate from the
design autosized cooling supply air flow rate and user
specified fraction.
Field:
Heating Design Supply Air Flow Rate Per Unit Heating Capacity
{m3/s-W}[LINK]
Enter the heating supply air volume flow rate per unit
heating capacity in m3/s-W. This input field is required when
the Heating Design air Flow Method is
FlowPerCoolingCapacity. This field may be left blank
if a heating coil is not included in the airloop or the
Heating Design air Flow Method is not
FlowPerHeatingCapacity. The program calculates the
airloop heating supply air volume flow rate from the design
autosized heating capacity and user specified Flow Per
Heating Capacity value.
The method used to calculate the system minimum outdoor air
flow. The two choices are ZoneSum and VentilationRateProcedure
(VRP). ZoneSum sums the outdoor air flows across all zones
served by the system. VRP uses the multi-zone equations
defined in 62.1-2007 to calculate the system outdoor air flow.
VRP considers zone air distribution effectiveness and zone
diversification of outdoor air fractions. VRP may also adjust
autosized air terminal maximum and minimum supply flow rates
if needed to ensure adequate outdoor air flow rate to each
zone.
This positive numeric input is the zone maximum outdoor air
fraction. For an air loop, when a zone requires outdoor air
higher than the user specified Zone
Maximum Outdoor Air Fraction, the zone supply air flow will be
increased to cap the outdoor air fraction at the maximum
value. This allows the system level outdoor air flow to be
reduced while the total supply air flow increases. Valid
values are from 0 to 1.0. Default is 1.0 which indicates zones
can have 100% outdoor air maintaining backward compatibility.
This inputs work for constant volume air systems, single and
dual duct VAV systems.
Enter the method used to determine the cooling design
capacity for scalable sizing. Input allowed is either
None, CoolingDesignCapacity,
CapacityPerFloorArea, and
FractionOfAutosizedCoolingCapacity. None is used when
a cooling coil is not included in the airloop. If this input
field is left blank, or None is specified, then the autosized
design cooling capacity determined by the program is used.
CoolingDesignCapacity means user specifies the
magnitude of cooling capacity or the program calculates the
design cooling capacity if autosize is specified.
CapacityPerFloorArea means the program calculates the
design cooling capacity from user specified cooling capacity
per floor area and floor area of the zones served by the
airloop. FractionOfAutosizedCoolingCapacity means the
program calculates the design cooling capacity from user
specified fraction and the auto-sized design cooling capacity.
If the value this input field is blank or specified as None,
then the next three input fields are not required. The default
method is CoolingDesignCapacity.
Enter the magnitude of the cooling capacity in Watts. This
input is an alternative to using the program auto-calculated
cooling capacity value. This input is a required field when
the Cooling Design Capacity Method is
CoolingDesignCapacity. This field may be left blank
if a cooling coil is not included in the air loop or
alternative method is specified. This input field is
autosizable.
Field:
Cooling Design Capacity Per Floor Area {W/m2}[LINK]
Enter the cooling capacity per unit floor area in m3/s-m2.
This field is required field when the Cooling Design Capacity
Method is CapacityPerFloorArea. This field may be
left blank if a cooling coil is not included in the airloop or
the Cooling Design Capacity Method is not
CapacityPerFloorArea. The program calculates the
cooling capacity from floor area of the zones served by the
airloop and the cooling capacity per unit floor area value
specified by the user.
Field:
Fraction of Autosized Cooling Design Capacity[LINK]
Enter the cooling capacity as a fraction of the autosized
cooling capacity. This input field is required when the
Cooling Design Capacity Method is
FractionOfAutosizedCoolingCapacity. This input field
may be left blank if a cooling coil is not included in the
zone HVAC equipment or the Cooling Design Capacity Method is
not FractionOfAutosizedCoolingCapacity. The program
calculates the cooling capacity from the design autosized
cooling capacity and user specified fraction. Design day
sizing run must be specified.
Enter the method used to determine the heating design
capacity for scalable sizing. Input allowed is either
None, HeatingDesignCapacity,
CapacityPerFloorArea, and
FractionOfAutosizedHeatingCapacity. None is
used when a heating coil is not included in the airloop. If
this input field is left blank, then the autosized design
heating capacity determined by the program is used.
HeatingDesignCapacity means user specifies the
magnitude of heating capacity or the program calculates the
design heating capacity if autosize is specified.
CapacityPerFloorArea means the program calculates the
design heating capacity from user specified heating capacity
per floor area and floor area of the zones served by the
airllop. FractionOfAutosizedHeatingCapacity means the
program calculates the design heating capacity from user
specified fraction and the auto-sized design heating capacity.
If the value this input field is blank or specified as None,
then the next three input fields are not required. The default
method is HeatingDesignCapacity.
Enter the magnitude of the heating capacity in Watts. This
input is an alternative to using the program auto-calculated
heating capacity value. This input is a required field when
the Heating Design Capacity Method is
HeatingDesignCapacity. This field may be left blank
if a heating coil is not included in the airloop or
alternative method is specified. This input field is
autosizable.
Field:
Heating Design Capacity Per Floor Area {W/m2}[LINK]
Enter the heating capacity per unit floor area in m3/s-m2.
This field is required field when the Heating Design Capacity
Method is CapacityPerFloorArea. This field may be
left blank if a heating coil is not included in the airloop or
the Heating Design Capacity Method is not
CapacityPerFloorArea. The program calculates the
heating capacity from floor area of the zones served by the
airloop and the heating capacity per unit floor area value
specified by the user.
Field:
Fraction of Autosized Heating Design Capacity[LINK]
Enter the heating capacity as a fraction of the autosized
heating capacity. This input field is required when the
Heating Design Capacity Method is
FractionOfAutosizedHeatingCapacity. This input field may be
left blank if heating coil is not included in the airloop or
the Heating Design Capacity Method is not
FractionOfAutosizedHeatingCapacity. The program calculates the
heating capacity from the design autosized cooling capacity
and user specified fraction.
Field:
Central Cooling Capacity Control Method[LINK]
Specifies how the central cooling coil will be controlled,
which affects the coil sizing calculation. There are 4
choices: VAV, Bypass, VT, and OnOff. Choose VAV if the cooling
output is controlled by varying the air flow. Bypass should be
chosen if the capacity is controlled by bypassing a variable
fraction of the mixed air around the coil face. VT indicates
that cooling coil output is controlled by varying the coil
exit temperature while the flow rate is constant. And OnOff
means that the cooling output is controlled by cycling the air
flow.
An IDF example:
Sizing:System,
VAV Sys 1, !- AirLoop Name
sensible, !- Type of Load to Size On
autosize, !- Design Outdoor Air Flow Rate {m3/s}
0.3, !- Minimum System Air Flow Ratio
4.5, !- Preheat Design Temperature {C}
.008, !- Preheat Design Humidity Ratio {kgWater/kgDryAir}
11.0, !- Precool Design Temperature {C}
.008, !- Precool Design Humidity Ratio {kgWater/kgDryAir}
12.8, !- Central Cooling Design Supply Air Temperature {C}
16.7, !- Central Heating Design Supply Air Temperature {C}
noncoincident, !- Sizing Option
no, !- 100% Outdoor Air in Cooling
no, !- 100% Outdoor Air in Heating
0.008, !- Central Cooling Design Supply Air Humidity Ratio {kgWater/kgDryAir}
0.008, !- Central Heating Design Supply Air Humidity Ratio {kgWater/kgDryAir}
designday, !- Cooling Supply Air Flow Rate Method
0, !- 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 Cooling Capacity {m3/s-W}
designday, !- Heating Supply Air Flow Rate Method
0, !- 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 Fraction of Autosized Cooling Supply Air Flow Rate {-}
, !- Heating Supply Air Flow Rate Per Unit Heating Capacity {m3/s-W}
ZoneSum, !- System Outdoor Air Method
0.5, !- Zone Maximum Outdoor Air Fraction
CoolingDesignCapacity, !- Cooling Design Capacity Method
autosize, !- Cooling Design Capacity {W}
, !- Cooling Design Capacity Per Floor Area {W/m2}
, !- Fraction of Autosized Cooling Design Capacity {-}
HeatingDesignCapacity, !- Heating Design Capacity Method
autosize, !- Heating Design Capacity {W}
, !- Heating Design Capacity Per Floor Area {W/m2}
; !- Fraction of Autosized Cooling Design Capacity {-}
The system design air flow rates and heating and cooling
capacities are output onto the local file
“eplusssz.<ext>” where <ext> is the extension from
the sizing style object (default is csv – a comma separated
file eplusssz.csv). The columns are clearly labeled.
It will easily import into Excel or other spreadsheet program
that accepts delimited files. The results are calculated
values and do not include any user input system flow
rates.
The calculated system design air flow rates and the user
input system design air flow rates are also reported on the
eplusout.eio file. The values are printed out for
each system as comma separated records beginning with
System Sizing. An example is:
! <System Sizing Information>c++, System Name, Field Description, Value
System Sizing, VAV SYS 1, Calculated Cooling Design Air Flow Rate [m3/s], 1.3194
System Sizing, VAV SYS 1, User Cooling Design Air Flow Rate [m3/s], 1.5000
System Sizing, VAV SYS 1, Calculated Heating Design Air Flow Rate [m3/s], 0.90363
System Sizing, VAV SYS 1, User Heating Design Air Flow Rate [m3/s], 1.0000
The Sizing:Plant
object contains the input needed for the program to calculate
plant loop flow rates and equipment capacities when
autosizing. This information is initially used by components
that use water for heating or cooling such as hot or chilled
water coils to calculate their maximum water flow rates. These
flow rates are then summed for use in calculating the Plant
Loop flow rates.
The program will size any number of chilled water, hot
water, condenser water and other plant loops. There should be
one Sizing:Plant
object for each plant loop that is to be autosized.
The name of a Plant Loop or Condenser Loop object
corresponding to this Sizing:Plant
object. This is the plant loop for which this data will be
used for calculating the loop flow rate.
The water temperature in degrees Celsius at the exit of the
supply side of the plant loop, Thus this is the temperature of
the water supplied to the inlet of chilled or hot water coils
and other equipment that places loads on a plant loop.
The design temperature rise (for cooling or condenser
loops) or fall (for heating loops) in degrees Celsius across
the demand side of a plant loop. This temperature difference
is used by component models to determine flow rates required
to meet design capacities. Larger values lead to smaller
design flow rates.
This field is optional. This field controls how concurrence
issues impact the plant loop design flow rate. If it is not
used then the program uses noncoincident method, which is the
historical behavior prior to version 8.3. There are two
choices, noncoincident and coincident. The use of Coincident
sizing option requires that the SimulationControl
object be set to YES for the input field called Do HVAC Sizing
Simulation for Sizing Periods.
This field is optional and is only used if the preceding
field is set to Coincident. This is the number of zone
timesteps used in a moving average to determine the design
flow rate from HVAC Sizing Simulation approach. This allows
using a broader average over time when using coincident plant
sizing. This is similar in concept to the similar field in Sizing:Parameters
which specifies the averaging window for zone loads. The
default is 1.
This field is only used if the sizing option is set to
Coincident. This field controls the behavior of coincident
sizing with respect to what, if any, sizing factor should be
applied to further modify the flow rate measured while running
HVAC Sizing Simulations. There are four options. Enter the
keword None to use the raw value for flow rate without
modification. Enter the keyword GlobalHeatingSizingFactor to
modify the flow by the sizing factor entered in the object
called Sizing:Parameters
for heating. Enter the keyword GlobalCoolingSizingFactor to
modify the flow by the sizing factor entered in the object
called Sizing:Parameters
for cooling. Enter the keyword LoopComponentSizingFactor to
modify the flow by a sizing factor determined from the
combination of component-level sizing factors in the
associated plant loop.
An IDF example:
Sizing:Plant,
Chilled Water Loop, ! name of loop
Cooling, ! type of loop
7.22, ! chilled water supply temperature
6.67, ! chilled water delta T
NonCoincident, !- Sizing Option
1, !- Zone Timesteps in Averaging Window
GlobalCoolingSizingFactor; !- Coincident Sizing Factor Mode
The loop flow rates are reported on the
eplusout.eio file along with the component sizing
results.
When coincident plant sizing method is used, the eio file
contains special summary report with various details and
interim values from the calculations, under the following
record header: ! , Plant Loop Name, Sizing Pass {#}, Measured
Mass Flow{kg/s}, Measured Demand {W}, Demand Calculated Mass
Flow{kg/s}, Sizes Changed {Yes/No}, Previous Volume Flow Rate
{m3/s}, New Volume Flow Rate {m3/s}, Demand Check Applied
{Yes/No}, Sizing Factor {}, Normalized Change {}, Specific
Heat{}.
Group – Design Objects[LINK]
Input for Design Calculations and Component Autosizing[LINK]
Overview[LINK]
In order for EnergyPlus to successfully calculate zone design heating and cooling loads and air flow rates and for the program to use these results to automatically size the HVAC components a number of input objects must be present and certain object input fields must be entered.
The input file should contain a SimulationControl object. The 1\(^{st}\) field Do Zone Sizing Calculation should be entered as Yes. This will cause a zone sizing simulation to be done using all the sizing periods in the input file as weather. If there are no air or water loops in the HVAC input fields 2 and 3 can be set to No. If there are one or more air loops (i.e., there is at least one AirLoopHVAC object in the input file) then the 2\(^{nd}\) field Do System Sizing Calculation should be entered as Yes. If there are one or more water loops (Plant Loop objects) then the 3\(^{rd}\) field Do Plant Sizing Calculation should be set to Yes. Finally either the 4\(^{th}\) field (Run Simulation for Sizing Periods) or the 5\(^{th}\) field (Run Simulation for Weather File Run Periods) should be set to Yes in order to autosize the components and do a real simulation using the autosized components. The component autosizing calculations are done on the first pass through the HVAC system in the real simulation.
There must be at least 2 (up to any number) SizingPeriod objects present. Normally one will be for summer conditions and one for winter. The summer day should normally have the field Day Type set to SummerDesignDay. The winter design day should normally have Day Type set to WinterDesignDay.
To apply a global sizing factor include the Sizing:Parameters object.
For each controlled zone in the input file there should be a corresponding Sizing:Zone object. Similarly for each AirLoopHVAC there should be a Sizing:System object. And for each Plant or Condenser Loop there should be a Sizing:Plant object. Note however that if a controlled zone has no corresponding Zone Sizing object the data from the first Zone Sizing object will be used. Thus if all the zone sizing information is the same only one Zone Sizing object need be entered.
Only controlled zones are included in the zone and system sizing calculations. Thus for a design air flow rate to be calculated for a zone, it must contain a thermostat even though it might not need or have a thermostat in the full simulation. An illustration would be a three zone building with a packaged single zone system and a thermostat in one of the zones. In order for the two slave zones to be included in the design air flow calculations they must be treated as if they have a thermostat: there must be a ZoneControl:Thermostat for each of the slave zones.
Some attention should be paid to schedules. In a weekly schedule object the 9\(^{th}\) and 10\(^{th}\) day schedules are for summer and winter design days respectively. This means that if a SizingPeriod object has field Day Type set to SummerDesignDay the day schedule for summer sizing periods will be in effect. Similarly if a SizingPeriod object has field Day Type set to WinterDesignDay the day schedule for winter sizing periods will be in effect. Some possible applications of this capability are:
1) setting internal loads (lights, equipment, occupancy) to maximum all day for cooling and to zero all day for heating;
2) setting heating and cooling thermostat set points to constant values (no set up or set back);
3) setting heating and cooling equipment to be always on.
None of these applications are necessarily recommended but these and other uses of the special summer/winter design day schedules may prove useful for specific situations.
Other than zone thermostat setpoints, the sizing calculations generally know nothing about the system control inputs such as setpoints and availability schedules. The user must coordinate sizing inputs with the actual simulation control inputs.
The sizing calculations only recognize the presence of central heating and cooling coils, preheat and precool coils and reheat coils. These are assumed to deliver the various supply temperatures specified in the Sizing:System and Sizing:Zone objects. The impact of other components such as heat recovery, dehumidifiers, and pumps are not accounted for in the sizing calculations. Central supply and return fan temperature rise is taken into account in sizing the central cooling coils.
Component Autosizing[LINK]
For autosizing to occur at the component level the user must enter the special value autosize in the numeric fields for which autosizing is available. Those fields can be found by looking at the Energy+.idd data dictionary file or under individual object details in this document. Fields that can be autosized are denoted with the comment \autosizable. The components and fields that are autosizable are listed in the following table. Note that spaces may be inserted in object names to facilitate readability.
There are 3 places in the input where the user can impose sizing factors.
1. In Sizing Parameters (object: Sizing:Parameters), the user can specify an over-all sizing factor. This factor is applied to all the zone design loads and air flow rates resulting from the zone sizing calculations.
2. In Zone Sizing (object: Sizing:Zone), the user can specify a sizing factor for a specific zone. The factor is applied to the calculated zone design loads and air flow rates for the zone named in the Sizing:Zone object. This sizing factor overrides the global sizing factor. That is, a zone sizing factor, if specified, replaces the global sizing factor for the named zone.
3. For some plant components (basically all central chillers, boilers and cooling towers) the user can specify a sizing factor that modifies the autosized component capacity and flow rates. These factors are applied after the application of global or zone sizing factors. They are primarily used to split the design load between multiple components. These sizing factors can change the autosizing of the associated loops and pumps. The following rules are followed the effect of plant component sizing factors on loops and pumps.
a. For supply side branches, the sizing factors of all components in series on the branch are summed and the result becomes the branch sizing factor. If there is a branch pump its autosized design flow rate is multiplied by the branch sizing factor.
b. For each loop, if the average of the branch sizing factors is less than 1, the loop sizing factor is set equal to the sum of the branch sizing factors. If the average is greater than 1, the loop sizing factor is set equal to the maximum of the branch sizing factors. The loop sizing factor is applied to the loop design flow rate (if autosized) and to the loop pump flow rate (if autosized).
Mixing User-Specified and Autosized Inputs[LINK]
Mixed user-specified and autosized inputs can be successfully used if the following points and suggestions are followed.
1. Each component is autosized independently. Thus user input for a flow rate in one component will have no effect on other components’ autosized flow rates. For instance, specifying the chilled water loop pump’s rated flow rate will have no effect on the autosizing of the chiller’s design evaporator flow rate or on the plant loop’s autosized maximum loop flow rate.
2. Within a component it is best to autosize all inputs are enter specified values for all inputs. For example, in a chiller, if only the nominal capaciity is user-specified, the autosized chilled water flow rate may not be consistent with the specified capacity.
3. Sizing information flows only from the sizing objects to the components. The sizing calculations have no knowledge of user-specified values in a component. The only exception to this rule is that plant loop sizing will collect all component design water flow rates whether autosized or user-specified.
4. If the user wants to specify a zone or system air flow rate it should be done using the Sizing:Zone and Sizing:System objects rather than done in the individual components.
5. The plant loop flow rates are sized from the total design demand of the components connected to each loop. The components demanding water need not be autosized for the plant loop autosizing to work successfully. So the user could specify all the air side components and autosize all the plant loops and plant components. Or specify the chilled water loop flow rate, chilled water pump inputs and chiller inputs and let the condenser loop and tower autosize.
Component Sizing Output[LINK]
The results of the component autosizing calculations are reported on the eplusout.eio file. For each component field that has been autosized the object type, object name, field description with unit, and value are printed out as comma separated data on a line beginning with Component Sizing. Examples of this are shown in the Output Details and Examples document.
The complete list of objects that have autosized fields is shown in the following table. Note that spaces may be inserted in object names to facilitate readability.
User or External Zone Design Flow Rate Inputs[LINK]
In EnergyPlus the autosizing calculations start with a calculation of the zone design air flow rates using zone by zone design day simulations. The resulting zone design air flow rates and daily air flow sequences are used in the subsequent HVAC and central plant air and fluid flow design calculations and in the component autosizing calculations. The user can override or change the calculated zone design air flow rates in several ways.
1) The user can enter a value for Sizing Factor in the Sizing:Parameters object (see description below).
2) The user can specify a zone level Zone Sizing Factor in each Sizing:Zone object.
3) For each zone the user can input a Cooling Design Air Flow Rate and/or a Heating Design Air Flow Rate (and specify Cooling Design Air Flow Method = Flow/Zone and Heating Design Air Flow Method = Flow/Zone). These user inputs override the calculated values. The program divides the user input cooling or heating design air flow rate by the calculated values and uses the result as a zone sizing factor to multiply all the elements in the design heating and cooling air flow and load sequences. From this point the design calculations proceed as usual.
User or External System Design Flow Rate Inputs[LINK]
Using the results of the zone design air flow rate calculation (including any user input or altered flow rates) EnergyPlus proceeds to calculate central air system flow rates and cooling and heating loads. The results of this calculation can be overridden in the following way.
For each system (AirLoopHVAC), in the corresponding Sizing:System object, specify Cooling Design Air Flow Method to be Flow/System and input a value for Cooling Design Air Flow Rate. Similarly for heating specify Heating Design Air Flow Method to be Flow/System and input a value for Heating Design Air Flow Rate.
DesignSpecification:OutdoorAir[LINK]
This object allows for the outdoor air requirements to be defined in a common location for use by other objects. This object may be referenced by name from other objects (e.g., VAV terminal units, AirTerminal:SingleDuct:Uncontrolled, and AirTerminal:SingleDuct:Mixer) as required to identify an outdoor air quantity for use by that object. Note that a zone name Is not included as an input to this zone outdoor air definition and the number of people in a zone, zone floor area, and zone volume can only be determined after this object has been referenced by another. A single zone outdoor air definition may be referenced by multiple objects to specify that the same outdoor air requirements are used by those objects or multiple zone outdoor air objects may be defined and referenced by other objects as needed. If multiple zone outdoor air definitions are used, each outdoor air definition must have a unique name.
Inputs[LINK]
Field: Name[LINK]
Unique identifying name. Any reference to this name by other objects will denote that the following outdoor air requirements will be used.
Field: Outdoor Air Method[LINK]
The input must be either Flow/Person, Flow/Area, Flow/Zone, AirChanges/Hour, Sum, Maximum, IndoorAirQualityProcedure, ProportionalControlBasedOnDesignOccupancy, or ProportionalControlBasedonOccupancySchedule. The default is Flow/Person.
Flow/Person means the program will use the input from the field Outdoor Air Flow per Person and the actual zone occupancy to calculate a zone outdoor air flow rate.
Flow/Area means that the program will use the input from the field Outdoor Air Flow per Zone Floor Area and the actual zone floor area as the zone outdoor air flow rate.
Flow/Zone means that the program will use the input of the field Outdoor Air Flow per Zone as the zone outdoor air flow rate.
AirChanges/Hour means that the program will use the input from the field Air Changes per Hour and the actual zone volume (divided by 3600 seconds per hour) as the zone outdoor air flow rate.
Sum means that the flows calculated from the fields Outdoor Air Flow per Person, Outdoor Air Flow per Area, Outdoor Air Flow per Zone, and Air Changes per Hour (using the associated conversions to m\(^{3}\)/s for each field) will be added to obtain the zone outdoor air flow rate.
Maximum means that the maximum flow derived from Outdoor Air Flow per Person, Outdoor Air Flow per Area, Outdoor Air Flow per Zone, and Air Changes per Hour (using the associated conversions to m\(^{3}\)/s for each field) will be used as the zone outdoor air flow rate.
IndoorAirQualityProcedure means that the program will use the other procedure defined in ASHRAE Standard 62.1-2007 to calculate the amount of outdoor air necessary in order to maintain the levels of indoor air carbon dioxide at or below the setpoint defined in the ZoneControl:ContaminantController object. Appendix A of the ASHRAE 62.1-2010 user’s manual discusses another method for implementing CO2-based DCV in a single zone system. The last two methods of Proportional Control calculate the required outdoor air flow rate which varies in proportion to the percentage of the CO2 signal range and has two choices to calculate occupancy-based outdoor air rate.
ProportionalControlBasedonOccupancySchedule uses the real occupancy at the current time step to calculate outdoor air rate.
ProportionalControlBasedonDesignOccupancy uses the design occupancy level to calculate outdoor air rate. The former choice is a good approach to estimate outdoor air rate. However, for practical applications, the zone controller usually does not have the real time occupancy information, and the design occupancy level is assumed. The latter choice is used in the design stage.
Field: Outdoor Air Flow per Person[LINK]
The design outdoor air volume flow rate per person for this zone in cubic meters per second per person. The default is 0.00944 (20 cfm per person). An outdoor air flow rate is calculated based on the total number of people for all People statements assigned to the zone. Occupancy schedule values are not applied during sizing calculations and are applied during the remainder of the simulation. This input is used if Outdoor Air Method is one of Outdoor Air Flow per Person, Sum, or Maximum.
Field: Outdoor Air Flow per Zone Floor Area[LINK]
The design outdoor air volume flow rate per square meter of floor area (units are m\(^{3}\)/s-m\(^{2}\)). This input is used if Outdoor Air Method is Flow/Area, Sum or Maximum. The default value for this field is 0.
Field: Outdoor Air Flow per Zone[LINK]
The design outdoor air flow rate for this zone in cubic meters per second. This input field is used if Outdoor Air Method is Flow/Zone, Sum or Maximum. The default value for this field is 0.
Field: Outdoor Air Flow Changes per Hour[LINK]
The design outdoor air volume flow rate in air changes per hour. This factor is used along with the Zone Volume and converted to cubic meters per second. This input field is used if Outdoor Air Method is AirChanges/Hour, Sum or Maximum. The default value for this field is 0.
Field: Outdoor Air Schedule Name[LINK]
This field is the name of schedule that defines how outdoor air requirements change over time. The field is optional. If left blank, the schedule defaults to 1.0. If used, then the schedule values are multiplied by the outdoor air flow rate defined by the previous fields. The schedule values must be between 0 and 1, inclusive.
If this DesignSpecification:OutdoorAir object is referenced by a Controller:MechanicalVentilation object (either directly or indirectly through Sizing:Zone), the schedule will be applied to all types of outdoor air calculations for the corresponding zone, regardless of the System Outdoor Air Method selected. If the schedule value is zero, then the zone will be completely removed from the system outdoor air calculations.
Field: Proportional Control Minimum Outdoor Air Flow Rate Schedule Name[LINK]
This field is the name of schedule that defines how minimum outdoor air requirements change over time. The field is optional. If left blank, the schedule defaults to 1.0. If used when the field System Outdoor Air Method = ProportionalControlBasedOnDesignOARate in Controller:MechanicalVentilation, then the schedule values are multiplied by the outdoor air flow rate.
An IDF example:
DesignSpecification:ZoneAirDistribution[LINK]
This object is used to describe the air distribution effectiveness and fraction of secondary recirculation air (return air not directly mixed with outdoor air) of a zone. It is referenced by the Sizing:Zone and Controller:MechanicalVentilation objects.
Inputs[LINK]
Field: Name[LINK]
The unique user assigned name for an instance of this object. Any other object referencing this object will use this name.
Field: Zone Air Distribution Effectiveness in Cooling Mode[LINK]
The positive numeric input for this field is the zone air distribution effectiveness when the zone is in cooling mode. Default value of this field is 1.0. ASHRAE Standard 62.1-2010 provides typical values.
Field: Zone Air Distribution Effectiveness in Heating Mode[LINK]
The positive numeric input for this field is the zone air distribution effectiveness when the zone is in heating mode. Default value of this field is 1.0. ASHRAE Standard 62.1-2010 provides typical values as follows:
Field: Zone Air Distribution Effectiveness Schedule Name[LINK]
This optional field input points to a schedule with values of zone air distribution effectiveness. It provides a more flexible way of specifying zone air distribution effectiveness if it changes with time and/or system operating status and controls. If the schedule is specified, the zone air distribution effectiveness in cooling mode and heating mode will be ignored.
Field: Zone Secondary Recirculation Fraction[LINK]
The non-negative numeric input for this field is the fraction of a zone’s recirculation air that does not directly mix with the outdoor air. The zone secondary recirculation fraction Er is determined by the designer based on system configuration. For plenum return systems with secondary recirculation (e.g., fan-powered VAV with plenum return) Er is usually less than 1.0, although values may range from 0.1 to 1.2 depending upon the location of the ventilation zone relative to other zones and the air handler. For ducted return systems with secondary recirculation (e.g., fan-powered VAV with ducted return), Er is typically 0.0, while for those with system-level recirculation (e.g, dual-fan dual-duct systems with ducted return) Er is typically 1.0. For other system types, Er is typically 0.75. Minimum is 0.0, and default is 0.0 for single-path systems (also to maintain backward compatibility). For parallel fan-powered VAV systems, the secondary ventilation path only functions (Er > 0.0) when the fans in the VAV boxes operate, which is during heating. The local ventilation path and the benefits of secondary recirculation disappear during cooling, when the local parallel fans are off (Er = 0.0).
Field: Minimum Zone Ventilation Efficiency[LINK]
This optional input sets a minimum on the ventilation efficiency for the zone. It is only used with the Ventilation Rate Procedure (VRP), single-path method. VRP should be chosen in Sizing System, System Outdoor Air Method = VentilationRateProcedure. Single-path method is indicated by leaving the previous input (Zone Secondary Recirculation Fraction) blank or setting it to 0.0. If the calculated value of ventilation efficiency for a zone is less than this value, it is raised to this minimum by raising the zone minimum air flow rate. This new value for zone minimum air flow rate then overrides other defaults and inputs in Sizing:Zone.
An example of this in an IDF context is shown:
Sizing:Parameters[LINK]
This object allows the user to specify global heating and cooling sizing ratios. These ratios will be applied at the zone level to all of the zone heating and cooling loads and air flow rates. These new loads and air flow rates are then used to calculate the system level flow rates and capacities and are used in all component sizing calculations.
The user can also specify the width (in load timesteps) of a moving average window which can be used to smooth the calculated zone design flow sequences. The use of this parameter is described below.
Inputs[LINK]
Field: Heating Sizing Factor[LINK]
The global heating sizing ratio applied to all of the zone design heating loads and air flow rates.
Field: Cooling Sizing Factor[LINK]
The global cooling sizing ratio applied to all of the zone design cooling loads and air flow rates
Field: Timesteps in Averaging Window[LINK]
The number of load timesteps in the zone design flow sequence averaging window. The default is 1, in which case the calculated zone design flow rates are averaged over the load timestep.
The zone design air flow rate calculation is performed assuming a potentially infinite supply of heating or cooling air at a fixed temperature. Thus the calculated design air flow rate will always be able to meet any load or change in load no matter how large or abrupt. In reality air flow rates are limited by duct sizes and fan capacities. The idealized zone design flow calculation may result in unrealistically large flow rates, especially if the user is performing the sizing calculations using thermostat schedules with night setup or setback. The calculated zone design flow rates are always averaged over the load timestep. The user may want to perform a broader average to mitigate the effect of thermostat setup and setback and prevent the warm up or cool down flow rates from dominating the design flow rate calculation.. Specifying the width of the averaging window allows the user to do this.
For example, if the load calculation timestep is 15 minutes and the user specifies the Timesteps in Averaging Window to be 4, the zone design air flows will be averaged over a time period of 1 hour. Specifying 8 would result in averaging over a 2 hour period.
Outputs[LINK]
The sizing factors and the averaging window size are reported out on the eplusout.eio file. An example is:
OutputControl:Sizing:Style[LINK]
As described early in the document (see: EnergyPlus Output Processing), the user may select the “style” for the sizing result files (epluszsz.<ext>, eplusssz.<ext>). This object applies to all sizing output files.
Inputs[LINK]
Field: Column Separator[LINK]
For this field, the desired separator for columns is entered. “Comma” creates comma separated fields/columns in the outputs (eplus<sizing type>.csv files are created). “Tab” creates tab separated fields/columns in the outputs (eplus<sizing type>.tab files are created). “Fixed” creates space separated fields/columns in the outputs (eplus<sizing type>.txt files are created) but these are not necessarily lined up for easy printing.
Note that both tab and comma separated files easily import into Excel™ or other spreadsheet programs. The tab delimited files can also be viewed by text editors, word processing programs and easily converted to “tables” within those programs.
Sizing:Zone[LINK]
The Sizing:Zone object provides the data needed to perform a zone design air flow calculation for a single zone. This calculation assumes a variable amount of supply air at a fixed temperature and humidity. The information needed consists of the zone inlet supply air conditions: temperature and humidity ratio for heating and cooling. The calculation is done for every design day included in the input. The maximum cooling load and air flow and the maximum heating load and air flow are then saved for the system level design calculations and for the component automatic sizing calculations.
The Sizing:Zone object is also the place where the user can specify the design outdoor air flow rate by referencing the name of a design specification outdoor air object. This can be specified in a number of ways (ref. DesignSpecification:OutdoorAir).This data is saved for use in the system sizing calculation or for sizing zone components that use outdoor air.
The user can also place limits on the heating and design cooling air flow rates. See Heating Design Air Flow Method and Cooling Design Air Flow Method below and the explanations of the various heating and cooling flow input fields.
The user can ask the zone design calculation to take into account the effect of a Dedicated Outdoor Air System on the zone design loads and airflow rates. The design calculation will calculate the heat addition rate to the zone of an idealized SOA system and add or subtract the result from the total zone loads and flow rates.
Inputs[LINK]
Field: Zone Name[LINK]
The name of the Zone corresponding to this Sizing:Zone object. This is the zone for which the design air flow calculation will be made using the input data of this Sizing:Zone Object.
Field: Zone Cooling Design Supply Air Temperature Input Method[LINK]
The input must be either SupplyAirTemperature or TemperatureDifference. SupplyAirTemperature means that the user inputs from the fields of Zone Cooling Design Supply Air Temperature will be used to determine the zone cooling design air flow rates. TemperatureDifference means that the user inputs from the fields of Zone Cooling Design Supply Air Temperature Difference will be used to determine the zone cooling design air flow rates.
Field: Zone Cooling Design Supply Air Temperature[LINK]
The supply air temperature in degrees Celsius for the zone cooling design air flow rate calculation. Air is supplied to the zone at this temperature during the cooling design day simulation, The zone load is met by varying the zone air flow rate. The maximum zone flow rate is saved as the zone cooling design air flow rate. This field is only used when Zone Cooling Design Supply Air Temperature Input Method = SupplyAirTemperature.
Field: Zone Cooling Design Supply Air Temperature Difference[LINK]
The temperature difference between cooling design supply air temperature and room air temperature in degrees Celsius for the zone cooling design air flow rate calculation. Air is supplied to the zone at this temperature during the cooling design day simulation. The zone load is met by varying the zone air flow rate. The maximum zone flow rate is saved as the zone cooling design air flow rate. This field is only used when Zone Cooling Design Supply Air Temperature Input Method = TemperatureDifference.
Field: Zone Heating Design Supply Air Temperature Input Method[LINK]
The input must be either SupplyAirTemperature or TemperatureDifference. SupplyAirTemperature means that the user inputs from the fields of Zone Heating Design Supply Air Temperature will be used to determine the zone heating design air flow rates. TemperatureDifference means that the user inputs from the fields of Zone Heating Design Supply Air Temperature Difference will be used to determine the zone heating design air flow rates.
Field: Zone Heating Design Supply Air Temperature[LINK]
The supply air temperature in degrees Celsius for the zone heating design air flow rate calculation. Air is supplied to the zone at this temperature during the heating design day simulation, The zone load is met by varying the zone air flow rate. The maximum zone flow rate is saved as the zone heating design air flow rate. This field is only used when Zone Heating Design Supply Air Temperature Input Method = SupplyAirTemperature.
Field: Zone Heating Design Supply Air Temperature Difference[LINK]
The temperature difference between heating design supply air temperature and room air temperature in degrees Celsius for the zone heating design air flow rate calculation. Air is supplied to the zone at this temperature during the heating design day simulation. The zone load is met by varying the zone air flow rate. The maximum zone flow rate is saved as the zone heating design air flow rate. This field is only used when Zone Heating Design Supply Air Temperature Input Method = TemperatureDifference.
Field: Zone Cooling Design Supply Air Humidity Ratio[LINK]
The humidity ratio in kilograms of water per kilogram of dry air of the supply air in the zone cooling design air flow rate calculation.
Field: Zone Heating Design Supply Air Humidity Ratio[LINK]
The humidity ratio in kilograms of water per kilogram of dry air of the supply air in the zone heating design air flow rate calculation.
Field: Design Specification Outdoor Air Object Name[LINK]
This alpha field specifies the name of a DesignSpecification:OutdoorAir object which specifies the design outdoor air flow rate for the zone.
When a choice of IndoorAirQualityProcedure is entered in the Outdoor Air Method field of the DesignSpecification:OutdoorAir object, the design outdoor airflow rate is calculated based on the choice of Sum in the same field.
When a choice of ProportionalControlBasedOnDesignOccupancy or ProportionalControlBasedonOccupancySchedule is entered, the design outdoor airflow rate is calculated based on equations specified in the "Proportional Control" section in the Engineering Reference.
Field: Zone Heating Sizing Factor[LINK]
This input is a zone level heating sizing ratio. The zone design heating air flow rates and loads will be multiplied by the number input in this field. This input overrides the building level sizing factor input in the Sizing:Parameters object. And, of course, if this field is blank or zero, the global heating sizing factor from the Sizing:Parameters object is used.
Field: Zone Cooling Sizing Factor[LINK]
This input is a zone level cooling sizing ratio. The zone design cooling air flow rates and loads will be multiplied by the number input in this field. This input overrides the building level sizing factor input in the Sizing:Parameters object. And, of course, if this field is blank or zero, the global cooling sizing factor from the Sizing:Parameters object is used.
Field: Cooling Design Air Flow Method[LINK]
The input must be either Flow/Zone, DesignDay, or DesignDayWithLimit. Flow/Zone means that the program will use the input of the field Cooling Design Air Flow Rate as the zone design cooling air flow rate. DesignDay means the program will calculate the zone design cooling air flow rate using the Sizing:Zone input data and a design day simulation without imposing any limits other than those set by the minimum outside air requirements. DesignDayWithLimit means that the maximum from Cooling Minimum Air Flow per Zone Floor Area and Cooling Minimum Air Flow will set a lower limit on the design maximum cooling air flow rate. The default method is DesignDay: i.e., the program uses the calculated design values subject to ventilation requirements.
Field: Cooling Design Air Flow Rate[LINK]
The design zone cooling air flow rate in cubic meters per second. This input is used if Cooling Design Air Flow Method is specified as Flow/Zone. This value will be multiplied by the global or zone sizing factor and by zone multipliers.
Field: Cooling Minimum Air Flow per Zone Floor Area[LINK]
The minimum zone cooling volumetric flow rate per square meter (units are m\(^{3}\)/s-m\(^{2}\)). This field is used when Cooling Design Air Flow Method is specified as DesignDayWithLimit. In this case it sets a lower bound on the zone design cooling air flow rate. In all cases the maximum flow derived from Cooling Minimum Air Flow per Zone Floor Area, Cooling Minimum Air Flow, Cooling Minimum Air Flow Fraction and the design outdoor air flow rate (including VRP adjustments) is used to set a minimum supply air flow rate for the zone for VAV systems. The default is 0.000762, corresponding to 0.15 cfm/ft\(^{2}\). The applicable sizing factor is not applied to this value.
Field: Cooling Minimum Air Flow[LINK]
The minimum zone cooling volumetric flow rate in m\(^{3}\)/s. This field is used when Cooling Design Air Flow Method is specified as DesignDayWithLimit. In this case it sets a lower bound on the zone design cooling air flow rate. In all cases the maximum flow derived from Cooling Minimum Air Flow per Zone Floor Area, Cooling Minimum Air Flow, Cooling Minimum Air Flow Fraction and the design outdoor air flow rate (including VRP adjustments) is used to set a minimum supply air flow rate for the zone for VAV systems. The default is zero. The applicable sizing factor is not applied to this value.
Field: Cooling Minimum Air Flow Fraction[LINK]
The minimum zone design cooling volumetric flow rate expressed as a fraction of the zone design cooling volumetric flow rate. In all cases the maximum flow derived from Cooling Minimum Air Flow per Zone Floor Area, Cooling Minimum Air Flow, Cooling Minimum Air Flow Fraction and the design outdoor air flow rate (including VRP adjustments) is used to set a minimum supply air flow rate for the zone for VAV systems. The default is 0.2. This input is currently used in sizing the VAV air terminal unit and fan minimum flow rate. It does not currently affect other component autosizing.
Field: Heating Design Air Flow Method[LINK]
The input must be either Flow/Zone, DesignDay, or DesignDayWithLimit. Flow/Zone means that the program will use the input of the field Heating Design Air Flow Rate as the zone design heating air flow rate. DesignDay means the program will calculate the zone design heating air flow rate using the Sizing:Zone input data and a design day simulation without imposing any limits other than those set by the minimum outside air requirements. DesignDayWithLimit means that the maximum from Heating Maximum Air Flow per Zone Floor Area and Heating Maximum Air Flow will set a lower limit on the design maximum heating air flow rate. The default method is DesignDay: i.e., the program uses the calculated design values subject to ventilation requirements.
Field: Heating Design Air Flow Rate[LINK]
The design zone heating air flow rate in cubic meters per second. This input is used if Heating Design Air Flow Method is specified as Flow/Zone. This value will be multiplied by the global or zone sizing factor and by zone multipliers.
Field: Heating Maximum Air Flow per Zone Floor Area[LINK]
The maximum zone heating volumetric flow rate per square meter (units are m\(^{3}\)/s-m\(^{2}\)). This field is used when Heating Design Air Flow Method is specified as DesignDayWithLimit. In this case it sets an upper bound on the zone design heating air flow rate. For this and the next two input fields, the maximum flow derived from Heating Maximum Air Flow per Zone Floor Area, Heating Maximum Air Flow, and Heating Maximum Air Flow Fraction is used to set a maximum heating supply air flow rate for the zone for VAV systems. The default is 0.002032, corresponding to 0.40 cfm/ft\(^{2}\). If the maximum heating design flow rate calculated using these input fields is greater than the design heating flow rate calculated during sizing, these input fields have no impact on sizing. It may be more appropriate to select only one of these three fields to calculate the maximum heating design flow rate (i.e., if one ore more of these three fields is 0, it will not be used in calculating the maximum heating design flow rate).
Field: Heating Maximum Air Flow[LINK]
The maximum zone heating volumetric flow rate in m\(^{3}\)/s. This field is used when Heating Design Air Flow Method is specified as DesignDayWithLimit. In this case it sets an upper bound on the zone design heating air flow rate. For this field and the two input fields just prior to and after this field,,the maximum flow derived from Heating Maximum Air Flow per Zone Floor Area, Heating Maximum Air Flow, and Heating Maximum Air Flow Fraction is used to set a maximum heating supply air flow rate for the zone for VAV systems. The default is 0.1415762, corresponding to 300 cfm. If the maximum heating design flow rate calculated using these input fields is greater than the design heating flow rate calculated during sizing, these input fields have no impact on sizing. It may be more appropriate to select only one of these three fields to calculate the maximum heating design flow rate (i.e., if one ore more of these three fields is 0, it will not be used in calculating the maximum heating design flow rate).
Field: Heating Maximum Air Flow Fraction[LINK]
The maximum zone design heating volumetric flow rate expressed as a fraction of the zone design cooling volumetric flow rate. For this and the previous two input fields, the maximum flow derived from Heating Maximum Air Flow per Zone Floor Area, Heating Maximum Air Flow, and Heating Maximum Air Flow Fraction is used to set a maximum heating supply air flow rate for the zone for VAV systems. The default is 0.3. If the maximum heating design flow rate calculated using these input fields is greater than the design heating flow rate calculated during sizing, these input fields have no impact on sizing. It may be more appropriate to select only one of these three fields to calculate the maximum heating design flow rate (i.e., if one ore more of these three fields is 0, it will not be used in calculating the maximum heating design flow rate).
Field: Design Specification Zone Air Distribution Object Name[LINK]
The name of the DesignSpecification:ZoneAirDistribution object, defining the air distribution effectiveness and secondary recirculation air fraction, that applies to the zone or zone list. This object may be used for the same zone in the Controller:MechanicalVentilation object if no such DesignSpecification:ZoneAirDistribution object is specified.
Field: Account for Dedicated Outdoor Air System[LINK]
This is a choice field with choices Yes or No. The default is No. Choosing Yes means that the zone sizing calculation will use the subsequent inputs to calculate the heat gain or loss (heat gains are positive, heat loss is negative) imposed on the zone by a Dedicated Outdoor Air System (DOAS). This heat gain is then added to the zone design heat gain for the zone and the zone design air flow rate is adjusted to meet the DOAS heat gain plus the zone design heat gain.
Field: Dedicated Outdoor Air System Control Strategy[LINK]
This is a choice field with a choice of three ideal control strategies for the DOA system. The choices are NeutralSupplyAir, NeutralDehumidifiedSupplyAir, or ColdSupplyAir. The default is NeutralSupplyAir.
NeutralSupplyAir implies that the ventilation air supplied to the zone will cause little heating or cooling. The air will be heated or cooled to keep it between the low and high temperature setpoints specified in the subsequent two fields. A good choice for these fields might be 21.1 and 23.9 degrees C.
NeutralDehumidifiedSupplyAir means that the ventilation air will be cooled and dehumidified and then reheated to a neutral temperature. The ventilation air is cooled to the lower setpoint temperature (if necessary) and reheated to the upper setpoint temperature. A good choice for the setpoints would be 14.4 and 22.2 degrees C.
ColdSupplyAir means that the ventilation air will be used to supply cooling to the zone. Cold outside air is heated to the upper setpoint; warm outside air is cooled to the lower setpoint. A good choice for the setpoints would be 12.2 and 14.4 degrees C.
Field: Dedicated Outdoor Air Low Temperatue Setpoint for Design[LINK]
The lower setpoint temperature to be used with the DOAS design control strategy. The units are degrees C. The default is autosized to the values given above for the three design control strategies.
Field: Dedicated Outdoor Air High Temperature Setpoint for Design[LINK]
The higher setpoint temperature to be used with the DOAS design control strategy. The units are degrees C. The default is autosized to the values given above for the three design control strategies.
An IDF example:
Outputs[LINK]
The zone design air flow rates and loads are output onto the local file “epluszsz.<ext>” where <ext> is the extension from the sizing style object (default is csv – a comma separated file epluszsz.csv). The columns are clearly labeled. It will easily import into Excel or other spreadsheet program that accepts delimited files. All of these values are design air flow rates and loads calculated by the program. No sizing factors have been applied.
The calculated zone design air flow rates and the user input or altered zone design air flow rates are also reported on the eplusout.eio file. The values are printed out for each zone as comma separated records beginning with Zone Sizing. Items output on the eio file are: zone name, load type (heating or cooling), design load, calculated design air flow rate, user design air flow rate, design day name, time of peak, outside temperature at peak, outside humidity ratio at peak.
DesignSpecification:ZoneHVAC:Sizing[LINK]
This object is used to describe general sizing and scalable sizing methods which are referenced by zone HVAC equipment objects. It is optional input field in zone HVAC objects. If a name of this optional input is not specified or is blank then the sizing method or input specified in the parent object is used. If the name of this object is entered, then the values or method specified overrides the sizing method in the parent zone HVAC objects. This object is meant to provide scalable sizing method to users. The name of this object is an optional input field in the zoneHVAC objects. When this name in not specified in the zone HVAC object the sizing method or the value specified in the zone HVAC object will be used.
List of zoneHVAC objects than can reference this object include:
ZoneHVAC:TerminalUnit:VariableRefrigerantFlow
ZoneHVAC:PackagedTerminalAirConditioner
ZoneHVAC:PackagedTerminalHeatPump
ZoneHVAC:WaterToAirHeatPump
ZoneHVAC:WindowAirConditioner
ZoneHVAC:UnitHeater
ZoneHVAC:UnitVentilator
ZoneHVAC:FourPipeFanCoil
ZoneHVAC:VentilatedSlab
ZoneHVAC:EvaporativeCoolerUnit
ZoneHVAC:IdealLoadsAirSystem
The sizing methods input fields available in this objects are for supply air flow and capacity for heating and cooling operating modes. Some zone HVAC equipment has single supply air flow rate input field that serves both cooling and heating operating modes. So entering either of the cooling or heating scalable sizing input field is sufficient. When there are separate input fields for cooling, heating, no-cooling, and no-heating operating modes, the corresponding input fields are specified. The child components supply air flow rate are also sized using scalable sizing methods specified in the parent objects. The methods allow users to enter a fixed or hard sized values, autosizable, or scalable sizing methods. Methods allowed for sizing supply air flow rates include: SupplyAirFlowRate, FractionOfAutosizedCoolingAirflow, FractionOfAutosizedHeatingAirflow, FlowPerFloorArea, FlowPerCoolingCapacity, and FlowPerHeatingCapacity. The different sizing options are defined as follows:
SupplyAirFlowRate: entered when it is intended that the user specified either hard value or the simulation engine autosize the supply air flow rates for cooling, heating, and no-cooling or no-heating operating modes.
FlowPerFloorArea: entered when it is intended that the simulation engine determine the supply air flow rates from the user specified supply air flow rates per unit floor area and the zone floor area of the zone served by the zone HVAC equipment.
FractionOfAutosizedCoolingAirflow: entered when it is intended that the simulation engine determines the supply air flow rates from the user specified flow fraction and autosized cooling design supply air flow rate.
FractionOfAutosizedHeatingAirflow: entered when it is intended that the simulation engine determines the supply air flow rates from the user specified flow fraction and autosized heating design supply air flow rate.
FlowPerCoolingCapacity: entered when it is intended t that he simulation engine determines the supply air flow rates from the user specified supply air flow per cooling capacity value and autosized cooling design capacity.
FlowPerHeatingCapacity: entered when it is intended that the simulation engine determines the supply air flow rates from the user specified supply air flow per heating capacity value and autosized heating design capacity.
The Design Specification ZoneHVAC Sizing object also has input fields for sizing or scalable sizing of cooling and heating capacity. However, most of the parent zone HVAC objects do not have input fields for sizing capacities. So, the capacity scalable sizing fields in the parent objects are used for sizing child components capacity sizings. The scalable capacity sizing may be indirectly impacted by the scalable supply air flow rates sizing values. Moreover, the autosized cold water, hot water and steam flow rates in the parent zone HVAC objects (e.g. FanCoils, UnitHeaters, UnitVentilators, and VentilatedSlabs) and capacity in child components are determined using the scalable sizing methods. Sizing methods allowed for cooling and heating capacity include: CoolingDesignCapacity, HeatingDesignCapacity, CapacityPerFloorArea, FractionOfAutosizedCoolingCapacity, FractionOfAutosizedHeatingCapacity.
CoolingDesignCapacity: entered when it is intended that user specifies either a hard sized cooling capacity value or the simulation engine autosizes cooling capacity value for the cooling design capacity.
HeatingDesignCapacity: entered when it is intended that user specifies either a hard sized heating capacity value or the simulation engine autosized heating capacity value for the heating design capacity.
CapacityPerFloorArea: is entered when it is intended that the simulation engine determines the cooling or heating capacity from user specified capacity per floor area value and the floor area of the zone served by the zone HVAC equipment.
FractionOfAutosizedCoolingCapacity: entered when it is intended that the simulation engine sizes the cooling capacity from the user specified capacity fraction and autosized cooling design capacity value.
FractionOfAutosizedHeatingCapacity: entered when it is intended that the simulation engine sizes the heating capacity from the user specified capacity fraction and autosized heating design capacity value.
Description of the input fields of the design specification zone HVAC sizing object “DesignSpecification:ZoneHVAC:Sizing”:
Inputs[LINK]
Field: Name[LINK]
Unique identifier name of the DesignSpecification:ZoneHVAC:Sizing object. This sizing specification object referenced by a zone HVAC equipment whose design calculation will be made using the input data of this object.
Field: Cooling Design Air Flow Method[LINK]
The input of this field must be the method used to determine the cooling supply air volume flow rate. Input allowed is either None, SupplyAirFlowRate, FlowPerFloorArea, FractionOfAutosizedCoolingAirflow, or FlowPerCoolingCapacity. None means cooling coil is not included in the zone HVAC equipment or this field may be left blank. SupplyAirFlowRate means the user specifies the magnitude of supply air flow rate or the program calculates the design cooling supply air volume flow rate if autosize is specified. FlowPerFloorArea means the program calculates the cooling supply air volume flow rate from zone floor area served by the zone HVAC unit and user specified Flow Per Floor Area value. FractionOfAutosizedCoolingAirflow means the program calculates the cooling supply air volume flow rate from user specified fraction and the autosized design cooling supply air volume flow rate value determined by the simulation. FlowPerCoolingCapacity means the supply air volume is calculated from user specified flow per cooling capacity and design cooling capacity determined by the simulation. The default method is SupplyAirFlowRate.
Field: Cooling Design Supply Air Flow Rate {m3/s}[LINK]
Enter the magnitude of the cooling supply air volume flow rate in m3/s. This input is an alternative to using the program auto-calculated value. This input is a required field when the Cooling Design air Flow Method is SupplyAirFlowRate. This field may be left blank if a cooling coil is not included in the zone HVAC equipment. This input field is also autosizable.
Field: Cooling Design Supply Air Flow Rate Per Floor Area {m3/s-m2}[LINK]
Enter the cooling supply air volume flow rate per zone conditioned floor area in m3/s-m2. This field is required field when the Cooling Design air Flow Method is FlowPerFloorArea. This field may be left blank if a cooling coil is not included in the zone HVAC equipment or the Cooling Design Air Flow Method is not FlowPerFloorArea. The program calculates the cooling supply air volume flow rate from the zone conditioned floor area served by the zone HVAC equipment and the flow per unit area value specified by the user. Zone sizing object (Sizing:Zone) is not required.
Field: Fraction of Autosized Cooling Design Supply Air Flow Rate[LINK]
Enter the cooling supply air volume flow rate as a fraction of the autosized cooling supply air flow rate. This input field is required when the Cooling Design air Flow Method is FractionOfAutosizedCoolingAirflow. This input field may be left blank if a cooling coil is not included in the zone HVAC equipment or the Cooling Design air Flow Method is not FractionOfAutosizedCoolingAirflow. The program calculates the cooling supply air volume flow rate from the design autosized cooling supply air flow rate and user specified fraction. Zone sizing object (Sizing:Zone) is required.
Field: Cooling Design Supply Air Flow Rate Per Unit Cooling Capacity {m3/s-W}[LINK]
Enter the cooling supply air volume flow rate per unit cooling capacity in m3/s-W. This input field is required when the Cooling Design air Flow Method is FlowPerCoolingCapacity. This field may be left blank if a cooling coil is not included in the zone HVAC equipment or the Cooling Design air Flow Method is not FlowPerCoolingCapacity. The program calculates the cooling supply air volume flow rate from the design autosized cooling capacity and user specified flow per cooling capacity value. Zone sizing object (Sizing:Zone) is required.
Field: Supply Air Flow Rate Method When No Cooling or Heating is Required[LINK]
Enter the method used to determine the supply air volume flow rate when No Cooling or Heating is required. Inputs allowed are None, SupplyAirFlowRate, FlowPerFloorArea, FractionOfAutosizedCoolingAirflow, and FractionOfAutosizedHeatingAirflow. None is used when a cooling or heating coil is not included in the zone HVAC equipment or this field may be left blank. SupplyAirFlowRate means user specifies the magnitude of supply air flow rate or the program calculates the design supply air volume flow rate if autosize is specified. FlowPerFloorArea means the program calculates the supply air volume flow rate from the zone floor area served by the zone HVAC unit and Flow Per Floor Area value specified by user. FractionOfAutosizedCoolingAirflow means the program calculates the supply air volume flow rate from user specified fraction and autosized design cooling supply air volume flow rate value determined by the program. FractionOfAutosizedHeatingAirflow means the program calculates the supply air volume flow rate from user specified fraction and autosized heating supply air flow rate value determined by the program. The default method is SupplyAirFlowRate.
Field: Supply Air Flow Rate When No Cooling or Heating is Required {m3/s}[LINK]
Enter the magnitude of the supply air volume flow rate when no cooling or heating is required in m3/s. This input is an alternative to using the program auto-calculated value. This input is a required field when the Supply Air Flow Rate Method When No Cooling or Heating is Required is SupplyAirFlowRate. This field may be left blank if a cooling coil is not included in the zone HVAC equipment. This input field is also autosizable.
Field: Supply Air Flow Rate Per Floor Area When No Clg or Htg is Required {m3/s-m2}[LINK]
Enter the magnitude of supply air volume flow rate per zone floor area in m3/s-m2. This input is a required field when Supply Air Flow Rate Method When No Cooling or Heating is Required is FlowPerFloorArea. The program calculates the supply air flow rate when no cooling or heating is required from user specified flow per floor area and the zone area served by current zoneHVAC equipment.
Field: Fraction of Design Cooling Supply Air Flow Rate When No Clg or Htg Required[LINK]
Enter the fraction of supply air volume flow rate as a fraction of the autosized cooling supply air flow rate. This input field is required field when Supply Air Flow Rate Method When No Cooling or Heating is Required is FractionOfAutosizedCoolingAirflow. The program calculates the supply air flow rate when no cooling or heating is required from user specified fraction and the design cooling autosized supply air flow rate.
Field: Fraction of Design Heating Supply Air Flow Rate When No Clg or Htg Required[LINK]
Enter the fraction of supply air volume flow rate as a fraction of the autosized cooling supply air flow rate. This input field is required field when Supply Air Flow Rate Method When No Cooling or Heating is Required is FractionOfAutosizedHeatingAirflow. The program calculates the supply air flow rate when no cooling or heating is required from user specified fraction and the design heating autosized supply air flow rate.
Field: Heating Design Air Flow Method[LINK]
The input of this field must be the method used to determine the heating supply air volume flow rate. Input allowed is either None, SupplyAirFlowRate, FlowPerFloorArea, FractionOfAutosizedCoolingAirflow, or FlowPerCoolingCapacity. None means heating coil is not included in the zone HVAC equipment or this field may be left blank. SupplyAirFlowRate means the user specifies the magnitude of supply air flow rate or the program calculates the design heating supply air volume flow rate if autosize is specified. FlowPerFloorArea means the program calculates the heating supply air volume flow rate from zone floor area served by the zone HVAC unit and user specified Flow Per Floor Area value. FractionOfAutosizedHeatingAirflow means the program calculates the heating supply air volume flow rate from user specified fraction and the autosized design heating supply air volume flow rate value determined by the simulation. FlowPerHeatingCapacity means the supply air volume is calculated from user specified flow per heating capacity and design heating capacity determined by the simulation. The default method is SupplyAirFlowRate.
Field: Heating Design Supply Air Flow Rate {m3/s}[LINK]
Enter the magnitude of the heating supply air volume flow rate in m3/s. This input is an alternative to using the program auto-calculated value. This input is a required field when the Heating Design air Flow Method is SupplyAirFlowRate. This field may be left blank if a heating coil is not included in the zone HVAC equipment. This input field is also autosizable.
Field: Heating Design Supply Air Flow Rate Per Floor Area {m3/s-m2}[LINK]
Enter the heating supply air volume flow rate per zone conditioned floor area in m3/s-m2. This field is required field when the Heating Design air Flow Method is FlowPerFloorArea. This field may be left blank if a heating coil is not included in the zone HVAC equipment or the Heating Design Air Flow Method is not FlowPerFloorArea. The program calculates the heating supply air volume flow rate from the zone conditioned floor area served by the zone HVAC equipment and the flow per unit area value specified by the user.
Field: Fraction of Autosized Heating Design Supply Air Flow Rate[LINK]
Enter the heating supply air volume flow rate as a fraction of the autosized heating supply air flow rate. This input field is required when the Heating Design air Flow Method is FractionOfAutosizedHeatingAirflow. This input field may be left blank if a heating coil is not included in the zone HVAC equipment or the Heating Design air Flow Method is not FractionOfAutosizedHeatingAirflow. The program calculates the heating supply air volume flow rate from the design autosized heating supply air flow rate and user specified fraction.
Field: Heating Design Supply Air Flow Rate Per Unit Heating Capacity {m3/s-W}[LINK]
Enter the heating supply air volume flow rate per unit heating capacity in m3/s-W. This input field is required when the Heating Design air Flow Method is FlowPerHeatingCapacity. This field may be left blank if a cooling coil is not included in the zone HVAC equipment or the Heating Design air Flow Method is not FlowPerHeatingCapacity. The program calculates the heating supply air volume flow rate from the design autosized heating capacity and user specified flow per unit heating capacity value.
Field Cooling Design Capacity Method[LINK]
Enter the method used to determine the cooling design capacity for scalable sizing. Input allowed is either None, CoolingDesignCapacity, CapacityPerFloorArea, and FractionOfAutosizedCoolingCapacity. None is used when a cooling coil is not included in the Zone HVAC equipment or this field may be left blank. If this input field is left blank, then the design cooling capacity is set to zero. CoolingDesignCapacity means user specifies the magnitude of cooling capacity or the program calculates the design cooling capacity if autosize is specified. CapacityPerFloorArea means the program calculates the design cooling capacity from user specified cooling capacity per floor area and floor area of the zone served by the HVAC unit. FractionOfAutosizedCoolingCapacity means the program calculates the design cooling capacity from user specified fraction and the auto-sized design cooling capacity. The default method is CoolingDesignCapacity.
Field: Cooling Design Capacity {W}[LINK]
Enter the magnitude of the cooling capacity in Watts. This input is an alternative to using the program auto-calculated cooling capacity value. This input is a required field when the Cooling Design Capacity Method is CoolingDesignCapacity. This field may be left blank if a cooling coil is not included in the zone HVAC equipment or alternative method is specified. This input field is autosizable. Design day sizing run must be specified.
Field: Cooling Design Capacity Per Floor Area {W/m2}[LINK]
Enter the cooling capacity per unit floor area in m3/s-m2. This field is required field when the Cooling Design Capacity Method is CapacityPerFloorArea. This field may be left blank if a cooling coil is not included in the zone HVAC equipment or the Cooling Design Capacity Method is not CapacityPerFloorArea. The program calculates the cooling capacity from floor area of the zone served by the zone HVAC equipment and the cooling capacity per unit floor area value specified by the user.
Field: Fraction of Autosized Cooling Design Capacity[LINK]
Enter the cooling capacity as a fraction of the autosized cooling capacity. This input field is required when the Cooling Design Capacity Method is FractionOfAutosizedCoolingCapacity. This input field may be left blank if a cooling coil is not included in the zone HVAC equipment or the Cooling Design Capacity Method is not FractionOfAutosizedCoolingCapacity. The program calculates the cooling capacity from the design autosized cooling capacity and user specified fraction. Design day sizing run must be specified.
Field: Heating Design Capacity Method[LINK]
Enter the method used to determine the heating design capacity for scalable sizing. Input allowed is either None, HeatingDesignCapacity, CapacityPerFloorArea, and FractionOfAutosizedHeatingCapacity. None is used when a heating coil is not included in the Zone HVAC equipment or this field may be left blank. If this input field is left blank, then the design heating capacity is set to zero. HeatingDesignCapacity means user specifies the magnitude of heating capacity or the program calculates the design heating capacity if autosize is specified. CapacityPerFloorArea means the program calculates the design heating capacity from user specified heating capacity per floor area and floor area of the zone served by the HVAC unit. FractionOfAutosizedHeatingCapacity means the program calculates the design heating capacity from user specified fraction and the auto-sized design heating capacity. The default method is HeatingDesignCapacity.
Field: Heating Design Capacity {W}[LINK]
Enter the magnitude of the heating capacity in Watts. This input is an alternative to using the program auto-calculated heating capacity value. This input is a required field when the Heating Design Capacity Method is HeatingDesignCapacity. This field may be left blank if a heating coil is not included in the zone HVAC equipment or alternative method is specified. This input field is autosizable. Design day sizing run must be specified.
Field: Heating Design Capacity Per Floor Area {W/m2}[LINK]
Enter the heating capacity per unit floor area in m3/s-m2. This field is required field when the Heating Design Capacity Method is CapacityPerFloorArea. This field may be left blank if a heating coil is not included in the zone HVAC equipment or the Heating Design Capacity Method is not CapacityPerFloorArea. The program calculates the heating capacity from floor area of the zone served by the zone HVAC equipment and the heating capacity per unit floor area value specified by the user.
Field: Fraction of Autosized Heating Design Capacity[LINK]
Enter the heating capacity as a fraction of the autosized heating capacity. This input field is required when the Heating Design Capacity Method is FractionOfAutosizedHeatingCapacity. This input field may be left blank if a heating coil is not included in the zone HVAC equipment or the Heating Design Capacity Method is not FractionOfAutosizedHeatingCapacity. The program calculates the heating capacity from the design autosized cooling capacity and user specified fraction. Design day sizing run must be specified.
DesignSpecification:AirTerminal:Sizing[LINK]
This object modifies the sizing of an air loop terminal unit. It may be referenced by a ZoneHVAC:AirDistributionUnit or AirTerminal:SingleDuct:Uncontrolled object. The values specified here are applied to the base sizing results from the corresponding Sizing:Zone inputs. Any given DesignSpecification:AirTerminal:Sizing object may be used by multiple terminal units with similar characteristics.
Inputs[LINK]
Field: Name[LINK]
Name of the design specification air terminal sizing object. This name may be referenced by a ZoneHVAC:AirDistributionUnit or AirTerminal:SingleDuct:Uncontrolled object.
Field: Fraction of Design Sensible Cooling Load[LINK]
The fraction of the design sensible cooling load to be met by this terminal unit. This fraction is applied after the Zone Cooling Sizing Factor (see Sizing:Zone).
Field: Cooling Design Supply Air Temperature Difference Ratio[LINK]
This ratio adjusts the supply air temperature difference used to calculate the cooling design supply air flow rate for this terminal unit.
Field: Fraction of Design Sensible Heating Load[LINK]
The fraction of the design sensible heating load to be met by this terminal unit. This fraction is applied after the Zone Heating Sizing Factor (see Sizing:Zone).
Field: Heating Design Supply Air Temperature Difference Ratio[LINK]
This ratio adjusts the supply air temperature difference used to calculate the heating design supply air flow rate for this terminal unit.
Field: Fraction of Minimum Outdoor Air Flow[LINK]
The fraction of the zone minimum outdoor air requirement to be met by this terminal unit.
An IDF example:
Sizing:System[LINK]
The Sizing:System object contains the input needed to perform a central forced air system design air flow, heating capacity, and cooling capacity calculation for a system serving one or more zones. The information needed consists of the outside environmental conditions and the design supply air temperatures, outdoor air flow rate, and minimum system air flow ratio.
The outside conditions come from the design days in the input. A system sizing calculation is performed for every design day in the input file and the resulting maximum heating and cooling air flow rates and capacities are saved for use in the component sizing calculations.
Supply air conditions are specified by inputting a supply air temperature for cooling, a supply air temperature for heating, and a preheat temperature.
The system sizing calculation sums the zone design air flow rates to obtain a system supply air flow rate. The design conditions and the outdoor air flow rate are used to calculate a design mixed air temperature. The temperature plus the design supply air temperatures allows the calculation of system design heating and cooling capacities.
Inputs[LINK]
Field: AirLoop Name[LINK]
The name of the AirLoopHVAC corresponding to this Sizing:System object. This is the air system for which the design calculation will be made using the input data of this Sizing:System Object.
Field: Type of Load to Size On[LINK]
The user specified type of load on which to size the central system. The choices are Sensible, Total and VentilationRequirement. Sensible and Total mean that the central system supply air flow rate will be determined by combining the zone design air flow rates, which have been calculated to meet the zone sensible loads from the design days. VentilationRequirement means that the central system supply air flow rate will be determined by the system ventilation requirement. In addition Sensible tells the program to size the central cooling coil using entering air flow rate and air conditions at the sensible load peak; Total indicates that the program should size the central cooling coil at the air flow rate and conditions at the total load peak. The central heating coil is always sized at the conditions at the peak sensible heating load.
Field: Design Outdoor Air Flow Rate[LINK]
The design outdoor air flow rate in cubic meters per second. Generally this should be the minimum outdoor air flow. It is used for both heating and cooling design calculations. The assumption for cooling is that any outdoor air economizer will be closed. If Autosize is input the outdoor air flow rate will be taken from the sum of the zone outdoor air flow rates or calculated based on the System Outdoor Air Method selection (field below).
Field: Central Heating Maximum System Air Flow Ratio[LINK]
The ratio of the maximum system air flow rate for heating to the maximum system air flow rate. The value must be between 0 and 1. For constant volume systems the ratio should be set to 1. This ratio should be set to reflect what the user expects the system flow rate to be when maximum heating demand occurs. This ratio is used in calculating the central system heating capacity. Thus if the system is VAV with the zone VAV dampers held at minimum flow when there is a zone heating demand, this ratio should be set to the minimum flow ratio. If the zone VAV dampers are reverse action and can open to full flow to meet heating demand, this ratio should be set to 1. The default is set to 0.5, reflecting the fact that VAV dampers are typically not allowed to fully open during heating.
This field can be set to AutoSize. When automatically calculated, the ratio is determined from the system heating design flow rate divided by the main (which is usually the max of heating and cooling design flow rates) design flow rate. The design flow rates are also adjusted to be more accurate by examining each of the air terminals attached to the air system and summing the heating and maximum flow rates.
Field: Preheat Design Temperature[LINK]
The design air temperature exiting the preheat coil (if any) in degrees Celsius.
Field: Preheat Design Humidity Ratio[LINK]
The design humidity ratio exiting the preheat coil (if any) in kilograms of water per kilogram of dry air. (kgWater/kgDryAir)
Field: Precool Design Temperature[LINK]
The design air temperature exiting the precooling coil (if any) in degrees Celsius.
Field: Precool Design Humidity Ratio[LINK]
The design humidity ratio exiting the precooling coil (if any) in kilograms of water per kilogram of dry air. (kgWater/kgDryAir)
Field: Central Cooling Design Supply Air Temperature[LINK]
The design supply air temperature for cooling in degrees Celsius. This should be the temperature of the air exiting the central cooling coil.
Field: Central Heating Design Supply Air Temperature[LINK]
The design supply air temperature for heating in degrees Celsius. This can be either the reset temperature for a single duct system or the actual hot duct supply air temperature for dual duct systems. It should be the temperature at the exit of the main heating coil. This value is also used for the sizing of zone equipment (e.g., reheat coil) for the system embedded with central heating coils, but it is not used if there is no central heating coil in the system.
Field: Type of Zone Sum to Use[LINK]
If the input is coincident the central system air flow rate will be sized on the sum of the coincident zone air flow rates. If the input is noncoincident the central system air flow rate will be sized on the sum of the noncoincident zone air flow rates. The default is noncoincident.
Field: 100% Outdoor Air in Cooling[LINK]
Entering Yes means the system will be sized for cooling using 100% outdoor air. Entering No means the system will be sized for cooling using minimum outside air (the default).
Field: 100% Outdoor Air in Heating[LINK]
Entering Yes means the system will be sized for heating using 100% outdoor air. Entering No means the system will be sized for heating using minimum outside air (the default).
Field: Central Cooling Design Supply Air Humidity Ratio[LINK]
The design humidity ratio in kilograms of water per kilogram of dry air at the exit of the central cooling coil. The default is 0.008 (kgWater/kgDryAir).
Field: Central Heating Design Supply Air Humidity Ratio[LINK]
The design humidity ratio in kilograms of water per kilogram of dry air at the exit of the central heating coil. This value is also used for the sizing of zone equipment (e.g., reheat coil) for the system embedded with central heating coils, but it is not used if there is no central heating coil in the system. The default is 0.008 (kgWater/kgDryAir).
Field: Cooling Supply Air Flow Rate Method[LINK]
The input of this field must be the method used to determine the airloop cooling supply air volume flow rate. The input must be either, DesignDay, Flow/System, FlowPerFloorArea, FractionOfAutosizedCoolingAirflow, or FlowPerCoolingCapacity. DesignDay means the program will calculate the system design cooling supply air volume flow rate using the System Sizing input data and a design day simulation. Flow/System means that the program will use the input of the field Cooling Design Air Flow Rate as the system design cooling supply air volume flow rate. FlowPerFloorArea means the program calculates the cooling supply air volume flow rate from zone floor area served by the airloop and user specified Flow Per Floor Area value. FractionOfAutosizedCoolingAirflow means the program calculates the cooling supply air volume flow rate from user specified fraction and the autosized design cooling supply air volume flow rate value determined by the simulation. FlowPerCoolingCapacity means the supply air volume is calculated from user specified flow per cooling capacity and design cooling capacity determined by the simulation. The default method is DesignDay: i.e., the program uses the calculated design values.
Field: Cooling Supply Air Flow Rate[LINK]
The design system cooling air flow rate in cubic meters per second. This input is an alternative to using the program autocalculated value. This input is used if Coolingi Supply Air Flow Rate Method is Flow/System. This value will not be multiplied by any sizing factor or by zone multipliers. If using zone multipliers, this value must be large enough to serve the multiplied zones.
Field: Cooling Supply Air Flow Rate Per Floor Area {m3/s-m2}[LINK]
Enter the cooling supply air volume flow rate per zone conditioned floor area in m3/s-m2. This field is required field when the Cooling Supply Air Flow Rate Method is FlowPerFloorArea. This field may be left blank if a cooling coil is not included in the airloop or the Cooling Supply Air Flow Rate Method is not FlowPerFloorArea. The program calculates the cooling supply air volume flow rate from the cooled floor area served by the air loop and the Flow Per Unit Area value specified by the user.
Field: Cooling Fraction of Autosized Cooling Design Supply Air Flow Rate[LINK]
Enter the cooling supply air volume flow rate as a fraction of the airloop autosized cooling supply air flow rate. This input field is required when the Cooling Supply Air Flow Rate Method is FractionOfAutosizedCoolingAirflow. This input field may be left blank if a cooling coil is not included in the airloop or the Cooling Supply Air Flow Rate Method is not FractionOfAutosizedCoolingAirflow. The program calculates the cooling supply air volume flow rate from the design autosized cooling supply air flow rate and user specified fraction.
Field: Cooling Supply Air Flow Rate Per Unit Cooling Capacity {m3/s-W}[LINK]
Enter the cooling supply air volume flow rate per unit cooling capacity in m3/s-W. This input field is required when the Cooling Supply Air Flow Rate Method is FlowPerCoolingCapacity. This field may be left blank if a cooling coil is not included in the airloop or the Cooling Supply Air Flow Rate Method is not FlowPerCoolingCapacity. The program calculates the airloop cooling supply air volume flow rate from the design autosized cooling capacity and user specified Flow Per Cooling Capacity value.
Field: Heating Supply Air Flow Rate Method[LINK]
The input of this field must be the method used to determine the airloop heating supply air volume flow rate. The input must be either, DesignDay, Flow/System, FlowPerFloorArea, FractionOfAutosizedHeatingAirflow, FractionOfAutosizedCoolingAirflow or FlowPerHeatingCapacity. DesignDay means the program will calculate the system design heating supply air volume flow rate using the System Sizing input data and a design day simulation. Flow/System means that the program will use the input of the field Heating Design Air Flow Rate as the system design heating supply air volume flow rate. FlowPerFloorArea means the program calculates the system heating supply air volume flow rate from zone floor area served by the airloop and user specified Flow Per Floor Area value. FractionOfAutosizedHeatingAirflow means the program calculates the system heating supply air volume flow rate from user specified fraction and the autosized system design heating supply air volume flow rate value determined by the simulation. FractionOfAutosizedCoolingAirflow means the program calculates the system heating supply air volume flow rate from user specified fraction and the autosized system design cooling supply air volume flow rate value determined by the simulation. FlowPerHeatingCapacity means the system heating supply air volume is calculated from user specified flow per heating capacity and design heating capacity determined by the simulation. The default method is DesignDay: i.e., the program uses the calculated design values.
Field: Heating Supply Air Flow Rate[LINK]
The design system heating air flow rate in cubic meters per second. This input is an alternative to using the program autocalculated value. This input is used if Heating Supply Air Flow Rate Method is Flow/System. This value will not be multiplied by any sizing factor or by zone multipliers. If using zone multipliers, this value must be large enough to serve the multiplied zones.
Field: Heating Supply Air Flow Rate Per Floor Area {m3/s-m2}[LINK]
Enter the heating supply air volume flow rate per zone conditioned floor area in m3/s-m2. This field is required field when the Heating Supply Air Flow Rate Method is FlowPerFloorArea. This field may be left blank if a heating coil is not included in the airloop or the Heating Supply Air Flow Rate Method is not FlowPerFloorArea. The program calculates the heating supply air volume flow rate from the heated or cooled floor area served by the air loop and the Flow Per Unit Area value specified by the user.
Field: Heating Fraction of Autosized Heating Supply Air Flow Rate[LINK]
Enter the heating supply air volume flow rate as a fraction of the airloop autosized heating supply air flow rate. This input field is required when the Heating Supply Air Flow Rate Method is FractionOfAutosizedHeatingAirflow. This input field may be left blank if heating coil is not included in the airloop or the Heating Supply Air Flow Rate Method is not FractionOfAutosizedHeatingAirflow. The program calculates the heating supply air volume flow rate from the design autosized heating supply air flow rate and user specified fraction.
Field: Heating Fraction of Autosized Cooling Supply Air Flow Rate[LINK]
Enter the heating supply air volume flow rate as a fraction of the airloop autosized cooling supply air flow rate. This input field is required when the Heating Supply Air Flow Rate Method is FractionOfAutosizedCoolingAirflow. This input field may be left blank if heating coil is not included in the airloop or the Heating Supply Air Flow Rate Method is not FractionOfAutosizedCoolingAirflow. The program calculates the heating supply air volume flow rate from the design autosized cooling supply air flow rate and user specified fraction.
Field: Heating Design Supply Air Flow Rate Per Unit Heating Capacity {m3/s-W}[LINK]
Enter the heating supply air volume flow rate per unit heating capacity in m3/s-W. This input field is required when the Heating Design air Flow Method is FlowPerCoolingCapacity. This field may be left blank if a heating coil is not included in the airloop or the Heating Design air Flow Method is not FlowPerHeatingCapacity. The program calculates the airloop heating supply air volume flow rate from the design autosized heating capacity and user specified Flow Per Heating Capacity value.
Field: System Outdoor Air Method[LINK]
The method used to calculate the system minimum outdoor air flow. The two choices are ZoneSum and VentilationRateProcedure (VRP). ZoneSum sums the outdoor air flows across all zones served by the system. VRP uses the multi-zone equations defined in 62.1-2007 to calculate the system outdoor air flow. VRP considers zone air distribution effectiveness and zone diversification of outdoor air fractions. VRP may also adjust autosized air terminal maximum and minimum supply flow rates if needed to ensure adequate outdoor air flow rate to each zone.
Field: Zone Maximum Outdoor Air Fraction[LINK]
This positive numeric input is the zone maximum outdoor air fraction. For an air loop, when a zone requires outdoor air higher than the user specified Zone Maximum Outdoor Air Fraction, the zone supply air flow will be increased to cap the outdoor air fraction at the maximum value. This allows the system level outdoor air flow to be reduced while the total supply air flow increases. Valid values are from 0 to 1.0. Default is 1.0 which indicates zones can have 100% outdoor air maintaining backward compatibility. This inputs work for constant volume air systems, single and dual duct VAV systems.
Field Cooling Design Capacity Method[LINK]
Enter the method used to determine the cooling design capacity for scalable sizing. Input allowed is either None, CoolingDesignCapacity, CapacityPerFloorArea, and FractionOfAutosizedCoolingCapacity. None is used when a cooling coil is not included in the airloop. If this input field is left blank, or None is specified, then the autosized design cooling capacity determined by the program is used. CoolingDesignCapacity means user specifies the magnitude of cooling capacity or the program calculates the design cooling capacity if autosize is specified. CapacityPerFloorArea means the program calculates the design cooling capacity from user specified cooling capacity per floor area and floor area of the zones served by the airloop. FractionOfAutosizedCoolingCapacity means the program calculates the design cooling capacity from user specified fraction and the auto-sized design cooling capacity. If the value this input field is blank or specified as None, then the next three input fields are not required. The default method is CoolingDesignCapacity.
Field: Cooling Design Capacity {W}[LINK]
Enter the magnitude of the cooling capacity in Watts. This input is an alternative to using the program auto-calculated cooling capacity value. This input is a required field when the Cooling Design Capacity Method is CoolingDesignCapacity. This field may be left blank if a cooling coil is not included in the air loop or alternative method is specified. This input field is autosizable.
Field: Cooling Design Capacity Per Floor Area {W/m2}[LINK]
Enter the cooling capacity per unit floor area in m3/s-m2. This field is required field when the Cooling Design Capacity Method is CapacityPerFloorArea. This field may be left blank if a cooling coil is not included in the airloop or the Cooling Design Capacity Method is not CapacityPerFloorArea. The program calculates the cooling capacity from floor area of the zones served by the airloop and the cooling capacity per unit floor area value specified by the user.
Field: Fraction of Autosized Cooling Design Capacity[LINK]
Enter the cooling capacity as a fraction of the autosized cooling capacity. This input field is required when the Cooling Design Capacity Method is FractionOfAutosizedCoolingCapacity. This input field may be left blank if a cooling coil is not included in the zone HVAC equipment or the Cooling Design Capacity Method is not FractionOfAutosizedCoolingCapacity. The program calculates the cooling capacity from the design autosized cooling capacity and user specified fraction. Design day sizing run must be specified.
Field: Heating Design Capacity Method[LINK]
Enter the method used to determine the heating design capacity for scalable sizing. Input allowed is either None, HeatingDesignCapacity, CapacityPerFloorArea, and FractionOfAutosizedHeatingCapacity. None is used when a heating coil is not included in the airloop. If this input field is left blank, then the autosized design heating capacity determined by the program is used. HeatingDesignCapacity means user specifies the magnitude of heating capacity or the program calculates the design heating capacity if autosize is specified. CapacityPerFloorArea means the program calculates the design heating capacity from user specified heating capacity per floor area and floor area of the zones served by the airllop. FractionOfAutosizedHeatingCapacity means the program calculates the design heating capacity from user specified fraction and the auto-sized design heating capacity. If the value this input field is blank or specified as None, then the next three input fields are not required. The default method is HeatingDesignCapacity.
Field: Heating Design Capacity {W}[LINK]
Enter the magnitude of the heating capacity in Watts. This input is an alternative to using the program auto-calculated heating capacity value. This input is a required field when the Heating Design Capacity Method is HeatingDesignCapacity. This field may be left blank if a heating coil is not included in the airloop or alternative method is specified. This input field is autosizable.
Field: Heating Design Capacity Per Floor Area {W/m2}[LINK]
Enter the heating capacity per unit floor area in m3/s-m2. This field is required field when the Heating Design Capacity Method is CapacityPerFloorArea. This field may be left blank if a heating coil is not included in the airloop or the Heating Design Capacity Method is not CapacityPerFloorArea. The program calculates the heating capacity from floor area of the zones served by the airloop and the heating capacity per unit floor area value specified by the user.
Field: Fraction of Autosized Heating Design Capacity[LINK]
Enter the heating capacity as a fraction of the autosized heating capacity. This input field is required when the Heating Design Capacity Method is FractionOfAutosizedHeatingCapacity. This input field may be left blank if heating coil is not included in the airloop or the Heating Design Capacity Method is not FractionOfAutosizedHeatingCapacity. The program calculates the heating capacity from the design autosized cooling capacity and user specified fraction.
Field: Central Cooling Capacity Control Method[LINK]
Specifies how the central cooling coil will be controlled, which affects the coil sizing calculation. There are 4 choices: VAV, Bypass, VT, and OnOff. Choose VAV if the cooling output is controlled by varying the air flow. Bypass should be chosen if the capacity is controlled by bypassing a variable fraction of the mixed air around the coil face. VT indicates that cooling coil output is controlled by varying the coil exit temperature while the flow rate is constant. And OnOff means that the cooling output is controlled by cycling the air flow.
An IDF example:
Outputs[LINK]
The system design air flow rates and heating and cooling capacities are output onto the local file “eplusssz.<ext>” where <ext> is the extension from the sizing style object (default is csv – a comma separated file eplusssz.csv). The columns are clearly labeled. It will easily import into Excel or other spreadsheet program that accepts delimited files. The results are calculated values and do not include any user input system flow rates.
The calculated system design air flow rates and the user input system design air flow rates are also reported on the eplusout.eio file. The values are printed out for each system as comma separated records beginning with System Sizing. An example is:
Sizing:Plant[LINK]
The Sizing:Plant object contains the input needed for the program to calculate plant loop flow rates and equipment capacities when autosizing. This information is initially used by components that use water for heating or cooling such as hot or chilled water coils to calculate their maximum water flow rates. These flow rates are then summed for use in calculating the Plant Loop flow rates.
The program will size any number of chilled water, hot water, condenser water and other plant loops. There should be one Sizing:Plant object for each plant loop that is to be autosized.
Inputs[LINK]
Field: Plant or Condenser Loop Name[LINK]
The name of a Plant Loop or Condenser Loop object corresponding to this Sizing:Plant object. This is the plant loop for which this data will be used for calculating the loop flow rate.
Field: Loop Type[LINK]
The possible inputs are Heating, Steam, Cooling, or Condenser.
Field: Design Loop Exit Temperature[LINK]
The water temperature in degrees Celsius at the exit of the supply side of the plant loop, Thus this is the temperature of the water supplied to the inlet of chilled or hot water coils and other equipment that places loads on a plant loop.
Field: Loop Design Temperature Difference[LINK]
The design temperature rise (for cooling or condenser loops) or fall (for heating loops) in degrees Celsius across the demand side of a plant loop. This temperature difference is used by component models to determine flow rates required to meet design capacities. Larger values lead to smaller design flow rates.
Field: Sizing Option[LINK]
This field is optional. This field controls how concurrence issues impact the plant loop design flow rate. If it is not used then the program uses noncoincident method, which is the historical behavior prior to version 8.3. There are two choices, noncoincident and coincident. The use of Coincident sizing option requires that the SimulationControl object be set to YES for the input field called Do HVAC Sizing Simulation for Sizing Periods.
Field: Zone Timesteps in Averaging Window[LINK]
This field is optional and is only used if the preceding field is set to Coincident. This is the number of zone timesteps used in a moving average to determine the design flow rate from HVAC Sizing Simulation approach. This allows using a broader average over time when using coincident plant sizing. This is similar in concept to the similar field in Sizing:Parameters which specifies the averaging window for zone loads. The default is 1.
Field: Coincident Sizing Factor Mode[LINK]
This field is only used if the sizing option is set to Coincident. This field controls the behavior of coincident sizing with respect to what, if any, sizing factor should be applied to further modify the flow rate measured while running HVAC Sizing Simulations. There are four options. Enter the keword None to use the raw value for flow rate without modification. Enter the keyword GlobalHeatingSizingFactor to modify the flow by the sizing factor entered in the object called Sizing:Parameters for heating. Enter the keyword GlobalCoolingSizingFactor to modify the flow by the sizing factor entered in the object called Sizing:Parameters for cooling. Enter the keyword LoopComponentSizingFactor to modify the flow by a sizing factor determined from the combination of component-level sizing factors in the associated plant loop.
An IDF example:
Outputs[LINK]
The loop flow rates are reported on the eplusout.eio file along with the component sizing results.
When coincident plant sizing method is used, the eio file contains special summary report with various details and interim values from the calculations, under the following record header: ! , Plant Loop Name, Sizing Pass {#}, Measured Mass Flow{kg/s}, Measured Demand {W}, Demand Calculated Mass Flow{kg/s}, Sizes Changed {Yes/No}, Previous Volume Flow Rate {m3/s}, New Volume Flow Rate {m3/s}, Demand Check Applied {Yes/No}, Sizing Factor {}, Normalized Change {}, Specific Heat{}.
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.