Input Output Reference — EnergyPlus 8.6

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Input Output Reference

Group Heating and Cooling Coils[LINK]

Several different coils may be added to zone equipment and air loops. This includes simple heating (gas, electric, and hot water) and a simple water-cooling coil as well as a more detailed flat fin water-cooling coil model. In general, the heating coil description can be used for a heating coil, a reheat coil, or a preheat coil in the air loop simulation or for zone equipment. Figure is an example of a heating and cooling coil in the air loop simulation in a dual duct system. This does show the basic node structure that will be referenced in the input description. The figure does show water coils since they are the most complex to input in the simulation compared to the Electric and Gas coils which only have air connections.

Example Air Loop Heating & Cooling Coil

Example Air Loop Heating & Cooling Coil

Coil:Cooling:Water[LINK]

The water cooling coil (Coil:Cooling:Water) has the ability to give detailed output with simplified inputs, inputting complicated coil geometry is not required by the user for this model instead the coil is sized in terms of auto-sizeable thermodynamic inputs. The coil requires thermodynamic inputs such as temperatures, mass flow rates and humidity ratios.

The coil is sized using auto-sized/user design input conditions and the UA values are calculated from the design conditions. A rough estimate of the coil area is provided along with percentage of surface wet and/or dry. This model uses the NTU-effectiveness approach to model heat transfer and has two types of flow arrangements cross-flow or counter-flow.

The basic underlying idea is - use auto sizable thermodynamic design inputs, calculate the coil UA s, use these UA values and operating conditions from the nodes connections, calculate the outlet stream conditions, and calculate the heat transfer rates.

See section Cooling Coil Model in the EnergyPlus Engineering Document for further details regarding this model.

Inputs[LINK]

Field: Name[LINK]

A unique user-assigned name for an instance of a cooling coil. Any reference to this cooling coil by another object will use this name.

Field:Availability Schedule Name[LINK]

Schedule that defines when the coil is available. The name of the schedule (ref: Schedule) that denotes whether the cooling coil can run during a given time period. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during a given time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit is off. If this field is blank, the schedule has a value of 1 for all time periods.

Field: Design Water Flow Rate[LINK]

The maximum possible water volume flow rate (m3/sec) through the coil. This is an auto sizable design input.

Field: Design Air Flow Rate[LINK]

The maximum possible air volume flow rate (m3/sec) through the coil. This is an auto sizable design input.

Field: Design Inlet Water Temperature[LINK]

The inlet water temperature for the design flow (C). This is an auto sizable design input.

Field: Design Inlet Air Temperature[LINK]

The inlet air temperature for the design flow (C). This is an auto sizable design input.

Field: Design Outlet Air Temperature[LINK]

The outlet air condition desired for design flow (C). This is an auto sizable design input.

Field: Design Inlet Air Humidity Ratio[LINK]

The highest value of humidity ratio possible for the Design inlet air stream (kgWater/kgDryAir). This is an auto sizable input.

Field: Design Outlet Air Humidity Ratio[LINK]

The value of humidity ratio for the Design outlet air stream (kgWater/kgDryAir), it is an auto sizable input.

Field: Water Inlet Node Name[LINK]

The name of the water coil inlet from the chilled water loop, i.e. Cooling Coil Water Inlet Node. It is from this node the operating inputs for water are transferred to the coil.

Field: Water Outlet Node Name[LINK]

The name of the water coil outlet from the chilled water loop, i.e. Cooling Coil Water Outlet Node. It is from this node the operating output for water are reported to the coil.

Field: Air Inlet Node Name[LINK]

The name of the air inlet to the water coil, i.e. Cooling Coil Air Inlet Node. It is from this node the operating inputs for air are transferred to the coil.

Field: Air Outlet Node Name[LINK]

The name of the air outlet from the water coil, i.e. Cooling Coil Air Outlet Node. It is from this node the operating output for airside is reported to the coil.

Field: Type of Analysis[LINK]

The coil has two modes of operation, termed as SimpleAnalysis and DetailedAnalysis. The difference between the two modes being, the simple mode reports the value of surface area fraction wet of the coil as dry or wet. The detailed mode give the exact value, however the execution time in detailed mode is noticeably higher.

Field: Heat Exchanger Configuration[LINK]

The coil is operable in two modes, Cross Flow for general A/C applications and Counter flow mode. Air-conditioning systems generally use cross flow heat exchangers, hence the default is set to cross flow.

Field: Condensate Collection Water Storage Tank Name[LINK]

This field is optional. It is used to describe where condensate from the coil is collected. If blank or omitted, then any coil condensate is discarded. Enter the name of Water Storage Tank object defined elsewhere and the condensate will then be collected in that tank.

Examples when auto sized in an IDF are as below:

Coil:Cooling:Water,
  Main Cooling Coil 1,       !- Coil Name
  CoolingCoilAvailSched,   !-Availability Schedule Name
  autosize,         !- Design Water Volume Flow Rate of Coil {m3/s}
  autosize,         !- Design Air Flow Rate of Coil {m3/s}
  autosize,         !- Design Inlet Water Temperature {C}
  autosize,         !- Design Inlet Air Temperature {C}
  autosize,         !- Design Outlet Air Temperature {C}
  autosize,         !- Design Inlet Air Humidity Ratio(kgWater/kgDryAir)
  autosize,         !- Design Outlet Air Humidity Ratio(kgWater/kgDryAir)
  Main Cooling Coil 1 Water Inlet Node,     !- Coil_Water_Inlet_Node
  Main Cooling Coil 1 Water Outlet Node,   !- Coil_Water_Outlet_Node
  Mixed Air Node 1,                                             !- Coil_Air_Inlet_Node
  Main Cooling Coil 1 Outlet Node;               !- Coil_Air_Outlet_Node

Examples when values (hard-sized) are input in an IDF are as below:

Coil:Cooling:Water,
  Main Cooling Coil 1,       !- Coil Name
  CoolingCoilAvailSched,   !-Availability Schedule Name
  0.0022,       !- Design Water Volume Flow Rate of Coil {m3/s}
  1.45,           !- Design Air Flow Rate of Coil {m3/s}
  6.1,             !- Design Inlet Water Temperature {C}
  25,               !- Design Inlet Air Temperature {C}
  10,               !- Design Outlet Air Temperature {C}
  0.012,         !- Design Inlet Air Humidity Ratio
  0.008,         !- Design Outlet Air Humidity Ratio
  Main Cooling Coil 1 Water Inlet Node,     !- Coil_Water_Inlet_Node
  Main Cooling Coil 1 Water Outlet Node,   !- Coil_Water_Outlet_Node
  Mixed Air Node 1,                                             !- Coil_Air_Inlet_Node
  Main Cooling Coil 1 Outlet Node;               !- Coil_Air_Outlet_Node

Outputs[LINK]

Following are the list of possible output output variables from this coil model:

  • HVAC,Sum,Cooling Coil Total Cooling Energy [J]

  • HVAC,Sum,Cooling Coil Sensible Cooling Energy [J]

  • HVAC,Average,Cooling Coil Total Cooling Rate [W]

  • HVAC,Average,Cooling Coil Sensible Cooling Rate [W]

  • HVAC,Average,Cooling Coil Wetted Area Fraction []

  • HVAC,Average,Cooling Coil Condensate Volume Flow Rate [m3/s]

  • HVAC,Sum,Cooling Coil Source Side Heat Transfer Energy [J]

  • HVAC,Sum,Cooling Coil Condensate Volume [m3]

Cooling Coil Total Cooling Energy (J)[LINK]

Cooling Coil Total Cooling Energy is the total amount of heat transfer taking place in the coil at the operating conditions.

Cooling Coil Sensible Cooling Energy (J)[LINK]

Cooling Coil Sensible Cooling Energy is the total amount of Sensible heat transfer taking place in the coil at the operating conditions. It only takes into account temperature difference in the inlet and outlet air streams at operating conditions.

Cooling Coil Total Cooling Rate (W)[LINK]

Cooling Coil Total Cooling Rate is the Rate of heat transfer taking place in the coil at the operating conditions. The units are (J/sec) or Watts.

Cooling Coil Sensible Cooling Rate (W)[LINK]

Cooling Coil Sensible Cooling Rate is the Rate of Sensible heat transfer taking place in the coil at the operating conditions.

Cooling Coil Wetted Area Fraction [] [LINK]

It defines the fraction of total surface area of coil which is wet due to moisture condensation on the surface of the coil. Value varies between 0.0 and 1.0.

In addition, if a Water Storage Tank is used to collect coil condensate, then the following outputs will be available.

Cooling Coil Condensate Volume Flow Rate [m3/s] [LINK]

Cooling Coil Condensate Volume [m3] [LINK]

These reports provide the rate and amount of condensate from the coil. Condensate is water condensed out of the air as a result of cooling. The condensate volume is also reported on the meter for OnSiteWater.

Cooling Coil Source Side Heat Transfer Energy [J] [LINK]

This is the energy extracted from the chilled water serving the coil, in Joules.

Coil:Heating:Water[LINK]

This simple heating coil model only does sensible heating of the air. The simple heating coil uses the Effectiveness-NTU algorithm and assumes a cross-flow heat exchanger.

Inputs[LINK]

Field: Name[LINK]

A unique identifying name for each coil.

Field:Availability Schedule Name[LINK]

Schedule that defines when the coil is available. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during a given time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit is off. If this field is blank, the schedule has a value of 1 for all time periods.

Field: U-Factor Times Area Value[LINK]

The UA value for the coil needed for the Effectiveness-NTU heat exchanger model. An estimate of the UA can be obtained from:

q=UA×(Twater,avgTair,avg)

where q is the heat transferred from water to the air in watts; Twater,avg is the average water temperature in degrees C; and Tair,avg is the average air temperature in degrees C. Or the LMTD temperature difference can be used. This field is used when Performance Input Method = UFactorTimesAreaAndDesignWaterFlowRate.This field is autosizable.

Field: Maximum Water Flow Rate[LINK]

The maximum possible water flow rate (m3/sec) through the coil. This field is used when Coil Performance Input Method = UFactorTimesAreaAndDesignWaterFlowRate. This field is autosizable.

Field: Water Inlet Node Name[LINK]

The name of the coil s water inlet node from the hot water loop.

Field: Water Outlet Node Name[LINK]

The name of the coil s water outlet node from the hot water loop.

Field: Air Inlet Node Name[LINK]

The name of the air inlet node to the water coil.

Field: Air Outlet Node Name[LINK]

The name of the air outlet node from the water coil.

Field: Performance Input Method[LINK]

The user can choose either UFactorTimesAreaAndDesignWaterFlowRate or NominalCapacity. If UFactorTimesAreaAndDesignWaterFlowRate is selected, the user must input values for UA of the Coil and Max Water FlowRate of the Coil (and Rated Capacity is ignored). If NominalCapacity is chosen, the user must input a Rated Capacity for the coil; UA of the Coil and Max Water FlowRate of the Coil will be ignored. Rated capacity is defined as the heating capacity in watts of the coil at the rating points (i.e., the rated inlet and outlet water/air temperatures defined in the input fields below). The rated capacity is used to calculate a water mass flow rate and a UA for the coil. The default is NominalCapacity.

To autosize the capacity, choose UfactorTimesAreaAndDesignWaterFlowRate and put autosize as the inputs for U-Factor Times Area Value, Maximum Water Flow Rate, and Rated Capacity. The program will use the Sizing inputs to size the coil. The rated temperatures (see below) are ignored in autosizing. These are used only when the user is specifying coil performance using the NominalCapacity input method.

Field: Gross Rated Heating Capacity[LINK]

The heating capacity of the coil in watts at the rated inlet and outlet air and water temperatures. The gross rated heating capacity does not account for the effect of supply air fan heat. This field is used when the Performance Input Method = Nominal Capacity. This field is autosizable. The rating points are given in the four subsequent input fields.

Field: Rated Inlet Water Temperature[LINK]

The inlet water temperature (degrees C) corresponding to the rated heating capacity. The default is 82.2 degrees C (180 degrees F).

Field: Rated Inlet Air Temperature[LINK]

The inlet air temperature (degrees C) corresponding to the rated heating capacity. The default is 16.6 degrees C (60 degrees F).

Field: Rated Outlet Water Temperature[LINK]

The outlet water temperature (degrees C) corresponding to the rated heating capacity. The default is 71.1 degrees C (160 degrees F).

Field: Rated Outlet Air Temperature[LINK]

The outlet air temperature (degrees C) corresponding to the nominal heating capacity. The default is 32.2 degrees C (90 degrees F).

Field: Rated Ratio for Air and Water Convection[LINK]

This is the ratio of convective heat transfers between air side and water side of the heating coil at the rated operating conditions. The default is .5. This ratio describes the geometry and the design of the coil and is defined by:

ratio=ηf(hA)air(hA)water

where,

ηf is the fin efficiency, (dimensionless)

h is the surface convection heat transfer coefficient

A is the surface area

An example input of the object is:

Coil:Heating:Water,
  SPACE3-1 Zone Coil,           !- Coil Name
  ReheatCoilAvailSched,       !- Availability Schedule Name
  ,                                               !- UA of the Coil {W/K}
  ,                                               !- Max Water Flow Rate of Coil {m3/s}
  SPACE3-1 Zone Coil Water In Node,   !- Coil_Water_Inlet_Node
  SPACE3-1 Zone Coil Water Out Node,   !- Coil_Water_Outlet_Node
  SPACE3-1 Zone Coil Air In Node,   !- Coil_Air_Inlet_Node
  SPACE3-1 In Node,               !- Coil_Air_Outlet_Node
  NominalCapacity,                 !- Coil Performance Input Method
  10000.,                                   !- Gross Rated Heating Capacity
  0.55;                                       !- Rated Ratio for Air and Water Convection

Outputs[LINK]

  • HVAC,Sum, Heating Coil Heating Energy [J]

  • HVAC,Sum,Heating Coil Source Side Heat Transfer Energy [J]

  • HVAC,Average,Heating Coil Heating Rate [W]

  • HVAC,Average, Heating Coil U Factor Times Area Value [W/K]

Heating Coil Heating Energy [J] [LINK]

Heating Coil Heating Energy is the total amount of heat transfer taking place in the coil at the operating conditions.

Heating Coil Heating Rate [W] [LINK]

Heating Coil Heating Rate is the Rate of heat transfer taking place in the coil at the operating conditions. The units are (J/sec) or Watts.

Heating Coil U Factor Times Area Value [W/K] [LINK]

This characterizes the overall heat transfer UA value, or U-factor times Area. The simple heating coil model adjusts UA value based on inlet temperatures and flow rates and this output contains the results from that adjustment.

Heating Coil Source Side Heat Transfer Energy [J] [LINK]

This is the same has the Heating Coil Heating Energy but it is also metered as a plant loop heating demand. This represents the heat in Joules extracted from the hot water serving the coil.

Coil:Heating:Steam[LINK]

The simple steam to air heating coil model only does sensible heating of the air. The steam to air coils condenses the steam and sub cools steam at loop pressure and discharges the condensate through steam traps at low pressure condensate line.

Inputs[LINK]

Field: Name[LINK]

A unique identifying name for each steam coil.

Field:Availability Schedule Name[LINK]

Schedule that defines when the coil is available. If the schedule s value is less than or equal to 0.0, then the coil is not available and flow will not be requested. If the schedule s value is > 0.0 (usually 1 is used), the coil is available. If this field is blank, the schedule has values of 1 for all time periods.

Field: Maximum Steam Flow Rate[LINK]

The maximum possible steam volumetric flow rate in m3/s through the steam heating coil. The steam volumetric flow rate is calculated at 100C and 101325 Pa. This field is autosizable.

Field: Degree of SubCooling[LINK]

Ideally the steam trap located at the outlet of steam coil should remove all the condensate immediately, however there is a delay in this process in actual systems which causes the condensate to SubCool by certain degree in the coil before leaving the coil, this SubCool occurs in the steam coil and this SubCool-heat is added to the zone. The minimum value is 2 ° Celsius and default is 5 ° Celsius.

Field: Degree of Loop SubCooling[LINK]

This essentially represents the heat loss to the atmosphere due to uninsulated condensate return piping to the boiler. Condensate return piping operates at atmospheric pressure and is not insulated. The condensate sub cools to certain degree before it is pumped back to the boiler. The minimum value is 10 ° Celsius and default is 20 ° Celsius.

Field: Water Inlet Node Name[LINK]

The name of the steam coil inlet from the steam loop, i.e. Steam Coil steam inlet node.

Field: Water Outlet Node Name[LINK]

The name of the steam coil outlet to the condensate loop, i.e. Steam Coil condensate outlet node.

Field: Air Inlet Node Name[LINK]

The name of the air inlet to the steam coil, i.e. Steam Coil Air Inlet Node.

Field: Air Outlet Node Name[LINK]

The name of the air outlet from the steam coil, i.e. Steam Coil Air Outlet Node.

Field:Coil Control Type[LINK]

Choice of either ZoneLoadControl steam coil or TemperatureSetpointControl steam coil. A zone coil is load controlled and an air loop steam coil is temperature controlled.

Field: Temperature Setpoint Node Name[LINK]

If the coil is used in the air loop simulation and is temperature controlled using a Set Point Manager (i.e., the previous file is TemperatureSetpointConrtol), then the node that is the control node needs to be specified here. If the coil is used in an air terminal unit, the coil is load controlled and a control node set point is not required (i.e., the previous field is ZoneLoadControl).

An example of a Steam Coil input statement (one each for Temperature Controlled and Load Controlled) from an IDF is given below:

Coil:Heating:Steam,
  VAV SYS 1 Heating Coil,                   !- Coil Name
  ReheatCoilAvailSched,                       !- Availability Schedule Name
  0.06,                                                       !- Max Steam volume Flow rate
  5.0,                                                         !- Deg of Subcooling Desired
  15.0,                                                        !- Loop Subcooling Desired
  VAV SYS 1 Heating Coil Steam Inlet,   !- Coil Steam Inlet Node
  VAV SYS 1 Heating Coil Steam Outlet, !- Coil Water Outlet Node
  VAV SYS 1 Cooling Coil Outlet,       !- Coil Air Inlet Node
  VAV SYS 1 Heating Coil Outlet,       !- Coil Air Outlet Node
  TemperatureSetPointControl,             !- field Coil Control Type
  VAV SYS 1 Heating Coil Outlet;       !- field Coil Temp Setpoint Node


  Coil:Heating:Steam,
  SPACE1-1 Reheat Coil,                             !- Coil Name
  ReheatCoilAvailSched,                             !- Availability Schedule Name
  autosize,                                                      !- Max Steam volume Flow rate
  5.0,                                                                !- Deg of Subcooling Desired
  15.0,                                                              !- Loop Subcooling Desired
  SPACE1-1 Reheat Coil Steam Inlet,     !- Coil Steam Inlet Node
  SPACE1-1 Reheat Coil Steam Outlet,   !- Coil Water Outlet Node
  SPACE1-1 Damper Outlet,                         !- Coil Air Inlet Node
  SPACE1-1 Supply Inlet,   !- Coil Air Outlet Node
  ZoneLoadControl;         !- field Coil Control Type

Heating Coil (Steam) Outputs:[LINK]

  • HVAC,Sum, Heating Coil Heating Energy [J]

  • HVAC,Average,Total Steam Coil Heating Rate [W]

  • HVAC,Average,Heating Coil Steam Trap Loss Rate [W]

  • HVAC, Average, Heating Coil Steam Inlet Temperature [C]

  • HVAC, Average, Heating Coil Steam Outlet Temperature [C]

  • HVAC, Average, Heating Coil Steam Mass Flow Rate [kg/s]

Heating Coil Heating Energy [J] [LINK]

Heating Coil Heating Energy is the total amount of heat transfer taking place in the coil at the operating conditions.

Heating Coil Heating Rate [W] [LINK]

Heating Coil Heating Rate is the Rate of heat transfer taking place in the coil at the operating conditions. The units are (J/sec) or Watts.

Heating Coil Steam Trap Loss Rate [W] [LINK]

Loop losses represent the unavoidable loss due to degree of sub cooling in the condensate return piping back to the boiler and the loss occurring due to flashing of steam across the steam trap due to pressure differential between the steam and the condensate side.

Heating Coil Steam Inlet Temperature [C] [LINK]

Heating Coil Steam Outlet Temperature [C] [LINK]

Heating Coil Steam Mass Flow Rate [kg/s] [LINK]

These outputs are the Steam inlet and condensate outlet temperatures and steam flow rate for the boiler.

Coil:Heating:Electric[LINK]

The electric heating coil is a simple capacity model with a user-inputted efficiency. In many cases, this efficiency for the electric coil will be 100%. This coil will be simpler than shown in Figure since it will only have air nodes to connect it in the system. The coil can be used in the air loop simulation or in the zone equipment as a reheat coil. Depending on where it is used determines if this coil is temperature or capacity controlled. If used in the air loop simulation it will be controlled to a specified temperature scheduled from the SetPoint Manager. If it is used in zone equipment, it will be controlled from the zone thermostat by meeting the zone demand.

Inputs[LINK]

Field: Name[LINK]

A unique identifying name for each coil.

Field:Availability Schedule Name[LINK]

Schedule that defines when the coil is available. If the schedule s value is 0.0, then the coil is not available and flow will not be requested. If the schedule s value is > 0.0 (usually 1 is used), the coil is available. If this field is blank, the schedule has values of 1 for all time periods. Schedule values must be > = 0 and < = 1.

Field: Efficiency[LINK]

This is user-inputted efficiency (decimal units, not percent) and can account for any loss. In most cases for the electric coil, this will be 100%.

Field: Nominal Capacity[LINK]

This is the maximum capacity of the coil (W). This controlled coil will only provide the needed capacity to meet the control criteria whether it is temperature or capacity controlled. This field is autosizable.

Field: Air Inlet Node Name[LINK]

The name of the air inlet to the electric coil, i.e. Heating Coil Air Inlet Node.

Field: Air Outlet Node Name[LINK]

The name of the air outlet from the electric coil, i.e. Heating Coil Air Outlet Node.

Field: Temperature Setpoint Node Name[LINK]

If the coil is used in the air loop simulation and is temperature controlled using a Set Point Manager, then the node that is the control node needs to be specified here. If the coil is used in an air terminal unit, the coil is load controlled and a control node set point is not required.

An example of IDF usage:

Coil:Heating:Electric,
  AHU Reheater,                     !- Name
  2,                                           !- Availability Schedule Name
  0.99,                                     !- Efficiency
  600000,                                 !- Nominal Capacity {W}
  DOAS Supply Fan Outlet, !- Air Inlet Node Name
  AHU Reheater Outlet,       !- Air Outlet Node Name
  AHU Reheater Outlet;       !- Temperature Setpoint Node Name

Outputs[LINK]

  • HVAC,Sum,Heating Coil Air Heating Energy [J]

  • HVAC,Average,Heating Coil Air Heating Rate [W]

  • HVAC,Sum,Heating Coil Electric Energy [J]

  • HVAC,Average,Heating Coil Electric Power [W]

Heating Coil Air Heating Energy (J)[LINK]

Heating Coil Air Heating Energy is the total amount of heat transfer taking place in the coil at the operating conditions.

Heating Coil Air Heating Rate [W] [LINK]

Heating Coil Air Heating Rate is the Rate of heat transfer taking place in the coil at the operating conditions. The units are (J/sec) or Watts.

Heating Coil Electric Energy [J] [LINK]

Heating Coil electric consumption after the efficiency of the coil has been taken into account in Joules for the timestep reported.

Heating Coil Electric Power [W] [LINK]

This field is the average Heating Coil electric power after the efficiency of the coil has been taken into account in Watts for the timestep reported.

Coil:Heating:Electric:MultiStage[LINK]

The multi stage electric heating coil is a simple capacity model with a user-inputted efficiencies at different stages. In many cases, the efficiencies for the electric coil will be 100%. This coil will only have air nodes to connect it in the system. The coil can be used in the air loop simulation or in the zone equipment as a reheat coil. Depending on where it is used determines if this coil is temperature or capacity controlled. If used in the air loop simulation it will be controlled to a specified temperature scheduled from the SetPoint Manager. If it is used in zone equipment, it will be controlled from the zone thermostat by meeting the zone demand. For the time being, this coil model can only be called by the parent object AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed.

Inputs[LINK]

Field: Name[LINK]

A unique identifying name for each coil.

Field:Availability Schedule Name[LINK]

Schedule that defines when the coil is available. If the schedule s value is 0.0, then the coil is not available and flow will not be requested. If the schedule s value is > 0.0 (usually 1 is used), the coil is available. If this field is blank, the schedule has values of 1 for all time periods. Schedule values must be > = 0 and < = 1.

Field: Air Inlet Node Name[LINK]

The name of the air inlet to the electric coil, i.e. Heating Coil Air Inlet Node.

Field: Air Outlet Node Name[LINK]

The name of the air outlet from the electric coil, i.e. Heating Coil Air Outlet Node.

Field: Temperature Setpoint Node Name[LINK]

If the coil is used in the air loop simulation and is temperature controlled using a Set Point Manager, then the node that is the control node needs to be specified here. If the coil is used in an air terminal unit, the coil is load controlled and a control node set point is not required. At present, the multistage electric heating coil does not model temperature setoint control.

Field: Stage 1 Efficiency[LINK]

This is stage 1 user-inputted efficiency (decimal units, not percent) and can account for any loss. In most cases for the electric coil, this will be 100%.

Field: Stage 1 Nominal Capacity[LINK]

This is stage 1 capacity of the coil (W). This field is autosizable.

Field: Stage 2 Efficiency[LINK]

This is stage 2 user-inputted efficiency (decimal units, not percent) and can account for any loss. In most cases for the electric coil, this will be 100%.

Field: Stage 2 Nominal Capacity[LINK]

This is stage 2 capacity of the coil (W). This field is autosizable.

Field: Stage 3 Efficiency[LINK]

This is stage 3 user-inputted efficiency (decimal units, not percent) and can account for any loss. In most cases for the electric coil, this will be 100%.

Field: Stage 3 Nominal Capacity[LINK]

This is stage 3 capacity of the coil (W). This field is autosizable.

Field: Stage 4 Efficiency[LINK]

This is stage 4 user-inputted efficiency (decimal units, not percent) and can account for any loss. In most cases for the electric coil, this will be 100%.

Field: Stage 4 Nominal Capacity[LINK]

This is stage 4 capacity of the coil (W). This field is autosizable.

An example in IDF form:

Coil:Heating:Electric:MultiStage,
  Heat Pump Heating Coil 1,                 !- Name
  FanAndCoilAvailSched,                         !- Availability Schedule Name
  Heating Coil Air Inlet Node,           !- Air Inlet Node Name
  SuppHeating Coil Air Inlet Node,   !- Air Outlet Node Name
  ,                                               !- Temp Setpoint node name
  3,                                             !- Number of Stages
  1,                                             !- Stage 1 Efficiency
  Autosize,                               !- Stage 1 Nominal Capacity {W}
  1,                                             !- Stage 2 Efficiency
  Autosize,                               !- Stage 2 Nominal Capacity {W}
  1,                                             !- Stage 3 Efficiency
  Autosize;                               !- Stage 3 Nominal Capacity {W}

Outputs[LINK]

  • HVAC,Sum,Heating Coil Energy[J]

  • HVAC,Average,Heating Coil Rate[W]

  • HVAC,Sum,Heating Coil Electric Consumption [J]

  • HVAC,Average,Heating Coil Electric Power [W]

Heating Coil Energy (J)[LINK]

Heating Coil Energy is the total amount of heat transfer taking place in the coil at the operating conditions.

Heating Coil Rate[W] [LINK]

Heating Coil Rate is the Rate of heat transfer taking place in the coil at the operating conditions. The units are (J/sec) or Watts.

Heating Coil Electric Consumption [J] [LINK]

Heating Coil electric consumption after the efficiency of the coil has been taken into account in Joules for the timestep reported.

Heating Coil Electric Power [W] [LINK]

This field is the average Heating Coil electric power after the efficiency of the coil has been taken into account in Watts for the timestep reported.

Coil:Heating:Desuperheater[LINK]

A simplified approach is used to determine the performance of this air heating coil. The model assumes that the heating energy provided by this coil is reclaimed from the superheated refrigerant gas leaving a compressor (i.e., a desuperheating refrigerant-to-air heating coil) and does not impact the performance of the compressor. This coil can be used in air loop simulations but can t be used by certain compound objects (e.g., AirLoopHVAC:UnitaryHeatPump:AirToAir, AirLoopHVAC:UnitaryHeatPump:WaterToAir, or Dehumidifier:Desiccant:NoFans) or any air distribution equipment (e.g., AirTerminal:SingleDuct:ConstantVolume:Reheat, AirTerminal:SingleDuct:VAV:Reheat, or AirTerminal:SingleDuct:SeriesPIU:Reheat).

The desuperheater heating coil input requires a coil name, an availability schedule, and a heat reclaim recovery efficiency. The reclaim recovery efficiency determines the amount of heat available for use by this heating coil. Approximately 25-30% of the energy rejected by typical refrigeration system condensers is to reduce the superheated refrigerant vapor temperature to the condensing temperature. Recovery efficiencies higher than 30% may cause the refrigerant gas to condense which in turn impacts the performance of the refrigeration system. For this reason, the maximum heat reclaim recovery efficiency for this coil is 30% for most sources of waste heat, including refrigeration compressor racks. The one exception to this 30% limit is a condenser that is part of a detailed refrigeration system. In a detailed refrigeration system, the portion of the rejected heat that lies within the superheated region is explicitly calculated. Therefore, the desuperheater coils supplied by a condenser attached to a detailed refrigeration system are subject to a maximum reclaim recovery efficiency of 90% of the heat within the superheated region.

The next two input items for the desuperheater heating coil are the node names for the inlet and outlet air streams. The following two input fields define the source of heating energy for the coil. This desuperheater heating coil may only be used with direct expansion (DX) cooling or refrigeration equipment. The first of these two inputs is the heating source object type while the second defines the name of the heating source. For proper modeling, the desuperheater heating coil must be placed downstream of a DX cooling coil when reclaiming heat from that cooling coil. Desuperheating heating coil placement is unrestricted when reclaiming heat from a Refrigeration:CompressorRack or Refrigeration:Condenser.

The next input field is optional and defines the set point node name if the desuperheater heating coil is to be controlled based on temperature. When a load-based control scheme is used, this field is left blank. A final optional input is used to model parasitic electric energy use of auxiliary equipment associated with the desuperheater heating coil (e.g., solenoid valve).

Inputs[LINK]

Field: Name[LINK]

This alpha field defines a unique user-assigned name for an instance of a desuperheater heating coil. Any reference to this desuperheater heating coil by another object will use this name.

Field: Availability Schedule Name[LINK]

This alpha field defines the name of the schedule (ref: Schedule) that denotes whether the desuperheater heating coil can run during a given time period. Schedule values must range from 0 to 1. A schedule value greater than 0 indicates that the coil can operate during the time period. A value equal to 0 denotes that the coil must be off for that time period. If this field is blank, the schedule has values of 1 for all time periods.

Field: Heat Reclaim Recovery Efficiency[LINK]

This numeric field defines the ratio of recovered waste heat from the superheated refrigerant gas to the total rejected waste heat from the heating source (as if no heat reclaim occurred). Values can range from 0.0 up to a maximum of 0.9 if the source is a refrigeration condenser and 0.3 for all other waste heat sources. If this input field is left blank, the default value is 0.8 for a refrigeration condenser source type and 0.25 for all other sources.

Field: Air Inlet Node Name[LINK]

This alpha field defines the name of the HVAC system node from which the desuperheater heating coil draws its inlet air.

Field: Air Outlet Node Name[LINK]

This alpha field defines the name of the HVAC system node to which the desuperheater heating coil sends its outlet air.

Field: Heating Source Object Type[LINK]

This alpha field defines the source of superheated refrigerant gas from which the desuperheater heating coil recovers energy. Valid choices are:

When the heating coil source is a DX Coil, the air loop s supply air fan control mode may be auto fan (cycling fan cycling coil), constant fan, or variable volume. When the heating source is a compressor rack for refrigerated cases or a refrigeration condenser, the supply air fan control mode should be either variable volume or constant fan.

NOTE: Use of the desuperheater heating coil in variable air volume systems should be done with caution since the model assumption of a fixed heat reclaim recovery efficiency may not be valid if the air flow rate over the coil varies significantly.

Field: Heating Source Name[LINK]

This alpha field defines the name of the desuperheater heating coil source (e.g., the name of a specific valid coil (as mentioned in the previous field) which provides waste heat to this desuperheater heating coil).

NOTE: When the heating source is a Refrigeration Compressor rack, the heat rejection location in the Refrigeration:CompressorRack object must be Outdoors . If the compressor rack heat rejection location is Zone , the total amount of heat rejection available for reclaim (e.g., by this desuperheater heating coil) is set to zero by the compressor rack object and the simulation proceeds.

Field: Temperature Setpoint Node Name[LINK]

This optional alpha field defines the name of the HVAC system node used for temperature-based control (e.g., controlling the heating coil s outlet air dry-bulb temperature to a setpoint). If the desuperheater heating coil is temperature controlled through the use of a Set Point Manager, then the control node specified in the Set Point Manager will be entered here. If the desuperheater heating coil is controlled based on a certain heating load to be met (e.g., using this heating coil as part of AirLoopHVAC:Unitary:Furnace:HeatCool for high humidity control), this field should be left blank.

Field: Parasitic Electric Load[LINK]

This optional numeric field defines the parasitic electric load (in Watts) due to control valves or other devices specific to the desuperheater heating coil. The load is applied whenever the coil is heating the air. The model assumes that this electric load is small and does not contribute to heating the air.

Following is an example input for a desuperheater heating coil.

Coil:Heating:Desuperheater,
  DesuperheaterCoil,                                   !- Coil Name
  FanAndCoilAvailSched,                             !- Availability Schedule
  0.3,                                                               !- Heat Reclaim Recovery Efficiency
  Cooling Coil Air Outlet Node,             !- Coil Air Inlet Node Name
  Air Loop Outlet Node,                             !- Coil Air Outlet Node Name
  Coil:Cooling:DX:SingleSpeed, !- Heating Source Type
  Furnace ACDXCoil 1,                                 !- Heating Source Name
  ,                                                                     !- Coil Temperature Setpoint Node Name
  0.1;                                                               !- Parasitic Electric Load {W}

Outputs[LINK]

  • HVAC,Average,Heating Coil Rate [W]

  • HVAC,Sum,Heating Coil Energy [J]

  • HVAC,Average,Heating Coil Electric Power [W]

  • HVAC,Sum,Heating Coil Electric Consumption [J]

  • HVAC,Average,Heating Coil Runtime Fraction []

  • HVAC,Average,Heating Coil Air Heating Rate [W]

  • HVAC,Sum,Heating Coil Air Heating Energy [J]

  • HVAC,Average,Heating Coil Electric Power [W]

  • HVAC,Sum,Heating Coil Electric Energy [J]

  • HVAC,Average,Heating Coil Runtime Fraction

Heating Coil Air Heating Rate [W] [LINK]

This output is the average heating rate of the desuperheater heating coil in Watts over the timestep being reported. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil.

Heating Coil Air Heating Energy [J] [LINK]

This output is the total heating output of the desuperheater heating coil in Joules over the timestep being reported. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil. This output is also added to a meter with Resource Type = EnergyTransfer, End Use Key = HeatingCoils, Group Key = System (ref. Output:Meter objects).

Heating Coil Electric Power [W] [LINK]

This output is the average electric consumption rate for the parasitic load associated with the desuperheater heating coil in Watts.

Heating Coil Electric Energy [J] [LINK]

This output is the electric consumption of the desuperheater heating coil parasitic load in Joules for the timestep being reported. This output is also added to a meter with Resource Type = Electricity, End Use Key = Heating, Group Key = System (ref. Output:Meter objects).

Heating Coil Runtime Fraction [] [LINK]

This is the runtime fraction of the desuperheater heating coil for the timestep being reported. Since the desuperheater heating coil can only provide heat when the heat source object is active, the runtime fraction of the desuperheater heating coil will always be less than or equal to the runtime fraction of the heat source object.

Coil:Cooling:DX:VariableRefrigerantFlow[LINK]

The variable refrigerant flow (VRF) DX cooling coil model is nearly identical to the single-speed DX cooling coil model (Ref. Coil:Cooling:DX:SingleSpeed). For this reason, an adaptation of the single-speed DX cooling coil model is used to model the variable-speed compression system used in VRF AC systems. The model inputs are quite similar to the input requirements for the single-speed DX cooling coil model, however, the location of a majority of the inputs have been moved to the variable refrigerant flow air conditioner object since multiple DX cooling coils will use the same DX compression system (Ref. AirConditioner:VariableRefrigerantFlow).

Inputs[LINK]

Field: Coil Name[LINK]

This alpha field defines a unique user-assigned name for an instance of a VRF DX cooling coil. Any reference to this DX cooling coil by another object will use this name. This cooling coil name must be entered in the AirConditioner:VariableRefrigerantFlow object. No other sytem type uses this specific coil.

Field: Availability Schedule Name[LINK]

This alpha field defines the name of the DX cooling coil availabiltiy schedule. Schedule values of 0 denote the DX cooling coil is off. A schedule value greater than 0 indicates that the coil can operate during the time period. If this field is blank, the schedule has values of 1 for all time periods.

Field: Gross Rated Total Cooling Capacity[LINK]

This numeric field defines the gross rated total cooling capacity of the DX cooling coil in watts. The total cooling capacity should be a gross , i.e., the effect of supply air fan heat NOT accounted for.

Field: Gross Ratio Sensible Heat Ratio[LINK]

This numeric field defines the gross sensible heat ratio (sensible capacity divided by total cooling capacity) of the DX cooling coil at rated conditions. Both the sensible and total cooling capacities used to define the Rated SHR should be gross (i.e., the effect of supply air fan heat is NOT accounted for)

Field: Rated Air Flow Rate[LINK]

The air volume flow rate, in m3 per second, across the DX cooling coil at rated conditions. The rated air volume flow rate should be between 0.00004027 m3/s and 0.00006041 m3/s per watt of rated total cooling capacity (300 to 450 cfm/ton). The gross rated total cooling capacity and gross rated SHR should be performance information for the unit with at this rated air volume flow rate.

Field: Cooling Capacity Ratio Modifier Function of Temperature Curve Name[LINK]

This alpha field defines the cooling capacity ratio modifier as a function of indoor wet-bulb temperature or indoor wet-bulb and outdoor dry-bulb temperatures. This curve is a linear, quadratic, or cubic curve if the cooling capacity is solely a function of indoor wet-bulb temperature (i.e., the indoor terminal units weighted average inlet air wet-bulb temperatures). Without specific manufacturers data indicating otherwise, the use of a single independent variable is recommended for this coil type. If, however, the user has reason to believe the cooling capacity is both a function of indoor wet-bulb temperature and outdoor dry-bulb temperature (and has manufacturers data to create the performance curve), a bi-quadratic equation using weighted average indoor wet-bulb temperature and condenser entering air dry-bulb temperature as the independent variables may be used. See the Engineering Reference for more discussion on using this input field.

Field: Cooling Capacity Modifier Curve Function of Flow Fraction Name[LINK]

This alpha field defines the name of a linear, quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of total cooling capacity as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated total cooling capacity and the total cooling capacity modifier curve (function of temperature) to give the gross total cooling capacity at the specific temperature and air flow conditions at which the coil is operating. The curve is normalized to have the value of 1.0 when the actual air flow rate equals the rated air flow rate.

Field: Coil Air Inlet Node Name[LINK]

This alpha field defines the name of the air inlet node entering the DX cooling coil.

Field: Coil Air Outlet Node Name[LINK]

This alpha field defines the name of the air outlet node exiting the DX cooling coil.

Field: Name of Water Storage Tank for Condensate Collection[LINK]

This field is optional. It is used to describe where condensate from the coil is collected. If blank or omitted, then any coil condensate is discarded. Enter the name of Water Storage Tank object defined elsewhere and the condensate will then be collected in that tank.

Following is an example input for a Coil:Cooling:DX:VariableRefrigerantFlow object.

COIL:Cooling:DX:VariableRefrigerantFlow,
  TU1 VRF DX Cooling Coil, !- Coil Name
  VRFAvailSched,                     !- Availability Schedule Name
  autosize,                               !- Gross Rated Total Cooling Capacity {W}
  autosize,                               !- Gross Rated Sensible Heat Ratio
  autosize,                               !- Rated Air Flow Rate {m3/s}
  VRFTUCoolCapFT,                   !- Cooling Capacity Ratio Modifier Function of Temperature Curve Name
  VRFACCoolCapFFF,                 !- Cooling Capacity Modifier Curve Function of Flow Fraction Name
  TU1 VRF DX CCoil Inlet Node,   !- Coil Air Inlet Node
  TU1 VRF DX CCoil Outlet Node;   !- Coil Air Outlet Node

Outputs[LINK]

  • HVAC,Average, Cooling Coil Total Cooling Rate [W]

  • HVAC,Sum, Cooling Coil Total Cooling Energy [J]

  • HVAC,Average, Cooling Coil Sensible Cooling Rate [W]

  • HVAC,Sum, Cooling Coil Sensible Cooling Energy [J]

  • HVAC,Average, Cooling Coil Latent Cooling Rate [W]

  • HVAC,Sum, Cooling Coil Latent Cooling Energy [J]

  • HVAC,Average, Cooling Coil Runtime Fraction []

Evaporative-cooled condenser:

  • HVAC,Average,Cooling Coil Condensate Volume Flow Rate [m3/s]

  • Zone,Meter,Condensate:OnSiteWater [m3]

  • HVAC,Sum,Cooling Coil Condensate Volume [m3]

Cooling Coil Total Cooling Rate [W] [LINK]

This field is the total (sensible and latent) cooling rate output of the DX coil in Watts. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Total Cooling Energy [J] [LINK]

This is the total (sensible plus latent) cooling output of the DX coil in Joules over the time step being reported. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil. This output is also added to a meter with Resource Type = EnergyTransfer, End Use Key = CoolingCoils, Group Key = System (Ref. Output:Meter objects).

Cooling Coil Sensible Cooling Rate [W] [LINK]

This output is the moist air sensible cooling rate output of the DX coil in Watts. This is determined by the inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Sensible Cooling Energy [J] [LINK]

This is the moist air sensible cooling output of the DX coil in Joules for the time step being reported. This is determined by the inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Latent Cooling Rate [W] [LINK]

This is the latent cooling rate output of the DX coil in Watts. This is determined by the inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Latent Cooling Energy [J] [LINK]

This is the latent cooling output of the DX coil in Joules for the time step being reported. This is determined by the inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Runtime Fraction [] [LINK]

This is the runtime fraction of the DX coil compressor and condenser fan(s) for the time step being reported.

Cooling Coil Condensate Volume Flow Rate [m3/s] [LINK]

Cooling Coil Condensate Volume [m3] [LINK]

These outputs are the rate and volume of water collected as condensate from the coil. These reports only appear if a water storage tank is named in the input object.

Coil:Heating:DX:VariableRefrigerantFlow[LINK]

The variable refrigerant flow (VRF) DX heating coil model uses performance information at rated conditions along with performance curves for variations in total capacity, energy input ratio and part load fraction to determine performance at part-load conditions. The impacts of defrost operation is modeled based a combination of user inputs and empirical models taken from the air-to-air heat pump algorithms in DOE-2.1E.

The VRF DX heating coil input requires an availability schedule, the gross rated heating capacity and the rated air volume flow rate. The rated air volume flow rate should be between 0.00008056 m3/s and 0.00002684 m3/s per watt of gross rated heating capacity.

Two performance curves are required. The first performance curve defines the heating capacity as a function of indoor air dry-bulb and outdoor condenser entering air wet-bulb temperature. This curve object is specified in the variable refrigerant flow air-to-air heat pump object. The second performance curve is specific the each VRF DX heating coil and defines the change in heating capacity as a function of air flow fraction. Each of these performance curves are further discussed here.

  1. Heating capacity modifier curve (function of temperature, specified in Heat Pump)

The heating capacity modifier curve (function of temperature) can be a function of both the outdoor wet-bulb temperature and indoor air dry-bulb temperature. Users have the choice of a bi-quadratic curve with two independent variables or a tri-quadratic curve with three independent variable. The tri-quadratic curve is recommended if sufficient manufacturer data is available as it provides sensitivity to the combined total capacity of all indoor units connected to the heat pump condenser and a more realistic output. The output of this curve is multiplied by the gross rated heating capacity to give the gross heating capacity at specific temperature operating conditions (i.e., at an outdoor or indoor air temperature different from the rating point temperature) and the combination ratio of the installed system.

  1. Heating capacity modifier curve (function of flow fraction, specified in DX coil)

The heating capacity modifier curve (function of flow fraction) is a quadratic or cubic curve with the independent variable being the ratio of the actual air flow rate across the heating coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated heating capacity and the heating capacity modifier curve (function of temperature) to give the gross heating capacity at the specific temperature and air flow conditions at which the coil is operating.

Inputs[LINK]

Field: Name[LINK]

This alpha field defines a unique user-assigned name for an instance of a VRF DX heating coil. Any reference to this DX heating coil by another object will use this name.

Field: Availability Schedule Name[LINK]

This alpha field defines the name of the schedule (ref: Schedule) that denotes whether the DX heating coil can run during a given time period. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off for the time period. If this field is blank, the schedule has values of 1 for all time periods.

Field: Gross Rated Heating Capacity[LINK]

This numeric field defines the total, full load gross heating capacity in watts of the DX coil unit at rated conditions (outside air dry-bulb temperature of 8.33 C, outside air wet-bulb temperature of 6.11 C, heating coil entering air dry-bulb temperature of 21.11 C, heating coil entering air wet-bulb temperature of 15.55 C, and a heating coil air flow rate defined by field rated air flow volume below). The value entered here must be greater than 0. The gross total heating capacity should not account for the effect of supply air fan heat.

Field: Rated Air Flow Rate[LINK]

This numeric field defines the volume air flow rate, in m3 per second, across the DX heating coil at rated conditions. The value entered here must be greater than 0. The rated air volume flow rate should be between 0.00004027 m3/s and 0.00006041 m3/s per watt of gross rated heating capacity. The gross rated heating capacity and the gross rated COP should be performance information for the unit with outside air dry-bulb temperature of 8.33 C, outside air wet-bulb temperature of 6.11 C, heating coil entering air dry-bulb temperature of 21.11 C, heating coil entering air wet-bulb temperature of 15.55 C, and the rated air volume flow rate defined here.

Field: Coil Air Inlet Node[LINK]

This alpha field defines the name of the HVAC system node from which the DX heating coil draws its inlet air.

Field: Coil Air Outlet Node[LINK]

This alpha field defines the name of the HVAC system node to which the DX heating coil sends its outlet air.

Field: Heating Capacity Ratio Modifier Function of Temperature Curve Name[LINK]

This alpha field defines the heating capacity ratio modifier as a function of indoor dry-bulb temperature or indoor dry-bulb and outdoor wet-bulb temperatures. This curve is a linear, quadratic, or cubic curve if the heating capacity is solely a function of indoor dry-bulb temperature (i.e., the indoor terminal units weighted average inlet air dry-bulb temperatures). Without specific manufacturers data indicating otherwise, the use of a single independent variable is recommended for this coil type. If, however, the user has reason to believe the heating capacity is both a function of indoor dry-bulb temperature and outdoor wet-bulb temperature (and has manufacturers data to create the performance curve), a bi-quadratic equation using weighted average indoor dry-bulb temperature and condenser entering air wet-bulb temperature as the independent variables may be used. See the Engineering Reference for more discussion on using this input field.

Note: The choice of using either outdoor dry-bulb temperature or outdoor wet-bulb temperature as the independent variable in this performance curve is set in the parent object AirConditioner: VariableRefrigerantFlow.

Field: Heating Capacity Ratio Modifier Function of Flow Fraction Curve Name[LINK]

This alpha field defines the name of a linear, quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of heating capacity as a function of the ratio of actual air flow rate across the heating coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated heating capacity and the heating capacity modifier curve (function of temperature) to give the gross heating capacity at the specific temperature and air flow conditions at which the coil is operating. The curve is normalized to have the value of 1.0 when the actual air flow rate equals the rated air flow rate.

Following is an example input for the object.

COIL:Heating:DX:VariableRefrigerantFlow,
  TU1 VRF DX Heating Coil, !- Coil Name
  VRFAvailSched,                     !- Availability Schedule
  autosize,                               !- Gross Rated Heating Capacity {W}
  autosize,                               !- Rated Air Flow Rate {m3/s}
  TU1 VRF DX CCoil Outlet Node,   !- Coil Air Inlet Node
  TU1 VRF DX HCoil Outlet Node,   !- Coil Air Outlet Node
  VRFTUHeatCapFT,                   !- Heating Capacity Ratio Modifier Function of Temperature Curve Name
  VRFACCoolCapFFF;                 !- Total heating capacity modifier curve Function of Flow Fraction

Outputs[LINK]

  • HVAC,Average, Heating Coil Total Heating Rate [W]

  • HVAC,Sum, Heating Coil Total Heating Energy [J]

  • HVAC,Average, Heating Coil Runtime Fraction []

Heating Coil Total Heating Rate [W] [LINK]

This field is the total heating rate output of the DX coil in Watts. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil.

Heating Coil Total Heating Energy [J] [LINK]

This is the total heating output of the DX coil in Joules over the time step being reported. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil. This output is also added to a meter with Resource Type = EnergyTransfer, End Use Key = HeatingCoils, Group Key = System (ref. Output:Meter objects).

Heating Coil Runtime Fraction [] [LINK]

This is the runtime fraction of the DX coil compressor and condenser fan(s) for the time step being reported.

Coil:Cooling:DX:VariableRefrigerantFlow:FluidTemperatureControl[LINK]

This coil object is specifically designed for the physics based VRF model applicable for Fluid Temperature Control (VRF-FluidTCtrl). It describes the performance of the indoor unit coil of the VRF system operating at cooling mode. The name of this object is entered as an input to the object ZoneHVAC:TerminalUnit:VariableRefrigerantFlow. The outdoor unit part of the VRF system is modeled separately (refer to AirConditioner:VariableRefrigerantFlow:FluidTemperatureControl object).

Inputs[LINK]

Field: Name[LINK]

This alpha field defines a unique user-assigned name for an instance of a VRF DX cooling coil. Any reference to this DX cooling coil by another object will use this name. This cooling coil name must be entered in the AirConditioner:VariableRefrigerantFlow:FluidTemperatureControl object. No other system type uses this specific coil.

Field: Availability Schedule Name[LINK]

This alpha field defines the name of the coil availability schedule. A name should be entered to define the availability of the coil. Schedule values of 0 denote the DX cooling coil is off. A schedule value greater than 0 indicates that the coil can operate during the time period. If this field is blank, the schedule has values of 1 for all time periods.

Field: Coil Air Inlet Node[LINK]

This alpha field defines the name of the air inlet node entering the DX cooling coil.

Field: Coil Air Outlet Node[LINK]

This alpha field defines the name of the air outlet node exiting the DX cooling coil.

Field: Rated Total Cooling Capacity[LINK]

This numeric field defines the gross rated total cooling capacity of the DX cooling coil in watts. The total cooling capacity should be a gross , i.e., the effect of supply air fan heat NOT accounted for. Note that if autosize is selected for this field, the cooling design supply air temperature provided in the Sizing:Zone object needs to be in accordance with the Indoor Unit Evaporating Temperature Function of Superheating Curve provided below in this object.

Field: Rated Sensible Heat Ratio[LINK]

This numeric field defines the gross sensible heat ratio (sensible capacity divided by total cooling capacity) of the DX cooling coil at rated conditions. Both the sensible and total cooling capacities used to define the Rated SHR should be gross (i.e., the effect of supply air fan heat is NOT accounted for)

Field: Indoor Unit Reference Superheating[LINK]

This numeric field defines the reference superheating degrees of the indoor unit. If this field is blank, the default value of 5.0 C is used.

Field: Indoor Unit Evaporating Temperature Function of Superheating Curve Name[LINK]

This alpha field defines the name of a quadratic performance curve that parameterizes the variation of indoor unit evaporating temperature as a function of superheating degrees. The output of this curve is the temperature difference between the coil surface air temperature and the evaporating temperature.

Field: Name of Water Storage Tank for Condensate Collection[LINK]

This field is optional. It is used to describe where condensate from the coil is collected. If blank or omitted, then any coil condensate is discarded. Enter the name of Water Storage Tank object defined elsewhere and the condensate will then be collected in that tank.

Following is an example input for a Coil:Cooling:DX:VariableRefrigerantFlow:FluidTemperatureControl object.

Coil:Cooling:DX:VariableRefrigerantFlow:FluidTemperatureControl,
  TU1 VRF DX Cooling Coil, !- Name
  VRFAvailSched,           !- Availability Schedule Name
  TU1 VRF DX CCoil Inlet Node,  !- Coil Air Inlet Node
  TU1 VRF DX CCoil Outlet Node,  !- Coil Air Outlet Node
  autosize,                !- Rated Total Cooling Capacity {W}
  autosize,                !- Rated Sensible Heat Ratio
  3,                       !- Indoor Unit Reference Superheating Degrees {C}    
  IUEvapTempCurve,         !- Indoor Unit Evaporating Temperature Function of Superheating Curve Name    
  ;                        !- Name of Water Storage Tank for Condensate Collection

  Curve:Quadratic,
  IUEvapTempCurve,         !- Name
  0,                       !- Coefficient1 Constant
  0.843,                   !- Coefficient2 x
  0,                       !- Coefficient3 x**2
  0,                       !- Minimum Value of x    
  15,                      !- Maximum Value of x    
  ,                        !- Minimum Curve Output
  ,                        !- Maximum Curve Output
  Temperature,             !- Input Unit Type for X
  Temperature;             !- Output Unit Type

Outputs[LINK]

  • HVAC,Average, Cooling Coil Total Cooling Rate [W]

  • HVAC,Sum, Cooling Coil Total Cooling Energy [J]

  • HVAC,Average, Cooling Coil Sensible Cooling Rate [W]

  • HVAC,Sum, Cooling Coil Sensible Cooling Energy [J]

  • HVAC,Average, Cooling Coil Latent Cooling Rate [W]

  • HVAC,Sum, Cooling Coil Latent Cooling Energy [J]

  • HVAC,Average, Cooling Coil Runtime Fraction []

  • HVAC,Average, Cooling Coil VRF Evaporating Temperature [C]

  • HVAC,Average, Cooling Coil VRF Super Heating Degrees [C]

Evaporative-cooled condenser:

  • HVAC,Average,Cooling Coil Condensate Volume Flow Rate [m3/s]

  • Zone,Meter,Condensate:OnSiteWater [m3]

  • HVAC,Sum,Cooling Coil Condensate Volume [m3]

Cooling Coil Total Cooling Rate [W] [LINK]

This field is the total (sensible and latent) cooling rate output of the DX coil in Watts. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Total Cooling Energy [J] [LINK]

This is the total (sensible plus latent) cooling output of the DX coil in Joules over the time step being reported. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil. This output is also added to a meter with Resource Type = EnergyTransfer, End Use Key = CoolingCoils, Group Key = System (Ref. Output:Meter objects).

Cooling Coil Sensible Cooling Rate [W] [LINK]

This output is the moist air sensible cooling rate output of the DX coil in Watts. This is determined by the inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Sensible Cooling Energy [J] [LINK]

This is the moist air sensible cooling output of the DX coil in Joules for the time step being reported. This is determined by the inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Latent Cooling Rate [W] [LINK]

This is the latent cooling rate output of the DX coil in Watts. This is determined by the inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Latent Cooling Energy [J] [LINK]

This is the latent cooling output of the DX coil in Joules for the time step being reported. This is determined by the inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Runtime Fraction [] [LINK]

This is the runtime fraction of the DX coil compressor and condenser fan(s) for the time step being reported.

Cooling Coil VRF Evaporating Temperature [C] [LINK]

This is the evaporating temperature of the VRF system operating at cooling mode. This value is manipulated by the VRF system considering the load conditions of all the zones it serves. It affects the cooling coil surface temperature and thus the cooling capacity of the coil.

Cooling Coil VRF Super Heating Degrees [C] [LINK]

This is the super heating degrees of the VRF system operating at cooling mode. This value is manipulated by each VRF terminal unit to adjust the cooling capacity of the coil considering the load conditions of the zone. It affects the cooling coil surface temperature and thus the cooling capacity of the coil.

Cooling Coil Condensate Volume Flow Rate [m3/s] [LINK]

This is the volumetric rate of water collected as condensate from the coil. This report only appears if a water storage tank is named in the input object.

Cooling Coil Condensate Volume [m3] [LINK]

This is the volume of water collected as condensate from the coil. This report only appears if a water storage tank is named in the input object.

Coil:Heating:DX:VariableRefrigerantFlow:FluidTemperatureControl[LINK]

This coil object is specifically designed for the physics based VRF model applicable for Fluid Temperature Control (VRF-FluidTCtrl). It describes the performance of the indoor unit coil of the VRF system operating at heating mode. The name of this object is entered as an input to the object ZoneHVAC:TerminalUnit:VariableRefrigerantFlow. The outdoor unit part of the VRF system is modeled separately (refer to AirConditioner:VariableRefrigerantFlow:FluidTemperatureControl object).

Inputs[LINK]

Field: Name[LINK]

This alpha field defines a unique user-assigned name for an instance of a VRF DX heating coil. Any reference to this DX heating coil by another object will use this name. This heating coil name must be entered in the AirConditioner:VariableRefrigerantFlow:FluidTemperatureControl object. No other system type uses this specific coil.

Field: Availability Schedule[LINK]

This alpha field defines the name of the schedule (ref: Schedule) that denotes whether the DX heating coil can run during a given time period. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off for the time period. If this field is blank the unit is always available.

Field: Coil Air Inlet Node[LINK]

This alpha field defines the name of the HVAC system node from which the DX heating coil draws its inlet air.

Field: Coil Air Outlet Node[LINK]

This alpha field defines the name of the HVAC system node to which the DX heating coil sends its outlet air.

Field: Rated Total Heating Capacity[LINK]

This numeric field defines the total, full load gross heating capacity in watts of the DX coil unit at rated conditions. The value entered here must be greater than 0. The gross total heating capacity should not account for the effect of supply air fan heat.

Field: Indoor Unit Reference Subcooling[LINK]

This numeric field defines the reference subcooling degrees of the indoor unit. If this field is blank, the default value of 5.0 C is used.

Field: Indoor Unit Condensing Temperature Function of Subcooling Curve Name[LINK]

This alpha field defines the name of a quadratic performance curve that parameterizes the variation of indoor unit condensing temperature as a function of subcooling degrees. The output of this curve is the temperature difference between the condensing temperature and the coil surface air temperature.

Following is an example input for a Coil:Heating:DX:VariableRefrigerantFlow:FluidTemperatureControl object.

Coil:Heating:DX:VariableRefrigerantFlow:FluidTemperatureControl,
  TU1 VRF DX Heating Coil, !- Name
  VRFAvailSched,           !- Availability Schedule
  TU1 VRF DX CCoil Outlet Node,  !- Coil Air Inlet Node
  TU1 VRF DX HCoil Outlet Node,  !- Coil Air Outlet Node
  autosize,                !- Rated Total Heating Capacity {W}
  5,                       !- Indoor Unit Reference Subcooling Degrees {C}    
  IUCondTempCurve;         !- Indoor Unit Condensing Temperature Function of Subcooling Curve Name

  Curve:Quadratic,
  IUCondTempCurve,         !- Name
  -1.85,                   !- Coefficient1 Constant
  0.411,                   !- Coefficient2 x
  0.0196,                  !- Coefficient3 x**2
  0,                       !- Minimum Value of x    
  20,                      !- Maximum Value of x    
  ,                        !- Minimum Curve Output
  ,                        !- Maximum Curve Output
  Temperature,             !- Input Unit Type for X
  Temperature;             !- Output Unit Type

Outputs[LINK]

  • HVAC,Average, Heating Coil Total Heating Rate [W]

  • HVAC,Sum, Heating Coil Total Heating Energy [J]

  • HVAC,Average, Heating Coil Runtime Fraction []

  • Heating Coil VRF Condensing Temperature [C]

  • Heating Coil VRF Subcooling Degrees [C]

Heating Coil Total Heating Rate [W] [LINK]

This field is the total heating rate output of the DX coil in Watts. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil.

Heating Coil Total Heating Energy [J] [LINK]

This is the total heating output of the DX coil in Joules over the time step being reported. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil. This output is also added to a meter with Resource Type = EnergyTransfer, End Use Key = HeatingCoils, Group Key = System (ref. Output:Meter objects).

Heating Coil Runtime Fraction [] [LINK]

This is the runtime fraction of the DX coil compressor and condenser fan(s) for the time step being reported.

Cooling Coil VRF Condensing Temperature [C] [LINK]

This is the condensing temperature of the VRF system operating at heating mode. This value is manipulated by the VRF system considering the load conditions of all the zones it serves. It affects the heating coil surface temperature and thus the heating capacity of the coil.

Cooling Coil VRF Subcooling Degrees [C] [LINK]

This is the subcooling degrees of the VRF system operating at heating mode. This value is manipulated by each VRF terminal unit to adjust the heating capacity of the coil considering the load conditions of the zone. It affects the heating coil surface temperature and thus the heating capacity of the coil.

Coil:Heating:Fuel[LINK]

The fuel heating coil is a simple capacity model with a user inputted gas burner efficiency. The default for the burner efficiency is 80%. This coil will be simpler than shown in Figure since it will only have air nodes to connect it in the system. The coil can be used in the air loop simulation or in the zone equipment as a reheat coil. Depending on where it is used determines if this coil is temperature or capacity controlled. If used in the air loop simulation it will be controlled to a specified temperature scheduled from the Setpoint Manager. If it is used in zone equipment, it will be controlled from the zone thermostat by meeting the zone demand.

Inputs[LINK]

Field: Name[LINK]

A unique identifying name for each coil.

Field: Availability Schedule Name[LINK]

Schedule that defines when the coil is available. If the schedule s value is 0.0, then the coil is not available and flow will not be requested. If the schedule s value is > 0.0 (usually 1 is used), the coil is available. If this field is blank, the schedule has values of 1 for all time periods. Schedule values must be > = 0 and < = 1.

Field: Fuel Type[LINK]

This field designates the appropriate fuel type for the coil. Valid fuel types are: Gas, NaturalGas, PropaneGas, FuelOil#1, FuelOil#2, Diesel, Gasoline, Coal, Steam, DistrictHeating, DistrictCooling, OtherFuel1 and OtherFuel2. The fuel type triggers the application of consumption amounts to the appropriate energy meters. NaturalGas is the default.

Field: Burner Efficiency[LINK]

This is user inputted gas burner efficiency (decimal, not percent) and is defaulted to 80%.

Field: Nominal Capacity[LINK]

This is the maximum capacity of the coil (W). This controlled coil will only provide the needed capacity to meet the control criteria whether it is temperature or capacity controlled. This field is autosizable.

Field: Air Inlet Node Name[LINK]

The name of the air inlet to the coil, i.e. Heating Coil Air Inlet Node.

Field: Air Outlet Node Name[LINK]

The name of the air outlet from the coil, i.e. Heating Coil Air Outlet Node.

Field: Temperature Setpoint Node Name[LINK]

If the coil is used in the air loop simulation and is temperature controlled using a Set Point Manager, then the node that is the control node needs to be specified here. If the coil is used in an air terminal unit, the coil is load controlled and a control node set point is not required.

Field: Parasitic Electric Load[LINK]

This is the parasitic electric load associated with the coil operation, such as an inducer fan, etc.. This will be modified by the PLR (or coil runtime fraction if a part-load fraction correlation is provided in the next input field) to reflect the time of operation in a simulation timestep.

Field: Part Load Fraction Correlation Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve (Ref: Performance Curves) that parameterizes the variation of fuel consumption rate by the heating coil as a function of the part load ratio (PLR, sensible heating load/nominal capacity of the heating coil). For any simulation timestep, the nominal fuel consumption rate (heating load/burner efficiency) is divided by the part-load fraction (PLF) if a part-load curve has been defined. The part-load curve accounts for efficiency losses due to transient coil operation.

The part-load fraction correlation should be normalized to a value of 1.0 when the part load ratio equals 1.0 (i.e., no efficiency losses when the heating coil runs continuously for the simulation timestep). For PLR values between 0 and 1 ( 0 < = PLR < 1), the following rules apply:

PLF > = 0.7 and PLF > = PLR

If PLF < 0.7 a warning message is issued, the program resets the PLF value to 0.7, and the simulation proceeds. The runtime fraction of the heating coil is defined a PLR/PLF. If PLF < PLR, then a warning message is issues and the runtime fraction of the coil is limited to 1.0.

A typical part load fraction correlation for a conventional gas heating coil (e.g., residential furnace) would be:

PLF = 0.8 + 0.2(PLR)

Field: Parasitic Fuel Load[LINK]

This numeric field is the parasitic fuel load associated with the coil’s operation (Watts), such as a standing pilot light. The model assumes that this parasitic load is consumed only for the portion of the simulation timestep where the heating coil is not operating.

Outputs[LINK]

  • HVAC,Sum,Heating Coil Air Heating Energy [J]

  • HVAC,Average,Heating Coil Air Heating Rate [W]

  • HVAC,Sum,Heating Coil Gas Energy [J]

  • HVAC,Average,Heating Coil <Fuel Type> Rate [W]

  • HVAC,Sum,Heating Coil Electric Energy [J]

  • HVAC,Average,Heating Coil Electric Power [W]

  • HVAC,Average,Heating Coil Runtime Fraction []

  • HVAC,Sum,Heating Coil Ancillary <Fuel Type> Energy [J]

  • HVAC,Average,Heating Coil Ancillary <Fuel Type> Rate [W]

Heating Coil Air Heating Energy [J] [LINK]

This field is the total heating output of the coil in Joules over the timestep being reported. This output is also added to a meter with Resource Type = EnergyTransfer, End Use Key = HeatingCoils, Group Key = System (ref. Output:Meter objects).

Heating Coil Air Heating Rate [W] [LINK]

This field is the average heating rate output of the coil in Watts over the timestep being reported.

Heating Coil <Fuel Type> Energy [J] [LINK]

This field is the fuel consumption of the heating coil in Joules over the timestep being reported, including the impacts of part-load performance if a part load fraction correlation is specified. This output is also added to a meter with Resource Type = Gas, End Use Key = Heating, Group Key = System (ref. Output:Meter objects).

Heating Coil <Fuel Type> Rate [W] [LINK]

This field is the average gas consumption rate of the coil in Watts over the timestep being reported, including the impacts of part-load performance if a part load fraction correlation is specified.

Heating Coil Electric Energy [J] [LINK]

This field is the electric consumption of the heating coil auxiliaries in Joules over the timestep being reported (e.g., inducer fan). This output is also added to a meter with Resource Type = Electricity, End Use Key = Heating, Group Key = System (ref. Output:Meter objects).

Heating Coil Electric Power [W] [LINK]

This field is the average electric consumption rate of the heating coil auxiliaries (e.g., inducer fan) in Watts over the timestep being reported.

Heating Coil Runtime Fraction [] [LINK]

This field is the runtime fraction of the coil over the timestep being reported.

Heating Coil Ancillary <Fuel Type> Energy [J] [LINK]

This field is the parasitic fuel consumption of the heating coil in Joules over the timestep being reported (e.g., standing pilot light). The model assumes that the parasitic load is accumulated only for the portion of the simulation timestep where the gas heating coil is not operating. This output is also added to a meter with Resource Type = ’<Fuel Type>’, End Use Key = Heating, Group Key = System (ref. Output:Meter objects).

Heating Coil Ancillary <Fuel Type> Rate [W] [LINK]

This field is the average parasitic gas consumption rate of the heating coil (e.g., standing pilot light) in Watts over the timestep being reported. The model assumes that the parasitic load is present only for the portion of the simulation timestep where the heating coil is not operating.

Coil:Heating:Gas:MultiStage[LINK]

The multi stage gas heating coil is a simple capacity model with a user inputted gas burner efficiencies at different stages. This coil will only have air nodes to connect it in the system. The coil can be used in the air loop simulation or in the zone equipment as a reheat coil. Depending on where it is used determines if this coil is temperature or capacity controlled. If used in the air loop simulation it will be controlled to a specified temperature scheduled from the Setpoint Manager. If it is used in zone equipment, it will be controlled from the zone thermostat by meeting the zone demand. For the time being, this coil model can only be called by the parent object AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed.

Inputs[LINK]

Field: Name[LINK]

A unique identifying name for each coil.

Field: Availability Schedule Name[LINK]

Schedule that defines when the coil is available. If the schedule s value is 0.0, then the coil is not available and flow will not be requested. If the schedule s value is > 0.0 (usually 1 is used), the coil is available. If this field is blank, the schedule has values of 1 for all time periods. Schedule values must be > = 0 and < = 1.

Field: Air Inlet Node Name[LINK]

The name of the air inlet to the gas coil, i.e. Heating Coil Air Inlet Node.

Field: Air Outlet Node Name[LINK]

The name of the air outlet from the gas coil, i.e. Heating Coil Air Outlet Node.

Field: Temperature Setpoint Node Name[LINK]

If the coil is used in the air loop simulation and is temperature controlled using a Set Point Manager, then the node that is the control node needs to be specified here. If the coil is used in an air terminal unit, the coil is load controlled and a control node set point is not required. At present, the multistage gas heating coil does not model temperature setoint control.

Field: Part Load Fraction Correlation Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve (Ref: Performance Curves) that parameterizes the variation of gas consumption rate by the heating coil as a function of the part load ratio (PLR, sensible heating load/nominal capacity of the heating coil). For any simulation timestep, the nominal gas consumption rate (heating load/burner efficiency) is divided by the part-load fraction (PLF) if a part-load curve has been defined. The part-load curve accounts for efficiency losses due to transient coil operation.

The part-load fraction correlation should be normalized to a value of 1.0 when the part load ratio equals 1.0 (i.e., no efficiency losses when the heating coil runs continuously for the simulation timestep). For PLR values between 0 and 1 ( 0 < = PLR < 1), the following rules apply:

PLF > = 0.7 and PLF > = PLR

If PLF < 0.7 a warning message is issued, the program resets the PLF value to 0.7, and the simulation proceeds. The runtime fraction of the heating coil is defined a PLR/PLF. If PLF < PLR, then a warning message is issues and the runtime fraction of the coil is limited to 1.0.

A typical part load fraction correlation for a conventional gas heating coil (e.g., residential furnace) would be:

PLF = 0.8 + 0.2(PLR)

Field: Parasitic Gas Load[LINK]

This numeric field is the parasitic gas load associated with the gas coil s operation (Watts), such as a standing pilot light. The model assumes that this parasitic load is consumed only for the portion of the simulation timestep where the gas heating coil is not operating.

Field: Stage 1 Gas Burner Efficiency[LINK]

This is user inputted stage 1 gas burner efficiency (decimal, not percent) and is defaulted to 80%.

Field: Stage 1 Nominal Capacity[LINK]

This is the stage 1 capacity of the coil (W). This controlled coil will only provide the needed capacity to meet the control criteria whether it is temperature or capacity controlled. This field is autosizable.

Field: Stage 1 Parasitic Electric Load[LINK]

This is the stage 1 parasitic electric load associated with the gas coil operation, such as an inducer fan, etc.. This will be modified by the PLR (or coil runtime fraction if a part-load fraction correlation is provided in the next input field) to reflect the time of operation in a simulation timestep.

Field: Stage 2 Gas Burner Efficiency[LINK]

This is user inputted stage 2 gas burner efficiency (decimal, not percent) and is defaulted to 80%.

Field: Stage 2 Nominal Capacity[LINK]

This is the stage 2 capacity of the coil (W). This controlled coil will only provide the needed capacity to meet the control criteria whether it is temperature or capacity controlled. This field is autosizable.

Field: Stage 2 Parasitic Electric Load[LINK]

This is the stage 2 parasitic electric load associated with the gas coil operation, such as an inducer fan, etc.. This will be modified by the PLR (or coil runtime fraction if a part-load fraction correlation is provided in the next input field) to reflect the time of operation in a simulation timestep.

Field: Stage 3 Gas Burner Efficiency[LINK]

This is user inputted stage 3 gas burner efficiency (decimal, not percent) and is defaulted to 80%.

Field: Stage 3 Nominal Capacity[LINK]

This is the stage 3 capacity of the coil (W). This controlled coil will only provide the needed capacity to meet the control criteria whether it is temperature or capacity controlled. This field is autosizable.

Field: Stage 3 Parasitic Electric Load[LINK]

This is the stage 3 parasitic electric load associated with the gas coil operation, such as an inducer fan, etc.. This will be modified by the PLR (or coil runtime fraction if a part-load fraction correlation is provided in the next input field) to reflect the time of operation in a simulation timestep.

Field: Stage 4 Gas Burner Efficiency[LINK]

This is user inputted stage 4 gas burner efficiency (decimal, not percent) and is defaulted to 80%.

Field: Stage 4 Nominal Capacity[LINK]

This is the stage 4 capacity of the coil (W). This controlled coil will only provide the needed capacity to meet the control criteria whether it is temperature or capacity controlled. This field is autosizable.

Field: Stage 4 Parasitic Electric Load[LINK]

This is the stage 4 parasitic electric load associated with the gas coil operation, such as an inducer fan, etc.. This will be modified by the PLR (or coil runtime fraction if a part-load fraction correlation is provided in the next input field) to reflect the time of operation in a simulation timestep.

An example in IDF form:

Coil:Heating:Gas:MultiStage,
  Heat Pump Heating Coil 1,                 !- Name
  FanAndCoilAvailSched,                         !- Availability Schedule Name
  Heating Coil Air Inlet Node,           !- Air Inlet Node Name
  SuppHeating Coil Air Inlet Node,   !- Air Outlet Node Name
  ,                                               !- Temp Setpoint node name
  ,                                               !- Part Load Fraction Correlation Curve Name
  ,                                               !- Parasitic Gas Load
  3,                                             !- Number of Speeds
  0.92,                                       !- Speed 1 Gas burner Efficiency
  Autosize,                               !- Speed 1 Nominal Capacity {W}
  ,                                               !- Stage 1 Parasitic Electric Load {W}
  0.88,                                       !- Speed 2 Gas burner Efficiency
  Autosize,                               !- Speed 2 Nominal Capacity {W}
  ,                                               !- Stage 2 Parasitic Electric Load {W}
  0.84,                                       !- Speed 3 Gas burner Efficiency
  Autosize,                               !- Speed 3 Nominal Capacity {W}
  ;                                               !- Stage 3 Parasitic Electric Load {W}

Outputs[LINK]

  • HVAC,Sum,Heating Coil Energy[J]

  • HVAC,Average,Heating Coil Rate[W]

  • HVAC,Sum,Heating Coil Gas Consumption [J]

  • HVAC,Average,Heating Coil Gas Consumption Rate [W]

  • HVAC,Sum,Heating Coil Electric Consumption [J]

  • HVAC,Average,Heating Coil Electric Power [W]

  • HVAC,Average,Heating Coil Runtime Fraction

  • HVAC,Sum,Heating Coil Parasitic Gas Consumption [J]

  • HVAC,Average,Heating Coil Parasitic Gas Consumption Rate [W]

Heating Coil Energy [J] [LINK]

This field is the total heating output of the coil in Joules over the timestep being reported. This output is also added to an output meter with Resource Type = EnergyTransfer, End Use Key = HeatingCoils, Group Key = System (ref. Output:Meter objects).

Heating Coil Rate [W] [LINK]

This field is the average heating rate output of the coil in Watts over the timestep being reported.

Heating Coil Gas Consumption [J] [LINK]

This field is the gas consumption of the heating coil in Joules over the timestep being reported, including the impacts of part-load performance if a part load fraction correlation is specified. This output is also added to an output meter with Resource Type = Gas, End Use Key = Heating, Group Key = System (ref. Output:Meter objects).

Heating Coil Gas Consumption Rate [W] [LINK]

This field is the average gas consumption rate of the coil in Watts over the timestep being reported, including the impacts of part-load performance if a part load fraction correlation is specified.

Heating Coil Electric Consumption [J] [LINK]

This field is the electric consumption of the heating coil auxiliaries in Joules over the timestep being reported (e.g., inducer fan). This output is also added to an output meter with Resource Type = Electricity, End Use Key = Heating, Group Key = System (ref. Output:Meter objects).

Heating Coil Electric Power [W] [LINK]

This field is the average electric consumption rate of the heating coil auxiliaries (e.g., inducer fan) in Watts over the timestep being reported.

Heating Coil Parasitic Gas Consumption [J] [LINK]

This field is the parasitic gas consumption of the heating coil in Joules over the timestep being reported (e.g., standing pilot light). The model assumes that the parasitic load is accumulated only for the portion of the simulation timestep where the gas heating coil is not operating. This output is also added to an output meter with Resource Type = Gas, End Use Key = Heating, Group Key = System (ref. Output:Meter objects).

Heating Coil Parasitic Gas Consumption Rate [W] [LINK]

This field is the average parasitic gas consumption rate of the heating coil (e.g., standing pilot light) in Watts over the timestep being reported. The model assumes that the parasitic load is present only for the portion of the simulation timestep where the gas heating coil is not operating.

Coil:Cooling:Water:DetailedGeometry[LINK]

This detailed flat fin coil model is for continuous plate fins. First, found in Type 12 from MODSIM, but now programmed directly from Elmahdy, A.H. and Mitalas, G.P. Then there was a discontinuity in their original model that was fixed in the EnergyPlus implementation. Now this model can be used in an interval halving solution technique for controlling this coil without the problems of non-convergence.

“A Model for Cooling and Dehumidifying Coils for Use in Energy Requirements for Buildings” ASHRAE Transactions, Vol. 83, Part 2, pp. 103-117 (1977). For fin efficiency see K.A. Gardner, “Efficiency of Extended ,” Transactions ASME, Vol. 67, pp. 621-631, 1945.

The following figures illustrate the geometry and circuits in a cooling coil.

Geometry of a Cooling Coil (CC)

Geometry of a Cooling Coil (CC)

Number of Coolant Circuits (CCNCC)

Number of Coolant Circuits (CCNCC)

Inputs[LINK]

Field: Name[LINK]

A unique identifying name for each coil.

Field:Availability Schedule Name[LINK]

Schedule that defines when the coil is available. If the schedule s value is 0.0, then the coil is not available and flow will not be requested. If the schedule s value is > 0.0 (usually 1 is used), the coil is available. If this field is blank, the schedule has values of 1 for all time periods.

Field: Maximum Water Flow Rate[LINK]

The maximum possible water flow rate (m3/sec) through the coil.

Field: Tube Outside Surface Area[LINK]

The outside surface area (m2) of the tubes that is exposed to air (i.e. the outside area of the unfinned tubes minus the area of tubes covered by the fins).

Field: Total Tube Inside Area[LINK]

The total surface area (m2) inside the tubes (water side).

Field: Fin Surface Area[LINK]

The total surface area (m2) of the fins attached to the coil.

Field: Minimum Air Flow Area[LINK]

The minimum cross sectional area (m2) available for air passage. Frequently calculated as

Amin  = (Amin/Afr)\*Afr

where Afr is the frontal area of the heat exchanger, and (Amin/Afr) is the ratio of the minimum airflow area to frontal area.

Field: Coil Depth[LINK]

The distance (m) from the front of the coil to the back of the coil in the airflow direction. Also called the fin depth. Illustrated in the figure (Figure. Geometry of a Cooling Coil (CC)).

Field: Fin Diameter[LINK]

The outside diameter (m) of the fins. Used instead of COIL HEIGHT

Field: Fin Thickness[LINK]

Thickness (m) of the air side fins.

Field: Tube Inside Diameter[LINK]

The inside diameter (m) of the tubes.

Field: Tube Outside Diameter[LINK]

The outside diameter (m) of the tubes.

Field: Tube Thermal Conductivity[LINK]

The thermal conductivity (W/m-K) of the tube material.

Field: Fin Thermal Conductivity[LINK]

The thermal conductivity (W/m-K) of the fin material.

Field: Fin Spacing[LINK]

The spacing (m) of the fins, centerline to centerline.

Field: Tube Depth Spacing[LINK]

The spacing (m) of the tube rows, centerline to centerline. Also called tube longitudinal spacing.

Field: Number of Tube Rows[LINK]

The number of tube rows in the direction of the airflow.

Field: Number of Tubes per Row[LINK]

The number of tubes per row. (NTPR in the above diagram)

Field: Water Inlet Node Name[LINK]

The name of the water coil inlet from the chilled water loop, i.e. Cooling Coil Water Inlet Node.

Field: Water Outlet Node Name[LINK]

The name of the water coil outlet from the chilled water loop, i.e. Cooling Coil Water Outlet Node.

Field: Air Inlet Node Name[LINK]

The name of the air inlet to the water coil, i.e. Cooling Coil Air Inlet Node.

Field: Air Outlet Node Name[LINK]

The name of the air outlet from the water coil, i.e. Cooling Coil Air Outlet Node.

Field: Condensate Collection Water Storage Tank Name[LINK]

This field is optional. It is used to describe where condensate from the coil is collected. If blank or omitted, then any coil condensate is discarded. Enter the name of Water Storage Tank object defined elsewhere and the condensate will then be collected in that tank.

Examples of these statements in an IDF are:

Coil:Cooling:Water:DetailedGeometry,
  Detailed Cooling Coil,   !Name of cooling coil
  CoolingCoilAvailSched,   !Cooling Coil Schedule
  0.0011,                   !Max Water Flow Rate of Coil m3/sec
  6.23816,                 !Tube Outside Surf Area
  6.20007018,           !Tube Inside Surf Area
  101.7158224,         !Fin Surf Area
  0.300606367,         !Min Air Flow Area
  0.165097968,         !Coil Depth
  0.43507152,           !Coil Height
  0.001499982,         !Fin Thickness
  0.014449958,         !Tube Inside Diameter
  0.015879775,         !Tube Outside Diameter
  386.0,                     !Tube Thermal Conductivity
  204.0,                     !Fin Thermal Conductivity
  0.001814292,         !Fin Spacing
  0.02589977,           !Tube Depth
  6,                             !Number of Tube Rows
  16,                           !Number of Tubes per Row
  NODE_32,NODE_33, !Coil Water Side Inlet & Outlet Node
  NODE_5, NODE_6;   !Coil Air Side Inlet & Outlet Node

Outputs[LINK]

  • HVAC,Sum,Cooling Coil Total Cooling Energy [J]

  • HVAC,Sum,Cooling Coil Sensible Cooling Energy [J]

  • HVAC,Average,Cooling Coil Total Cooling Rate [W]

  • HVAC,Average,Cooling Coil Sensible Cooling Rate [W]

  • HVAC,Average,Cooling Coil Condensate Volume Flow Rate [m3/s]

  • HVAC,Sum,Cooling Coil Source Side Heat Transfer Energy [J]

  • HVAC,Sum,Cooling Coil Condensate Volume [m3]

Cooling Coil Total Cooling Energy (J)[LINK]

Cooling Coil Total Cooling Energy is the total amount of heat transfer taking place in the coil at the operating conditions.

Cooling Coil Sensible Cooling Energy (J)[LINK]

Cooling Coil Sensible Cooling Energy is the total amount of Sensible heat transfer taking place in the coil at the operating conditions. It only takes into account temperature difference in the inlet and outlet air streams at operating conditions.

Cooling Coil Total Cooling Rate (W)[LINK]

Cooling Coil Total Cooling Rate is the Rate of heat transfer taking place in the coil at the operating conditions. The units are (J/sec) or Watts.

Cooling Coil Sensible Cooling Rate (W)[LINK]

Cooling Coil Sensible Cooling Rate is the Rate of Sensible heat transfer taking place in the coil at the operating conditions.

In addition, if a Water Storage Tank is used to collect coil condensate, then the following outputs will be available.

Cooling Coil Condensate Volume Flow Rate [m3/s] [LINK]

Cooling Coil Condensate Volume [m3] [LINK]

These reports provide the rate and amount of condensate from the coil. Condensate is water condensed out of the air as a result of cooling. The condensate volume is also reported on the meter for OnSiteWater.

Cooling Coil Source Side Heat Transfer Energy [J] [LINK]

This is the energy extracted from the chilled water serving the cooling coil, in Joules.

Coil:Cooling:DX:SingleSpeed[LINK]

This DX cooling coil input requires an availability schedule, the gross rated total cooling capacity, the gross rated SHR, the gross rated COP, and the rated air volume flow rate. The latter 4 inputs determine the coil performance at the rating point (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb and air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb). The rated air volume flow rate should be between .00004027 m3/s and .00006041 m3/s per watt of gross rated total cooling capacity (300 to 450 cfm/ton).

The rated volumetric air flow to total cooling capacity ratio for 100% dedicated outdoor air (DOAS) application DX cooling coils should be between 0.00001677 (m3/s)/W (125 cfm/ton) and 0.00003355 (m3/s)/W (250 cfm/ton).

Pumped refrigerant economizer integrated with the single speed DX cooling coil model will use exactly the same model except that performance curves use lookup table to cover the pumped refrigerant economizer and the compressor operating ranges. One or two independent variables may used to represent the performance data.

This model requires 5 curves as follows:

  1. The total cooling capacity modifier curve (function of temperature) is a curve with two independent variables: wet-bulb temperature of the air entering the cooling coil, and dry-bulb temperature of the air entering the air-cooled condenser coil (wet-bulb temperature if modeling an evaporative-cooled condenser). The output of this curve is multiplied by the gross rated total cooling capacity to give the gross total cooling capacity at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures). This curve is typically a biquadratic but any curve or table with two independent variables can be used.

  2. The total cooling capacity modifier curve (function of flow fraction) is a curve or lookup table with the independent variable being the ratio of the actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated total cooling capacity and the total cooling capacity modifier curve (function of temperature) to give the gross total cooling capacity at the specific temperature and air flow conditions at which the coil is operating. This curve is typically a quadratic or cubic but any curve or table with one independent variables can be used.

  3. The energy input ratio (EIR) modifier curve (function of temperature) is a curve with two independent variables: wet-bulb temperature of the air entering the cooling coil, and dry-bulb temperature of the air entering the air-cooled condenser coil (wet-bulb temperature if modeling an evaporative-cooled condenser). The output of this curve is multiplied by the rated EIR (inverse of the rated COP) to give the EIR at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures). This curve is typically a biquadratic but any curve or table with two independent variables can be used.

  4. The energy input ratio (EIR) modifier curve (function of flow fraction) is a curve or lookup table with the independent variable being the ratio of the actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the rated EIR (inverse of the rated COP) and the EIR modifier curve (function of temperature) to give the EIR at the specific temperature and air flow conditions at which the coil is operating. This curve is typically a quadratic or cubic but any curve or table with one independent variables can be used.

  5. The part load fraction correlation (function of part load ratio) is a curve or a lookup table with the independent variable being part load ratio (sensible cooling load / steady-state sensible cooling capacity). The output of this curve is used in combination with the rated EIR and EIR modifier curves to give the effective EIR for a given simulation timestep. The part load fraction (PLF) correlation accounts for efficiency losses due to compressor cycling. The curve should be normalized to a value of 1.0 when the part-load ratio equals 1.0 (i.e., the compressor(s) run continuously for the simulation timestep). This curve is typically a quadratic or cubic but any curve or table with one independent variables can be used.

The curves are simply specified by name. Curve inputs are described in the curve manager section of this document (see Performance Curves in this document).

The next four input fields are optional and relate to the degradation of latent cooling capacity when the supply air fan operates continuously while the cooling coil/compressor cycle on and off to meet the cooling load. The fan operating mode is determined in the partent object and is considered to either be constant (e.g. CoilSystem:Cooling:DX) or can be scheduled (e.g. AirLoopHVAC:UnitaryHeatCool). When scheduled, the schedule value must be greater than 0 to calculate degradation of latent cooling capacity. At times when the parent object s supply air fan operating mode schedule is 0, latent degradation will be ignored. When modeling latent capacity degradation, these next four input fields must all have positive values.

The next input specifies the outdoor air node used to define the conditions of the air entering the outdoor condenser. If this field is left blank, the outdoor temperature entering the condenser is taken directly from the weather data. If this field is not blank, the node name specified must be listed in an OutdoorAir:Node object where the height of the node is taken into consideration when calculating outdoor temperature from the weather data. Alternately, the node name must be specified in an OutdoorAir:NodeList object where the outdoor temperature entering the condenser is taken directly from the weather data.

The next input describes the type of outdoor condenser coil used with the DX cooling coil (Air Cooled or Evap Cooled). The following three inputs are required when modeling an evaporative-cooled condenser: evaporative condenser effectiveness, evaporative condenser air volume flow rate, and the power consumed by the evaporative condenser pump. Crankcase heater capacity and cutout temperature are entered in the next two input fields. These two fields for this object define the name of the water storage tank for supply and condensate collection. See section DX Cooling Coil Model in the EnergyPlus Engineering Document for further details regarding this model.

The last two input fields following the Basin Heater Operating Schedule Name are the Sensible Heat Ratio (SHR) modifier cruve names for temperature and flow fraction. These two input fields are optional and used only when a user intends to override SHR calculated using the apparatus dew point (ADP) and bypass factor (BF) method. See section SHR Calculation Using User Specified SHR Modifier Curves in the EnergyPlus Engineering Document for further details.

Inputs[LINK]

Field: Name[LINK]

A unique user-assigned name for an instance of a DX cooling coil. Any reference to this DX coil by another object will use this name.

Field: Availability Schedule Name[LINK]

The name of the schedule (ref: Schedule) that denotes whether the DX cooling coil can run during a given time period. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during a given time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off. If this field is blank, the schedule has values of 1 for all time periods.

Field: Gross Rated Total Cooling Capacity[LINK]

The total, full load gross cooling capacity (sensible plus latent) in watts of the DX coil unit at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and a cooling coil air flow rate defined by field rated air flow rate below). Capacity should be gross (i.e., the effect of supply air fan heat is NOT accounted for). When used in a heat pump, the gross rated total cooling capacity should be within 20% of the gross rated heating capacity, otherwise a warning message is issued.

Field: Gross Rated Sensible Heat Ratio[LINK]

The sensible heat ratio (SHR = gross sensible cooling capacity divided by gross total cooling capacity) of the DX cooling coil at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb), and a cooling coil air flow rate defined by field rated air flow rate below). Both the sensible and total cooling capacities used to define the Rated SHR should be gross (i.e., the effect of supply air fan heat is NOT accounted for).

Field: Gross Rated Cooling COP[LINK]

The coefficient of performance is the ratio of the gross total cooling capacity in watts to electrical power input in watts of the DX cooling coil unit at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/ 23.9 °C wetbulb, and a cooling coil air flow rate defined by field rated air flow rate below). The input power includes electric power for the compressor(s) and condenser fan(s) but does not include the power consumption of the supply air fan. The gross COP should NOT account for the supply air fan. If this input field is left blank, the default value is 3.0.

Field: Rated Air Flow Rate[LINK]

The air volume flow rate, in m3 per second, across the DX cooling coil at rated conditions. The rated air volume flow rate should be between 0.00004027 m3/s and 0.00006041 m3/s per watt of gross rated total cooling capacity (300 to 450 cfm/ton). For DOAS applications the rated air volume flow rate should be between 0.00001677 m3/s and 0.00003355 m3/s per watt of gross rated total cooling capacity (125 to 250 cfm/ton). The gross rated total cooling capacity, gross rated SHR and gross rated COP should be performance information for the unit with air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and the rated air volume flow rate defined here.

Field: Rated Evaporator Fan Power Per Volume Flow Rate[LINK]

This field is the electric power for the evaporator (cooling coil) fan per air volume flow rate through the coil at the rated conditions in W/(m3/s). The default value is 773.3 W/(m3/s) (365 W/1000 cfm) if this field is left blank. If a value is entered, it must be > = 0.0 and < = 1250 W/(m3/s). This value is only used to calculate Seasonal Energy Efficiency Ratio (SEER), Energy Efficiency Ratio (EER), Integrated Energy Efficiency Ratio (IEER) and the Standard Rating (Net) Cooling Capacity which will be outputs in the EnergyPlus eio file (ref. EnergyPlus Engineering Reference, Single Speed DX Cooling Coil, Standard Ratings). This value is not used for modeling the evaporator (cooling coil) fan during simulations; instead, it is used for calculating SEER, EER, IEER and Standard Rating Cooling Capacity to assist the user in verifying their inputs for modeling this type of equipment.

Field: Air Inlet Node Name[LINK]

The name of the HVAC system node from which the DX cooling coil draws its inlet air.

Field: Air Outlet Node Name[LINK]

The name of the HVAC system node to which the DX cooling coil sends its outlet air.

Field: Total Cooling Capacity Function of Temperature Curve Name[LINK]

The name of a performance curve (ref: Performance Curves) that parameterizes the variation of the gross total cooling capacity as a function of the wet-bulb temperature of the air entering the cooling coil, and the dry-bulb temperature of the air entering the air-cooled condenser coil (wet-bulb temperature if modeling an evaporative-cooled condenser). The output of this curve is multiplied by the gross rated total cooling capacity to give the gross total cooling capacity at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures). The curve is normalized to have the value of 1.0 at the rating point. This curve is typically a biquadratic but any curve or table with two independent variables can be used.

Field: Total Cooling Capacity Function of Flow Fraction Curve Name[LINK]

The name of a quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of the gross total cooling capacity as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated total cooling capacity and the total cooling capacity modifier curve (function of temperature) to give the gross total cooling capacity at the specific temperature and air flow conditions at which the coil is operating. The curve is normalized to have the value of 1.0 when the actual air flow rate equals the rated air flow rate.

Field: Energy Input Ratio Function of Temperature Curve Name[LINK]

The name of a performance curve (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the wet-bulb temperature of the air entering the cooling coil, and the dry-bulb temperature of the air entering the air-cooled condenser coil (wet-bulb temperature if modeling an evaporative-cooled condenser). The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR (inverse of rated COP) to give the EIR at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures). The curve is normalized to a value of 1.0 at the rating point. This curve is typically a biquadratic but any curve or table with two independent variables can be used.

Field: Energy Input Ratio Function of Flow Fraction Curve Name[LINK]

The name of a performance curve (Ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR and the EIR modifier curve (function of temperature) to give the EIR at the specific temperature and air flow conditions at which the cooling coil is operating. This curve is normalized to a value of 1.0 when the actual air flow rate equals the rated air flow rate. This curve is typically a quadratic or cubic but any curve or table with one independent variables can be used.

Field: Part Load Fraction Correlation Curve Name[LINK]

This alpha field defines the name of a performance curve (Ref: Performance Curves) that parameterizes the variation of electrical power input to the DX unit as a function of the part load ratio (PLR, sensible cooling load/steady-state sensible cooling capacity). The product of the rated EIR and EIR modifier curves is divided by the output of this curve to give the effective EIR for a given simulation timestep. The part load fraction (PLF) correlation accounts for efficiency losses due to compressor cycling. This curve is typically a quadratic or cubic but any curve or table with one independent variables can be used.

The part load fraction correlation should be normalized to a value of 1.0 when the part load ratio equals 1.0 (i.e., no efficiency losses when the compressor(s) run continuously for the simulation timestep). For PLR values between 0 and 1 (0 < = PLR < 1), the following rules apply:

PLF > = 0.7 and PLF > = PLR

If PLF < 0.7 a warning message is issued, the program resets the PLF value to 0.7, and the simulation proceeds. The runtime fraction of the coil is defined as PLR/PLF. If PLF < PLR, then a warning message is issued and the runtime fraction of the coil is limited to 1.0.

A typical part load fraction correlation for a conventional, single-speed DX cooling coil (e.g., residential unit) would be:

PLF = 0.85 + 0.15(PLR)

If the user wishes to model no efficiency degradation due to compressor cycling, the part load fraction correlation should be defined as follows:

PLF = 1.0 + 0.0(PLR)

Field: Nominal Time for Condensate Removal to Begin[LINK]

The nominal time (in seconds) after startup for condensate to begin leaving the coil’s condensate drain line at the coil’s rated airflow and temperature conditions, starting with a dry coil. Nominal time is equal to the ratio of the energy of the coil’s maximum condensate holding capacity (J) to the coil’s steady-state latent capacity (W). Suggested value is 1000; zero value means the latent degradation model is disabled. The default value for this field is zero. The supply air fan operating mode must be continuous (i.e., the supply air fan operating mode may be specified in other parent objects and is assumed continuous in some objects (e.g., CoilSystem:Cooling:DX) or can be scheduled in other objects [e.g., AirloopHVAC:UnitaryHeatCool]), and this field as well as the next three input fields for this object must have positive values in order to model latent capacity degradation.

Field: Ratio of Initial Moisture Evaporation Rate and Steady State Latent Capacity[LINK]

Ratio of the initial moisture evaporation rate from the cooling coil (when the compressor first turns off, in Watts) and the coil’s steady-state latent capacity (Watts) at rated airflow and temperature conditions. Suggested value is 1.5; zero value means the latent degradation model is disabled. The default value for this field is zero. The supply air fan operating mode must be continuous (i.e., the supply air fan operating mode may be specified in other parent objects and is assumed continuous in some objects (e.g., CoilSystem:Cooling:DX) or can be scheduled in other objects [e.g., AirloopHVAC:UnitaryHeatCool]); and this field, the previous field and the next two fields must have positive values in order to model latent capacity degradation.

Field: Maximum Cycling Rate[LINK]

The maximum on-off cycling rate for the compressor (cycles per hour), which occurs at 50% run time fraction. Suggested value is 3; zero value means latent degradation model is disabled. The default value for this field is zero. The supply air fan operating mode must be continuous (i.e., the supply air fan operating mode may be specified in other parent objects and is assumed continuous in some objects (e.g., CoilSystem:Cooling:DX) or can be scheduled in other objects [e.g., AirloopHVAC:UnitaryHeatCool]); and this field, the previous two fields and the next field must have positive values in order to model latent capacity degradation.

Field: Latent Capacity Time Constant[LINK]

Time constant (in seconds) for the cooling coil’s latent capacity to reach steady state after startup. Suggested value is 45: supply air fan operating mode must be continuous. That is, the supply air fan operating mode may be specified in other parent objects and is assumed continuous in some objects (e.g., CoilSystem:Cooling:DX) or can be scheduled in other objects (e.g., AirloopHVAC:UnitaryHeatCool), and this field as well as the previous three input fields for this object must have positive values in order to model latent capacity degradation.

Field: Condenser Air Inlet Node Name[LINK]

This optional alpha field specifies the outdoor air node name used to define the conditions of the air entering the outdoor condenser. If this field is left blank, the outdoor air temperature entering the condenser (dry-bulb or wet-bulb) is taken directly from the weather data. If this field is not blank, the node name specified must also be specified in an OutdoorAir:Node object where the height of the node is taken into consideration when calculating outdoor air temperature from the weather data. Alternately, the node name may be specified in an OutdoorAir:NodeList object where the outdoor air temperature is taken directly from the weather data.

Field: Condenser Type[LINK]

The type of condenser used by the DX cooling coil. Valid choices for this input field are AirCooled or EvaporativelyCooled. The default for this field is AirCooled.

Field: Evaporative Condenser Effectiveness[LINK]

The effectiveness of the evaporative condenser, which is used to determine the temperature of the air entering the outdoor condenser coil as follows:

Tcondinlet=(Twb,o)+(1EvapCondEffectiveness)(Tdb,oTwb,o)

where

Tcondinlet = the temperature of the air entering the condenser coil (C)

Twb,o = the wet-bulb temperature of the outdoor air (C)

Tdb,o = the dry-bulb temperature of the outdoor air (C)

The resulting condenser inlet air temperature is used by the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature). The default value for this field is 0.9, although valid entries can range from 0.0 to 1.0. This field is not used when Condenser Type = Air Cooled.

If the user wants to model an air-cooled condenser, they should simply specify AirCooled in the field Condenser Type. In this case, the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature) input fields for this object should reference performance curves that are a function of outdoor dry-bulb temperature.

If the user wishes to model an evaporative-cooled condenser AND they have performance curves that are a function of the wet-bulb temperature of air entering the condenser coil, then the user should specify Condenser Type = Evap Cooled and the evaporative condenser effectiveness value should be entered as 1.0. In this case, the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature) input fields for this object should reference performance curves that are a function of the wet-bulb temperature of air entering the condenser coil.

If the user wishes to model an air-cooled condenser that has evaporative media placed in front of it to cool the air entering the condenser coil, then the user should specify Condenser Type = Evap Cooled. The user must also enter the appropriate evaporative effectiveness for the media. In this case, the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature) input fields for this object should reference performance curves that are a function of outdoor dry-bulb temperature. Be aware that the evaporative media will significantly reduce the dry-bulb temperature of the air entering the condenser coil, so the Total Cooling Capacity and EIR Modifier Curves must be valid for the expected range of dry-bulb temperatures that will be entering the condenser coil.

Field: Evaporative Condenser Air Flow Rate[LINK]

The air volume flow rate, in m3 per second, entering the evaporative condenser. This value is used to calculate the amount of water used to evaporatively cool the condenser inlet air. The minimum value for this field must be greater than zero, and this input field is autosizable (equivalent to 0.000144 m3/s per watt of rated total cooling capacity [850 cfm/ton]). This field is not used when Condenser Type = Air Cooled.

Field: Evaporative Condenser Pump Rated Power Consumption[LINK]

The rated power of the evaporative condenser water pump in Watts. This value is used to calculate the power required to pump the water used to evaporatively cool the condenser inlet air. The default value for this input field is zero, but it is autosizable (equivalent to 0.004266 W per watt [15 W/ton] of rated total cooling capacity). This field is not used when Condenser Type = Air Cooled.

Field: Crankcase Heater Capacity[LINK]

This numeric field defines the crankcase heater capacity in Watts. When the outdoor air dry-bulb temperature is below the value specified in the input field Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation (described below), the crankcase heater is enabled during the time that the compressor is not running. If this cooling coil is used as part of an air-to-air heat pump (Ref. AirLoopHVAC:UnitaryHeatPump:AirToAir or PackageTerminal: HeatPump:AirToAir), the crankcase heater defined for this DX cooling coil is ignored and the crankcase heater power defined for the DX heating coil (Ref. Coil:Heating:DX:SingleSpeed) is enabled during the time that the compressor is not running for either heating or cooling. The value for this input field must be greater than or equal to 0, and the default value is 0. To simulate a DX cooling coil without a crankcase heater, enter a value of 0.

Field: Maximum Outdoor Dry-Bulb Temperature for Crankcase Heater Operation[LINK]

This numeric field defines the outdoor air dry-bulb temperature above which the compressor s crankcase heater is disabled. The value for this input field must be greater than or equal to 0.0 °C, and the default value is 10 °C.

Field: Supply Water Storage Tank Name[LINK]

This field is optional. It is used to describe where the coil obtains water used for evaporative cooling of its condenser. If blank or omitted, then the unit will obtain water directly from the mains. If the name of a Water Storage Tank object is used here, then the unit will obtain its water from that tank. If a tank is specified, the unit will attempt to obtain all the water it uses from the tank. However if the tank cannot provide all the water the condenser needs, then the unit will still operate and obtain the rest of the water it needs from the mains (referred to as StarvedWater).

Field: Condensate Collection Water Storage Tank Name[LINK]

This field is optional. It is used to describe where condensate from the coil is collected. If blank or omitted, then any coil condensate is discarded. Enter the name of Water Storage Tank object defined elsewhere and the condensate will then be collected in that tank.

Field: Basin Heater Capacity[LINK]

This numeric field contains the capacity of the DX coil s electric evaporative cooler basin heater in watts per degree Kelvin. This field only applies for Condenser Type = EvaporativelyCooled. This field is used in conjunction with the Basin Heater Setpoint Temperature described in the following field. The basin heater electric power is equal to this field multiplied by the difference between the basin heater set point temperature and the outdoor dry-bulb temperature. The basin heater only operates when the DX coil is off, regardless of the basin heater schedule described below. The basin heater capacity must be greater than or equal to zero, with a default value of zero if this field is left blank.

Field: Basin Heater Setpoint Temperature[LINK]

This numeric field contains the set point temperature (˚C) for the basin heater described in the previous field. This field only applies for Condenser Type = EvaporativelyCooled. The basin heater is active when the outdoor air dry-bulb temperature falls below this setpoint temperature, as long as the DX coil is off. This set point temperature must be greater than or equal to 2˚C, and the default value is 2˚C if this field is left blank.

Field: Basin Heater Operating Schedule Name[LINK]

This alpha field contains the name of the basin heater operating schedule. This field only applies for Condenser Type = EvaporativelyCooled. The basin heater operating schedule is assumed to be an on/off schedule and the heater is available to operate any time the schedule value is greater than 0. The basin heater operates when scheduled on and the outdoor air dry-bulb temperature is below the set point temperature described in the previous field. If this field is left blank, the basin heater is available to operate throughout the simulation. Regardless of this schedule, the basin heater may only operate when the DX coil is off.

Field: Sensible Heat Ratio Function of Temperature Curve Name[LINK]

The name of a biquadratic normalized curve (Ref: Performance Curves) that parameterizes the variation of the sensible heat ratio (SHR) as a function of DX cooling coil entering air wet-bulb and dry-bulb temperatures. The output of this curve is multiplied by the rated SHR and the SHR modifier curve (function of flow fraction) to give the SHR at the specific coil entering air temperature and air flow conditions at which the cooling coil is operating. This curve is normalized to a value of 1.0 at the rated condition. This input field is optional.

Field: Sensible Heat Ratio Function of Flow Fraction Curve Name[LINK]

The name of a quadratic or cubic normalized curve (Ref: Performance Curves) that parameterizes the variation of the sensible heat ratio (SHR) as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the rated SHR and the SHR modifier curve (function of temperature) to give the SHR at the specific temperature and air flow conditions at which the cooling coil is operating. This curve is normalized to a value of 1.0 when the actual air flow rate equals the rated air flow rate. This input field is optional.

Field: Zone Name for Condenser Placement[LINK]

This input field is name of a conditioned or unconditioned zone where the secondary coil (condenser) of DX system or a heat pump is to be placed. This is an optional input field specified only when user desires to reject the condenser heat into a zone. The heat rejected is modeled as sensible internal gain of a secondary zone.

Following is an example input for a Coil:Cooling:DX:SingleSpeed coil.

Coil:Cooling:DX:SingleSpeed,
  Zone1WindACDXCoil,               ! Coil Name
  FanAndCoilAvailSched,         ! Availability Schedule
  10548,           ! Gross Rated Total Cooling Capacity
  0.75,             ! Gross Rated Sensible Heat Ratio
  3.0,               ! Gross Rated Cooling COP
  0.637,           ! Rated Air Flow Rate (m3/s)
  773.3,           ! Rated Evaporator Fan Power Per Volume Flow Rate {W/(m3/s)}
  Zone1WindACFanOutletNode, ! Coil Air Inlet Node
  Zone1WindACAirOutletNode, ! Coil Air Outlet Node
  WindACCoolCapFT,                   ! Total Cooling Capacity Modifier Curve (function of temperature)
  WindACCoolCapFFF,                 ! Total Cooling Capacity Modifier Curve (function of flow fraction)
  WindACEIRFT,                           ! Energy Input Ratio Modifier Curve (function of temperature)
  WindACEIRFFF,                         ! Energy Input Ratio Modifier Curve (function of flow fraction)
  WindACPLFFPLR,                       ! Part Load Fraction Correlation (function of part load ratio)
  1000.,                         ! Nominal Time for Condensate Removal to Begin {s}
  1.5,                             ! Ratio of Initial Moisture Evaporation Rate and Steady-state Latent Capacity
  3.0,                             ! Maximum ON/OFF Cycling Rate {cycles/hr}
  45.0,                           ! Latent Capacity Time Constant {s}
  ,                                   ! Condenser Air Inlet Node Name
  AirCooled,               ! Condenser Type
  ,                                   ! Evaporative Condenser Effectiveness
  ,                                   ! Evaporative Condenser Air Volume Flow Rate {m3/s}
  ,                                   ! Evaporative Condenser Pump Rated Power Consumption {W}
  30.,                             ! Crankcase Heater Capacity {W}
  10.;                             ! Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation {C}

Coil:Cooling:DX:TwoSpeed[LINK]

This component models a two-speed (or variable speed) DX compressor and fan. The method is based on the model used for the cycling, single speed DX unit. The single speed unit is described by single full load capacity, SHR, COP, and air flow rate at rated conditions. Off rated full load performance is obtained by the use of 4 modifier curves. At partial load the unit cycles on/off and the cycling losses are described by a part load fraction curve.

The multispeed unit is described by specifying the performance at two states: high speed compressor, high speed fan; and low speed compressor, low speed fan. When the unit load is above the high speed capacity, the unit runs with high speed compressor and fan. When the load on the unit is below the high speed capacity but above the low speed capacity, the unit will run with performance intermediate between high speed and low speed. When the load is less than the low speed capacity, the unit will cycle on/off just like the single speed unit.

The multispeed unit model requires 2 full sets of performance data. There must be a high and low speed capacity, SHR, COP, and evaporator air flow rate; as well as high and low speed performance curves total cooling capacity modifier curve (function of temperature) and energy input ratio modifier curve (function of temperature).

The multispeed DX component should be used for all cases in which a DX VAV system is being simulated. Obviously this model in which performance is obtained by interpolating between 2 specified states - is an oversimplification of how real multi-speed and variable speed DX cooling units are controlled. But detailed descriptions of how actual units perform and are controlled are not available. This model should give a good average prediction of multispeed and variable speed DX cooling unit performance. The last four input fields following the Basin Heater Operating Schedule Name are the Sensible Heat Ratio (SHR) modifier cruve names for temperature and flow fraction for high and low speed DX cooling coils. These four input fields are optional and used only when a user intends to override SHR calculated using the apparatus dew point (ADP) and bypass factor (BF) method. See section SHR Calculation Using User Specified SHR Modifier Curves in the EnergyPlus Engineering Document for further details..

Inputs[LINK]

Field: Name[LINK]

A unique user-assigned name for an instance of a multispeed DX cooling coil. Any reference to this DX coil by another object will use this name.

Field: Availability Schedule Name[LINK]

The name of the schedule (ref: Schedule) that denotes whether the DX cooling coil can run during a given time period. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off for the time period. If this field is blank, the schedule has values of 1 for all time periods.

Field: High Speed Gross Rated Total Cooling Capacity[LINK]

The total, full load gross cooling capacity (sensible plus latent) in watts of the DX coil unit for high speed compressor and high speed fan at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and a cooling coil air flow rate defined by field rated air flow rate below). Capacity should be gross (i.e., the effect of supply air fan heat is NOT accounted for).

Field: High Speed Gross Rated Sensible Heat Ratio[LINK]

The sensible heat ratio (gross sensible capacity divided by gross total cooling capacity) of the DX cooling coil for high speed compressor and high speed fan at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and a cooling coil air flow rate defined by field rated air flow rate below). Both the sensible and total cooling capacities used to define the Rated SHR should be gross (i.e., the effect of supply air fan heat is NOT accounted for).

Field: High Speed Gross Rated Cooling COP[LINK]

The coefficient of performance is the ratio of the gross total cooling capacity in watts to electrical power input in watts) of the DX cooling coil unit for high speed compressor and high speed fan at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and a cooling coil air flow rate defined by field rated air flow rate below). The input power includes electric power for the compressor(s) and condenser fan(s) but does not include the power consumption of the supply air fan. The gross COP should NOT account for the supply air fan. If this input field is left blank, the default value is 3.0.

Field: High Speed Rated Air Flow Rate[LINK]

The high speed air volume flow rate, in m3 per second, across the DX cooling coil at rated conditions. The rated air volume flow rate should be between 0.00004027 m3/s and 0.00006041 m3/s per watt of gross rated total cooling capacity. For DOAS applications the rated air volume flow rate should be between 0.00001677 m3/s and 0.00003355 m3/s per watt of gross rated total cooling capacity (125 to 250 cfm/ton). The gross rated total cooling capacity, gross rated SHR and gross rated COP should be performance information for the unit with air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and the rated air volume flow rate defined here.

Field: Unit Internal Static Air Pressure[LINK]

If this coil is used with a Fan:VariableVolume to model a packaged variable-air-volume unit, then ratings for standard rated net capacity, EER, and IEER will be calculated per ANSI/AHRI Standard 340/360-2007 with Addenda 1 and 2. This field is to specify the internal static air pressure, in units of Pascals, associated with the unit s supply air flow for rating purposes. This field does not affect the performance during operation. This field is optional. If this field is used, then the internal static air pressure is used with the associated fan characteristics when calculating standard rated net capacity, EER, and IEER. If this field is not used, then the standard ratings are still performed but use a default for specific fan power of 773.3 (W/(m3/s)). The air pressure drop/rise input here should be internal in the sense that it is for the entire package of unitary equipment as it would be tested in a laboratory (including other non-cooling sections inside the package for filters, dampers, and.or heating coils) but none of the external pressure drop for distributing supply air throughout the building. This is different from the input field called Pressure Rise in the fan object which includes both the external static pressure and the internal static pressure. The results of standard rating calculations are reported to the EIO file and to predefined output tables called DX Cooling Coils and VAV DX Cooling Standard Rating Details.

Field: Air Inlet Node[LINK]

The name of the HVAC system node from which the DX cooling coil draws its inlet air.

Field: Air Outlet Node[LINK]

The name of the HVAC system node to which the DX cooling coil sends its outlet air.

Field: Total Cooling Capacity Function of Temperature Curve Name[LINK]

The name of a biquadratic performance curve (ref: Performance Curves) that parameterizes the variation of the gross total cooling capacity as a function of the wet-bulb temperature of the air entering the cooling coil, and the dry-bulb temperature of the air entering the air-cooled condenser (wet-bulb temperature if modeling an evaporative-cooled condenser). The output of this curve is multiplied by the gross rated total cooling capacity to give the gross total cooling capacity at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures). The curve is normalized to have the value of 1.0 at the rating point. This curve is used for performance at the high speed compressor, high speed fan operating point.

Field: Total Cooling Capacity Function of Flow Fraction Curve Name[LINK]

The name of a quadratic performance curve (ref: Performance Curves) that parameterizes the variation of gross total cooling capacity as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated total cooling capacity and the total cooling capacity modifier curve (function of temperature) to give the gross total cooling capacity at the specific temperature and air flow conditions at which the coil is operating. The curve is normalized to have the value of 1.0 when the actual air flow rate equals the rated air flow rate. This curve is applied only at the high speed compressor, high speed fan operating point. There is no corresponding curve for the low speed operating point.

Field: Energy Input Ratio Function of Temperature Curve Name[LINK]

The name of a biquadratic performance curve (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the wet-bulb temperature of the air entering the cooling coil and the dry-bulb temperature of the air entering the air-cooled condenser (wet-bulb temperature if modeling an evaporative-cooled condenser). The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR (inverse of rated COP) to give the EIR at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures). The curve is normalized to a value of 1.0 at the rating point. This curve is used for performance at the high speed compressor, high speed fan operating point.

Field: Energy Input Ratio Function of Flow Fraction Curve Name[LINK]

The name of a quadratic performance curve (Ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR and the EIR modifier curve (function of temperature) to give the EIR at the specific temperature and air flow conditions at which the cooling coil is operating. This curve is normalized to a value of 1.0 when the actual air flow rate equals the rated air flow rate. This curve is applied only at the high speed compressor, high speed fan operating point. There is no corresponding curve for the low speed operating point.

Field: Part Load Fraction Correlation Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve (Ref: Performance Curves) that parameterizes the variation of electrical power input to the DX unit as a function of the part load ratio (PLR, sensible cooling load/steady-state sensible cooling capacity). The product of the rated EIR and EIR modifier curves is divided by the output of this curve to give the effective EIR for a given simulation timestep. The part load fraction (PLF) correlation accounts for efficiency losses due to compressor cycling.

The part load fraction correlation should be normalized to a value of 1.0 when the part load ratio equals 1.0 (i.e., no efficiency losses when the compressor(s) run continuously for the simulation timestep). For PLR values between 0 and 1 (0 < = PLR < 1), the following rules apply:

PLF > = 0.7 and PLF > = PLR

If PLF < 0.7 a warning message is issued, the program resets the PLF value to 0.7, and the simulation proceeds. The runtime fraction of the coil is defined as PLR/PLF. If PLF < PLR, then a warning message is issued and the runtime fraction of the coil is limited to 1.0.

A typical part load fraction correlation for a conventional, single-speed DX cooling coil (e.g., residential unit) would be:

PLF = 0.85 + 0.15(PLR)

If the user wishes to model no efficiency degradation due to compressor cycling, the part load fraction correlation should be defined as follows:

PLF = 1.0 + 0.0(PLR)

Field: Low Speed Gross Rated Total Cooling Capacity[LINK]

The total, full load gross total cooling capacity (sensible plus latent) in watts of the DX coil unit for low speed compressor and low speed fan at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and a cooling coil air flow rate defined by field rated air flow rate, low speed below). Capacity should be gross (i.e., the effect of supply air fan heat is NOT accounted for).

Field: Low Speed Gross Rated Sensible Heat Ratio[LINK]

The sensible heat ratio (SHR = gross sensible capacity divided by gross total cooling capacity) of the DX cooling coil for low speed compressor and low speed fan at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and a cooling coil air flow rate defined by field rated air flow rate, low speed below). Both the sensible and total cooling capacities used to define the Rated SHR should be gross (i.e., the effect of supply air fan heat is NOT accounted for).

Field: Low Speed Gross Rated Cooling COP[LINK]

The coefficient of performance is the ratio of gross total cooling capacity in watts to electrical power input in watts) of the DX cooling coil unit for low speed compressor and low speed fan at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and a cooling coil air flow rate defined by field rated air volume flow rate, low speed below). The input power includes power for the compressor(s) and condenser fan(s) but does not include the power consumption of the supply air fan. The gross COP should NOT account for the supply air fan. If this input field is left blank, the default value is 3.0.

Field: Low Speed Rated Air Flow Rate[LINK]

The low speed volume air flow rate, in m3 per second, across the DX cooling coil at rated conditions. The rated air volume flow rate should be between 0.00004027 m3/s and 0.00006041 m3/s per watt of the gross rated total cooling capacity. For DOAS applications the rated air volume flow rate should be between 0.00001677 m3/s and 0.00003355 m3/s per watt of gross rated total cooling capacity (125 to 250 cfm/ton). The gross rated total cooling capacity, gross rated SHR and gross rated COP should be performance information for the unit with air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and the rated air volume flow rate defined here.

Field: Low Speed Total Cooling Capacity Function of Temperature Curve Name[LINK]

The name of a biquadratic performance curve (ref: Performance Curves) that parameterizes the variation of the gross total cooling capacity as a function of the wet-bulb temperature of the air entering the cooling coil, and the dry-bulb temperature of the air entering the air-cooled condenser (wet-bulb temperature if modeling an evaporative-cooled condenser). The output of this curve is multiplied by the gross rated total cooling capacity to give the gross total cooling capacity at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures). The curve is normalized to have the value of 1.0 at the rating point. This curve is used for performance at the low speed compressor, low speed fan operating point.

Field: Low Speed Energy Input Ratio Function of Temperature Curve Name[LINK]

The name of a biquadratic performance curve (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the wetbulb temperature of the air entering the cooling coil and the drybulb temperature of the air entering the air-cooled condenser (wetbulb temperature if modeling an evaporative-cooled condenser). The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR (inverse of rated COP) to give the EIR at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures). The curve is normalized to a value of 1.0 at the rating point. This curve is used for performance at the low speed compressor, low speed fan operating point.

Field: Condenser Air Inlet Node Name[LINK]

This optional alpha field specifies the outdoor air node name used to define the conditions of the air entering the outdoor condenser. If this field is left blank, the outdoor air temperature entering the condenser (dry-bulb or wet-bulb) is taken directly from the weather data. If this field is not blank, the node name specified must also be specified in an OutdoorAir:Node object where the height of the node is taken into consideration when calculating outdoor air temperature from the weather data. Alternately, the node name may be specified in an OutdoorAir:NodeList object where the outdoor air temperature is taken directly from the weather data.

Field: Condenser Type[LINK]

The type of condenser used by the multi-speed DX cooling coil. Valid choices for this input field are AirCooled or EvaporativelyCooled. The default for this field is AirCooled.

Field: High Speed Evaporative Condenser Effectiveness[LINK]

The effectiveness of the evaporative condenser at high compressor/fan speed, which is used to determine the temperature of the air entering the outdoor condenser coil as follows:

Tcondinlet=(Twb,o)+(1EvapCondEffectivenessHighSpeed)(Tdb,oTwb,o)

where

Tcondinlet = the temperature of the air entering the condenser coil (C)

Twb,o = the wet-bulb temperature of the outdoor air (C)

Tdb,o = the dry-bulb temperature of the outdoor air (C)

The resulting condenser inlet air temperature is used by the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature). The default value for this field is 0.9, although valid entries can range from 0.0 to 1.0. This field is not used when Condenser Type = Air Cooled.

If the user wants to model an air-cooled condenser, they should simply specify AirCooled in the field Condenser Type. In this case, the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature) input fields for this object should reference performance curves that are a function of outdoor dry-bulb temperature.

If the user wishes to model an evaporative-cooled condenser AND they have performance curves that are a function of the wet-bulb temperature of air entering the condenser coil, then the user should specify Condenser Type = Evap Cooled and the evaporative condenser effectiveness value should be entered as 1.0. In this case, the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature) input fields for this object should reference performance curves that are a function of the wet-bulb temperature of air entering the condenser coil.

If the user wishes to model an air-cooled condenser that has evaporative media placed in front of it to cool the air entering the condenser coil, then the user should specify Condenser Type = Evap Cooled. The user must also enter the appropriate evaporative effectiveness for the media. In this case, the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature) input fields for this object should reference performance curves that are a function of outdoor dry-bulb temperature. Be aware that the evaporative media will significantly reduce the dry-bulb temperature of the air entering the condenser coil, so the Total Cooling Capacity and EIR Modifier Curves must be valid for the expected range of dry-bulb temperatures that will be entering the condenser coil.

Field: High Speed Evaporative Condenser Air Flow Rate[LINK]

The air volume flow rate, in m3 per second, entering the evaporative condenser at high compressor/fan speed. This value is used to calculate the amount of water used to evaporatively cool the condenser inlet air. The minimum value for this field must be greater than zero, and this input field is autosizable (equivalent to 0.000144 m3/s per watt of rated high-speed total cooling capacity [850 cfm/ton]). This field is not used when Condenser Type = Air Cooled.

Field: High Speed Evaporative Condenser Pump Rated Power Consumption[LINK]

The rated power of the evaporative condenser water pump in Watts at high compressor/fan speed. This value is used to calculate the power required to pump the water used to evaporatively cool the condenser inlet air. The default value for this input field is zero, but it is autosizable (equivalent to 0.004266 W per watt [15 W/ton] of rated high-speed total cooling capacity). This field is not used when Condenser Type = Air Cooled.

Field: Low Speed Evaporative Condenser Effectiveness[LINK]

The effectiveness of the evaporative condenser at low compressor/fan speed, which is used to determine the temperature of the air entering the outdoor condenser coil as follows:

Tcondinlet=(Twb,o)+(1EvapCondEffectivenessLowSpeed)(Tdb,oTwb,o)

where

Tcondinlet = the temperature of the air entering the condenser coil (C)

Twb,o = the wet-bulb temperature of the outdoor air (C)

Tdb,o = the dry-bulb temperature of the outdoor air (C)

The resulting condenser inlet air temperature is used by the Total Cooling Capacity Modifier Curve, low speed (function of temperature) and the Energy Input Ratio Modifier Curve, low speed (function of temperature). The default value for this field is 0.9, although valid entries can range from 0.0 to 1.0. This field is not used when Condenser Type = Air Cooled. See field Evaporative Condenser Effectiveness, High Speed above for further information.

Field: Low Speed Evaporative Condenser Air Flow Rate[LINK]

The air volume flow rate, in m3 per second, entering the evaporative condenser at low compressor/fan speed. This value is used to calculate the amount of water used to evaporatively cool the condenser inlet air. The minimum value for this field must be greater than zero, and this input field is autosizable (equivalent to 0.000048 m3/s per watt of rated high-speed total cooling capacity [280 cfm/ton]). This field is not used when Condenser Type = Air Cooled.

Field: Low Speed Evaporative Condenser Pump Rated Power Consumption[LINK]

The rated power of the evaporative condenser water pump in Watts at low compressor/fan speed. This value is used to calculate the power required to pump the water used to evaporatively cool the condenser inlet air. The default value for this input field is zero, but it is autosizable (equivalent to 0.001422 W per watt [5 W/ton] of rated high-speed total capacity). This field is not used when Condenser Type = Air Cooled.

Field: Supply Water Storage Tank Name[LINK]

This field is optional. It is used to describe where the coil obtains water used for evaporative cooling. If blank or omitted, then the cooler will obtain water directly from the mains. If the name of a Water Storage Tank object is used here, then the cooler will obtain its water from that tank. If a tank is specified, the coil will attempt to obtain all the water it uses from the tank. However if the tank cannot provide all the water the cooler needs, then the cooler will still operate and obtain the rest of the water it needs from the mains (referred to as StarvedWater).

Field: Condensate Collection Water Storage Tank Name[LINK]

This field is optional. It is used to describe where condensate from the coil is collected. If blank or omitted, then any coil condensate is discarded. Enter the name of Water Storage Tank object defined elsewhere and the condensate will then be collected in that tank.

Field: Basin Heater Capacity[LINK]

This numeric field contains the capacity of the DX coil s electric evaporative cooler basin heater in watts per degree Kelvin. This field only applies for Condenser Type = EvaporativelyCooled. This field is used in conjunction with the Basin Heater Setpoint Temperature described in the following field. The basin heater electric power is equal to this field multiplied by the difference between the basin heater set point temperature and the outdoor dry-bulb temperature. The basin heater only operates when the DX coil is off, regardless of the basin heater schedule described below. The basin heater capacity must be greater than or equal to zero, with a default value of zero if this field is left blank.

Field: Basin Heater Setpoint Temperature[LINK]

This numeric field contains the set point temperature (˚C) for the basin heater described in the previous field. This field only applies for Condenser Type = EvaporativelyCooled. The basin heater is active when the outdoor air dry-bulb temperature falls below this setpoint temperature, as long as the DX coil is off. This set point temperature must be greater than or equal to 2˚C, and the default value is 2˚C if this field is left blank.

Field: Basin Heater Operating Schedule Name[LINK]

This alpha field contains the name of the basin heater operating schedule. This field only applies for Condenser Type = EvaporativelyCooled. The basin heater operating schedule is assumed to be an on/off schedule and the heater is available to operate any time the schedule value is greater than 0. The basin heater operates when scheduled on and the outdoor air dry-bulb temperature is below the set point temperature described in the previous field. If this field is left blank, the basin heater is available to operate throughout the simulation. Regardless of this schedule, the basin heater may only operate when the DX coil is off.

Field: Sensible Heat Ratio Function of Temperature Curve Name[LINK]

The name of a biquadratic normalized curve (Ref: Performance Curves) that parameterizes the variation of the sensible heat ratio (SHR) as a function of DX cooling coil entering air wet-bulb and dry-bulb temperatures. The output of this curve is multiplied by the rated SHR and the SHR modifier curve (function of flow fraction) to give the SHR at the specific coil entering air temperature and air flow conditions at which the cooling coil is operating. This curve is normalized to a value of 1.0 at the rated condition. This input field is optional.

Field: Sensible Heat Ratio Function of Flow Fraction Curve Name[LINK]

The name of a quadratic or cubic normalized curve (Ref: Performance Curves) that parameterizes the variation of the sensible heat ratio (SHR) as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the rated SHR and the SHR modifier curve (function of temperature) to give the SHR at the specific temperature and air flow conditions at which the cooling coil is operating. This curve is normalized to a value of 1.0 when the actual air flow rate equals the rated air flow rate. This input field is optional.

Field: Low Sensible Heat Ratio Function of Temperature Curve Name[LINK]

The name of a biquadratic normalized curve (Ref: Performance Curves) that parameterizes the variation of the sensible heat ratio (SHR) as a function of DX cooling coil entering air wet-bulb and dry-bulb temperatures. The output of this curve is multiplied by the rated SHR and the SHR modifier curve (function of flow fraction) to give the SHR at the specific coil entering air temperature and air flow conditions at which the cooling coil is operating. This curve is normalized to a value of 1.0 at the rated condition. This input field is optional.

Field: Low Sensible Heat Ratio Function of Flow Fraction Curve Name[LINK]

The name of a quadratic or cubic normalized curve (Ref: Performance Curves) that parameterizes the variation of the sensible heat ratio (SHR) as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the rated SHR and the SHR modifier curve (function of temperature) to give the SHR at the specific temperature and air flow conditions at which the cooling coil is operating. This curve is normalized to a value of 1.0 when the actual air flow rate equals the rated air flow rate. This input field is optional.

Field: Zone Name for Condenser Placement[LINK]

This input field is name of a conditioned or unconditioned zone where the secondary coil (condenser) of DX system or a heat pump is to be placed. This is an optional input field specified only when user desires to reject the condenser heat into a zone. The heat rejected is modeled as sensible internal gain of a secondary zone.

Following are example inputs for the object.

Coil:Cooling:DX:TwoSpeed,
  Main Cooling Coil 1,         !- Name
  CoolingCoilAvailSched,     !- Availability Schedule Name
  autosize,                               !- Gross Rated High Speed Total Cooling Capacity {W}
  0.68,                                       !- Gross Rated High Speed Sensible Heat Ratio
  3.0,                                         !- Gross Rated High Speed Cooling COP
  autosize,                               !- Rated High Speed Air Flow Rate {m3/s}
  ,                                               !- Unit Internal Static Air Pressure Drop {Pa}
  Mixed Air Node 1,               !- Air Inlet Node Name
  Main Cooling Coil 1 Outlet Node,   !- Air Outlet Node Name
  VarSpeedCoolCapFT,             !- Total Cooling Capacity Function of Temperature Curve Name
  PackagedRatedCoolCapFFlow,   !- Total Cooling Capacity Function of Flow Fraction Curve Name
  VarSpeedCoolEIRFT,             !- Energy Input Ratio Function of Temperature Curve Name
  PackagedRatedCoolEIRFFlow,   !- Energy Input Ratio Function of Flow Fraction Curve Name
  VarSpeedCyclingPLFFPLR,   !- Part Load Fraction Correlation Curve Name
  autosize,                               !- Rated Low Speed Total Cooling Capacity {W}
  0.69,                                       !- Rated Low Speed Sensible Heat Ratio
  4.2,                                         !- Rated Low Speed COP
  autosize,                               !- Rated Low Speed Air Flow Rate {m3/s}
  VarSpeedCoolCapLSFT,         !- Low Speed Total Cooling Capacity Function of Temperature Curve Name
  VarSpeedCoolEIRLSFT,         !- Low Speed Energy Input Ratio Function of Temperature Curve Name
  Main Cooling Coil 1 Condenser Node;   !- Condenser Air Inlet Node Name


  Coil:Cooling:DX:TwoSpeed,
  Main Cooling Coil 1,         !- Name
  CoolingCoilAvailSched,     !- Availability Schedule Name
  autosize,                               !- High Speed Rated Total Cooling Capacity {W}
  0.68,                                       !- High Speed Rated Sensible Heat Ratio
  3.0,                                         !- High Speed Rated Cooling COP
  autosize,                               !- High Speed Rated Air Flow Rate {m3/s}
  ,                                               !- Unit Internal Static Air Pressure Drop {Pa}
  Mixed Air Node 1,               !- Air Inlet Node Name
  Main Cooling Coil 1 Outlet Node,   !- Air Outlet Node Name
  VarSpeedCoolCapFT,             !- Total Cooling Capacity Function of Temperature Curve Name
  PackagedRatedCoolCapFFlow,   !- Total Cooling Capacity Function of Flow Fraction Curve Name
  VarSpeedCoolEIRFT,             !- Energy Input Ratio Function of Temperature Curve Name
  PackagedRatedCoolEIRFFlow,   !- Energy Input Ratio Function of Flow Fraction Curve Name
  VarSpeedCyclingPLFFPLR,   !- Part Load Fraction Correlation Curve Name
  autosize,                               !- Low Speed Rated Total Cooling Capacity {W}
  0.69,                                       !- Low Speed Rated Sensible Heat Ratio
  4.2,                                         !- Low Speed Rated Cooling COP
  autosize,                               !- Low Speed Rated Air Flow Rate {m3/s}
  VarSpeedCoolCapLSFT,         !- Low Speed Total Cooling Capacity Function of Temperature Curve Name
  VarSpeedCoolEIRLSFT,         !- Low Speed Energy Input Ratio Function of Temperature Curve Name
  Main Cooling Coil 1 Condenser Node;   !- Condenser Air Inlet Node Name
  ,                                               !- Condenser Type
  ,                                               !- High Speed Evaporative Condenser Effectiveness {dimensionless}
  ,                                               !- High Speed Evaporative Condenser Air Flow Rate {m3/s}
  ,                                               !- High Speed Evaporative Condenser Pump Rated Power Consumption {W}
  ,                                               !- Low Speed Evaporative Condenser Effectiveness {dimensionless}
  ,                                               !- Low Speed Evaporative Condenser Air Flow Rate {m3/s}
  ,                                               !- Low Speed Evaporative Condenser Pump Rated Power Consumption {W}
  ,                                               !- Supply Water Storage Tank Name
  ,                                               !- Condensate Collection Water Storage Tank Name
  ,                                               !- Basin Heater Capacity {W/K}
  ,                                               !- Basin Heater Setpoint Temperature {C}
  ,                                               !- Basin Heater Operating Schedule Name
  DOAS DX Coil SHR-FT,         !- High Speed Sensible Heat Ratio Function of Temperature Curve Name
  DOAS DX Coil SHR-FF,         !- High Speed Sensible Heat Ratio Function of Flow Fraction Curve Name
  DOAS DX Coil SHR-FT,         !- Low Speed Sensible Heat Ratio Function of Temperature Curve Name
  DOAS DX Coil SHR-FF;         !- Low Speed Sensible Heat Ratio Function of Flow Fraction Curve Name


  Curve:Quadratic,
  DOAS DX Coil SHR-FF,                                                                         !- Name
  0.9317,                                                                                                   !- Coefficient1 Constant
  -0.0077,                                                                                                   !- Coefficient2 x
  0.0760,                                                                                                   !- Coefficient3 x**2
  0.69,                                                                                                       !- Minimum Value of x
  1.30;                                                                                                       !- Maximum Value of x


  Curve:Biquadratic,
  DOAS DX Coil SHR-FT,                                                                         !- Name
  1.3294540786,                                                                                       !- Coefficient1 Constant
  -0.0990649255,                                                                                     !- Coefficient2 x
  0.0008310043,                                                                                       !- Coefficient3 x**2
  0.0652277735,                                                                                       !- Coefficient4 y
  -0.0000793358,                                                                                     !- Coefficient5 y**2
  -0.0005874422,                                                                                     !- Coefficient6 x*y
  24.44,                                                                                                     !- Minimum Value of x
  26.67,                                                                                                     !- Maximum Value of x
  29.44,                                                                                                     !- Minimum Value of y
  46.1,                                                                                                       !- Maximum Value of y
  0.6661,                                                                                                   !- Minimum Curve Output
  1.6009,                                                                                                   !- Maximum Curve Output
  Temperature,                                                                                         !- Input Unit Type for X
  Temperature,                                                                                         !- Input Unit Type for Y
  Dimensionless;                                                                                     !- Output Unit Type

Coil:Cooling:DX:TwoStageWithHumidityControlMode[LINK]

The multimode DX coil is functionally equivalent to Coil:Cooling:DX:SingleSpeed but with multiple performance modes. It is capable of modeling two-stage DX units and units with an enhanced dehumidification mode such as coil bypass or subcool reheat. This object contains one-time specifications for the DX unit such as node names and crankcase heater specifications. It references one or more CoilPerformance:DX:Cooling objects which define the performance for each mode of operation. It can have up to 4 performance modes to accommodate a 2-stage 2-mode unit.

The multimode DX coil can be used only as a component of CoilSystem:Cooling:DX or AirLoopHVAC:UnitaryHeatCool:VAVChangeoverBypass (parent object). These parent objects pass a load and dehumidification mode to this coil. If the coil has 2 capacity stages, the multimode coil model determines the stage sequencing.

Inputs[LINK]

Field: Name[LINK]

A unique user-assigned name for an instance of a DX cooling coil. Any reference to this DX coil by another object will use this name.

Field: Availability Schedule Name[LINK]

The name of the schedule (ref: Schedule) that denotes whether the DX cooling coil can run during a given time period. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during a given time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off. If this field is blank, the schedule has values of 1 for all time periods.

Field: Air Inlet Node Name[LINK]

The name of the HVAC system node from which the DX cooling coil draws its inlet air.

Field: Air Outlet Node Name[LINK]

The name of the HVAC system node to which the DX cooling coil sends its outlet air.

Field: Crankcase Heater Capacity[LINK]

This numeric field defines the crankcase heater capacity in Watts. When the outdoor air dry-bulb temperature is below the value specified in the input field Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation (described below), the crankcase heater is enabled during the time that the compressor is not running. If this cooling coil is used as part of an air-to-air heat pump (Ref. AirLoopHVAC:UnitaryHeatCool:VAVChangeoverBypass), the crankcase heater defined for this DX cooling coil is ignored and the crankcase heater power defined for the DX heating coil (Ref. Coil:Heating:DX:SingleSpeed) is enabled during the time that the compressor is not running for either heating or cooling. The value for this input field must be greater than or equal to 0, and the default value is 0. To simulate a DX cooling coil without a crankcase heater, enter a value of 0.

Field: Maximum Outdoor Dry-Bulb Temperature for Crankcase Heater Operation[LINK]

This numeric field defines the outdoor air dry-bulb temperature above which the compressor s crankcase heater is disabled. The value for this input field must be greater than or equal to 0.0 °C, and the default value is 10 °C.

Field: Number of Capacity Stages[LINK]

This integer field defines the number of capacity stages. The value for this input field must be either 1 or 2, and the default value is 1. Larger DX units often have two capacity stages, which are often two completely independent compressor/coil circuits with the evaporator coils arranged in parallel in the supply air stream. 2-stage operation affects cycling losses and latent degradation due to re-evaporation of moisture with continuous fan operation.

Field: Number of Enhanced Dehumidification Modes[LINK]

This integer field defines the number of enhanced dehumidification modes available. The value for this input field must be 0 or 1, and the default value is 0. If the DX unit can switch operating modes to increase dehumidification based on a humidistat signal, then set this to 1. This field just specified the availability of enhanced dehumidification. Actual control of the operating mode is handled by the coil’s parent component.

Field: Normal Mode Stage 1 Coil Performance Object Type[LINK]

Field: Normal Mode Stage 1 Coil Performance Object Name[LINK]

This pair of fields specifies the object type and name for the coil performance object which specifies the DX coil performance for stage 1 operation without enhanced dehumidification (normal mode). The only valid performance object type is CoilPerformance:DX:Cooling.

Field: Normal Mode Stage 1+2 Coil Performance Object Type[LINK]

Field: Normal Mode Stage 1+2 Coil Performance Object Name[LINK]

This pair of fields specifies the object type and name for the coil performance object which specifies the DX coil performance for stage 1+2 operation (both stages active) without enhanced dehumidification (normal mode). The only valid performance object type is CoilPerformance:DX:Cooling.

Field: Dehumidification Mode 1 Stage 1 Coil Performance Object Type[LINK]

Field: Dehumidification Mode 1 Stage 1 Coil Performance Object Name[LINK]

This pair of fields specifies the object type and name for the coil performance object which specifies the DX coil performance for stage 1 operation with enhanced dehumidification active. The only valid performance object type is CoilPerformance:DX:Cooling.

Field: Dehumidification Mode 1 Stage 1+2 Coil Performance Object Type[LINK]

Field: Dehumidification Mode 1 Stage 1+2 Coil Performance Object Name[LINK]

This pair of fields specifies the object type and name for the coil performance object which specifies the DX coil performance for stage 1+2 operation (both stages active) with enhanced dehumidification active. The only valid performance object type is CoilPerformance:DX:Cooling.

Field: Supply Water Storage Tank Name[LINK]

This field is optional. It is used to describe where the coil obtains water used for evaporative cooling. If blank or omitted, then the cooler will obtain water directly from the mains. If the name of a Water Storage Tank object is used here, then the cooler will obtain its water from that tank. If a tank is specified, the coil will attempt to obtain all the water it uses from the tank. However if the tank cannot provide all the water the cooler needs, then the cooler will still operate and obtain the rest of the water it needs from the mains (referred to as StarvedWater).

Field: Condensate Collection Water Storage Tank Name[LINK]

This field is optional. It is used to describe where condensate from the coil is collected. If blank or omitted, then any coil condensate is discarded. Enter the name of Water Storage Tank object defined elsewhere and the condensate will then be collected in that tank.

Field: Basin Heater Capacity[LINK]

This numeric field contains the capacity of the DX coil s electric evaporative cooler basin heater in watts per degree Kelvin. This field only applies for Condenser Type = EvaporativelyCooled. This field is used in conjunction with the Basin Heater Setpoint Temperature described in the following field. The basin heater electric power is equal to this field multiplied by the difference between the basin heater set point temperature and the outdoor dry-bulb temperature. The basin heater only operates when the DX coil is off, regardless of the basin heater schedule described below. The basin heater capacity must be greater than or equal to zero, with a default value of zero if this field is left blank.

Field: Basin Heater Setpoint Temperature[LINK]

This numeric field contains the set point temperature (˚C) for the basin heater described in the previous field. This field only applies for Condenser Type = EvaporativelyCooled. The basin heater is active when the outdoor air dry-bulb temperature falls below this setpoint temperature, as long as the DX coil is off. This set point temperature must be greater than or equal to 2˚C, and the default value is 2˚C if this field is left blank.

Field: Basin Heater Operating Schedule Name[LINK]

This alpha field contains the name of the basin heater operating schedule. This field only applies for Condenser Type = EvaporativelyCooled. The basin heater operating schedule is assumed to be an on/off schedule and the heater is available to operate any time the schedule value is greater than 0. The basin heater operates when scheduled on and the outdoor air dry-bulb temperature is below the set point temperature described in the previous field. If this field is left blank, the basin heater is available to operate throughout the simulation. Regardless of this schedule, the basin heater may only operate when the DX coil is off.

Following is an example IDF use of the object:

Coil:Cooling:DX:TwoStageWithHumidityControlMode,
  DOAS Cooling Coil,                          !- Name
  HVACTemplate-Always 1,                      !- Availability Schedule Name
  DOAS Supply Fan Outlet,                     !- Air Inlet Node Name
  DOAS Cooling Coil Outlet,                   !- Air Outlet Node Name
  ,                                           !- Crankcase Heater Capacity
  ,                                           !- Maximum Outdoor Dry-Bulb Temperature for Crankcase Heater
  2,                                          !- Number of Capacity Stages
  1,                                          !- Number of Enhanced Dehumidification Modes
  CoilPerformance:DX:Cooling,                 !- Normal Mode Stage 1 Coil Performance Object Type
  DOAS Standard Perf 1,                       !- Normal Mode Stage 1 Coil Performance Name
  CoilPerformance:DX:Cooling,                 !- Normal Mode Stage 1+2 Coil Performance Object Type
  DOAS Standard Perf 1+2,                     !- Normal Mode Stage 1+2 Coil Performance Name
  CoilPerformance:DX:Cooling,                 !- Dehumidification Mode 1 Stage 1 Coil Performance Object Type
  DOAS Dehumid Perf 1,                        !- Dehumidification Mode 1 Stage 1 Coil Performance Name
  CoilPerformance:DX:Cooling,                 !- Dehumidification Mode 1 Stage 1+2 Coil Performance Object Type
  DOAS Dehumid Perf 1+2;                      !- Dehumidification Mode 1 Stage 1+2 Coil Performance Name

Coil:Cooling:DX:MultiSpeed[LINK]

This component models a DX cooling unit with multiple discrete levels of cooling capacity. Depending on input choices, the user can model a single compressor with multiple operating speeds, or a unit with a single cooling coil fed by multiple compressors (e.g., row split or intertwined coil circuiting). Currently, this cooling coil can only be referenced by a AirLoopHVAC:UnitaryHeatPump:AirToAir:Multispeed object. Refer to Coil:Cooling:DX:TwoStageWithHumidityControlMode if the user wishes to model a cooling coil with discrete levels of cooling and the possibility of air bypass during low speed operation (e.g. face-split coil circuiting), or if cooling coil operation based on dehumidification requirements is desired.

The multispeed DX cooling coil can have from two to four operating speeds. When the coil operates at Speed 1 (the lowest speed), its performance is very similar to the single speed DX coil where the impacts of part-load ratio and latent capacity degradation can be included. When the coil operates at higher speeds (above Speed 1), the linear approximation methodology is applied. The coil outputs at two consecutive speeds are linearly interpolated to meet the required cooling capacity during an HVAC system timestep. When the coil performs above the lowest speed, the user can chose if they want to include part-load ratio and latent capacity degradation impacts at the higher speeds.

The multispeed unit is described by specifying the performance at different operating speeds. Each speed has its own set of input specifications: full load capacity, SHR, COP and air flow rate at rated conditions, along with modifier curves to determine performance when actual operating conditions are different from the rated conditions.

The coil operates to meet the sensible capacity being requested. When this requested capacity is above the sensible capacity of the highest operating speed, the coil runs continuously at the highest speed. When the requested capacity is between the sensible capacities of two consecutive speeds, the unit will operate a portion of the time at each speed to meet the request. When the requested capacity is less than the low speed (Speed 1) capacity, the unit will cycle on/off as needed.

Inputs[LINK]

Field: Name[LINK]

A unique user-assigned name for an instance of a multispeed DX cooling coil. Any reference to this DX coil by another object will use this name.

Field: Availability Schedule Name[LINK]

The name of the schedule (ref: Schedule) that denotes whether the DX cooling coil can run during a given time period. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off for the time period. If this field is blank, the schedule has values of 1 for all time periods.

Field: Air Inlet Node Name[LINK]

The name of the HVAC system node from which the DX cooling coil draws its inlet air.

Field: Air Outlet Node Name[LINK]

The name of the HVAC system node to which the DX cooling coil sends its outlet air.

Field: Condenser Air Inlet Node Name[LINK]

This optional alpha field specifies the outdoor air node name used to define the conditions of the air entering the outdoor condenser. If this field is left blank, the outdoor air temperature entering the condenser (dry-bulb or wet-bulb) is taken directly from the weather data. If this field is not blank, the node name specified must also be specified in an OutdoorAir:Node object where the height of the node is taken into consideration when calculating outdoor air temperature from the weather data. Alternately, the node name may be specified in an OutdoorAir:NodeList object where the outdoor air temperature is taken directly from the weather data.

Field: Condenser Type[LINK]

The type of condenser used by the multispeed DX cooling coil. Valid choices for this input field are AirCooled or EvaporativelyCooled. The default for this field is AirCooled.

Field: Supply Water Storage Tank Name[LINK]

This field is optional. It is used to describe where the coil obtains water used for evaporative cooling. If blank or omitted, then the evaporative cooler will obtain water directly from the mains. If the name of a Water Storage Tank object is used here, then the cooler will obtain its water from that tank. If a tank is specified, the coil will attempt to obtain all the water it uses from the tank. However if the tank cannot provide all the water the cooler needs, then the cooler will still operate and obtain the rest of the water it needs from the mains (referred to as StarvedWater).

Field: Condensate Collection Water Storage Tank Name[LINK]

This field is optional. It is used to describe where condensate from the coil is collected. If blank or omitted, then any coil condensate is discarded. Enter the name of Water Storage Tank object defined elsewhere and the condensate will then be collected in that tank.

Field: Apply Part Load Fraction to Speeds Greater than 1[LINK]

This field determines whether part-load impacts on coil energy use are applied when the coil is operating at speeds greater than speed 1. The allowed choices are Yes or No, with the default being No if this field is left blank. Other input fields in this object allow the user to specify a part-load fraction correlation for each speed to account for compressor start up losses (cycle on/off). For the case of a single multi-speed compressor, the part load losses may only be significant when the compressor cycles between speed 1 and off, but the losses may be extremely small when the compressor operates between speed 1 and speed 2 (or between speeds 2 and 3, etc.). In this case, the user may chose to specify NO for this input field to neglect part-load impacts on energy use at higher operating speeds. If part-load impacts on coil energy use are thought to be significant (e.g., interwined cooling coil with multiple compressors feeding individual refrigerant circuits), then the user may chose to specify YES and the part-load fraction correlations specified for speeds 2 through 4 will be applied as appropriate. The selection for this input field does not affect part-load impacts when the compressor cycles between speed 1 and off (i.e., the part-load fraction correlation for speed 1 is always applied).

Field: Apply Latent Degradation to Speeds Greater than 1[LINK]

This field determines whether latent capacity degradation is applied when the coil is operating at speeds greater than speed 1. The allowed choices are Yes or No, with the default being No if this field is left blank. Other input fields in this object allow the user to specify latent capacity degradation at each speed.

The latent capacity degradation model only applies when the ContinuousFanWithCyclingCompressor supply air fan operating mode is specified, to account for moisture evaporation from the wet cooling coil when the compressor cycles off but the supply air fan continues to operate. For the case of a single multi-speed compressor, latent capacity degradation may only be significant when the compressor cycles between speed 1 and off, but the losses may be extremely small when the compressor operates between speed 1 and speed 2 (or between speeds 2 and 3, etc.). In this case, the user may chose to specify NO for this input field to neglect latent capacity degradation impacts at higher operating speeds. If latent capacity degradation is thought to be significant (e.g., interwined or row-split cooling coil with multiple compressors feeding individual refrigerant circuits), then the user may chose to specify YES and the latent capacity degradation model will be applied for speeds 2 through 4 as appropriate. The selection for this input field does not affect latent capacity degradation between speed 1 and off.

Field: Crankcase Heater Capacity[LINK]

This numeric field defines the crankcase heater capacity in Watts. When the outdoor air dry-bulb temperature is below the value specified in the input field Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation (described below), the crankcase heater is enabled during the time that the compressor is not running. The value for this input field must be greater than or equal to 0. If this input field is left blank, the default value is 0. To simulate a unit without a crankcase heater, enter a value of 0.

Field: Maximum Outdoor Dry-Bulb Temperature for Crankcase Heater Operation[LINK]

This numeric field defines the outdoor air dry-bulb temperature above which the compressor s crankcase heater is disabled. The value for this input field must be greater than or equal to 0.0 °C. If this input field is left blank, the default value is 10 °C.

Field: Basin Heater Capacity[LINK]

This numeric field contains the capacity of the DX coil s electric evaporative cooler basin heater in watts per degree Kelvin. This field only applies for Condenser Type = EvaporativelyCooled. This field is used in conjunction with the Basin Heater Setpoint Temperature described in the following field. The basin heater electric power is equal to this field multiplied by the difference between the basin heater set point temperature and the outdoor dry-bulb temperature. The basin heater only operates when the DX coil is off, regardless of the basin heater schedule described below. The basin heater capacity must be greater than or equal to zero, with a default value of zero if this field is left blank.

Field: Basin Heater Setpoint Temperature[LINK]

This numeric field contains the set point temperature (˚C) for the basin heater described in the previous field. This field only applies for Condenser Type = EvaporativelyCooled. The basin heater is active when the outdoor air dry-bulb temperature falls below this setpoint temperature, as long as the DX coil is off. This set point temperature must be greater than or equal to 2˚C, and the default value is 2˚C if this field is left blank.

Field: Basin Heater Operating Schedule Name[LINK]

This alpha field contains the name of the basin heater operating schedule. This field only applies for Condenser Type = EvaporativelyCooled. The basin heater operating schedule is assumed to be an on/off schedule and the heater is available to operate any time the schedule value is greater than 0. The basin heater operates when scheduled on and the outdoor air dry-bulb temperature is below the set point temperature described in the previous field. If this field is left blank, the basin heater is available to operate throughout the simulation. Regardless of this schedule, the basin heater may only operate when the DX coil is off.

Field: Fuel Type[LINK]

This alpha field determines the type of fuel that this cooling coil uses. This field has seven choices: Electricity, NaturalGas, PropaneGas, Coal, Diesel, Gasoline, FuelOil#1, FuelOil#2, OtherFuel1 and OtherFuel2. The default is NaturalGas.

Field: Number of Speeds[LINK]

This field specifies the number of sets of data being entered for rated specifications, performance curves, evaporative condenser data, latent degradation data, and waste heat specifications for each cooling speed. The rated specifications consist of gross rated capacity, gross rated SHR, gross rated COP, and rated air flow rate. The performance curves consist of a total capacity modifier curve as a function of temperature, total capacity modifier curve as a function of flow fraction, energy input ratio modifier curve as a function of temperature, energy input ratio modifier curve as a function of flow fraction, and part load fraction correlation as a function of part load ratio. The evaporative condenser data consists of effectiveness, condenser air volume flow rate, and rated pump power consumption. The latent degradation data consists of nominal time for condensate removal to begin, ratio of initial moisture evaporation rate and steady-state latent capacity, maximum On/Off cycling rate, and latent capacity time constant. The latent degradation data are only applied if the supply air fan operation mode is specified as ContinuousFanWithCyclingCompressor. The waste heat specifications include the fraction of energy input to the cooling coil at the fully loaded and rated conditions, and a temperature modifier. The minimum number of speeds for cooling is 2 and the maximum number is 4. The number of speeds should be the same as the number of speeds for cooling defined in its parent object (AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed). The first set of performance inputs is for Speed 1 and should be for low speed, and the last set of performance inputs should be for high speed. For example, if only three cooling speeds are defined, the first set should be for low speed (Speed 1), the second set should be for medium speed (Speed 2), and the third set should be for high speed (Speed 3). In this example, any performance inputs for Speed 4 would be neglected (since this input field specifies that the coil only has three cooling speeds).

Field Group: Rated Specification, Performance Curves, Latent Capacity Degradation Inputs, and Evaporative Cooled Condenser Data[LINK]

The performance for each cooling speed must be specified as shown below. All inputs for Speed 1 are required first, followed by the inputs for Speed 2, Speed 3 and Speed 4.

Field: Speed <x> Gross Rated Total Cooling Capacity[LINK]

The total, full load gross cooling capacity (sensible plus latent) in watts of the DX coil unit for Speed <x> operation at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and a cooling coil air flow rate defined by field Rated Air Flow Rate, Speed <x> below). Capacity should be gross (i.e., the effect of supply air fan heat is NOT accounted for).

Field: Speed <x> Gross Rated Sensible Heat Ratio[LINK]

The sensible heat ratio (SHR = gross sensible capacity divided by gross total cooling capacity) of the DX cooling coil for Speed <x> operation at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and a cooling coil air flow rate defined by field Rated Air Flow Rate, Speed <x> below). Both the sensible and total cooling capacities used to define the Rated SHR should be gross (i.e., the effect of supply air fan heat is NOT accounted for).

Field: Speed <x> Gross Rated Cooling COP[LINK]

The coefficient of performance is the ratio of the gross total cooling capacity in watts to electrical power input in watts) of the DX cooling coil unit for Speed <x> operation at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and a cooling coil air flow rate defined by field Rated Air Flow Rate, Speed <x> below). The input power includes power for the compressor(s) and condenser fan(s) but does not include the power consumption of the supply air fan. The gross COP should NOT account for the supply air fan. If this input field is left blank, the default value is 3.0.

Field: Speed <x> Rated Air Flow Rate[LINK]

The volumetric air flow rate for Speed <x>, in m3 per second, across the DX cooling coil at rated conditions. The rated air volume flow rate for Speed <x> should be between 0.00004027 m3/s and 0.00006041 m3/s per watt of the gross rated total cooling capacity for Speed <x>. The gross rated total cooling capacity, gross rated SHR and gross rated COP for Speed <x> should be performance information for the unit with air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and the rated air volume flow rate defined here.

Field: Speed <X> Rated Evaporator Fan Power Per Volume Flow Rate[LINK]

This field is the electric power for the evaporator (cooling coil) fan per air volume flow rate through the coil at the rated conditions for Speed <x> in W/(m3/s). The default value is 773.3 W/(m3/s) (365 W/1000 cfm) if this field is left blank. If a value is entered, it must be > = 0.0 and < = 1250 W/(m3/s). This value is only used to calculate Seasonal Energy Efficiency Ratio (SEER), and the Standard Rating (Net) Cooling Capacity which will be outputs in the EnergyPlus eio file (ref. EnergyPlus Engineering Reference, Multi-Speed DX Cooling Coil, Standard Ratings). This value is not used for modeling the evaporator (cooling coil) fan during simulations; instead, it is used for calculating SEER and Standard Rating Cooling Capacity to assist the user in verifying their inputs for modeling this type of equipment.

Field: Speed <x> Total Cooling Capacity Function of Temperature Curve Name[LINK]

The name of a biquadratic performance curve (ref: Performance Curves) that parameterizes the variation of the gross total cooling capacity for Speed <x> as a function of the wet-bulb temperature of the air entering the cooling coil, and the dry-bulb temperature of the air entering the air-cooled condenser (wet-bulb temperature if modeling an evaporative-cooled condenser). The output of this curve is multiplied by the gross rated total cooling capacity for Speed <x> to give the gross total cooling capacity at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures). The curve is normalized to have the value of 1.0 at the rating point.

Field: Speed <x> Total Cooling Capacity Function of Flow Fraction Curve Name[LINK]

The name of a quadratic performance curve (ref: Performance Curves) that parameterizes the variation of the gross total cooling capacity for Speed <x> as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate for Speed <x> (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated total cooling capacity and the total cooling capacity modifier curve (function of temperature) to give the gross total cooling capacity for Speed <x> at the specific temperature and air flow conditions at which the coil is operating. The curve is normalized to have the value of 1.0 when the actual air flow rate equals the rated air flow rate for Speed <x>.

Field: Speed <x> Energy Input Ratio Function of Temperature Curve Name[LINK]

The name of a biquadratic performance curve (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) for Speed <x> as a function of the wetbulb temperature of the air entering the cooling coil and the drybulb temperature of the air entering the air-cooled condenser (wetbulb temperature if modeling an evaporative-cooled condenser). The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR for Speed <x> (inverse of rated COP for Speed <x>) to give the EIR for Speed <x> at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures). The curve is normalized to a value of 1.0 at the rating point.

Field: Speed <x> Energy Input Ratio Function of Flow Fraction Curve Name[LINK]

The name of a quadratic performance curve (Ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) for Speed <x> as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate for Speed <x> (i.e., fraction of full load flow). The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR and the EIR modifier curve (function of temperature) to give the EIR for Speed <x> at the specific temperature and air flow conditions at which the cooling coil is operating. This curve is normalized to a value of 1.0 when the actual air flow rate equals the rated air flow rate for Speed <x>.

Field: Speed <x> Part Load Fraction Correlation Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve (Ref: Performance Curves) that parameterizes the variation of electrical power input to the DX unit as a function of the part load ratio (PLR, sensible cooling load/steady-state sensible cooling capacity for Speed <x>). The product of the rated EIR and EIR modifier curves is divided by the output of this curve to give the effective EIR for a given simulation timestep for Speed <x>. The part load fraction (PLF) correlation accounts for efficiency losses due to compressor cycling.

The part load fraction correlation should be normalized to a value of 1.0 when the part load ratio equals 1.0 (i.e., no efficiency losses when the compressor(s) run continuously for the simulation timestep). For PLR values between 0 and 1 (0 < = PLR < 1), the following rules apply:

PLF > = 0.7     and     PLF > = PLR

If PLF < 0.7 a warning message is issued, the program resets the PLF value to 0.7, and the simulation proceeds. The runtime fraction of the coil is defined as PLR/PLF. If PLF < PLR, then a warning message is issued and the runtime fraction of the coil is limited to 1.0.

A typical part load fraction correlation for a conventional DX cooling coil (Speed <x>) would be:

PLF = 0.85 + 0.15(PLR)

If the user wishes to model no efficiency degradation due to compressor cycling, the part load fraction correlation should be defined as follows:

PLF = 1.0 + 0.0(PLR)

Field: Speed <x> Nominal Time for Condensate Removal to Begin[LINK]

For Speed <x>, the nominal time (in seconds) after startup for condensate to begin leaving the coil’s condensate drain line at the coil’s rated airflow and temperature conditions, starting with a dry coil. Nominal time is equal to the ratio of the energy of the coil’s maximum condensate holding capacity (J) to the coil’s steady-state latent capacity (W). Suggested value is 1000; zero value means the latent degradation model is disabled. The default value for this field is zero. The supply air fan operating mode must be continuous (i.e., the supply air fan operating mode may be specified in other parent objects and is assumed continuous in some objects (e.g., CoilSystem:Cooling:DX) or can be scheduled in other objects [e.g., AirloopHVAC:UnitaryHeatCool]), and this field as well as the next three input fields for this object must have positive values in order to model latent capacity degradation for Speed <x>.

Field: Speed <x> Ratio of Initial Moisture Evaporation Rate and Steady State Latent Capacity[LINK]

For Speed <x>, the ratio of the initial moisture evaporation rate from the cooling coil (when the compressor first turns off, in Watts) and the coil’s steady-state latent capacity (Watts) for Speed <x> at rated airflow and temperature conditions. Suggested value is 1.5; zero value means the latent degradation model is disabled. The default value for this field is zero. The supply air fan operating mode must be continuous (i.e., the supply air fan operating mode may be specified in other parent objects and is assumed continuous in some objects (e.g., CoilSystem:Cooling:DX) or can be scheduled in other objects [e.g., AirloopHVAC:UnitaryHeatCool]); and this field, the previous field and the next two fields must have positive values in order to model latent capacity degradation for Speed <x>.

Field: Speed <x> Maximum Cycling Rate[LINK]

For Speed <x>, the maximum on-off cycling rate for the compressor (cycles per hour), which occurs at 50% run time fraction. Suggested value is 3; zero value means latent degradation model is disabled. The default value for this field is zero. The supply air fan operating mode must be continuous (i.e., the supply air fan operating mode may be specified in other parent objects and is assumed continuous in some objects (e.g., CoilSystem:Cooling:DX) or can be scheduled in other objects [e.g., AirloopHVAC:UnitaryHeatCool]); and this field, the previous two fields and the next field must have positive values in order to model latent capacity degradation for Speed <x>.

Field: Speed <x> Latent Capacity Time Constant[LINK]

For Speed <x>, the time constant (in seconds) for the cooling coil’s latent capacity to reach steady state after startup. Suggested value is 45; zero value means latent degradation model is disabled. The default value for this field is zero. The supply air fan operating mode must be continuous (i.e., the supply air fan operating mode may be specified in other parent objects and is assumed continuous in some objects (e.g., CoilSystem:Cooling:DX) or can be scheduled in other objects [e.g., AirloopHVAC:UnitaryHeatCool]), and this field as well as the previous three input fields for this object must have positive values in order to model latent capacity degradation for Speed <x>.

Field: Speed <x> Rated Waste Heat Fraction of Power Input[LINK]

The fraction of energy input to the cooling coil that is available as recoverable waste heat at full load and rated conditions for Speed <x>.

Field: Speed <x> Waste Heat Function of Temperature Curve Name[LINK]

The name of a biquadratic performance curve (ref: Performance Curves) that parameterizes the variation of the waste heat recovery as a function of outdoor dry-bulb temperature and the entering coil dry-bulb temperature at Speed <x>. The output of this curve is multiplied by the rated waste heat fraction at specific temperature operating conditions (i.e., at temperatures different from the rating point). The curve is normalized to a value of 1.0 at the rating point. When the fuel type is electricity, this field can remain blank since it is ignored by the program in this instance. When the fuel type is not electricity and the parent object AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed does not require waste heat calculations, this field is ignored. If the field is blank, a warning will be issued and simulation continues. When the fuel type is not electricity and the parent object AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed requires waste heat calculations, if this field is left blank, the program assumes a constant value of 1 to make simulation continue and a warning will be issued.

Field: Speed <x> Evaporative Condenser Effectiveness[LINK]

The effectiveness of the evaporative condenser at Speed <x>, which is used to determine the temperature of the air entering the outdoor condenser coil as follows:

Tcondinlet=(Twb,o)+(1EvapCondEffectivenessSpeed1)(Tdb,oTwb,o)

where

Tcondinlet = the temperature of the air entering the condenser coil (C)

Twb,o = the wet-bulb temperature of the outdoor air (C)

Tdb,o = the dry-bulb temperature of the outdoor air (C)

The resulting condenser inlet air temperature is used by the Total Cooling Capacity Modifier Curve, Speed <x> (function of temperature) and the Energy Input Ratio Modifier Curve, Speed <x> (function of temperature). The default value for this field is 0.9, although valid entries can range from 0.0 to 1.0. This field is not used when Condenser Type = Air Cooled.

If the user wants to model an air-cooled condenser, they should simply specify AirCooled in the field Condenser Type. In this case, the Total Cooling Capacity Modifier Curve, Speed <x> (function of temperature) and the Energy Input Ratio Modifier Curve, Speed <x> (function of temperature) input fields for this object should reference performance curves that are a function of outdoor dry-bulb temperature.

If the user wishes to model an evaporative-cooled condenser AND they have performance curves that are a function of the wet-bulb temperature of air entering the condenser coil, then the user should specify Condenser Type = Evap Cooled and the evaporative condenser effectiveness value should be entered as 1.0. In this case, the Total Cooling Capacity Modifier Curve, Speed <x> (function of temperature) and the Energy Input Ratio Modifier Curve, Speed <x> (function of temperature) input fields for this object should reference performance curves that are a function of the wet-bulb temperature of air entering the condenser coil.

If the user wishes to model an air-cooled condenser that has evaporative media placed in front of it to cool the air entering the condenser coil, then the user should specify Condenser Type = Evap Cooled. The user must also enter the appropriate evaporative effectiveness for the media. In this case, the Total Cooling Capacity Modifier Curve, Speed <x> (function of temperature) and the Energy Input Ratio Modifier Curve, Speed <x> (function of temperature) input fields for this object should reference performance curves that are a function of outdoor dry-bulb temperature. Be aware that the evaporative media will significantly reduce the dry-bulb temperature of the air entering the condenser coil, so the Total Cooling Capacity and EIR Modifier Curves for Speed <x> must be valid for the expected range of dry-bulb temperatures that will be entering the condenser coil.

Field: Speed <x> Evaporative Condenser Air Flow Rate[LINK]

The air volume flow rate, in m3 per second, entering the evaporative condenser at Speed <x>. This value is used to calculate the amount of water used to evaporatively cool the condenser inlet air. The minimum value for this field must be greater than zero, and this input field is autosizable (equivalent to 0.000114 m3/s per watt of rated total cooling capacity for Speed <x> [850 cfm/ton]). This field is not used when Condenser Type = Air Cooled.

Field: Speed <x> Rated Evaporative Condenser Pump Power Consumption[LINK]

The rated power of the evaporative condenser water pump in Watts at Speed <x>. This value is used to calculate the power required to pump the water used to evaporatively cool the condenser inlet air. The default value for this input field is zero, but it is autosizable (equivalent to 0.004266 W per watt [15 W/ton] of rated total capacity for Speed <x>). This field is not used when Condenser Type = Air Cooled.

Field: Zone Name for Condenser Placement[LINK]

This input field is name of a conditioned or unconditioned zone where the secondary coil (condenser) of DX system or a heat pump is to be placed. This is an optional input field specified only when user desires to reject the condenser heat into a zone. The heat rejected is modeled as sensible internal gain of a secondary zone.

Following is an example input for this multispeed DX cooling coil.

Coil:Cooling:DX:MultiSpeed,
  Heat Pump ACDXCoil 1,       !- Coil Name
  FanAndCoilAvailSched,       !- Availability Schedule
  DX Cooling Coil Air Inlet Node,   !- Coil Air Inlet Node
  Heating Coil Air Inlet Node,         !- Coil Air Outlet Node
  Outdoor Condenser Air Node,           !- Condenser Air Inlet Node Name
  AirCooled,                           !- Condenser Type
  ,                                               !- Name of Water Storage Tank for Supply
  ,                                               !- Name of Water Storage Tank for Condensate Collection
  No,                                           !- Apply Part Load Fraction to Speeds greater than 1
  No,                                           !- Apply latent degradation to Speeds greater than 1
  200.0,                                     !- Crankcase Heater Capacity {W}
  10.0,                                       !- Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation
  ,                                               !- Basin Heater Capacity {W/K}
  ,                                               !- Basin Heater Setpoint Temperature {C}
  ,                                               !- Basin Heater Operating Schedule Name
  NaturalGas,                           !- Fuel Type
  4,                                             !- Number of speeds
  7500,                                       !- Gross Rated Total Cooling Capacity, Speed 1 {W}
  0.75,                                       !- Gross Rated Sensible Heat Ratio, Speed 1 {dimensionless}
  3.0,                                         !- Gross Rated Cooling COP, Speed 1 {dimensionless}
  0.40,                                       !- Rated Air Flow Rate, Speed 1 {m3/s}
  ,                                               !- Rated Evaporator Fan Power Per Volume Flow Rate, Speed 1 {W/(m3/s)}
  HPACCoolCapFT Speed 1,     !- Total Cooling Capacity Modifier Curve, Speed 1 (temperature)
  HPACCoolCapFF Speed 1,     !- Total Cooling Capacity Modifier Curve, Speed 1 (flow fraction)
  HPACCOOLEIRFT Speed 1,     !- Energy Input Ratio Modifier Curve, Speed 1 (temperature)
  HPACCOOLEIRFF Speed 1,     !- Energy Input Ratio Modifier Curve, Speed 1 (flow fraction)
  HPACCOOLPLFFPLR Speed 1, !- Part Load Fraction Correlation, Speed 1 (part load ratio)
  1000.0,                                   !- Nominal Time for Condensate Removal to Begin, Speed 1 {s}
  1.5,                                         !- Ratio of Initial Moisture Evaporation Rate and Steady-state Latent
  3.0,                                         !- Maximum ON/OFF Cycling Rate, Speed 1 {cycles/hr}
  45.0,                                       !- Latent Capacity Time Constant, Speed 1 {s}
  0.2,                                         !- Rated waste heat fraction of power input, Speed 1 {dimensionless}
  HAPCCoolWHFT Speed 1,       !- Waste heat modifier curve, Speed 1 (temperature)
  0.9,                                         !- Evaporative Condenser Effectiveness, Speed 1 {dimensionless}
  0.05,                                       !- Evaporative Condenser Air Volume Flow Rate, Speed 1 {m3/s}
  50,                                           !- Evaporative Condenser Pump Rated Power Consumption, Speed 1 {W}
  17500,                                     !- Gross Rated Total Cooling Capacity, Speed 2 {W}
  0.75,                                       !- Gross Rated Sensible Heat Ratio, Speed 2 {dimensionless}
  3.0,                                         !- Gross Rated Cooling COP, Speed 2 {dimensionless}
  0.85,                                       !- Rated Air Flow Rate, Speed 2 {m3/s}
  ,                                               !- Rated Evaporator Fan Power Per Volume Flow Rate, Speed 2 {W/(m3/s)}
  HPACCoolCapFT Speed 2,     !- Total Cooling Capacity Modifier Curve, Speed 2 (temperature)
  HPACCoolCapFF Speed 2,     !- Total Cooling Capacity Modifier Curve, Speed 2 (flow fraction)
  HPACCOOLEIRFT Speed 2,     !- Energy Input Ratio Modifier Curve, Speed 2 (temperature)
  HPACCOOLEIRFF Speed 2,     !- Energy Input Ratio Modifier Curve, Speed 2 (flow fraction)
  HPACCOOLPLFFPLR Speed 1, !- Part Load Fraction Correlation, Speed 2 (part load ratio)
  1000.0,                                   !- Nominal Time for Condensate Removal to Begin, Speed 2
  1.5,                                         !- Ratio of Initial Moisture Evaporation Rate and Steady-state Latent
  3.0,                                         !- Maximum ON/OFF Cycling Rate, Speed 2
  45.0,                                       !- Latent Capacity Time Constant, Speed 2
  0.2,                                         !- Rated waste heat fraction of power input, Speed 2 {dimensionless}
  HAPCCoolWHFT Speed 2,       !- Waste heat modifier curve, Speed 2 (temperature)
  0.9,                                         !- Evaporative Condenser Effectiveness, Speed 2 {dimensionless}
  0.1,                                         !- Evaporative Condenser Air Volume Flow Rate, Speed 2 {m3/s}
  60,                                           !- Evaporative Condenser Pump Rated Power Consumption, Speed 2 {W}
  25500,                                     !- Gross Rated Total Cooling Capacity, Speed 3 {W}
  0.75,                                       !- Gross Rated Sensible Heat Ratio, Speed 3 {dimensionless}
  3.0,                                         !- Gross Rated Cooling COP, Speed 3 {dimensionless}
  1.25,                                       !- Rated Air Flow Rate, Speed 3 {m3/s}
  ,                                               !- Rated Evaporator Fan Power Per Volume Flow Rate, Speed 3 {W/(m3/s)}
  HPACCoolCapFT Speed 3,     !- Total Cooling Capacity Modifier Curve, Speed 3 (temperature)
  HPACCoolCapFF Speed 3,     !- Total Cooling Capacity Modifier Curve, Speed 3 (flow fraction)
  HPACCOOLEIRFT Speed 3,     !- Energy Input Ratio Modifier Curve, Speed 3 (temperature)
  HPACCOOLEIRFF Speed 3,     !- Energy Input Ratio Modifier Curve, Speed 3 (flow fraction)
  HPACCOOLPLFFPLR Speed 1, !- Part Load Fraction Correlation, Speed 3 (part load ratio)
  1000.0,                                   !- Nominal Time for Condensate Removal to Begin, Speed 3 {s}
  1.5,                                         !- Ratio of Initial Moisture Evaporation Rate and Steady-state Latent
  3.0,                                         !- Maximum ON/OFF Cycling Rate, Speed 3 {cycles/hr}
  45.0,                                       !- Latent Capacity Time Constant, Speed 3 {s}
  0.2,                                         !- Rated waste heat fraction of power input, Speed 3 {dimensionless}
  HAPCCoolWHFT Speed 3,       !- Waste heat modifier curve, Speed 3 (temperature)
  0.9,                                         !- Evaporative Condenser Effectiveness, Speed 3 {dimensionless}
  0.2,                                         !- Evaporative Condenser Air Volume Flow Rate, Speed 3 {m3/s}
  80,                                           !- Evaporative Condenser Pump Rated Power Consumption, Speed 3 {W}
  35500,                                     !- Gross Rated Total Cooling Capacity, Speed 4 {W}
  0.75,                                       !- Gross Rated Sensible Heat Ratio, Speed 4 {dimensionless}
  3.0,                                         !- Gross Rated Cooling COP, Speed 4 {dimensionless}
  1.75,                                       !- Rated Air Flow Rate, Speed 4 {m3/s}
  ,                                               !- Rated Evaporator Fan Power Per Volume Flow Rate, Speed 4 {W/(m3/s)}
  HPACCoolCapFT Speed 4,     !- Total Cooling Capacity Modifier Curve, Speed 4 (temperature)
  HPACCoolCapFF Speed 4,     !- Total Cooling Capacity Modifier Curve, Speed 4 (flow fraction)
  HPACCOOLEIRFT Speed 4,     !- Energy Input Ratio Modifier Curve, Speed 4 (temperature)
  HPACCOOLEIRFF Speed 4,     !- Energy Input Ratio Modifier Curve, Speed 4 (flow fraction)
  HPACCOOLPLFFPLR Speed 1, !- Part Load Fraction Correlation, Speed 4 (part load ratio)
  1000.0,                                   !- Nominal Time for Condensate Removal to Begin, Speed 4 {s}
  1.5,                                         !- Ratio of Initial Moisture Evaporation Rate and Steady-state Latent                                                     !- Capacity, Speed 4 {dimensionless}
  3.0,                                         !- Maximum ON/OFF Cycling Rate, Speed 4 {cycles/hr}
  45.0,                                       !- Latent Capacity Time Constant, Speed 4 {s}
  0.2,                                         !- Rated waste heat fraction of power input, Speed 4 {dimensionless}
  HAPCCoolWHFT Speed 4,       !- Waste heat modifier curve, Speed 4 (temperature)
  0.9,                                         !- Evaporative Condenser Effectiveness, Speed 4 {dimensionless}
  0.3,                                         !- Evaporative Condenser Air Volume Flow Rate, Speed 4 {m3/s}
  100;                                         !- Evaporative Condenser Pump Rated Power Consumption, Speed 4 {W}

Outputs[LINK]

  • HVAC,Average,Cooling Coil Total Cooling Rate [W]

  • HVAC,Sum,Cooling Coil Total Cooling Energy [J]

  • HVAC,Average,Cooling Coil Sensible Cooling Rate [W]

  • HVAC,Sum,Cooling Coil Sensible Cooling Energy [J]

  • HVAC,Average,Cooling Coil Latent Cooling Rate [W]

  • HVAC,Sum,Cooling Coil Latent Cooling Energy [J]

  • HVAC,Average,Cooling Coil Electric Power[W]

  • HVAC,Sum,Cooling Coil Electric Energy [J]

  • HVAC,Average,Cooling Coil Runtime Fraction []

If not part of AirLoopHVAC:UnitaryHeatPump:AirToAir (if part of a heat pump, crankcase heater is reported only for the heating coil):

  • HVAC,Average,Cooling Coil Crankcase Heater Electric Power[W]

  • HVAC,Sum,Cooling Coil Crankcase Heater Electric Energy [J]

Evaporative-cooled condenser:

  • HVAC,Average,Cooling Coil Condenser Inlet Temperature [C]

  • HVAC,Sum,Cooling Coil Evaporative Condenser Water Volume[m3]

  • HVAC,Average,Cooling Coil Evaporative Condenser Pump Electric Power[W]

  • HVAC,Sum,Cooling Coil Evaporative Condenser Pump Electric Energy [J]

  • HVAC,Average,Cooling Coil Basin Heater Electric Power[W]

  • HVAC,Sum,Cooling Coil Basin Heater Electric Energy [J]

  • HVAC,Sum,Cooling Coil Evaporative Condenser Mains Supply Water Volume [m3]

Additional variables for Coil:Cooling:DX:TwoStageWithHumidityControlMode only:

  • HVAC,Average,Cooling Coil Stage 2 Runtime Fraction []

  • HVAC,Average,Cooling Coil Dehumidification Mode []

Additional variables when condensate is collected using a storage tank:

  • HVAC,Average,Cooling Coil Condensate Volume Flow Rate [m3/s]

  • Zone,Meter,Condensate:OnSiteWater [m3]

  • HVAC,Sum,Cooling Coil Condensate Volume [m3]

Additional variables for Coil:Cooling:DX:Multispeed:

If Fuel Type is not Electricity:

  • HVAC,Average,DX Cooling Coil <Fuel Type> Power[W]

  • HVAC,Sum,DX Cooling Coil <Fuel Type> Consumption[J]

Cooling Coil Total Cooling Rate [W] [LINK]

This field is the total (sensible and latent) cooling rate output of the DX coil in Watts. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Total Cooling Energy [J] [LINK]

This is the total (sensible plus latent) cooling output of the DX coil in Joules over the timestep being reported. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil. This output is also added to a meter with Resource Type = EnergyTransfer, End Use Key = CoolingCoils, Group Key = System (Ref. Output:Meter objects).

Cooling Coil Sensible Cooling Rate [W] [LINK]

This output is the moist air sensible cooling rate output of the DX coil in Watts. This is determined by the inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Sensible Cooling Energy [J] [LINK]

This is the moist air sensible cooling output of the DX coil in Joules for the timestep being reported. This is determined by the inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Latent Cooling Rate [W] [LINK]

This is the latent cooling rate output of the DX coil in Watts. This is determined by the inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Latent Cooling Energy [J] [LINK]

This is the latent cooling output of the DX coil in Joules for the timestep being reported. This is determined by the inlet and outlet air conditions and the air mass flow rate through the coil.

Cooling Coil Electric Power [W] [LINK]

This output is the electricity consumption rate of the DX coil compressor and condenser fan(s) in Watts. This value is calculated for each HVAC system timestep, and the results are averaged for the timestep being reported.

Cooling Coil Electric Energy [J] [LINK]

This is the electricity consumption of the DX coil compressor and condenser fan(s) in Joules for the timestep being reported. This output is also added to a meter with Resource Type = Electricity, End Use Key = Cooling, Group Key = System (Ref. Output:Meter objects).

Cooling Coil Runtime Fraction [] [LINK]

This is the runtime fraction of the DX coil compressor and condenser fan(s) for the timestep being reported.

Cooling Coil Crankcase Heater Electric Power[W] [LINK]

This is the average electricity consumption rate of the DX coil compressor s crankcase heater in Watts for the timestep being reported. If the DX Cooling Coil is used in a heat pump, the crankcase heater is reported only for the heating coil.

Cooling Coil Crankcase Heater Electric Energy [J] [LINK]

This is the electricity consumption of the DX coil compressor s crankcase heater in Joules for the timestep being reported. This output is also added to a meter with Resource Type = Electricity, End Use Key = Cooling, Group Key = System (ref. Output:Meter objects). This output variable appears only when the DX Cooling Coil is not used as part of a heat pump, otherwise the crankcase heater is reported only for the heating coil.

Cooling Coil Condenser Inlet Temperature [C] [LINK]

This is the inlet air temperature to the condenser coil in degrees C. This value can represent the outdoor air dry-bulb temperature, wet-bulb temperature, or somewhere in between from the weather data being used, depending on the value used in the input field Evaporative Condenser Effectiveness . The temperature reported here is used in the various modifier curves related to temperature (e.g., Total Cooling Capacity Modifier Curve [function of temperature]). This output variable appears only when the DX Cooling Coil is not used as part of a heat pump, otherwise the crankcase heater is reported only for the heating coil.

Cooling Coil Evaporative Condenser Water Volume [m3] [LINK]

This output is the amount of water used to evaporatively cool the condenser coil inlet air, in cubic meters. This output is also added to a meter with Resource Type = Water, End Use Key = Cooling, Group Key = System (ref. Output:Meter objects). This output variable appears only when the DX Cooling Coil is evaporatively cooled.

Cooling Coil Evaporative Condenser Mains Supply Water Volume [m3] [LINK]

This is the volume of water drawn from mains water service for the evaporatively cooled condenser.

Cooling Coil Evaporative Condenser Pump Electric Power [W] [LINK]

This is the average electricity consumption rate of the evaporative condenser water pump in Watts for the timestep being reported. This output variable appears only when the DX Cooling Coil is evaporatively cooled.

Cooling Coil Evaporative Condenser Pump Electric Energy [J] [LINK]

This is the electricity consumption rate of the evaporative condenser water pump in Joules for the timestep being reported. This output is also added to a meter with Resource Type = Electricity, End Use Key = Cooling, Group Key = System (ref. Output:Meter objects). This output variable appears only when the DX Cooling Coil is evaporatively cooled.

Cooling Coil Stage 2 Runtime Fraction [] [LINK]

This is the runtime fraction of the stage 2 DX coil compressor and condenser fan(s) for the timestep being reported. Applicable only for COIL Coil:Cooling:DX:TwoStageWithHumidityControlMode when 2 capacity stages are specified. For 2-stage systems, Cooling Coil Runtime Fraction is the stage 1 runtime fraction. These runtime fractions overlap, because stage 2 will not run unless stage 1 is already running. For example, a system where stage 1 is 60% of total capacity is passed a load of 70%. The Cooling Coil Runtime Fraction (stage 1) will be 1.0, and the Cooling Coil Stage 2 Runtime Fraction will be 0.25 [(70%-60%)/(100%-60%)].

Cooling Coil Dehumidification Mode [] [LINK]

This is the dehumidification mode for the timestep being reported. Applicable only for Coil:Cooling:DX:TwoStageWithHumidityControlMode when enhanced dehumidification mode is available. A value of 0 indicates normal mode (extra dehumidification not active). A value of 1 indicates dehumidification mode 1 is active. Note that this is an averaged variable, so fractional values are likely to be reported for reporting frequencies longer than “detailed”.

Cooling Coil Condensate Volume Flow Rate [m3/s] [LINK]

Cooling Coil Condensate Volume [m3] [LINK]

These outputs are the rate and volume of water collected as condensate from the coil. These reports only appear if a water storage tank is named in the input object.

Cooling Coil Evaporative Condenser Mains Supply Water Volume [m3] [LINK]

This is the water consumed by the DX Cooling Coil evaporatively cooled condenser that is met by the mains water. This output variable appears only when the DX Cooling Coil is evaporatively cooled.

Cooling Coil Basin Heater Electric Power [W] [LINK]

This is the average electricity consumption rate of the basin heater in Watts for the timestep being reported. This output variable appears only when the DX Cooling Coil is evaporatively cooled and the Basin Heater Capacity is greater than 0.

Cooling Coil Basin Heater Electric Energy [J] [LINK]

This is the electricity consumption rate of the basin heater in Joules for the timestep being reported. This output is also added to a meter with Resource Type = Electricity, End Use Key = Cooling, Group Key = System (ref. Output:Meter objects). This output variable appears only when the DX Cooling Coil is evaporatively cooled and the Basin Heater Capacity is greater than 0.

Cooling Coil <Fuel Type> Power [W] [LINK]

This output variable appears only when using the Coil:Cooling:DX:Multispeed object and a fuel type other than electricity is used. This variable describes the input fuel type power for the cooling coil in Watts, averaged during the timestep being reported.

Cooling Coil <Fuel Type> Energy [J] [LINK]

This output variable appears only when using the Coil:Cooling:DX:Multispeed object and a fuel type other than electricity is used. This variable describes the input fuel type consumption for the multispeed cooling coil in the unit of Joules, summed for the timestep being reported. The electric consumption is excluded..This output is added to a meter with Resource Type = <Fuel Type>, End Use Key = Cooling, Group Key = System (ref. Output:Meter objects).

Note: <Fuel Type> in the above two output variables depends on the user specified input for the Fuel Type field. In addition to Electricity, valid fuel types are NaturalGas, Propane, FuelOil#1, FuelOil#2, Coal, Diesel, Gasoline, OtherFuel1 and OtherFuel2.

Coil:Cooling:DX:VariableSpeed[LINK]

The Variable-Speed DX Cooling Coil is a collection of performance curves that represent the cooling coil at various speed levels. The performance curves should be generated from a Reference Unit data. This is an equation-fit model that resembles a black box with no usage of heat transfer equations. On the other hand, the model uses the bypass factor approach to calculate sensible heat transfer rate, similar to the one used in the single-speed DX coil. The number of speed levels can range from 1 to 10. The cooling coil has two indoor air side connections, and one optional condenser air node connection. The user needs to specify a nominal speed level, at which the gross rated total cooling capacity, and rated volumetric air rate are sized. The rated capacity and rated volumetric flow rate represent the real situation in the air loop, and are used to determine and flow rates at various speed levels in the parent objects, e.g. of AirLoopHVAC:UnitaryHeatCool, ZoneHVAC:PackagedTerminalAirConditioner, AirLoopHVAC:UnitaryHeatPump:AirToAir and ZoneHVAC:PackagedTerminalHeatPump. It shall be mentioned that the performance correction curves, i.e. the temperature and flow fraction correction curves, should be normalized to the capacity and flow rate at each individual speed and at the rated conditions, similar to the performance curves used in the single-speed DX coil. However, the performance values, e.g. capacities, COPs, SHRs and flow rates at individual speed levels, should be given regarding a specific unit from the Reference Unit catalog data. In the following content, the statement started with Reference Unit means the actual Reference Unit catalog data. The rated conditions for obtaining the capacities, COPs and SHRs are at indoor dry-bulb temperature of 26.67 ˚C (80 ˚F), wet bulb temperature of 19.44 ˚C (67 ˚F), and the condenser entering air temperature of 35 ˚C (95 ˚F). Some equations are provided below to help explain the function of the various performance curves and data fields.

Inputs[LINK]

Field: Name[LINK]

This alpha field contains the identifying name for the variable-speed cooling coil.

Field: Air Inlet Node Name[LINK]

This alpha field contains the cooling coil load side inlet node name.

Field: Air Outlet Node Name[LINK]

This alpha field contains the cooling coil load side outlet node name.

Field: Number of Speeds[LINK]

This numeric field contains the maximum number of speed levels that the module uses. The number of speeds, for which the user input the performance data and curves, should be equal or higher than the maximum number. The performance inputs at higher speed levels are ignored.

Field: Nominal Speed Level[LINK]

This numeric field defines the nominal speed level, at which the rated capacity and rated air rate are correlated.

Field: Gross Rated Total Cooling Capacity at Selected Nominal Speed Level[LINK]

This numeric field contains the gross rated total cooling capacity at the nominal speed level. This field is autosizable. The gross rated total cooling capacity is used to determine a capacity scaling factor, as compared to the Reference Unit capacity at the nominal speed level.

CapacityScaleFactor=GrossRatedTotalCoolingCapacityReferenceUnitCapacity@NominalSpeedLevel

And then, this scaling factor is used to determine capacities at rated conditions for other speed levels, as below,

GrossRatedCapacity@SpeedLevel(x)=CapacityScaleFactor×ReferenceUnitCapacity@SpeedLevel(x)

Field: Rated Air Flow Rate at Selected Nominal Speed Level[LINK]

This numeric field contains the rated volumetric air flow rate on the load side of the DX unit, corresponding to the nominal speed level. This field is autosizable. The value is used to determine an internal scaling factor, and calculate the air flow rates in the parent objects. It is recommended that the ratio of the rated volumetric air flow rate to the rated capacity is the same as the unit performance from the Reference Unit data.

AirFlowScaleFactor=RatedVolumetricAirFlowRateReferenceUnitVolAirFlowRate@NominalSpeedLevel×CapacityScaleFactor

And the volumetric air flow rates in the parent objects are calculated as below,

LoopVolumetricAirFlowRate@SpeedLevel(x)=AirFlowScaleFactor×ReferenceUnitVolAirFlowRate@SpeedLevel(x)×CapacityScaleFactor

Field: Nominal Time for Condensate Removal to Begin[LINK]

This numeric field defines the nominal time (in seconds) after startup for condensate to begin leaving the coil’s condensate drain line at the coil’s rated airflow and temperature conditions, starting with a dry coil. Nominal time is equal to the ratio of the energy of the coil’s maximum condensate holding capacity (J) to the coil’s steady-state latent capacity (W). Suggested value is 1000; zero value means the latent degradation model is disabled. The default value for this field is zero.

Field: Ratio of Initial Moisture Evaporation Rate and Steady State Latent Capacity[LINK]

This numeric field defines ratio of the initial moisture evaporation rate from the cooling coil (when the compressor first turns off, in Watts) and the coil’s steady-state latent capacity (Watts) at rated airflow and temperature conditions. Suggested value is 1.5; zero value means the latent degradation model is disabled. The default value for this field is zero.

Field: Part Load Fraction Correlation Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve (Ref: Performance Curves) that parameterizes the variation of electrical power input to the unit as a function of the part load ratio (PLR, sensible or latent load/steady-state sensible or latent cooling capacity for Speed 1), in the case that the unit operates under the lowest speed, i.e. on/off. The product of the rated EIR and EIR modifier curves is divided by the output of this curve to give the effective EIR for a given simulation timestep for Speed 1. The part load fraction (PLF) correlation accounts for efficiency losses due to compressor cycling. The part load fraction correlation should be normalized to a value of 1.0 when the part load ratio equals 1.0 (i.e., no efficiency losses when the compressor(s) run continuously for the simulation timestep).

Field: Condenser Air Inlet Node Name[LINK]

This optional alpha field specifies the outdoor air node name used to define the conditions of the air entering the outdoor condenser. If this field is left blank, the outdoor air temperature entering the condenser (dry-bulb or wet-bulb) is taken directly from the weather data. If this field is not blank, the node name specified must also be specified in an OutdoorAir:Node object where the height of the node is taken into consideration when calculating outdoor air temperature from the weather data. Alternately, the node name may be specified in an OutdoorAir:NodeList object where the outdoor air temperature is taken directly from the weather data.

Field: Condenser Type[LINK]

The type of condenser used by the DX cooling coil. Valid choices for this input field are AirCooled or EvaporativelyCooled. The default for this field is AirCooled.

Field: Evaporative Condenser Pump Rated Power Consumption[LINK]

The rated power of the evaporative condenser water pump in Watts. This value is used to calculate the power required to pump the water used to evaporatively cool the condenser inlet air. The default value for this input field is zero, but it is autosizable (equivalent to 0.004266 W per watt [15 W/ton] of rated total cooling capacity). This field is not used when Condenser Type = Air Cooled.

Field: Crankcase Heater Capacity[LINK]

This numeric field defines the crankcase heater capacity in Watts. When the outdoor air drybulb temperature is below the value specified in the input field Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation (described below), the crankcase heater is enabled during the time that the compressor is not running. If this cooling coil is used as part of an air-to-air heat pump, the crankcase heater defined for this DX cooling coil is ignored and the crankcase heater power defined for the DX heating coil (Ref. Coil:Heating:DX:SingleSpeed) is enabled during the time that the compressor is not running for either heating or cooling. The value for this input field must be greater than or equal to 0, and the default value is 0. To simulate a DX cooling coil without a crankcase heater, enter a value of 0.

Field: Maximum Outdoor Dry-Bulb Temperature for Crankcase Heater Operation[LINK]

This numeric field defines the outdoor air dry-bulb temperature above which the compressor s crankcase heater is disabled. The value for this input field must be greater than or equal to 0.0 °C, and the default value is 10 °C.

Field: Supply Water Storage Tank Name[LINK]

This field is optional. It is used to describe where the coil obtains water used for evaporative cooling of its condenser. If blank or omitted, then the unit will obtain water directly from the mains. If the name of a Water Storage Tank object is used here, the unit will obtain its water from that tank. If a tank is specified, the unit will attempt to obtain all the water it uses from the tank. However if the tank cannot provide all the water the condenser needs, then the unit will still operate and obtain the rest of the water it needs from the mains (referred to as StarvedWater).

Field: Condensate Collection Water Storage Tank Name[LINK]

This field is optional. It is used to describe where condensate from the coil is collected. If blank or omitted, then any coil condensate is discarded. Enter the name of Water Storage Tank object defined elsewhere and the condensate will then be collected in that tank.

Field: Basin Heater Capacity[LINK]

This numeric field contains the capacity of the DX coil s electric evaporative cooler basin

heater in watts per degree Kelvin. This field only applies for Condenser Type = EvaporativelyCooled. This field is used in conjunction with the Basin Heater Setpoint temperature described in the following field. The basin heater electric power is equal to this field multiplied by the difference between the basin heater set point temperature and the outdoor dry-bulb temperature. The basin heater only operates when the DX coil is off, regardless of the basin heater schedule described below. The basin heater capacity must be greater than or equal to zero, with a default value of zero if this field is left blank.

Field: Basin Heater Setpoint Temperature[LINK]

This numeric field contains the set point temperature (˚C) for the basin heater described in the previous field. This field only applies for Condenser Type = EvaporativelyCooled. The basin heater is active when the outdoor air dry-bulb temperature falls below this setpoint temperature, as long as the DX coil is off. This set point temperature must be greater than or equal to 2˚C, and the default value is 2˚C if this field is left blank.

Field: Basin Heater Operating Schedule Name[LINK]

This alpha field contains the name of the basin heater operating schedule. This field only applies for Condenser Type = EvaporativelyCooled. The basin heater operating schedule is assumed to be an on/off schedule and the heater is available to operate any time the schedule value is greater than 0. The basin heater operates when scheduled on and the outdoor air dry-bulb temperature is below the set point temperature described in the previous field. If this field is left blank, the basin heater is available to operate throughout the simulation. Regardless of this schedule, the basin heater may only operate when the DX coil is off.

Field Group: Rated specification, performance curves[LINK]

The performance for each cooling speed must be specified as shown below. They should be directly given from the Reference Unit catalog data. All inputs for Speed 1 are required, followed by the optional inputs for other speeds.

Field: Speed <x> Reference Unit Gross Rated Total Cooling Capacity[LINK]

This numeric field defines the total, full load gross cooling capacity in watts of the air-to-air cooling coil unit at rated conditions for Speed <x> operation. The value entered here must be greater than 0. Capacity should not account for supply air fan heat.

Field: Speed <x> Reference Unit Gross Rated Sensible Heat Ratio[LINK]

This numeric field defines sensible heat transfer ratio (SHR = gross sensible cooling capacity divided by gross total cooling capacity) of the cooling coil unit at rated conditions for Speed <x> operation. The value entered here must be greater than 0.0 and less than 1.0. This value should be obtained from the Reference Unit data.

Field: Speed <x> Reference Unit Gross Rated Cooling COP[LINK]

This numeric field defines the coefficient of performance (COP = the gross total cooling capacity in watts divided by electrical power input in watts) of the cooling coil unit at rated conditions for Speed <x> operation. The value entered here must be greater than 0. The input power includes power for the compressor(s), condenser fan and accessories, but does not include the supply air fan. The gross COP should Not account for the supply air fan.

Field: Speed <x> Reference Unit Rated Air Flow Rate[LINK]

This numeric field defines the volumetric air flow rate, in m3 per second, across the cooling coil at rated conditions for Speed <x> operation. The value entered here should be directly from the Reference Unit data, corresponding to the given cooling capacity and COP at the speed, as above.

Field: Speed <x> Reference Unit Rated Condenser Air Flow Rate[LINK]

This numeric field defines the condenser volumetric air flow rate, in m3 per second, across the condenser coil at rated conditions for Speed <x> operation. The value entered here should be directly from the Reference Unit data. This field is used to calculate water evaporation rate for an evaporatively-cooled condenser. For an air-cooled condenser, this input is not used.

Field: Speed <x> Reference Unit Rated Pad Effectiveness of Evap Precooling[LINK]

This numeric field defines the effectiveness of condenser evaporative precooling pad at rated condition. The values of effectiveness are given at individual speed levels, since varied condenser air flow rates impact the effectiveness.

Field: Speed <x> Total Cooling Capacity Function of Temperature Curve Name[LINK]

This alpha field defines the name of a bi-quadratic performance curve for Speed <x> (ref: Performance Curves) that parameterizes the variation of the gross total cooling capacity as a function of the both the indoor wet-bulb and source side entering air temperature, from the Reference Unit. The output of this curve is multiplied by the gross rated total cooling capacity at the speed to give the gross total cooling capacity at specific temperature operating conditions (i.e., at an indoor air wet-bulb temperature or outdoor entering air temperature different from the rating point temperature). It should be noted that the curve is normalized to the cooling capacity at Speed<x> from the Reference Unit data, and have the value of 1.0 at the rating point.

Field: Speed <x> Total Cooling Capacity Function of Air Flow Fraction Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve for Speed <x> (ref: Performance Curves) that parameterizes the variation of the gross total cooling capacity as a function of the ratio of actual air flow rate across the cooling coil to the design air flow rate (i.e., fraction of full load flow at Speed <x>, from the Reference Unit data). The curve is normalized to have the value of 1.0 when the actual air flow rate equals the design air flow rate, at Speed <x>.

Field: Speed <x> Energy Input Ratio Function of Temperature Curve Name[LINK]

This alpha field defines the name of a bi-quadratic performance curve for Speed <x> (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the both the indoor air wet-bulb and condenser entering air temperatures The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR (inverse of rated COP at Speed <x> from the Reference Unit data) to give the EIR at specific temperature operating conditions (i.e., at an indoor air wet-bulb temperature or condenser entering air temperature different from the rating point temperature). The curve is normalized to have the value of 1.0 at the rating point.

Field: Speed <x> Energy Input Ratio Function of Air Flow Fraction Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve for Speed <x> (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the ratio of actual air flow rate across the cooling coil to the design air flow rate (i.e., fraction of full load flow, at Speed <x> from the Reference Unit data). The EIR is the inverse of the COP. This curve is normalized to a value of 1.0 when the actual air flow rate equals the design air flow rate.

An example of this statement in an IDF is:

Coil:Cooling:DX:VariableSpeed,
  Heat Pump ACDXCoil 1,                       !- Name
  DX Cooling Coil Air Inlet Node,   !- Air Inlet Node Name
  Heating Coil Air Inlet Node,         !- Air Outlet Node Name
  10.0,                                     !- Number of Speeds {dimensionless}
  10.0,                                     !- Nominal Speed Level {dimensionless}
  32000,                                   !- Gross Rated Total Cooling Capacity {W}
  1.7,                                       !- Rated Air Flow Rate {m3/s}
  0.0,                                       !- Nominal Time for Condensate to Begin Leaving the Coil {s}
  0.0,   !- Initial Moisture Evaporation Rate Divided by Steady-State AC Latent Capacity {dimensionless}
  HPACCOOLPLFFPLR,                     !- Part Load Fraction Correlation Curve Name
  ,                                      ! - Condenser Air Inlet Node Name
  AirCooled,                                ! - Condenser Type
  ,                                      ! - Evaporative Condenser Pump Rated Power Consumption
  200.0,                                      ! - Crankcase Heater Capacity, {w}
  10.0,                                     !- Maximum Outdoor Dry-Bulb Temperature for Crankcase Heater Operation {C}
  ,                               ! - Supply Water Storage Tank Name
  ,                                ! - Condensate Collection Water Storage Tank Name
  ,                                             ! - Basin Heater Capacity
  ,                               ! - Basin Heater Setpoint Temperature
  ,                                             ! - Basin Heater Operating Schedule Name
  1524.1,                                 !- Speed 1 Gross Rated Total Cooling Capacity {w}
  0.75,                                     !- Speed 1 Gross Rated Sensible Heat Ratio {dimensionless}
  4.0,                                       !- Speed 1 Gross Rated Cooling COP {dimensionless}
  0.1359072,                           !- Speed 1 Rated Air Flow Rate {m3/s}
  0.26,                                     ! - Speed 1 Rated Condenser Air Flow Rate {m3/s}, for evaporatively cooled
  ,                                             ! - Evaporative precooling effectiveness
  HPACCoolCapFT,                   !- Total Cooling Capacity Function of Temperature Curve Name
  HPACCoolCapFFF,                 !- Total Cooling Capacity Function of Flow Fraction Curve Name
  HPACCOOLEIRFT,                   !- Energy Input Ratio Function of Temperature Curve Name
  HPACCOOLEIRFFF,                 !- Energy Input Ratio Function of Flow Fraction Curve Name
  1877.9,                                 !- Speed 2 Gross Rated Total Cooling Capacity {w}
  0.75,                                     !- Speed 2 Gross Rated Sensible Heat Ratio {dimensionless}
  4.0,                                       !- Speed 2 Gross Rated Cooling COP {dimensionless}
  0.151008,                             !- Speed 2 Rated Air Flow Rate {m3/s}
  0.30,                                     ! - Speed 2 Rated Condenser Air Flow Rate {m3/s}, for evaporatively cooled
  ,                                             ! - Evaporative precooling effectiveness
  HPACCoolCapFT,                   !- Total Cooling Capacity Function of Temperature Curve Name
  HPACCoolCapFFF,                 !- Total Cooling Capacity Function of Flow Fraction Curve Name
  HPACCOOLEIRFT,                   !- Energy Input Ratio Function of Temperature Curve Name
  HPACCOOLEIRFFF,                 !- Energy Input Ratio Function of Flow Fraction Curve Name
  2226.6,                                 !- Speed 3 Gross Rated Total Cooling Capacity {w}
  0.75,                                     !- Speed 3 Gross Rated Sensible Heat Ratio {dimensionless}
  4.0,                                       !- Speed 3 Gross Rated Cooling COP {dimensionless}
  0.1661088,                           !- Speed 3 Rated Air Flow Rate {m3/s}
  0.33,                                     !- Speed 3 Rated Condenser Air Flow Rate {m3/s}, for evaporatively cooled
  ,                                             !- Evaporative precooling effectiveness
  HPACCoolCapFT,                   !- Total Cooling Capacity Function of Temperature Curve Name
  HPACCoolCapFFF,                 !- Total Cooling Capacity Function of Flow Fraction Curve Name
  HPACCOOLEIRFT,                   !- Energy Input Ratio Function of Temperature Curve Name
  HPACCOOLEIRFFF,                 !- Energy Input Ratio Function of Flow Fraction Curve Name
  2911.3,                                 !- Speed 4 Gross Rated Total Cooling Capacity {w}
  0.75,                                     !- Speed 4 Gross Rated Sensible Heat Ratio {dimensionless}
  4.0,                                       !- Speed 4 Gross Rated Cooling COP {dimensionless}
  0.1963104,                           !- Speed 4 Rated Air Flow Rate {m3/s}
  0.38,                                     !- Speed 4 Rated Condenser Air Flow Rate {m3/s}, for evaporatively cooled
  ,                                             !- Evaporative precooling effectiveness
  HPACCoolCapFT,                   !- Total Cooling Capacity Function of Temperature Curve Name
  HPACCoolCapFFF,                 !- Total Cooling Capacity Function of Flow Fraction Curve Name
  HPACCOOLEIRFT,                   !- Energy Input Ratio Function of Temperature Curve Name
  HPACCOOLEIRFFF,                 !- Energy Input Ratio Function of Flow Fraction Curve Name
  3581.7,                                 !- Speed 5 Gross Rated Total Cooling Capacity {w}
  0.75,                                     !- Speed 5 Gross Rated Sensible Heat Ratio {dimensionless}
  4.0,                                       !- Speed 5 Gross Rated Cooling COP {dimensionless}
  0.226512,                             !- Speed 5 Rated Air Flow Rate {m3/s}
  0.44,                                     !- Speed 5 Rated Condenser Air Flow Rate {m3/s}, for evaporatively cooled
  ,                                             !- Evaporative precooling effectiveness
  HPACCoolCapFT,                   !- Total Cooling Capacity Function of Temperature Curve Name
  HPACCoolCapFFF,                 !- Total Cooling Capacity Function of Flow Fraction Curve Name
  HPACCOOLEIRFT,                   !- Energy Input Ratio Function of Temperature Curve Name
  HPACCOOLEIRFFF,                 !- Energy Input Ratio Function of Flow Fraction Curve Name
  4239.5,                                 !- Speed 6 Gross Rated Total Cooling Capacity {w}
  0.75,                                     !- Speed 6 Gross Rated Sensible Heat Ratio {dimensionless}
  4.0,                                       !- Speed 6 Gross Rated Cooling COP {dimensionless}
  0.2567136,                           !- Speed 6 Rated Air Flow Rate {m3/s}
  0.50,                                     ! - Speed 6 Rated Condenser Air Flow Rate {m3/s}, for evaporatively cooled
  ,                                             ! - Evaporative precooling effectiveness
  HPACCoolCapFT,                   !- Total Cooling Capacity Function of Temperature Curve Name
  HPACCoolCapFFF,                 !- Total Cooling Capacity Function of Flow Fraction Curve Name
  HPACCOOLEIRFT,                   !- Energy Input Ratio Function of Temperature Curve Name
  HPACCOOLEIRFFF,                 !- Energy Input Ratio Function of Flow Fraction Curve Name
  4885.7,                                 !- Speed 7 Gross Rated Total Cooling Capacity {w}
  0.75,                                     !- Speed 7 Gross Rated Sensible Heat Ratio {dimensionless}
  4.0,                                       !- Speed 7 Gross Rated Cooling COP {dimensionless}
  0.2869152,                           !- Speed 7 Rated Air Flow Rate {m3/s}
  0.57,                                     ! - Speed 7 Rated Condenser Air Flow Rate {m3/s}, for evaporatively cooled
  ,                                             ! - Evaporative precooling effectiveness
  HPACCoolCapFT,                   !- Total Cooling Capacity Function of Temperature Curve Name
  HPACCoolCapFFF,                 !- Total Cooling Capacity Function of Flow Fraction Curve Name
  HPACCOOLEIRFT,                   !- Energy Input Ratio Function of Temperature Curve Name
  HPACCOOLEIRFFF,                 !- Energy Input Ratio Function of Flow Fraction Curve Name
  5520.7,                                 !- Speed 8 Gross Rated Total Cooling Capacity {w}
  0.75,                                     !- Speed 8 Gross Rated Sensible Heat Ratio {dimensionless}
  4.0,                                       !- Speed 8 Gross Rated Cooling COP {dimensionless}
  0.3171168,                           !- Speed 8 Rated Air Flow Rate {m3/s}
  0.63,                                     ! - Speed 8 Rated Condenser Air Flow Rate {m3/s}, for evaporatively cooled
  ,                                             ! - Evaporative precooling effectiveness
  HPACCoolCapFT,                   !- Total Cooling Capacity Function of Temperature Curve Name
  HPACCoolCapFFF,                 !- Total Cooling Capacity Function of Flow Fraction Curve Name
  HPACCOOLEIRFT,                   !- Energy Input Ratio Function of Temperature Curve Name
  HPACCOOLEIRFFF,                 !- Energy Input Ratio Function of Flow Fraction Curve Name
  6144.8,                                 !- Speed 9 Gross Rated Total Cooling Capacity {w}
  0.75,                                     !- Speed 9 Gross Rated Sensible Heat Ratio {dimensionless}
  4.0,                                       !- Speed 9 Rated Cooling COP {dimensionless}
  0.3473184,                           !- Speed 9 Rated Air Flow Rate {m3/s}
  0.69,                                     ! - Speed 9 Rated Condenser Air Flow Rate {m3/s}, for evaporatively cooled
  ,                                             ! - Evaporative precooling effectiveness
  HPACCoolCapFT,                   !- Total Cooling Capacity Function of Temperature Curve Name
  HPACCoolCapFFF,                 !- Total Cooling Capacity Function of Flow Fraction Curve Name
  HPACCOOLEIRFT,                   !- Energy Input Ratio Function of Temperature Curve Name
  HPACCOOLEIRFFF,                 !- Energy Input Ratio Function of Flow Fraction Curve Name
  6758.0,                                 !- Speed 10 Gross Rated Total Cooling Capacity {w}
  0.75,                                     !- Speed 10 Gross Rated Sensible Heat Ratio {dimensionless}
  4.0,                                       !- Speed 10 Gross Rated Cooling COP {dimensionless}
  0.37752,                               !- Speed 10 Rated Air Flow Rate {m3/s}
  0.74,                                     ! - Speed 10 Rated Condenser Air Flow Rate {m3/s}, for evaporatively cooled
  ,                                             ! - Evaporative precooling effectiveness
  HPACCoolCapFT,                   !- Total Cooling Capacity Function of Temperature Curve Name
  HPACCoolCapFFF,                 !- Total Cooling Capacity Function of Flow Fraction Curve Name
  HPACCOOLEIRFT,                   !- Energy Input Ratio Function of Temperature Curve Name
  HPACCOOLEIRFFF;                 !- Energy Input Ratio Function of Flow Fraction Curve Name

Outputs[LINK]

  • HVAC,Average,Cooling Coil Electric Power [W]

  • HVAC,Average,Cooling Coil Total Cooling Rate [W]

  • HVAC,Average,Cooling Coil Sensible Cooling Rate [W]

  • HVAC,Average,Cooling Coil Source Side Heat Transfer Rate [W]

  • HVAC,Average,Cooling Coil Part Load Ratio []

  • HVAC,Average, Cooling Coil Runtime Fraction []

  • HVAC,Average, Cooling Coil Air Mass Flow Rate [kg/s]

  • HVAC,Average,Cooling Coil Air Inlet Temperature [C]

  • HVAC,Average,Cooling Coil Air Inlet Humidity Ratio [kgWater/kgDryAir]

  • HVAC,Average,Cooling Coil Air Outlet Temperature [C]

  • HVAC,Average,Cooling Coil Air Outlet Humidity Ratio [kgWater/kgDryAir]

  • HVAC,Average,Cooling Coil Upper Speed Level []

  • HVAC,Average,Cooling Coil Neighboring Speed Levels Ratio []

  • HVAC,Average,VSAirtoAirHP Recoverable Waste Heat [W]

  • HVAC,Sum,Cooling Coil Electric Energy [J]

  • HVAC,Sum,Cooling Coil Total Cooling Energy [J]

  • HVAC,Sum,Cooling Coil Sensible Cooling Energy [J]

  • HVAC,Sum,Cooling Coil Latent Cooling Energy [J]

  • HVAC,Sum,Cooling Coil Source Side Heat Transfer Energy [J]

  • HVAC,Average,Cooling Coil Crankcase Heater Electric Power [W]

  • HVAC,Sum,Cooling Coil Crankcase Heater Electric Energy [J]

  • HVAC,Average,Cooling Coil Condensate Volume Flow Rate [m3/s]

  • HVAC,Sum,Cooling Coil Condensate Volume [m3]

  • HVAC,Average,Cooling Coil Condenser Inlet Temperature [C]

  • HVAC,Sum,Cooling Coil Evaporative Condenser Water Volume [m3]

  • HVAC,Sum,Cooling Coil Evaporative Condenser Mains Water Volume [m3]

  • HVAC,Average,Cooling Coil Evaporative Condenser Pump Electric Power[W]

  • HVAC,Sum,Cooling Coil Evaporative Condenser Pump Electric Energy [J]

  • HVAC,Average,Cooling Coil Basin Heater Electric Power [W]

  • HVAC,Sum,Cooling Coil Basin Heater Electric Energy [J]

Cooling Coil Electric Power [W] [LINK]

This output variable is the average electric consumption rate of the heat pump in Watts over the timestep being reported.

Cooling Coil Total Cooling Rate [W] [LINK]

The output variable is the average total cooling load provide by the heat pump which includes the sensible and latent load in Watts over the timestep being reported.

Cooling Coil Sensible Cooling Rate [W] [LINK]

The output variable is the average sensible cooling load provide by the heat pump in Watts over the timestep being reported.

Cooling Coil Source Side Heat Transfer Rate [W] [LINK]

The output variable is the average heat rejected to the water at the heat pump condenser in Watts over the timestep being reported.

Cooling Coil Part Load Ratio [] [LINK]

This output variable is the ratio of the part-load capacity to the steady state capacity of the VSAirtoAirHP coil. For the cycling fan mode, the runtime fraction for the heat pump compressor may be different from the compressor part-load ratio reported here due to the part-load performance of the VSAirtoAirHP coil (delay at start-up to reach steady-state output). In general, runtime fractions are reported by individual components where appropriate.

Cooling Coil Runtime Fraction [] [LINK]

This output variable is the function of the part load ratio (PLR, part-load capacity/ steady state capacity). The runtime fraction, or duty factor, accounts for efficiency losses due to compressor cycling.

Cooling Coil Air Mass Flow Rate [kg/s] [LINK]

The output variable is the average air mass flow rate on the load side going through the heat pump over the timestep being reported.

Cooling Coil Air Inlet Temperature [C] [LINK]

The output variable is the average entering air dry-bulb temperature over the timestep being reported.

Cooling Coil Air Inlet Humidity Ratio [kgWater/kgDryAir] [LINK]

The output variable is the average entering air dry humidity ratio over the timestep being reported.

Cooling Coil Air Outlet Temperature [C] [LINK]

The output variable is the average leaving air dry-bulb temperature over the timestep being reported.

Cooling Coil Air Outlet Humidity Ratio [kgWater/kgDryAir] [LINK]

The output variable is the average leaving air dry humidity ratio over the timestep being reported.

Cooling Coil Upper Speed Level [] [LINK]

The output variable is the average upper speed level, for interpolating performances between two neighboring speed levels.

Cooling Coil Neighboring Speed Levels Ratio [] [LINK]

The output variable is the average speed ratio, for interpolating performances between two neighboring speed levels.

Cooling Coil Electric Energy [J] [LINK]

The output variable is the electric consumption of the heat pump in Joules over the timestep being reported.

Cooling Coil Total Cooling Energy [J] [LINK]

The output variable is the total cooling output of the coil in Joules over the timestep being reported.

Cooling Coil Sensible Cooling Energy [J] [LINK]

The output variable is the total sensible cooling output of the coil in Joules over the timestep being reported

Cooling Coil Latent Cooling Energy [J] [LINK]

Cooling Coil Latent Cooling Rate [W] [LINK]

These output variables are the total latent cooling output of the coil in Joules or Watts over the timestep being reported.

Cooling Coil Source Side Heat Transfer Energy [J] [LINK]

The output variable is the total source side heat transfer of the coil in Joules over the timestep being reported.

Cooling Coil Crankcase Heater Electric Power [W] [LINK]

The output variable is the average power used for crankcase heater, in Watts over the timestep being reported.

Cooling Coil Crankcase Heater Electric Energy [J] [LINK]

The output variable is the total electric energy usage of the coil for crankcase heater, in Joules over the timestep being reported.

Cooling Coil Condensate Volume Flow Rate [m3/s] [LINK]

The output variable is the average water condensate volumetric flow rate from the cooling coil, in m3/s over the timestep being reported, if choosing to use CondensatetoTank.

Cooling Coil Condensate Volume [m3] [LINK]

The output variable is the total water condensate volume from the cooling coil, in m3 over the timestep being reported.

Cooling Coil Condenser Inlet Temperature [C] [LINK]

The output variable is the average air temperature entering the condenser coil, in °C over the timestep being reported.

Cooling Coil Evaporative Condenser Water Volume [m3] [LINK]

The output variable is the total water volume consumed for condenser evaporative pre-cooling, in m3 over the timestep being reported.

Cooling Coil Evaporative Condenser Mains Water Volume [m3] [LINK]

The output variable is the total water volume for condenser evaporative pre-cooling, obtained from the Mains Water supply, in m3 over the timestep being reported.

Cooling Coil Evaporative Condenser Pump Electric Power[W] [LINK]

The output variable is the average power consumption rate of the evaporative condenser pump, in Watts over the timestep being reported.

Cooling Coil Evaporative Condenser Pump Electric Energy [J] [LINK]

The output variable is the total power consumption of the evaporative condenser pump, in Joules over the timestep being reported.

Cooling Coil Basin Heater Electric Power [W] [LINK]

The output variable is the average power consumption rate by the basin heater, in Watts over the timestep being reported.

Cooling Coil Basin Heater Electric Energy [J] [LINK]

The output variable is the total power consumption by the basin heater, in Joules over the timestep being reported.

CoilPerformance:DX:Cooling[LINK]

This coil performance object is used to specify DX coil performance for one mode of operation for a Coil:Cooling:DX:TwoStageWithHumidityControlMode. A single Coil:Cooling:DX:TwoStageWithHumidityControlMode object will reference one to four CoilPerformance:DX:Cooling objects depending on the number of available stages and dehumidification modes as specified in the two stage DX object. For example, a standard 2-stage DX system will use two of these performance objects, one to defined the capacity and performance for stage 1 operation, and a second one for stage 1+2 (both stages active) operation. In nearly all cases, the Rated Air Volume Flow Rate will be the same for all performance objects associated with a given multimode DX coil. If bypass is specified, the Rated Air Volume Flow Rate includes both the bypassed flow and the flow through the active coil.

This DX coil model is identical to Coil:Cooling:DX:SingleSpeed with addition of bypass and multi-stage capabilities. This DX cooling coil model and input are quite different from that for the heating and cooling water coils. The simple water coils use an NTU-effectiveness heat exchanger model. The single speed DX coil model uses performance information at rated conditions along with curve fits for variations in total capacity, energy input ratio and part-load fraction to determine performance at part-load conditions. Sensible/latent capacity splits are determined by the rated sensible heat ratio (SHR) and the apparatus dewpoint/bypass factor (ADP/BF) approach. This approach is analogous to the NTU-effectiveness calculations used for sensible-only heat exchanger calculations, extended to a cooling and dehumidifying coil.

An alternative to ADP/BF method for sensible/latent capacity split is to use SHR modifier curves for temperature and flow fraction. These two optional input fields are used only when a user specified SHR calculation method desired over the (ADP/BF) method. Sensible heat ratio calculated using these two SHR modifier curves override the value calculated by ADP/BF method. See section SHR Calculation Using User Specified SHR Modifier Curves in the EnergyPlus Engineering Document for further details.

The DX cooling coil input requires the gross rated total cooling capacity, the gross rated SHR, the gross rated COP, the rated air volume flow rate, and the fraction of air flow which is bypassed around the coil. The first 4 inputs determine the coil performance at the rating point (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb and air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb). The rated air volume flow rate (less any bypassed fraction) should be between .00004027 m3/s and .00006041 m3/s per watt of gross rated total cooling capacity (300 to 450 cfm/ton). The rated volumetric air flow to gross total cooling capacity ratio for 100% dedicated outdoor air (DOAS) application DX cooling coils should be between 0.00001677 (m3/s)/W (125 cfm/ton) and 0.00003355 (m3/s)/W (250 cfm/ton).

This model requires 5 curves as follows:

  1. The total cooling capacity modifier curve (function of temperature) is a biquadratic curve with two independent variables: wet-bulb temperature of the air entering the cooling coil, and dry-bulb temperature of the air entering the air-cooled condenser coil (wet-bulb temperature if modeling an evaporative-cooled condenser). The output of this curve is multiplied by the gross rated total cooling capacity to give the gross total cooling capacity at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures).

  2. The total cooling capacity modifier curve (function of flow fraction) is a quadratic or cubic curve with the independent variable being the ratio of the actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated total cooling capacity and the total cooling capacity modifier curve (function of temperature) to give the gross total cooling capacity at the specific temperature and air flow conditions at which the coil is operating.

  3. The energy input ratio (EIR) modifier curve (function of temperature) is a biquadratic curve with two independent variables: wet-bulb temperature of the air entering the cooling coil, and dry-bulb temperature of the air entering the air-cooled condenser coil (wet-bulb temperature if modeling an evaporative-cooled condenser). The output of this curve is multiplied by the rated EIR (inverse of the rated COP) to give the EIR at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures).

  4. The energy input ratio (EIR) modifier curve (function of flow fraction) is a quadratic or cubic curve with the independent variable being the ratio of the actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the rated EIR (inverse of the rated COP) and the EIR modifier curve (function of temperature) to give the EIR at the specific temperature and air flow conditions at which the coil is operating.

  5. The part load fraction correlation (function of part load ratio) is a quadratic or cubic curve with the independent variable being part load ratio (sensible cooling load / steady-state sensible cooling capacity). The output of this curve is used in combination with the rated EIR and EIR modifier curves to give the effective EIR for a given simulation timestep. The part load fraction (PLF) correlation accounts for efficiency losses due to compressor cycling. The curve should be normalized to a value of 1.0 when the part-load ratio equals 1.0 (i.e., the compressor(s) run continuously for the simulation timestep).

The curves are simply specified by name. Curve inputs are described in the curve manager section of this document (see Performance Curves in this document).

The next four input fields are optional and relate to the degradation of latent cooling capacity when the supply air fan operates continuously while the cooling coil/compressor cycle on and off to meet the cooling load. The fan operating mode is either considered to be constant (e.g. CoilSystem:Cooling:DX) or can be scheduled in the parent object (e.g. AirLoopHVAC:UnitaryHeatCool). When scheduled, the schedule value must be greater than 0 to calculate degradation of latent cooling capacity. At times when the parent object s supply air fan operating mode schedule is 0, latent degradation will be ignored. When used, these next four input fields must all have positive values in order to model latent capacity degradation.

The next input specifies the outdoor air node used to define the conditions of the air entering the outdoor condenser. If this field is not blank, the node name specified must be listed in an OutdoorAir:Node object where the height of the node is taken into consideration when calculating outdoor temperature from the weather data. Alternately, the node name must be specified in an OutdoorAir:NodeList object where the outdoor temperature entering the condenser is taken directly from the weather data. This field may also be left blank, if this is the case then the outdoor temperature entering the condenser is taken directly from the weather data.

The next input describes the type of outdoor condenser coil used with the DX cooling coil (Air Cooled or Evap Cooled). The following three inputs are required when modeling an evaporative-cooled condenser: evaporative condenser effectiveness, evaporative condenser air volume flow rate, and the power consumed by the evaporative condenser pump. See section DX Cooling Coil Model in the EnergyPlus Engineering Document for further details regarding this model.

Inputs[LINK]

Field: Name[LINK]

This alpha field is a unique user-assigned name for an instance of DX cooling coil performance. Any reference to this DX coil performance object by another object will use this name.

Field: Gross Rated Total Cooling Capacity[LINK]

The total, full load gross cooling capacity (sensible plus latent) in watts of the DX coil unit at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and a cooling coil air flow rate defined by field rated air flow rate below). Capacity should be gross (i.e., the effect of supply air fan heat is NOT accounted for).

Field: Gross Rated Sensible Heat Ratio[LINK]

The sensible heat ratio (SHR = gross sensible capacity divided by gross total cooling capacity) of the DX cooling coil at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and a cooling coil air flow rate defined by field rated air flow rate below). Both the sensible and total cooling capacities used to define the Rated SHR should be gross (i.e., the effect of supply air fan heat is NOT accounted for).

Field: Gross Rated Cooling COP[LINK]

The coefficient of performance is the ratio of the gross total cooling capacity in watts to electrical power input in watts) of the DX cooling coil unit at rated conditions (air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/ 23.9 °C wetbulb, and a cooling coil air flow rate defined by field rated air flow rate below). The input power includes electric power for the compressor(s) and condenser fan(s) but does not include the power consumption of the supply air fan. If this input field is left blank, the default value is 3.0.

Field: Rated Air Flow Rate[LINK]

The air volume flow rate, in m3 per second, across the DX cooling coil at rated conditions. The gross rated total cooling capacity, gross rated SHR and gross rated COP should be performance information for the unit with air entering the cooling coil at 26.7 °C drybulb/19.4 °C wetbulb, air entering the outdoor condenser coil at 35 °C drybulb/23.9 °C wetbulb, and the rated air volume flow rate defined here.

Field: Fraction of Air Flow Bypassed Around Coil[LINK]

This numeric field specifies the fraction of the Rated Air Volume Flow Rate which bypasses the active cooling coil for this performance mode. The remaining portion of the flow should be between 0.00004027 m3/s and .00006041 m3/s per watt of gross rated total cooling capacity (300 to 450 cfm/ton) for this performance mode. For DOAS applications the remaining portion of rated air volume flow rate should be between 0.00001677 m3/s and 0.00003355 m3/s per watt of gross rated total cooling capacity (125 to 250 cfm/ton). This is used to model face-split coils on multi-stage units or bypass dampers. If total flow rate varies during simulation, the same fraction is bypassed. This input may range from 0.0 to <1.0. The default is 0.0. For a multi-stage face-split coil in which stage 1 is 60% of total capacity, this field would be set to 0.4 for the Stage 1 performance and set to 0.0 for the Stage 1+2 performance. For a DX system which activates a bypass damper for improved dehumidification, this field would be set to 0.0 for normal mode performance and set to something greater than zero for enhanced dehumidification mode performance.

Field: Total Cooling Capacity Function of Temperature Curve Name[LINK]

The name of a biquadratic performance curve (ref: Performance Curves) that parameterizes the variation of the total gross cooling capacity as a function of the wet-bulb temperature of the air entering the cooling coil, and the dry-bulb temperature of the air entering the air-cooled condenser coil (wet-bulb temperature if modeling an evaporative-cooled condenser). The output of this curve is multiplied by the gross rated total cooling capacity to give the gross total cooling capacity at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures). The curve is normalized to have the value of 1.0 at the rating point.

Field: Total Cooling Capacity Function of Flow Fraction Curve Name[LINK]

The name of a quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of the gross total cooling capacity as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated total cooling capacity and the total cooling capacity modifier curve (function of temperature) to give the gross total cooling capacity at the specific temperature and air flow conditions at which the coil is operating. The curve is normalized to have the value of 1.0 when the actual air flow rate equals the rated air flow rate.

Field: Energy Input Ratio Function of Temperature Curve Name[LINK]

The name of a biquadratic performance curve (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the wet-bulb temperature of the air entering the cooling coil, and the dry-bulb temperature of the air entering the air-cooled condenser coil (wet-bulb temperature if modeling an evaporative-cooled condenser). The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR (inverse of rated COP) to give the EIR at specific temperature operating conditions (i.e., at temperatures different from the rating point temperatures). The curve is normalized to a value of 1.0 at the rating point.

Field: Energy Input Ratio Function of Flow Fraction Curve Name[LINK]

The name of a quadratic or cubic performance curve (Ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR and the EIR modifier curve (function of temperature) to give the EIR at the specific temperature and air flow conditions at which the cooling coil is operating. This curve is normalized to a value of 1.0 when the actual air flow rate equals the rated air flow rate.

Field: Part Load Fraction Correlation Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve (Ref: Performance Curves) that parameterizes the variation of electrical power input to the DX unit as a function of the part load ratio (PLR, sensible cooling load/steady-state sensible cooling capacity). The product of the rated EIR and EIR modifier curves is divided by the output of this curve to give the effective EIR for a given simulation timestep. The part load fraction (PLF) correlation accounts for efficiency losses due to compressor cycling.

The part load fraction correlation should be normalized to a value of 1.0 when the part load ratio equals 1.0 (i.e., no efficiency losses when the compressor(s) run continuously for the simulation timestep). For PLR values between 0 and 1 (0 < = PLR < 1), the following rules apply:

PLF > = 0.7 and PLF > = PLR

If PLF < 0.7 a warning message is issued, the program resets the PLF value to 0.7, and the simulation proceeds. The runtime fraction of the coil is defined as PLR/PLF. If PLF < PLR, then a warning message is issued and the runtime fraction of the coil is limited to 1.0.

A typical part load fraction correlation for a conventional, single-speed DX cooling coil (e.g., residential unit) would be:

PLF = 0.85 + 0.15(PLR)

If the user wishes to model no efficiency degradation due to compressor cycling, the part load fraction correlation should be defined as follows:

PLF = 1.0 + 0.0(PLR)

Field: Nominal Time for Condensate Removal to Begin[LINK]

The nominal time (in seconds) after startup for condensate to begin leaving the coil’s condensate drain line at the coil’s rated airflow and temperature conditions, starting with a dry coil. Nominal time is equal to the ratio of the energy of the coil’s maximum condensate holding capacity (J) to the coil’s steady-state latent capacity (W). Suggested value is 1000; zero value means the latent degradation model is disabled. The default value for this field is zero. The supply air fan operating mode must be continuous (i.e., the supply air fan operating mode may be specified in other parent objects and is assumed continuous in some objects (e.g., CoilSystem:Cooling:DX) or can be scheduled in other objects [e.g., AirloopHVAC:UnitaryHeatCool]), and this field as well as the next three input fields for this object must have positive values in order to model latent capacity degradation.

Field: Ratio of Initial Moisture Evaporation Rate and Steady State Latent Capacity[LINK]

Ratio of the initial moisture evaporation rate from the cooling coil (when the compressor first turns off, in Watts) and the coil’s steady-state latent capacity (Watts) at rated airflow and temperature conditions. Suggested value is 1.5; zero value means the latent degradation model is disabled. The default value for this field is zero. The supply air fan operating mode must be continuous (i.e., the supply air fan operating mode may be specified in other parent objects and is assumed continuous in some objects (e.g., CoilSystem:Cooling:DX) or can be scheduled in other objects [e.g., AirloopHVAC:UnitaryHeatCool]); and this field, the previous field and the next two fields must have positive values in order to model latent capacity degradation.

Field: Maximum Cycling Rate[LINK]

The maximum on-off cycling rate for the compressor (cycles per hour), which occurs at 50% run time fraction. Suggested value is 3; zero value means latent degradation model is disabled. The default value for this field is zero. The supply air fan operating mode must be continuous (i.e., the supply air fan operating mode may be specified in other parent objects and is assumed continuous in some objects (e.g., CoilSystem:Cooling:DX) or can be scheduled in other objects [e.g., AirloopHVAC:UnitaryHeatCool]); and this field, the previous two fields and the next field must have positive values in order to model latent capacity degradation.

Field: Latent Capacity Time Constant[LINK]

Time constant (in seconds) for the cooling coil’s latent capacity to reach steady state after startup. Suggested value is 45; zero value means latent degradation model is disabled. The default value for this field is zero. The supply air fan operating mode must be continuous (i.e., the supply air fan operating mode may be specified in other parent objects and is assumed continuous in some objects (e.g., CoilSystem:Cooling:DX) or can be scheduled in other objects [e.g., AirloopHVAC:UnitaryHeatCool]), and this field as well as the previous three input fields for this object must have positive values in order to model latent capacity degradation.

Field: Condenser Air Inlet Node Name[LINK]

This optional alpha field specifies the outdoor air node name used to define the conditions of the air entering the outdoor condenser. If this field is left blank, the outdoor air temperature entering the condenser (dry-bulb or wet-bulb) is taken directly from the weather data. If this field is not blank, the node name specified must also be specified in an OutdoorAir:Node object where the height of the node is taken into consideration when calculating outdoor air temperature from the weather data. Alternately, the node name may be specified in an OutdoorAir:NodeList object where the outdoor air temperature is taken directly from the weather data.

Field: Condenser Type[LINK]

The type of condenser used by the DX cooling coil. Valid choices for this input field are AirCooled or EvaporativelyCooled. The default for this field is AirCooled.

Field: Evaporative Condenser Effectiveness[LINK]

The effectiveness of the evaporative condenser, which is used to determine the temperature of the air entering the outdoor condenser coil as follows:

Tcondinlet=(Twb,o)+(1EvapCondEffectiveness)(Tdb,oTwb,o)

where

Tcondinlet = the temperature of the air entering the condenser coil (C)

Twb,o = the wet-bulb temperature of the outdoor air (C)

Tdb,o = the dry-bulb temperature of the outdoor air (C)

The resulting condenser inlet air temperature is used by the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature). The default value for this field is 0.9, although valid entries can range from 0.0 to 1.0. This field is not used when Condenser Type = Air Cooled.

If the user wants to model an air-cooled condenser, they should simply specify AirCooled in the field Condenser Type. In this case, the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature) input fields for this object should reference performance curves that are a function of outdoor dry-bulb temperature.

If the user wishes to model an evaporative-cooled condenser AND they have performance curves that are a function of the wet-bulb temperature of air entering the condenser coil, then the user should specify Condenser Type = Evap Cooled and the evaporative condenser effectiveness value should be entered as 1.0. In this case, the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature) input fields for this object should reference performance curves that are a function of the wet-bulb temperature of air entering the condenser coil.

If the user wishes to model an air-cooled condenser that has evaporative media placed in front of it to cool the air entering the condenser coil, then the user should specify Condenser Type = Evap Cooled. The user must also enter the appropriate evaporative effectiveness for the media. In this case, the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature) input fields for this object should reference performance curves that are a function of outdoor dry-bulb temperature. Be aware that the evaporative media will significantly reduce the dry-bulb temperature of the air entering the condenser coil, so the Total Cooling Capacity and EIR Modifier Curves must be valid for the expected range of dry-bulb temperatures that will be entering the condenser coil.

Field: Evaporative Condenser Air Flow Rate[LINK]

The air volume flow rate, in m3 per second, entering the evaporative condenser. This value is used to calculate the amount of water used to evaporatively cool the condenser inlet air. The minimum value for this field must be greater than zero, and this input field is autosizable (equivalent to 0.000144 m3/s per watt of rated total cooling capacity [850 cfm/ton]). This field is not used when Condenser Type = Air Cooled.

Field: Evaporative Condenser Pump Rated Power Consumption[LINK]

The rated power of the evaporative condenser water pump in Watts. This value is used to calculate the power required to pump the water used to evaporatively cool the condenser inlet air. The default value for this input field is zero, but it is autosizable (equivalent to 0.004266 W per watt [15 W/ton] of rated total cooling capacity). This field is not used when Condenser Type = AirCooled.

Field: Sensible Heat Ratio Function of Temperature Curve Name[LINK]

The name of a biquadratic normalized curve (Ref: Performance Curves) that parameterizes the variation of the sensible heat ratio (SHR) as a function of DX cooling coil entering air wet-bulb and dry-bulb temperatures. The output of this curve is multiplied by the rated SHR and the SHR modifier curve (function of flow fraction) to give the SHR at the specific coil entering air temperature and air flow conditions at which the cooling coil is operating. This curve is normalized to a value of 1.0 at the rated condition. This input field is optional.

Field: Sensible Heat Ratio Function of Flow Fraction Curve Name[LINK]

The name of a quadratic or cubic normalized curve (Ref: Performance Curves) that parameterizes the variation of the sensible heat ratio (SHR) as a function of the ratio of actual air flow rate across the cooling coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the rated SHR and the SHR modifier curve (function of temperature) to give the SHR at the specific temperature and air flow conditions at which the cooling coil is operating. This curve is normalized to a value of 1.0 when the actual air flow rate equals the rated air flow rate. This input field is optional.

Following is an example input for a Coil:Cooling:DX:TwoStageWithHumidityControlMode with 2 capacity stages and one enhanced dehumidification mode so it requires four CoilPerformance:DX:Cooling objects.

Coil:Cooling:DX:TwoStageWithHumidityControlMode,
  DXSystem 1 Cooling Coil, !- Coil Name
  OfficeHeatCoolAvail,         !- Availability Schedule
  DXSystem 1 Mixed Air Node,   !- Coil Air Inlet Node
  DXSystem 1 Fan Air Inlet Node,   !- Coil Air Outlet Node
  ,                                               !- Crankcase Heater Capacity {W}
  ,                                               !- Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation {C}
  2,                                             !- Number of Capacity Stages
  1,                                             !- Number of Enhanced Dehumidification Modes
  CoilPerformance:DX:Cooling,   !- Normal Mode Stage 1 Coil Performance Object Type
  DXSystem 1 DX Coil Standard Mode-Stage 1,   !- Normal Mode Stage 1 Coil Performance Object Name
  CoilPerformance:DX:Cooling,   !- Normal Mode Stage 1+2 Coil Perf Object Type
  DXSystem 1 DX Coil Standard Mode-Stage 1&2,   !- Normal Mode Stage 1+2 Coil Perf Object Name
  CoilPerformance:DX:Cooling,   !- Dehumid Mode 1 Stage 1 Coil Perf Object Type
  DXSystem 1 DX Coil SubCoolReheat Mode-Stage 1,   !- Dehumid Mode 1 Stage 1 Coil Perf Object Name
  CoilPerformance:DX:Cooling,   !- Dehumid Mode 1 Stage 1+2 Coil Perf Object Type
  DXSystem 1 DX Coil SubCoolReheat Mode-Stage 1&2;   !- Dehumid Mode 1 Stage 1+2 Coil Perf Object Name


  CoilPerformance:DX:Cooling,
  DXSystem 1 DX Coil Standard Mode-Stage 1,   !- Coil Performance Specification Name
  21327.57812,                         !- Gross Rated Total Cooling Capacity {W}
  0.68,                                       !- Gross Rated Sensible Heat Ratio
  3.56,                                       !- Gross Rated Cooling COP
  1.695372105,                         !- Rated Air Flow Rate {m3/s}
  0.4,                                         !- Fraction of Air Flow Bypassed Around Coil
  HPACCoolCapFT,                     !- Total Cooling Capacity Modifier Curve (function of temperature)
  HPACCoolCapFFF,                   !- Total Cooling Capacity Modifier Curve (function of flow fraction)
  HPACCOOLEIRFT,                     !- Energy Input Ratio Modifier Curve (function of temperature)
  HPACCOOLEIRFFF,                   !- Energy Input Ratio Modifier Curve (function of flow fraction)
  HPACCOOLPLFFPLR,                 !- Part Load Fraction Correlation (function of part load ratio)
  1000,                                       !- Nominal Time for Condensate Removal to Begin {s}
  1.5, !- Ratio of Initial Moisture Evaporation Rate and Steady-state Latent Capacity {dimensionless}
  3,                                             !- Maximum ON/OFF Cycling Rate {cycles/hr}
  45,                                           !- Latent Capacity Time Constant {s}
  ,                                               !- Condenser Air Inlet Node Name
  ,                                               !- Condenser Type
  ,                                               !- Evaporative Condenser Effectiveness
  ,                                               !- Evaporative Condenser Air Flow Rate
  ,                                               !- Evaporative Condenser Pump Rated Power Consumption
  DOAS DX Coil SHR-FT,         !- Sensible Heat Ratio Function of Temperature Curve Name
  DOAS DX Coil SHR-FF;         !- Sensible Heat Ratio Function of Flow Fraction Curve Name


  CoilPerformance:DX:Cooling,
  DXSystem 1 DX Coil Standard Mode-Stage 1&2,   !- Coil Performance Specification Name
  35545.96484,                         !- Gross Rated Total Cooling Capacity {W}
  0.68,                                       !- Gross Rated Sensible Heat Ratio
  3.56,                                       !- Gross Rated Cooling COP
  1.695372105,                         !- Rated Air Flow Rate {m3/s}
  0.0,                                         !- Fraction of Air Flow Bypassed Around Coil
  HPACCoolCapFT,                     !- Total Cooling Capacity Modifier Curve (function of temperature)
  HPACCoolCapFFF,                   !- Total Cooling Capacity Modifier Curve (function of flow fraction)
  HPACCOOLEIRFT,                     !- Energy Input Ratio Modifier Curve (function of temperature)
  HPACCOOLEIRFFF,                   !- Energy Input Ratio Modifier Curve (function of flow fraction)
  HPACCOOLPLFFPLR,                 !- Part Load Fraction Correlation (function of part load ratio)
  1000,                                       !- Nominal Time for Condensate Removal to Begin {s}
  1.5, !- Ratio of Initial Moisture Evaporation Rate and Steady-state Latent Capacity {dimensionless}
  3,                                             !- Maximum ON/OFF Cycling Rate {cycles/hr}
  45,                                           !- Latent Capacity Time Constant {s}
  ,                                               !- Condenser Air Inlet Node Name
  ,                                               !- Condenser Type
  ,                                               !- Evaporative Condenser Effectiveness
  ,                                               !- Evaporative Condenser Air Flow Rate
  ,                                               !- Evaporative Condenser Pump Rated Power Consumption
  DOAS DX Coil SHR-FT,         !- Sensible Heat Ratio Function of Temperature Curve Name
  DOAS DX Coil SHR-FF;         !- Sensible Heat Ratio Function of Flow Fraction Curve Name


  CoilPerformance:DX:Cooling,
  DXSystem 1 DX Coil SubCoolReheat Mode-Stage 1,   !- Coil Performance Specification Name
  19962.61328,                         !- Gross Rated Total Cooling Capacity (gross) {W}
  0.60,                                       !- Gross Rated SHR
  3.31,                                       !- Gross Rated Cooling COP
  1.695372105,                         !- Rated Air Flow Rate {m3/s}
  0.4,                                         !- Fraction of Air Flow Bypassed Around Coil
  SubCoolReheatCoolCapFT,   !- Total Cooling Capacity Modifier Curve (function of temperature)
  SubCoolReheatCoolCapFFF, !- Total Cooling Capacity Modifier Curve (function of flow fraction)
  SubCoolReheatCOOLEIRFT,   !- Energy Input Ratio Modifier Curve (function of temperature)
  SubCoolReheatCoolEIRFFF, !- Energy Input Ratio Modifier Curve (function of flow fraction)
  SubCoolReheatCoolPLFFPLR, !- Part Load Fraction Correlation (function of part load ratio)
  1000,                                       !- Nominal Time for Condensate Removal to Begin {s}
  1.5, !- Ratio of Initial Moisture Evaporation Rate and Steady-state Latent Capacity {dimensionless}
  3,                                             !- Maximum ON/OFF Cycling Rate {cycles/hr}
  45,                                           !- Latent Capacity Time Constant {s}
  ,                                               !- Condenser Air Inlet Node Name
  ,                                               !- Condenser Type
  ,                                               !- Evaporative Condenser Effectiveness
  ,                                               !- Evaporative Condenser Air Flow Rate
  ,                                               !- Evaporative Condenser Pump Rated Power Consumption
  DOAS DX Coil SHR-FT,         !- Sensible Heat Ratio Function of Temperature Curve Name
  DOAS DX Coil SHR-FF;         !- Sensible Heat Ratio Function of Flow Fraction Curve Name


  CoilPerformance:DX:Cooling,
  DXSystem 1 DX Coil SubCoolReheat Mode-Stage 1&2,   !- Coil Performance Specification Name
  33271.01953,                         !- Gross Rated Total Cooling Capacity (gross) {W}
  0.60,                                       !- Gross Rated SHR
  3.31,                                       !- Gross Rated Cooling COP
  1.695372105,                         !- Rated Air Flow Rate {m3/s}
  0.0,                                         !- Fraction of Air Flow Bypassed Around Coil
  SubCoolReheatCoolCapFT,   !- Total Cooling Capacity Modifier Curve (function of temperature)
  SubCoolReheatCoolCapFFF, !- Total Cooling Capacity Modifier Curve (function of flow fraction)
  SubCoolReheatCOOLEIRFT,   !- Energy Input Ratio Modifier Curve (function of temperature)
  SubCoolReheatCoolEIRFFF, !- Energy Input Ratio Modifier Curve (function of flow fraction)
  SubCoolReheatCoolPLFFPLR, !- Part Load Fraction Correlation (function of part load ratio)
  1000,                                       !- Nominal Time for Condensate Removal to Begin {s}
  1.5, !- Ratio of Initial Moisture Evaporation Rate and Steady-state Latent Capacity {dimensionless}
  3,                                             !- Maximum ON/OFF Cycling Rate {cycles/hr}
  45,                                           !- Latent Capacity Time Constant {s}
  ,                                               !- Condenser Air Inlet Node Name
  ,                                               !- Condenser Type
  ,                                               !- Evaporative Condenser Effectiveness
  ,                                               !- Evaporative Condenser Air Flow Rate
  ,                                               !- Evaporative Condenser Pump Rated Power Consumption
  DOAS DX Coil SHR-FT,         !- Sensible Heat Ratio Function of Temperature Curve Name
  DOAS DX Coil SHR-FF;         !- Sensible Heat Ratio Function of Flow Fraction Curve Name

Outputs[LINK]

The CoilPerformance:DX:Cooling object does not have specific output variables. To request reports, use the parent object Coil:Cooling:DX:TwoStageWithHumidityControlMode output variable options (ref. DX Cooling Coil Outputs). When requesting specific output variables by name, use the name of the parent object as the Key Value for Output:Variable reporting objects (ref. Output:Variable object). The name of the CoilPerformance:DX:Cooling object cannot be used as a Key Value in the Output:Variable object.

Coil:Heating:DX:SingleSpeed[LINK]

The single speed heating DX coil model uses performance information at rated conditions along with curve fits for variations in total capacity, energy input ratio and part load fraction to determine performance at part-load conditions. The impacts of various defrost strategies (reverse cycle, resistive, timed or on-demand) are modeled based on a combination of user inputs and empirical models taken from the air-to-air heat pump algorithms in DOE-2.1E.

The single speed heating DX coil input requires an availability schedule, the gross rated heating capacity, the gross rated COP and the rated air volume flow rate. The latter 3 inputs determine the coil performance at the rating point (outdoor air dry-bulb temperature of 8.33 C, outdoor air wet-bulb temperature of 6.11 C, coil entering air dry-bulb temperature of 21.11 C, coil entering air wet-bulb temperature of 15.55 C). The rated air volume flow rate should be between .00004027 m3/s and .00006041 m3/s per watt of gross rated heating capacity.

Up to 6 curves are required depending on the defrost strategy selected.

  1. The heating capacity modifier curve (function of temperature) can be a function of both the outdoor and indoor air dry-bulb temperature or only the outdoor air dry-bulb temperature. User has the choice of a bi-quadratic curve with two independent variables or a quadratic curve as well as a cubic curve with a single independent variable. The bi-quadratic curve is recommended if sufficient manufacturer data is available as it provides sensitivity to the indoor air dry-bulb temperature and a more realistic output. The output of this curve is multiplied by the gross rated heating capacity to give the gross heating capacity at specific temperature operating conditions (i.e., at an outdoor or indoor air temperature different from the rating point temperature).

  2. The heating capacity modifier curve (function of flow fraction) is a quadratic or cubic curve with the independent variable being the ratio of the actual air flow rate across the heating coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated heating capacity and the heating capacity modifier curve (function of temperature) to give the gross heating capacity at the specific temperature and air flow conditions at which the coil is operating.

  3. The energy input ratio (EIR) modifier curve (function of temperature) can be a function of both the outdoor and indoor air dry-bulb temperature or only the outdoor air dry-bulb temperature. User has the choice of a bi-quadratic curve with two independent variables or a quadratic curve as well as a cubic curve with a single independent variable. The bi-quadratic curve is recommended if sufficient manufacturer data is available as it provides sensitivity to the indoor air dry-bulb temperature and a more realistic output. The output of this curve is multiplied by the rated EIR (inverse of the rated COP) to give the EIR at specific temperature operating conditions (i.e., at an outdoor or indoor air temperature different from the rating point temperature).

  4. The energy input ratio (EIR) modifier curve (function of flow fraction) is a quadratic or cubic curve with the independent variable being the ratio of the actual air flow rate across the heating coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the rated EIR (inverse of the rated COP) and the EIR modifier curve (function of temperature) to give the EIR at the specific temperature and air flow conditions at which the coil is operating.

  5. The part load fraction correlation (function of part load ratio) is a quadratic or cubic curve with the independent variable being part load ratio (sensible heating load / steady-state heating capacity). The output of this curve is used in combination with the rated EIR and EIR modifier curves to give the effective EIR for a given simulation timestep. The part load fraction correlation accounts for efficiency losses due to compressor cycling.

  6. The defrost energy input ratio (EIR) modifier curve (function of temperature) is a bi-quadratic curve with two independent variables: outdoor air dry-bulb temperature and the heating coil entering air wet-bulb temperature. The output of this curve is multiplied by the heating coil capacity, the fractional defrost time period and the runtime fraction of the heating coil to give the defrost power at the specific temperatures at which the coil is operating. This curve is only required when a reverse-cycle defrost strategy is specified.

The curves are simply specified by name. Curve inputs are described in the curve manager section of this document (ref. Performance Curves).

The next input item for the coil is the supply air fan operation mode. Either the supply air fan runs continuously while the DX coil cycles on/off, or the fan and coil cycle on/off together. The next two inputs define the minimum outdoor dry-bulb temperature that the heat pump compressor will operate and the maximum outdoor dry-bulb temperature for defrost operation. Crankcase heater capacity and cutout temperature are entered in the following two inputs. The final four inputs cover the type of defrost strategy (reverse-cycle or resistive), defrost control (timed or on-demand), the fractional defrost time period (timed defrost control only), and the resistive defrost heater capacity if a resistive defrost strategy is selected.

Inputs[LINK]

Field: Name[LINK]

This alpha field defines a unique user-assigned name for an instance of a DX heating coil. Any reference to this DX heating coil by another object will use this name.

Field: Availability Schedule Name[LINK]

This alpha field defines the name of the schedule (ref: Schedule) that denotes whether the DX heating coil can run during a given time period. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off for the time period. If this field is blank, the schedule has values of 1 for all time periods.

Field: Gross Rated Heating Capacity[LINK]

This numeric field defines the total, full load gross heating capacity in watts of the DX coil unit at rated conditions (outdoor air dry-bulb temperature of 8.33 C, outdoor air wet-bulb temperature of 6.11 C, heating coil entering air dry-bulb temperature of 21.11 C, heating coil entering air wet-bulb temperature of 15.55 C, and a heating coil air flow rate defined by field rated air flow volume below). The value entered here must be greater than 0. Capacity should not account for supply air fan heat. The gross rated heating capacity should be within 20% of the gross rated total cooling capacity, otherwise a warning message is issued. The gross heating capacity should NOT include the effect of supply air fan heat.

Field: Gross Rated Heating COP[LINK]

This numeric field defines the coefficient of performance (COP = the gross heating capacity in watts divided by electrical power input in watts) of the DX heating coil unit at rated conditions (outdoor air dry-bulb temperature of 8.33 C, outdoor air wet-bulb temperature of 6.11 C, coil entering air dry-bulb temperature of 21.11 C, coil entering air wet-bulb temperature of 15.55 C, and a heating coil air flow rate defined by field rated air flow volume rate below). The value entered here must be greater than 0. The input power includes power for the compressor(s) and outdoor fan(s) but does not include the power consumption of the indoor supply air fan. The gross COP should NOT account for the supply air fan.

Field: Rated Air Flow Rate[LINK]

This numeric field defines the volume air flow rate, in m3 per second, across the DX heating coil at rated conditions. The value entered here must be greater than 0. The rated air volume flow rate should be between 0.00004027 m3/s and 0.00006041 m3/s per watt of the gross rated heating capacity. The gross rated heating capacity and gross rated COP should be performance information for the unit with outdoor air dry-bulb temperature of 8.33 C, outdoor air wet-bulb temperature of 6.11 C, heating coil entering air dry-bulb temperature of 21.11 C, heating coil entering air wet-bulb temperature of 15.55 C, and the rated air volume flow rate defined here.

Field: Rated Evaporator Fan Power Per Volume Flow Rate[LINK]

This field is the electric power for the evaporator (heating coil) fan per air volume flow rate through the coil at the rated conditions in W/(m3/s). The default value is 773.3 W/(m3/s) (365 W/1000 cfm) if this field is left blank. If a value is entered, it must be > = 0.0 and < = 1250 W/(m3/s). This value is only used to calculate High Temperature Heating Standard (Net) Rating Capacity, Low Temperature Heating Standard (Net) Rating Capacity and Heating Seasonal Performance Factor (HSPF) which will be outputs in the EnergyPlus eio file (ref. EnergyPlus Engineering Reference, Single Speed DX Heating Coil, Standard Ratings). This value is not used for modeling the evaporator (heating coil) fan during simulations; instead, it is used for calculating the above standard ratings to assist the user in verifying their inputs for modeling this type of equipment.

Field: Air Inlet Node Name[LINK]

This alpha field defines the name of the HVAC system node from which the DX heating coil draws its inlet air.

Field: Air Outlet Node Name[LINK]

This alpha field defines the name of the HVAC system node to which the DX heating coil sends its outlet air.

Field: Heating Capacity Function of Temperature Curve Name[LINK]

This alpha field defines the name of a bi-quadratic, quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of the total heating capacity as a function of the both the indoor and outdoor air dry-bulb temperature or just the outdoor air dry-bulb temperature depending on the type of curve selected. The bi-quadratic curve is recommended if sufficient manufacturer data is available as it provides sensitivity to the indoor air dry-bulb temperature and a more realistic output. The output of this curve is multiplied by the gross rated heating capacity to give the gross total heating capacity at specific temperature operating conditions (i.e., at an indoor air dry-bulb temperature or outdoor air dry-bulb temperature different from the rating point temperature). The curve is normalized to have the value of 1.0 at the rating point.

Field: Heating Capacity Function of Flow Fraction Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of total heating capacity as a function of the ratio of actual air flow rate across the heating coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated heating capacity and the heating capacity modifier curve (function of temperature) to give the gross heating capacity at the specific temperature and air flow conditions at which the coil is operating. The curve is normalized to have the value of 1.0 when the actual air flow rate equals the rated air flow rate.

Field: Energy Input Ratio Function of Temperature Curve Name[LINK]

This alpha field defines the name of a bi-quadratic, quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the both the indoor and outdoor air dry-bulb temperature or just the outdoor air dry-bulb temperature depending on the type of curve selected. The bi-quadratic curve is recommended if sufficient manufacturer data is available as it provides sensitivity to the indoor air dry-bulb temperature and a more realistic output. The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR (inverse of rated COP) to give the EIR at specific temperature operating conditions (i.e., at an indoor air dry-bulb temperature or outdoor air dry-bulb temperature different from the rating point temperature). The curve is normalized to have the value of 1.0 at the rating point.

Field: Energy Input Ratio Function of Flow Fraction Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the ratio of actual air flow rate across the heating coil to the rated air flow rate (i.e., fraction of full load flow). The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR and the EIR modifier curve (function of temperature) to give the EIR at the specific temperature and air flow conditions at which the coil is operating. This curve is normalized to a value of 1.0 when the actual air flow rate equals the rated air flow rate.

Field: Part Load Fraction Correlation Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve (Ref: Performance Curves) that parameterizes the variation of electrical power input to the DX unit as a function of the part load ratio (PLR, sensible cooling load/steady-state sensible cooling capacity). The product of the rated EIR and EIR modifier curves is divided by the output of this curve to give the effective EIR for a given simulation timestep. The part load fraction (PLF) correlation accounts for efficiency losses due to compressor cycling.

The part load fraction correlation should be normalized to a value of 1.0 when the part load ratio equals 1.0 (i.e., no efficiency losses when the compressor(s) run continuously for the simulation timestep). For PLR values between 0 and 1 (0 < = PLR < 1), the following rules apply:

PLF > = 0.7 and PLF > = PLR

If PLF < 0.7 a warning message is issued, the program resets the PLF value to 0.7, and the simulation proceeds. The runtime fraction of the coil is defined as PLR/PLF. If PLF < PLR, then a warning message is issued and the runtime fraction of the coil is limited to 1.0.

A typical part load fraction correlation for a conventional, single-speed DX cooling coil (e.g., residential unit) would be:

PLF = 0.85 + 0.15(PLR)

If the user wishes to model no efficiency degradation due to compressor cycling, the part load fraction correlation should be defined as follows:

PLF = 1.0 + 0.0(PLR)

Field: Defrost Energy Input Ratio Function of Temperature Curve Name[LINK]

This alpha field defines the name of a bi-quadratic performance curve (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) during reverse-cycle defrost periods as a function of the outdoor air dry-bulb temperature and the wet-bulb temperature of the air entering the indoor coil. The EIR is the inverse of the COP. The output of this curve is multiplied by the coil capacity, the fractional defrost time period and the runtime fraction of the heating coil to give the defrost power at the specific temperatures at which the indoor and outdoor coils are operating. This curve is only required when a reverse-cycle defrost strategy is selected. The curve is normalized to a value of 1.0 at the rating point conditions.

Field: Minimum Outdoor Dry-Bulb Temperature for Compressor Operation[LINK]

This numeric field defines the minimum outdoor air dry-bulb temperature where the heating coil compressor turns off. The temperature for this input field must be greater than or equal to 20 C. If this input field is left blank, the default value is -8 C.

Field: Outdoor Dry-Bulb Temperature to Turn On Compressor[LINK]

This numeric field defines the outdoor air dry-bulb temperature when the compressor is automatically turned back on following an automatic shut off because of low outdoor temperature. This field is only used for the calculation heating seasonal performance factor (HSPF) of heating coil. If this field is not provided, outdoor bin temperature is always considered to be greater than this temperature and Minimum Outdoor dry-bulb Temperature for Compressor Operation field described above.

Field: Maximum Outdoor Dry-Bulb Temperature for Defrost Operation[LINK]

This numeric field defines the outdoor air dry-bulb temperature above which outdoor coil defrosting is disabled. The temperature for this input field must be greater than or equal to 0 C and less than or equal to 7.22 C. If this input field is left blank, the default value is 5 C.

Field: Crankcase Heater Capacity[LINK]

This numeric field defines the crankcase heater capacity in Watts. When the outdoor air dry-bulb temperature is below the value specified in the input field Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation (described below), the crankcase heater is enabled during the time that the compressor is not running. If this heating coil is used as part of an air-to-air heat pump (Ref. AirLoopHVAC:UnitaryHeatPump:AirToAir or ZoneHVAC:PackagedTerminalHeatPump), the crankcase heater defined for this DX heating coil is enabled during the time that the compressor is not running for either heating or cooling (and the crankcase heater power defined in the DX cooling coil object is disregarded in this case). The value for this input field must be greater than or equal to 0. If this input field is left blank, the default value is 0. To simulate a unit without a crankcase heater, enter a value of 0.

Field: Maximum Outdoor Dry-Bulb Temperature for Crankcase Heater Operation[LINK]

This numeric field defines the outdoor air dry-bulb temperature above which the compressor s crankcase heater is disabled. The value for this input field must be greater than or equal to 0.0 C. If this input field is left blank, the default value is 10 C.

Field: Defrost Strategy[LINK]

This alpha field has two choices: reverse-cycle or resistive. If the reverse-cycle strategy is selected, the heating cycle is reversed periodically to provide heat to melt frost accumulated on the outdoor coil. If a resistive defrost strategy is selected, the frost is melted using an electric resistance heater. If this input field is left blank, the default defrost strategy is reverse-cycle.

Field: Defrost Control[LINK]

This alpha field has two choices: timed or on-demand. If timed control is selected, the defrost time period is calculated based on a fixed value or compressor runtime whether or not frost has actually accumulated. For timed defrost control, the fractional amount of time the unit is in defrost is entered in the input field Defrost Time Period Fraction described below. If on-demand defrost control is selected, the defrost time period is calculated based on outdoor weather (humidity ratio) conditions. Regardless of which defrost control is selected, defrost does not occur above the user specified outdoor temperature entered in the input field Maximum Outdoor Dry-bulb Temperature for Defrost Operation described above. If this input field is left blank, the default defrost control is timed.

Field: Defrost Time Period Fraction[LINK]

This numeric field defines the fraction of compressor runtime when the defrost cycle is active, and only applies to timed defrost (see Defrost Control input field above). For example, if the defrost cycle is active for 3.5 minutes for every 60 minutes of compressor runtime, then the user should enter 3.5/60 = 0.058333. The value for this input field must be greater than or equal to 0. If this input field is left blank, the default value is 0.058333.

Field: Resistive Defrost Heater Capacity[LINK]

This numeric field defines the capacity of the resistive defrost heating element in Watts. This input field is used only when the selected defrost strategy is resistive (see input field Defrost Strategy above). The value for this input field must be greater than or equal to 0. If this input field is left blank, the default value is 0.

Field: Region Number[LINK]

This optional numeric field defines the region number which is used to calculate HSPF of heating coil. The value for this input field must be between 1 and 6. If this input field is left blank, the default value is 4.

Field: Evaporator Air Inlet Node Name[LINK]

This optional alpha field specifies the outdoor air node name used to define the conditions of the air entering the outdoor evaporator. If this field is left blank, the outdoor air temperature entering the evaporator is taken directly from the weather data. If this field is not blank, the node name specified must also be specified in an OutdoorAir:Node object where the height of the node is taken into consideration when calculating outdoor air temperature from the weather data. Alternately, the node name may be specified in an OutdoorAir:NodeList object where the outdoor air temperature is taken directly from the weather data.

Field: Zone Name for Evaporator Placement[LINK]

This input field is name of a conditioned or unconditioned zone where the secondary coil (evaporator) of a heat pump is installed. This is an optional input field specified only when user desires to extract heat from the zone via secondary coil. Heat extracted is modeled as internal gain. If the primary DX system is a heat pump, then the zone name should be the same as the zone name specified for placing the secondary cooling DX coil.

Field: Secondary Coil Air Flow Rate[LINK]

This input value is the secondary coil (evaporator) air flow rate when the heat pump is working in heating mode or the secondary coil (condenser) air flow rate when the heat pump is working in cooling mode. This input field is auto-sizable.

Field: Secondary Coil Fan Flow Scaling Factor[LINK]

This input field is scaling factor for autosizing the secondary DX coil fan flow rate. The secondary air flow rate is determined by multiplying the primary DX coil rated air flow rate by the fan flow scaling factor. Default value is 1.25. If the secondary coil fan flow rate is not autosized, then the secondary coil fan flow scaling factor is set to 1.0.

Field: Nominal Sensible Heat Ratio of Secondary Coil[LINK]

This input value is the nominal sensible heat ratio used to split the heat extracted by a secondary DX coil (evaporator) of a heat pump into sensible and latent components. This is an optional input field. If this input field is left blank, then pure sensible internal heat gain is assumed, i.e., sensible heat ratio of 1.0.

Field: Sensible Heat Ratio Modifier Function of Temperature Curve Name[LINK]

This input field is name of sensible heat ratio modifier biquadratic curve. The value of this curve modifies the nominal sensible heat ratio for current time step depending on the secondary zone air node wet-bulb temperature and the heating DX coil entering air dry-bulb temperature. This is an optional input field. If this input field is left blank, then the nominal sensible heat ratio modifier curve value for temperature is set to 1.0.

Field: Sensible Heat Ratio Modifier Function of Flow Fraction Curve Name[LINK]

This input field is name of sensible heat ratio modifier curve as function of secondary air flow fraction. The value of this curve modifies the nominal sensible heat ratio for current time step depending on the secondary coil air flow fraction. This is an optional input field. If this input field is left blank, then the sensible heat ratio modifier curve value for flow fraction is set to 1.0.

Following is an example input for the object.

Coil:Heating:DX:SingleSpeed,
  Heat Pump DX Heating Coil 1,     ! Name of heating coil
  FanAndCoilAvailSched,                   ! Heating coil schedule
  35000,                                                 ! Gross Rated Heating Capacity
  2.75,                                                   ! Gross Rated Heating COP
  1.7,                                                     !rated air flow rate (m3/s)
  ,                                                       !rated evaporator fan power per volume flow rate (m3/s)
  Heating Coil Air Inlet Node,     !heating coil air side inlet node
  SuppHeating Coil Air Inlet Node, !Heating coil air side outlet node
  HPACHeatCapFT,     ! heating cap modifier curve (temperature, C)
  HPACHeatCapFFF,   ! heating cap modifier curve (flow fraction)
  HPACHeatEIRFT,     ! energy input ratio modifier curve (temperature, C)
  HPACHeatEIRFFF,   ! energy input ratio modifier curve (flow fraction)
  HPACCOOLPLFFPLR, ! part load fraction modifier curve (function of part load ratio)
  ,                 ! defrost EIR modifier curve (temp, C) not required for resistive defrost
  -5.0,                       ! minimum OAT for compressor operation   (C)
  ,                               ! outdoor dry-bulb temperature to turn on compressor   (C)
  5.0,                         ! maximum outdoor dry-bulb temp for defrost operation (C)
  200.0,                     ! Crankcase heater capacity (W)
  10.0,                       ! Maximum outdoor temp for crankcase heater operation (C)
  Resistive,             ! Defrost strategy (resistive or reverse-cycle)
  Timed,                     ! Defrost control (timed or on-demand)
  0.166667,             ! Defrost time period fraction (used for timed defrost control only)
  20000;! Resistive defrost heater capacity (used for resistive defrost strategy only)

Outputs[LINK]

  • HVAC,Average,Heating Coil Total Heating Rate [W]

  • HVAC,Sum,Heating Coil Total Heating Energy [J]

  • HVAC,Average,Heating Coil Electric Power[W]

  • HVAC,Sum,Heating Coil Electric Energy [J]

  • HVAC,Average,Heating Coil Defrost Electric Power[W]

  • HVAC,Sum,Heating Coil Defrost Electric Energy [J]

  • HVAC,Average,Heating Coil Crankcase Heater Electric Power[W]

  • HVAC,Sum,Heating Coil Crankcase Heater Electric Energy [J]

  • HVAC,Average,Heating Coil Runtime Fraction []

Heating Coil Total Heating Rate [W] [LINK]

This field is the total heating rate output of the DX coil in Watts. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil.

Heating Coil Total Heating Energy [J] [LINK]

This is the total heating output of the DX coil in Joules over the timestep being reported. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil. This output is also added to a meter with Resource Type = EnergyTransfer, End Use Key = CoolingCoils, Group Key = System (ref. Output:Meter objects).

Heating Coil Electric Power [W] [LINK]

This output is the electricity consumption rate of the DX coil compressor and outdoor fan(s) in Watts. This rate is applicable when the unit is providing heating to the conditioned zone(s), and excludes periods when the unit is in reverse-cycle defrost mode.

Heating Coil Electric Energy [J] [LINK]

This is the electricity consumption of the DX coil compressor and condenser fan(s) in Joules for the timestep being reported. This consumption is applicable when the unit is providing heating to the conditioned zone(s), and excludes periods when the unit is in reverse-cycle defrost mode. This output is also added to a meter with Resource Type = Electricity, End Use Key = Cooling, Group Key = System (ref. Output:Meter objects).

Heating Coil Defrost Electric Power [W] [LINK]

This is the electricity consumption rate of the DX coil unit in Watts when the unit is in defrost mode (reverse-cycle or resistive).

Heating Coil Defrost Electric Energy [J] [LINK]

This is the electricity consumption of the DX coil unit in Joules for the timestep being reported. This consumption is applicable when the unit is in defrost mode (reverse-cycle or resistive).

Heating Coil Crankcase Heater Electric Power [W] [LINK]

This is the average electricity consumption rate of the DX coil compressor s crankcase heater in Watts for the timestep being reported.

Heating Coil Crankcase Heater Electric Energy [J] [LINK]

This is the electricity consumption of the DX coil compressor s crankcase heater in Joules for the timestep being reported. This output is also added to a meter with Resource Type = Electricity, End Use Key = Miscellaneous, Group Key = System (ref. Output:Meter objects).

Heating Coil Runtime Fraction [] [LINK]

This is the runtime fraction of the DX heating coil compressor and outdoor fan(s) for the timestep being reported.

Coil:Heating:DX:MultiSpeed[LINK]

This component models a DX heating unit with multiple discrete levels of heating capacity. Currently, this heating coil can only be referenced by a AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed compound object. The multispeed DX heating coil can have from two to four operating speeds. When the coil operates at Speed 1 (the lowest speed), its performance is very similar to the Coil:Heating:DX:SingleSpeed object where the impacts of part-load ratio can be included. When the coil operates at higher speeds (above Speed 1), the linear approximation methodology is applied. The coil outputs at two consecutive speeds are linearly interpolated to meet the required heating capacity during an HVAC system timestep. When the coil performs above the lowest speed, the user can choose if they want to include part-load ratio impacts at the higher speeds.

The multispeed unit is described by specifying the performance at different operating speeds. Each speed has its own set of input specifications: full load capacity, COP and air flow rate at rated conditions, along with modifier curves to determine performance when actual operating conditions are different from the rated conditions.

The coil operates to meet the sensible capacity being requested. When this requested capacity is above the sensible capacity of the highest operating speed, the coil runs continuously at the highest speed. When the requested capacity is between the sensible capacities of two consecutive speeds, the unit will operate a portion of the time at each speed to meet the request. When the requested capacity is less than the low speed (Speed 1) capacity, the unit will cycle on/off as needed.

The next input defines the minimum outdoor dry-bulb temperature where the compressor will operate. The followed two inputs are related to crankcase heater operation: capacity and maximum outdoor dry-bulb temperature for crankcase heater operation. The next six inputs cover defrost operation: defrost EIR modifier curve, the maximum outdoor dry-bulb temperature for defrost operation, the type of defrost strategy (reverse-cycle or resistive), defrost control (timed or on-demand), the fractional defrost time period (timed defrost control only), and the resistive defrost heater capacity if a resistive defrost strategy is selected. The activation of defrost is dependent on outdoor conditions. The capacity reduction and energy use modification are independent of speed. The defrost EIR modifier is described below:

The defrost energy input ratio (EIR) modifier curve (function of temperature) is a bi-quadratic curve with two independent variables: outdoor air dry-bulb temperature and the heating coil entering air wet-bulb temperature. The output of this curve is multiplied by the heating coil capacity, the fractional defrost time period and the runtime fraction of the heating coil to give the defrost power at the specific temperatures at which the coil is operating. This curve is only required when a reverse-cycle defrost strategy is specified.

The next input allows the user to choose whether to apply the part load fraction correlation to speeds greater than 1 or not. The following input is the type of fuel.

Then the number of speed for heating is entered. The rest of inputs are speed dependent. Each set of data consists of gross rated heating capacity, gross rated COP, and the rated air volume flow rate. These three inputs determine the coil performance at the rating point (outdoor air dry-bulb temperature of 8.33 °C, outdoor air wet-bulb temperature of 6.11 °C, coil entering air dry-bulb temperature of 21.11 °C, coil entering air wet-bulb temperature of 15.55 °C). The rated air volume flow rate should be between .00004027 m3/s and .00006041 m3/s per watt of gross rated heating capacity. The rated waste heat fraction is needed to calculate how much waste heat is available at the rated conditions. In addition, up to 6 modifier curves are required per speed.

  1. The heating capacity modifier curve (function of temperature) can be a function of both the outdoor and indoor air dry-bulb temperature or only the outdoor air dry-bulb temperature. User has the choice of a bi-quadratic curve with two independent variables or a quadratic curve as well as a cubic curve with a single independent variable. The bi-quadratic curve is recommended if sufficient manufacturer data is available as it provides sensitivity to the indoor air dry-bulb temperature and a more realistic output. The output of this curve is multiplied by the gross rated heating capacity to give the gross total heating capacity at specific temperature operating conditions (i.e., at an outdoor or indoor air temperature different from the rating point temperature).

  2. The heating capacity modifier curve (function of flow fraction) is a quadratic or cubic curve with the independent variable being the ratio of the actual air flow rate across the heating coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated heating capacity and the heating capacity modifier curve (function of temperature) to give the gross heating capacity at the specific temperature and air flow conditions at which the coil is operating.

  3. The energy input ratio (EIR) modifier curve (function of temperature) can be a function of both the outdoor and indoor air dry-bulb temperature or only the outdoor air dry-bulb temperature. User has the choice of a bi-quadratic curve with two independent variables or a quadratic curve as well as a cubic curve with a single independent variable. The bi-quadratic curve is recommended if sufficient manufacturer data is available as it provides sensitivity to the indoor air dry-bulb temperature and a more realistic output. The output of this curve is multiplied by the rated EIR (inverse of the rated COP) to give the EIR at specific temperature operating conditions (i.e., at an outdoor or indoor air temperature different from the rating point temperature).

  4. The energy input ratio (EIR) modifier curve (function of flow fraction) is a quadratic or cubic curve with the independent variable being the ratio of the actual air flow rate across the heating coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the rated EIR (inverse of the rated COP) and the EIR modifier curve (function of temperature) to give the EIR at the specific temperature and air flow conditions at which the coil is operating.

  5. The part load fraction correlation (function of part load ratio) is a quadratic or cubic curve with the independent variable being part load ratio (sensible heating load / steady-state heating capacity). The output of this curve is used in combination with the rated EIR and EIR modifier curves to give the effective EIR for a given simulation timestep. The part load fraction correlation accounts for efficiency losses due to compressor cycling.

  6. The waste heat modifier curve (function of temperature) is a bi-quadratic curve with two independent variables: outdoor air dry-bulb temperature and the heating coil entering air dry-bulb temperature. The output of this curve is multiplied by the heating input energy, the waste heat fraction of heat input to give the recoverable waste heat.

The curves are simply specified by name. Curve inputs are described in the curve manager section of this document (ref. Performance Curves).

Inputs[LINK]

Field: Name[LINK]

This alpha field defines a unique user-assigned name for an instance of a multispeed DX heating coil. Any reference to this DX heating coil by another object will use this name. The only allowed parent is AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed.

Field: Availability Schedule Name[LINK]

This alpha field defines the name of the schedule (ref: Schedule) that denotes whether the multispeed DX heating coil can run during a given time period. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off for the time period. If this field is blank, the schedule has values of 1 for all time periods.

Field: Air Inlet Node name[LINK]

This alpha field defines the name of the HVAC system node from which the DX heating coil draws its inlet air.

Field: Air Outlet Node Name[LINK]

This alpha field defines the name of the HVAC system node to which the DX heating coil sends its outlet air.

Field: Minimum Outdoor Dry-Bulb Temperature for Compressor Operation[LINK]

This numeric field defines the minimum outdoor air dry-bulb temperature where the heating coil compressor turns off. The temperature for this input field must be greater than or equal to 20 °C. If this input field is left blank, the default value is -8 °C.

Field: Crankcase Heater Capacity[LINK]

This numeric field defines the crankcase heater capacity in Watts. When the outdoor air dry-bulb temperature is below the value specified in the input field Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation (described below), the crankcase heater is enabled during the time that the compressor is not running. The value for this input field must be greater than or equal to 0. If this input field is left blank, the default value is 0. To simulate a unit without a crankcase heater, enter a value of 0.

Field: Maximum Outdoor Dry-Bulb Temperature for Crankcase Heater Operation[LINK]

This numeric field defines the outdoor air dry-bulb temperature above which the compressor s crankcase heater is disabled. The value for this input field must be greater than or equal to 0.0 °C. If this input field is left blank, the default value is 10 °C.

Field: Defrost Energy Input Ratio Function of Temperature Curve Name[LINK]

This alpha field defines the name of a bi-quadratic performance curve (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) during reverse-cycle defrost periods as a function of the outdoor air dry-bulb temperature and the wet-bulb temperature of the air entering the indoor coil. The EIR is the inverse of the COP. The output of this curve is multiplied by the coil capacity, the fractional defrost time period and the runtime fraction of the heating coil to give the defrost power at the specific temperatures at which the indoor and outdoor coils are operating. This curve is only required when a reverse-cycle defrost strategy is selected. The curve is normalized to a value of 1.0 at the rating point conditions.

Field: Maximum Outdoor Dry-Bulb Temperature for Defrost Operation[LINK]

This numeric field defines the outdoor air dry-bulb temperature above which outdoor coil defrosting is disabled. The temperature for this input field must be greater than or equal to 0 °C and less than or equal to 7.22 °C. If this input field is left blank, the default value is 5 °C.

Field: Defrost Strategy[LINK]

This alpha field has two choices: reverse-cycle or resistive. If the reverse-cycle strategy is selected, the heating cycle is reversed periodically to provide heat to melt frost accumulated on the outdoor coil. If a resistive defrost strategy is selected, the frost is melted using an electric resistance heater. If this input field is left blank, the default defrost strategy is reverse-cycle.

Field: Defrost Control[LINK]

This alpha field has two choices: timed or on-demand. If timed control is selected, the defrost time period is calculated based on a fixed value or compressor runtime whether or not frost has actually accumulated. For timed defrost control, the fractional amount of time the unit is in defrost is entered in the input field Defrost Time Period Fraction described below. If on-demand defrost control is selected, the defrost time period is calculated based on outdoor weather (humidity ratio) conditions. Regardless of which defrost control is selected, defrost does not occur above the user specified outdoor temperature entered in the input field Maximum Outdoor Dry-bulb Temperature for Defrost Operation described above. If this input field is left blank, the default defrost control is timed.

Field: Defrost Time Period Fraction[LINK]

This numeric field defines the fraction of compressor runtime when the defrost cycle is active, and only applies to timed defrost (see Defrost Control input field above). For example, if the defrost cycle is active for 3.5 minutes for every 60 minutes of compressor runtime, then the user should enter 3.5/60 = 0.058333. The value for this input field must be greater than or equal to 0. If this input field is left blank, the default value is 0.058333.

Field: Resistive Defrost Heater Capacity[LINK]

This numeric field defines the capacity of the resistive defrost heating element in Watts. This input field is used only when the selected defrost strategy is resistive (see input field Defrost Strategy above). The value for this input field must be greater than or equal to 0. If this input field is left blank, the default value is 0.

Field: Apply Part Load Fraction to Speeds Greater than 1[LINK]

This field determines whether part-load impacts on coil energy use are applied when the coil is operating at speeds greater than speed 1. The allowed choices are Yes or No, with the default being No if this field is left blank. Other input fields in this object allow the user to specify a part-load fraction correlation for each speed to account for compressor start up losses (cycle on/off). For the case of a single multi-speed compressor, the part load losses may only be significant when the compressor cycles between speed 1 and off, but the losses may be extremely small when the compressor operates between speed 1 and speed 2 (or between speeds 2 and 3, etc.). In this case, the user may chose to specify No for this input field to neglect part-load impacts on energy use at higher operating speeds. If part-load impacts on coil energy use are thought to be significant (e.g., interwined cooling coil with multiple compressors feeding individual refrigerant circuits), then the user may chose to specify Yes and the part-load fraction correlations specified for speeds 2 through 4 will be applied as appropriate. The selection for this input field does not affect part-load impacts when the compressor cycles between speed 1 and off (i.e., the part-load fraction correlation for speed 1 is always applied).

Field: Fuel Type[LINK]

This alpha field determines the type of fuel that the chiller uses. This field has seven choices: Electricity, NaturalGas, PropaneGas, Coal, Diesel, Gasoline, FuelOil#1, FuelOil#2, OtherFuel1 and OtherFuel2. The default is NaturalGas.

Field: Number of Speeds[LINK]

This field specifies the number of sets of data being entered for rated specifications, performance curves, and waste heat specifications for each cooling speed. The rated specifications consist of gross rated capacity, gross rated COP, and rated air flow rate. The performance curves consist of a total capacity modifier curve as a function of temperature, total capacity modifier curve as a function of flow fraction, energy input ratio modifier curve as a function of temperature, energy input ratio modifier curve as a function of flow fraction, and part load fraction correlation as a function of part load ratio. The waste heat specifications include the fraction of energy input to the heating coil at the fully loaded and rated conditions, and a temperature modifier. The minimum number of speeds for heating is 2 and the maximum number is 4. The number of speeds should be the same as the number of speeds for heating defined in its parent object (AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed). The first set of performance inputs is for Speed 1 and should be for low speed, and the last set of performance inputs should be for high speed. For example, if only three heating speeds are defined, the first set should be for low speed (Speed 1), the second set should be for medium speed (Speed 2), and the third set should be for high speed (Speed 3). In this example, any performance inputs for Speed 4 would be neglected (since this input field specifies that the coil only has three heating speeds).

Field Group: Rated Specification, Performance Curves, and Waste Heat Data[LINK]

The performance for each heating speed must be specified as shown below. All inputs for Speed 1 are required first, followed by the inputs for Speed 2, Speed 3 and Speed 4.

Field: Speed <x> Gross Rated Heating Capacity[LINK]

This numeric field defines the total, full load gross heating capacity in watts of the DX coil unit at rated conditions for Speed <x> operation (outdoor air dry-bulb temperature of 8.33 °C, outdoor air wet-bulb temperature of 6.11 °C, heating coil entering air dry-bulb temperature of 21.11 °C, heating coil entering air wet-bulb temperature of 15.55 °C, and a heating coil air flow rate defined by field Rated Air Flow Rate, Speed <x> below). The value entered here must be greater than 0. The gross heating capacity should not account for the effect of supply air fan heat.

Field: Speed <x> Gross Rated Heating COP[LINK]

This numeric field defines the coefficient of performance (COP = gross heating capacity in watts divided by electrical power input in watts) of the DX heating coil unit at rated conditions for Speed <x> operation (outdoor air dry-bulb temperature of 8.33 °C, outdoor air wet-bulb temperature of 6.11 °C, coil entering air dry-bulb temperature of 21.11 °C, coil entering air wet-bulb temperature of 15.55 °C, and a heating coil air flow rate defined by field Speed <x> Rated Air Flow Rate below). The value entered here must be greater than 0. The input power includes power for the compressor(s) and outdoor fan(s) but does not include the power consumption of the indoor supply air fan. The gross heating capacity is the value entered above in the field Gross Rated Heating Capacity . The gross COP should NOT account for the supply air fan.

Field: Speed <x> Rated Air Flow Rate[LINK]

This numeric field defines the volume air flow rate, in m3 per second, across the DX heating coil at rated conditions for Speed <x> operation. The value entered here must be greater than 0. The rated air volume flow rate should be between 0.00004027 m3/s and 0.00006041 m3/s per watt of gross rated heating capacity. The gross rated heating capacity and gross rated COP should be performance information for the unit with outdoor air dry-bulb temperature of 8.33 °C, outdoor air wet-bulb temperature of 6.11 °C, heating coil entering air dry-bulb temperature of 21.11 °C, heating coil entering air wet-bulb temperature of 15.55 °C, and the rated air volume flow rate defined here.

Field: Speed <x> Heating Capacity Function of Temperature Curve Name[LINK]

This alpha field defines the name of a bi-quadratic, quadratic or cubic performance curve for Speed <x> (ref: Performance Curves) that parameterizes the variation of the total heating capacity as a function of the both the indoor and outdoor air dry-bulb temperature or just the outdoor air dry-bulb temperature depending on the type of curve selected. The bi-quadratic curve is recommended if sufficient manufacturer data is available as it provides sensitivity to the indoor air dry-bulb temperature and a more realistic output. The output of this curve is multiplied by the gross rated heating capacity to give the gross total heating capacity at specific temperature operating conditions (i.e., at an indoor air dry-bulb temperature or outdoor air dry-bulb temperature different from the rating point temperature). The curve is normalized to have the value of 1.0 at the rating point.

Field: Speed <x> Heating Capacity Function of Flow Fraction Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve for Speed <x> (ref: Performance Curves) that parameterizes the variation of heating capacity as a function of the ratio of actual air flow rate across the heating coil to the rated air flow rate (i.e., fraction of full load flow). The output of this curve is multiplied by the gross rated heating capacity and the gross heating capacity modifier curve (function of temperature) to give the gross heating capacity at the specific temperature and air flow conditions at which the coil is operating. The curve is normalized to have the value of 1.0 when the actual air flow rate equals the rated air flow rate.

Field: Speed <x> Energy Input Ratio Function of Temperature Curve Name[LINK]

This alpha field defines the name of a bi-quadratic, quadratic or cubic performance curve for Speed <x> (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the both the indoor and outdoor air dry-bulb temperature or just the outdoor air dry-bulb temperature depending on the type of curve selected. The bi-quadratic curve is recommended if sufficient manufacturer data is available as it provides sensitivity to the indoor air dry-bulb temperature and a more realistic output. The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR (inverse of rated COP) to give the EIR at specific temperature operating conditions (i.e., at an indoor air dry-bulb temperature or outdoor air dry-bulb temperature different from the rating point temperature). The curve is normalized to have the value of 1.0 at the rating point.

Field: Speed <x> Energy Input Ratio Function of Flow Fraction Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve for Speed <x> (ref: Performance Curves) that parameterizes the variation of the energy input ratio (EIR) as a function of the ratio of actual air flow rate across the heating coil to the rated air flow rate (i.e., fraction of full load flow). The EIR is the inverse of the COP. The output of this curve is multiplied by the rated EIR and the EIR modifier curve (function of temperature) to give the EIR at the specific temperature and air flow conditions at which the coil is operating. This curve is normalized to a value of 1.0 when the actual air flow rate equals the rated air flow rate.

Field: Speed <x>Part Load Fraction Correlation Curve Name[LINK]

This alpha field defines the name of a quadratic or cubic performance curve for Speed <x> (Ref: Performance Curves) that parameterizes the variation of electrical power input to the DX unit as a function of the part load ratio (PLR, sensible cooling load/steady-state sensible cooling capacity). The product of the rated EIR and EIR modifier curves is divided by the output of this curve to give the effective EIR for a given simulation timestep. The part load fraction (PLF) correlation accounts for efficiency losses due to compressor cycling.

The part load fraction correlation should be normalized to a value of 1.0 when the part load ratio equals 1.0 (i.e., no efficiency losses when the compressor(s) run continuously for the simulation timestep). For PLR values between 0 and 1 (0 < = PLR < 1), the following rules apply:

PLF > = 0.7     and     PLF > = PLR

If PLF < 0.7 a warning message is issued, the program resets the PLF value to 0.7, and the simulation proceeds. The runtime fraction of the coil is defined as PLR/PLF. If PLF < PLR, then a warning message is issued and the runtime fraction of the coil is limited to 1.0.

A typical part load fraction correlation for a conventional DX heating coil (Speed <x>) would be:

PLF = 0.85 + 0.15(PLR)

If the user wishes to model no efficiency degradation due to compressor cycling, the part load fraction correlation should be defined as follows:

PLF = 1.0 + 0.0(PLR)

Field: Speed <x> Rated Waste Heat Fraction of Power Input[LINK]

The fraction of heat input to heating that is available as recoverable waste heat at full load and rated conditions for Speed <x> operation.

Field: Speed <x> Waste Heat Function of Temperature Curve Name[LINK]

The name of a bi-quadratic performance curve (ref: Performance Curves) that parameterizes the variation of the waste heat recovery as a function of outdoor dry-bulb temperature and the entering coil dry-bulb temperature for Speed <x>. The output of this curve is multiplied by the rated recoverable waste heat at specific temperature operating conditions (i.e., at temperatures different from the rating point). The curve is normalized to a value of 1.0 at the rating point. When the fuel type is electricity, the field is either left blank or ignored by the program. When the fuel type is not electricity and the parent object AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed does not require waste heat calculations, this field is ignored. If the field is blank, a warning will be issued and simulation continues. When the fuel type is not electricity and the parent object AirLoopHVAC:UnitaryHeatPump:AirToAir:MultiSpeed requires waste heat calculations, if this field is left blank, the program assumes a constant value of 1 to make simulation continue and a warning will be issued.

Field: Zone Name for Evaporator Placement[LINK]

This input field is name of a conditioned or unconditioned zone where the secondary coil (evaporator) of a heat pump is installed. This is an optional input field specified only when user desires to extract heat from the zone via secondary coil. Heat extracted is modeled as internal gain. If the primary DX system is a heat pump, then the zone name should be the same as the zone name specified for placing the secondary cooling DX coil.

Field: Speed <x> Secondary Coil Air Flow Rate[LINK]

This input value is the secondary coil (evaporator) air flow rate when the heat pump is working in heating mode or the secondary coil (condenser) air flow rate when the heat pump is working in cooling mode. This input field is auto-sizable.

Field: Speed <x> Secondary Coil Fan Flow Scaling Factor[LINK]

This input field is scaling factor for autosizing the secondary DX coil fan flow rate. The secondary air flow rate is determined by multiplying the primary DX coil rated air flow rate by the fan flow scaling factor. Default value is 1.25. If the secondary coil fan flow rate is not autosized, then the secondary coil fan flow scaling factor is set to 1.0.

Field: Speed <x> Nominal Sensible Heat Ratio of Secondary Coil[LINK]

This input value is the nominal sensible heat ratio used to split the heat extracted by a secondary DX coil (evaporator) of a heat pump into sensible and latent components. This is an optional input field. If this input field is left blank, then pure sensible internal heat gain is assumed, i.e., sensible heat ratio of 1.0.

Field: Speed <x> Sensible Heat Ratio Modifier Function of Temperature Curve Name[LINK]

This input field is name of sensible heat ratio modifier biquadratic curve. The value of this curve modifies the nominal sensible heat ratio for current time step depending on the secondary zone air node wet-bulb temperature and the heating DX coil entering air dry-bulb temperature. This is an optional input field. If this input field is left blank, then the nominal sensible heat ratio modifier curve value for temperature is set to 1.0.

Field: Speed <x> Sensible Heat Ratio Modifier Function of Flow Fraction Curve Name[LINK]

This input field is name of sensible heat ratio modifier curve as function of secondary air flow fraction. The value of this curve modifies the nominal sensible heat ratio for current time step depending on the secondary coil air flow fraction. This is an optional input field. If this input field is left blank, then the sensible heat ratio modifier curve value for flow fraction is set to 1.0.

Following is an example input for a multi-speed heating DX coil.

COIL:Heating:DX:MultiSpeed,
  Heat Pump DX Heating Coil 1,   !- Name of heat pump heating coil
  FanAndCoilAvailSched,       !- Availability Schedule
  Heating Coil Air Inlet Node,   !- Coil Air Inlet Node
  SuppHeating Coil Air Inlet Node,   !- Coil Air Outlet Node
  -8.0,                                       !- Minimum Outdoor Dry-bulb Temperature for Compressor Operation {C}
  200.0,                                     !- Crankcase Heater Capacity {W}
  10.0,                                       !- Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation {C}
  HPACDefrostCAPFT,               !- Defrost energy input ratio modifier curve (temperature)
  7.22,                                       !- Maximum Outdoor Dry-bulb Temperature for Defrost Operation
  reverse-cycle,                     !- Defrost Strategy
  timed,                                     !- Defrost Control
  0.058333,                               !- Defrost Time Period Fraction
  2000.0,                                   !- Resistive Defrost Heater Capacity {W}
  No,                                           !- Apply Part Load Fraction to Speeds greater than 1
  NaturalGas,                           !- Fuel type
  4,                                             !- Number of speeds
  7500,                                       !- Gross Rated Heating Capacity, Speed 1 {W}
  2.75,                                       !- Gross Rated Heating COP, Speed 1
  0.45,                                       !- Rated Air Flow Rate, Speed 1 {m3/s}
  HPACHeatCapFT Speed 1,     !- Heating Capacity Modifier Curve, Speed 1 (temperature)
  HPACHeatCapFF Speed 1,     !- Heating capacity modifier curve, Speed 1 (flow fraction)
  HPACHeatEIRFT Speed 1,     !- Energy input ratio modifier curve, Speed 1 (temperature)
  HPACHeatEIRFF Speed 1,     !- Energy input ratio modifier curve, Speed 1 (flow fraction)
  HPACHeatPLFFPLR Speed 1, !- Part load fraction correlation, Speed 1 (part load ratio)
  0.2,                                         !- Rated waste heat fraction of power input, Speed 1
  HAPCHeatWHFT Speed 1,       !- Waste heat modifier curve, Speed 1 (temperature)
  17500,                                     !- Gross Rated Heating Capacity, Speed 2 {W}
  2.75,                                       !- Gross Rated Heating COP, Speed 2
  0.85,                                       !- Rated Air Flow Rate, Speed 2 {m3/s}
  HPACHeatCapFT Speed 2,     !- Heating Capacity Modifier Curve, Speed 2 (temperature)
  HPACHeatCapFF Speed 2,     !- Heating capacity modifier curve, Speed 2 (flow fraction)
  HPACHeatEIRFT Speed 2,     !- Energy input ratio modifier curve, Speed 2 (temperature)
  HPACHeatEIRFF Speed 2,     !- Energy input ratio modifier curve, Speed 2 (flow fraction)
  HPACHeatPLFFPLR Speed 2, !- Part load fraction correlation, Speed 2 (part load ratio)
  0.2,                                         !- Rated waste heat fraction of power input, Speed 2
  HAPCHeatWHFT Speed 2,       !- Waste heat modifier curve, Speed 2 (temperature)
  25500,                                     !- Gross Rated Heating Capacity, Speed 3 {W}
  2.75,                                       !- Gross Rated Heating COP, Speed 3
  1.25,                                       !- Rated Air Flow Rate, Speed 3 {m3/s}
  HPACHeatCapFT Speed 3,     !- Heating Capacity Modifier Curve, Speed 3 (temperature)
  HPACHeatCapFF Speed 3,     !- Heating capacity modifier curve, Speed 3 (flow fraction)
  HPACHeatEIRFT Speed 3,     !- Energy input ratio modifier curve, Speed 3 (temperature)
  HPACHeatEIRFF Speed 3,     !- Energy input ratio modifier curve, Speed 3 (flow fraction)
  HPACHeatPLFFPLR Speed 3, !- Part load fraction correlation, Speed 3 (part load ratio)
  0.2,                                         !- Rated waste heat fraction of power input, Speed 3
  HAPCHeatWHFT Speed 3,       !- Waste heat modifier curve, Speed 3 (temperature)
  35500,                                     !- Gross Rated Heating Capacity, Speed 4 {W}
  2.75,                                       !- Gross Rated Heating COP, Speed 4
  1.75,                                       !- Rated Air Flow Rate, Speed 4 {m3/s}
  HPACHeatCapFT Speed 4,     !- Heating Capacity Modifier Curve, Speed 4 (temperature)
  HPACHeatCapFF Speed 4,     !- Heating capacity modifier curve, Speed 4 (flow fraction)
  HPACHeatEIRFT Speed 4,     !- Energy input ratio modifier curve, Speed 4 (temperature)
  HPACHeatEIRFF Speed 4,     !- Energy input ratio modifier curve, Speed 4 (flow fraction)
  HPACHeatPLFFPLR Speed 4, !- Part load fraction correlation, Speed 4 (part load ratio)
  0.2,                                         !- Rated waste heat fraction of power input, Speed 4
  HAPCHeatWHFT Speed 4;       !- Waste heat modifier curve, Speed 4 (temperature)

Outputs[LINK]

  • HVAC,Average,Heating Coil Total Heating Rate [W]

  • HVAC,Sum,Heating Coil Total Heating Energy [J]

  • HVAC,Average,Heating Coil Electric Power[W]

  • HVAC,Sum,Heating Coil Electric Energy [J]

  • HVAC,Average,Heating Coil Defrost Electric Power[W]

  • HVAC,Sum,Heating Coil Defrost Electric Energy [J]

  • HVAC,Average,Heating Coil Defrost Gas Rate [W]

  • HVAC,Sum,Heating Coil Defrost Gas Energy [J]

  • HVAC,Average,Heating Coil Crankcase Heater Electric Power[W]

  • HVAC,Sum,Heating Coil Crankcase Heater Electric Energy [J]

  • HVAC,Average,Heating Coil Runtime Fraction []

If Fuel Type is not Electricity:

  • HVAC,Average, Heating Coil <Fuel Type> Rate [W]

  • HVAC,Sum, Heating Coil <Fuel Type> Energy [J]

Heating Coil Total Heating Rate [W] [LINK]

This field is the total heating rate output of the DX coil in Watts. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil.

Heating Coil Total Heating Energy [J] [LINK]

This is the total heating output of the DX coil in Joules over the timestep being reported. This is determined by the coil inlet and outlet air conditions and the air mass flow rate through the coil. This output is also added to a meter with Resource Type = EnergyTransfer, End Use Key = HeatingCoil, Group Key = System (ref. Output:Meter objects).

Heating Coil Electric Power [W] [LINK]

This output variable is the input fuel type power for the heating coil in the unit of Watts, averaged during the report period. If Fuel Type is not Electricity, the value is zero.

Cooling Coil Electric Energy [J] [LINK]

This output variable is the input fuel type consumption for the multispeed heating coil in the unit of Joules, summed during the report period. This output is also added to a meter with Resource Type = Electricity, End Use Key = Heating, Group Key = System (ref. Output:Meter objects). If Fuel Type is not Electricity, the value is zero.

Heating Coil Defrost Electric Power [W] [LINK]

This is the electricity consumption rate of the DX coil unit in Watts when the unit is in defrost mode (reverse-cycle or resistive). The variable is available when the defrost mode is resistive or the fuel type is electricity.

Heating Coil Defrost Electric Energy [J] [LINK]

This is the electricity consumption of the DX coil unit in Joules for the timestep being reported. This consumption is applicable when the unit is in defrost mode (reverse-cycle or resistive). The variable is available when the defrost mode is resistive or the fuel type is electricity.

Heating Coil Defrost <Fuel Type> Rate [W] [LINK]

This is the fuel consumption rate of the DX coil unit in Watts when the unit is in defrost mode (reverse-cycle). The variable is available when the defrost mode is reverse-cycle and the fuel type is non-electricity.

Heating Coil Defrost <Fuel Type> Energy [J] [LINK]

This is the fuel consumption of the DX coil unit in Joules for the timestep being reported. This consumption is applicable when the unit is in defrost mode (reverse-cycle). The variable is available when the defrost mode is reverse-cycle and the fuel type is non-electricity.

Heating Coil Crankcase Heater Electric Power [W] [LINK]

This is the average electricity consumption rate of the DX coil compressor s crankcase heater in Watts for the timestep being reported. When a companion cooling coil exits, the crankcase heater power of the companion cool coil is alos reported in this variable.

Heating Coil Crankcase Heater Electric Energy [J] [LINK]

This is the electricity consumption of the DX coil compressor s crankcase heater in Joules for the timestep being reported. This output is also added to a meter with Resource Type = Electricity, End Use Key = Heating, Group Key = System (ref. Output:Meter objects). When a companion cooling coil exits, the crankcase heater power of the companion cool coil is alos reported in this variable.

Heating Coil Runtime Fraction [] [LINK]

This is the runtime fraction of the DX heating coil compressor and outdoor fan(s) for the timestep being reported. When the heating speed is above 1, this output is the run time fraction for the higher speed.

Heating Coil <Fuel Type> Rate [W] [LINK]

This output variable is the input fuel type power for the heating coil in the unit of Watts, averaged during the report period. The electric power is excluded. If Fuel Type is Electricity, this output variable is not reported.

Cooling Coil <Fuel Type> Energy [J] [LINK]

This output variable is the input fuel type consumption for the multispeed heating coil in the unit of Joules, summed during the report period. The electric consumption is excluded. This output is also added to a meter with Resource Type = <Fuel Type>, End Use Key = Heating, Group Key = System (ref. Output:Meter objects). If Fuel Type is Electricity, this output variable is not reported.

Note: The Fuel Type defined in the above two output variables depends on the input in the fuel type filed. In addition to Electricity, Valid fuel types are NaturalGas, Propane, FuelOil#1, FuelOil#2, Coal, Diesel, Gasoline, OtherFuel1 and OtherFuel2.

Coil:Heating:DX:VariableSpeed[LINK]

The Variable-Speed Air-to-Air Heating DX Coil is a collection of performance curves that represent the heating coil at various speed levels. The performance curves should be generated from the heat pump Reference Unit catalog data. This is an equation-fit model that resembles a black box with no usage of heat transfer equations. The number of speed levels can range from 1 to 10. The heating coil has two air side node connections. The user needs to specify a nominal speed level, at which the gross rated capacity and rated volumetric air flow rate are sized. The gross rated capacity and rated volumetric flow rate represent the real situation in the air loop, and are used to determine the flow rates at various speed levels in the parent objects, e.g. AirLoopHVAC:UnitaryHeatPump:AirToAir,