Fix crankcase energy for Coil:Cooling:DX when part of air-to-air heat pump is not ignored#11452
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joseph-robertson wants to merge 11 commits intodevelopfrom
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Fix crankcase energy for Coil:Cooling:DX when part of air-to-air heat pump is not ignored#11452joseph-robertson wants to merge 11 commits intodevelopfrom
joseph-robertson wants to merge 11 commits intodevelopfrom
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joseph-robertson
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Mar 6, 2026
| \(\dot{Q}_{cap,crankcase}\) is the crankcase heater capacity (W). | ||
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| If this cooling coil is used as part of an air-to-air heat pump (Ref. AirLoopHVAC:UnitaryHeat-Pump:AirToAir), the crankcase heater defined for this DX cooling coil is disregarded and the associated output variable is omitted. Instead, the crankcase heater defined for the DX heating coil (Coil:Heating:DX:SingleSpeed) is enabled during the time that the compressor is not running for either heating or cooling. In this instance, RTF in the above equations would be the runtime fraction of the heat pump's heating coil or cooling coil, whichever is greater. | ||
| If this cooling coil is used as part of an air-to-air heat pump (e.g., AirLoopHVAC:UnitaryHeatPump:AirToAir, AirLoopHVAC:UnitarySystem, or ZoneHVAC:PackagedTerminalHeatPump), the crankcase heater defined for this DX cooling coil is disregarded and the associated output variable is omitted. Instead, the crankcase heater defined for the DX heating coil (e.g., Coil:Heating:DX:SingleSpeed) is enabled during the time that the compressor is not running for either heating or cooling. In this instance, RTF in the above equations would be the runtime fraction of the heat pump's heating coil or cooling coil, whichever is greater. |
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Single-Speed Electric DX Air Cooling Coil
| The main reason using the above approach is that outlet conditions are calculated in the same way in low and high speed operation. | ||
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| The crankcase heater defined for this DX cooling coil is enabled during the time that the compressor is not running for either heating or cooling. The crankcase heater power use from either heating or cooling is reported in the heating coil (Coil:Heating:DX:MultiSpeed). | ||
| The crankcase heater defined for this DX cooling coil is enabled during the time that the compressor is not running for either heating or cooling. The crankcase heater power use from either heating or cooling is reported in the heating coil (e.g., Coil:Heating:DX:MultiSpeed). |
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Multi-Speed Electric DX Air Cooling Coil
| \({Q_{cap,crankcase}}\) is the crankcase heater capacity (W). | ||
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| If this heating coil is used as part of an air-to-air heat pump (Ref. AirLoopHVAC:UnitaryHeat-Pump:AirToAir), 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). In this instance, RTF in the above equations would be the runtime fraction of the heat pump's heating coil or cooling coil, whichever is greater. | ||
| If this heating coil is used as part of an air-to-air heat pump (e.g., AirLoopHVAC:UnitaryHeatPump:AirToAir, AirLoopHVAC:UnitarySystem, 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). In this instance, RTF in the above equations would be the runtime fraction of the heat pump's heating coil or cooling coil, whichever is greater. |
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Single-Speed Electric Heat Pump DX Air Heating Coil
| The main reason for using the above approach is that outlet air conditions are calculated in the same way for all operating speeds. | ||
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| 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. The crankcase heater power use from either heating or cooling is reported in the heating coil. | ||
| 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. The crankcase heater power use from either heating or cooling is reported in the heating coil (e.g., Coil:Heating:DX:MultiSpeed). |
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Multi-Speed Electric Heat Pump DX Air Heating Coil
| \paragraph{Field: Crankcase Heater Capacity} | ||
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| 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. | ||
| 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 (e.g., AirLoopHVAC:UnitarySystem or ZoneHVAC:PackagedTerminalHeatPump), the crankcase heater defined for this DX cooling coil is ignored and the crankcase heater power defined for the DX heating coil (e.g., 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. |
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Coil:Cooling:DX:CurveFit:Performance
| \paragraph{Field: Crankcase Heater Capacity}\label{field-crankcase-heater-capacity-3} | ||
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| 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. \hyperref[coilheatingdxsinglespeed]{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. | ||
| 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 (e.g., AirLoopHVAC:UnitaryHeatPump:AirToAir, AirLoopHVAC:UnitarySystem, or ZoneHVAC:PackagedTerminalHeatPump), the crankcase heater defined for this DX cooling coil is ignored and the crankcase heater power defined for the DX heating coil (e.g., 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. |
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Coil:Cooling:DX:VariableSpeed
| HVAC,Sum,Cooling Coil Source Side Heat Transfer Energy {[}J{]} | ||
| \end{itemize} | ||
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| If not part of a heat pump (if part of a heat pump, crankcase heater is reported only for the heating coil): |
| \paragraph{Field: Crankcase Heater Capacity}\label{field-crankcase-heater-capacity-4} | ||
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| 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. \hyperref[airloophvacunitaryheatpumpairtoair]{AirLoopHVAC:UnitaryHeatPump:AirToAir} or \hyperref[zonehvacpackagedterminalheatpump]{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. | ||
| 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 (e.g., AirLoopHVAC:UnitaryHeatPump:AirToAir, AirLoopHVAC:UnitarySystem, 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. |
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Coil:Heating:DX:SingleSpeed
| \paragraph{Field: Crankcase Heater Capacity}\label{field-crankcase-heater-capacity-5} | ||
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| 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. | ||
| 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 (e.g., AirLoopHVAC:UnitarySystem), 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. |
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Coil:Heating:DX:MultiSpeed
| \paragraph{Field: Crankcase Heater Capacity}\label{field-crankcase-heater-capacity-6} | ||
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| 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. 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. | ||
| 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 (e.g., AirLoopHVAC:UnitaryHeatPump:AirToAir, AirLoopHVAC:UnitarySystem, 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. |
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Coil:Heating:DX:VariableSpeed
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rraustad
reviewed
Mar 13, 2026
| this->m_HeatingCoilType_Num == HVAC::CoilDX_HeatingEmpirical) { | ||
| auto &newCoil = state.dataCoilCoolingDX->coilCoolingDXs[this->m_CoolingCoilIndex]; | ||
| newCoil.performance->ReportCoolingCoilCrankcasePower = false; | ||
| } |
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So what is the benefit of checking for a subset of heating coil types? This is an HVAC::CoilDX_Cooling so isn't it a given to throw the crankcase heater report over to the heating coil regardless of heating coil type? Do those other coil types not have a crankcase heater? I assume that's the reason for this special consideration.
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I think, yes, those other types do not have a crankcase heater. We are assuming this only applies when the cooling coil is part of an air-to-air heat pump. (Plus, the precedent is that this was originally implemented only in DXCoils.cc.)
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OK, but those other 3 coil types are DX and allowing the cooling coil to model the crankcase heater for those other heating coil types will likely show crankcase heater energy when those heating coil types are operating and the cooling coil is not. Maybe that should be a follow up issue, at least to check if crankcase heater energy is calculated correctly.
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In the IDD, I see 12 objects with the Crankcase Heater Capacity field. All of those objects are air-source. So perhaps it makes the most sense to allow/show crankcase heater energy when those (water-source) heating coil types are operating?
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…g:DX in VariableSpeedCoils.
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