Missing EMS Actuator for Unitary Heat Pump air-to-air

asked 2025-10-27 13:04:00 -0500

Hello, I am trying to customize Heat pump operation using EMS codes. I am using one of the .idf files available for residential dwellings sourced from https://www.energycodes.gov/prototype.... AirLoopHVAC:UnitaryHeatPump:AirToAir object is used for modeling the HP with separate objects for heating (Coil:Heating:DX:SingleSpeed) and cooling (Coil:Cooling:DX:SingleSpeed). My EMS codes involve limiting the heat pump heating capacity based on the cooling capacity and this requires the EMS actuator to scale down the auto-sized heating capacity by some factors (heating demand is higher by default due to outdoor climate). Unfortunately, the EDD file contains an actuator for the autosized capacity for the Cooling:DX:SingleSpeed (EnergyManagementSystem:Actuator Available,DX COOLING COIL_UNIT1,Coil:Cooling:DX:SingleSpeed,Autosized Rated Total Cooling Capacity,[W]), but there are no actuators for the Heating:DX:SingleSpeed. The EDD file only mentions following EMS Actuators available for this object:

EnergyManagementSystem:Actuator Available,MAIN DX HEATING COIL_UNIT1,Coil:Heating:DX:SingleSpeed,Frost Heating Capacity Multiplier,[] EnergyManagementSystem:Actuator Available,MAIN DX HEATING COIL_UNIT1,Coil:Heating:DX:SingleSpeed,Frost Heating Input Power Multiplier,[]

Does anybody know why this is happening? TIA!

answered 2025-10-27 16:00:12 -0500

shorowit

12830 ●227 ●9 https://www.nrel.gov/b...

EMS is used to change building values during the simulation (e.g., look at a value calculated during one timestep and change some other property during that same timestep), but it sounds like you simply want to make an adjustment to the autosized equipment capacities?

If so, one option is to change the Fraction of Autosized Cooling Design Capacity and Fraction of Autosized Heating Design Capacity fields in the Sizing:System object.

You may also be interested in a new feature HP sizing feature developed by @rraustad coming in EnergyPlus v25.2 (due out by the end of the year) that adds a new Maximum Heating Capacity To Cooling Capacity Sizing Ratio field to the Sizing:System object.

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Thanks for the workaround. But I am more interested in why the EMS actuator is not available for the Gross Capacity field for the Heating:DX:SingleSpeed object. Is it simply not available or I am doing something wrong therefore it is not showing up?

Abir Ahsan ( 2025-10-27 16:31:36 -0500 )edit

It is simply not available. You could request the feature at https://github.com/NREL/EnergyPlus/is... if you want, I don't see any existing request for it.