Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
TL;DR: You shouldn't assign the wrapped DX coil of a HPWH to a branch -- you should instead assign the compound HPWH system object that contains the wrapped DX coil to a branch.
The Coil:WaterHeating:AirToWaterHeatPump:Wrapped object is meant to be one component of a heat pump water heater (HPWH), specifically the DX air-to-water coil that heats water on the condenser while cooling air on the evaporator. There are multiple other objects that are also needed:
WaterHeater:HeatPump:WrappedCondenser: compound object that represents the entire HPWH systemWaterHeater:Mixed or WaterHeater:Stratified: storage tankFan:OnOff, etc.: fan to blow air across the evaporatorSo, when defining where the wrapped DX coil is located, it is assigned as an internal component of the WaterHeater:HeatPump:WrappedCondenser object, which is what is actually assigned to a branch. This is why the only nodes to define for the wrapped DX coil object are the evaporator air inlet & outlet nodes.
You can see an example of this wrapped HPWH compound object and it's internal components in the SingleFamilyHouse_HP_Slab.idf example file that comes with your EnergyPlus installation.
| | 2 | No.2 Revision |
TL;DR: You shouldn't assign the wrapped DX coil of a HPWH to a branch -- you should instead assign the compound HPWH system object that contains the wrapped DX coil to a branch.
The Coil:WaterHeating:AirToWaterHeatPump:Wrapped object is meant to be one component of a heat pump water heater (HPWH), specifically the DX air-to-water coil that heats water on the condenser while cooling air on the evaporator. There are multiple other objects that are also needed:
WaterHeater:HeatPump:WrappedCondenser: compound object that represents the entire HPWH systemWaterHeater:MixedWaterHeater:Stratified: storage tankFan:OnOff, etc.: fan to blow air across the evaporatorSo, when defining where the wrapped DX coil is located, it is assigned as an internal component of the WaterHeater:HeatPump:WrappedCondenser object, which is what is actually assigned to a branch. This is why the only nodes to define for the wrapped DX coil object are the evaporator air inlet & outlet nodes.
You can see an example of this wrapped HPWH compound object and it's internal components in the SingleFamilyHouse_HP_Slab.idf example file that comes with your EnergyPlus installation.
