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UnitaryHeatPump:AirToAir - Low number of outputs

asked 2021-07-30 03:21:04 -0500

MPK gravatar image

updated 2021-08-16 09:11:25 -0500

While working with the standard EnergyPlus model Small Office, I noticed the lack of outputs of the heat pump model that is used in this building. Only these three:

  • HVAC, Average, Unitary System Fan Part Load Ratio []
  • HVAC, Average, Unitary System Compressor Part Load Ratio []
  • HVAC, Average, Unitary System Dehumidification Induced Heating Demand Rate [W]

I am curious if there is a particular reason for that. I don't see why it doesn't have basic outputs like thermal and electric power.

And related to that, a second question: Is there a straight-forward way to export the thermal and electric power or is the easiest option to replace it with something like the AirToAir:MultiSpeed model, which has more outputs available?

Links:

https://www.energycodes.gov/prototype...

https://bigladdersoftware.com/epx/doc...

https://bigladdersoftware.com/epx/doc...

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I only have experience with AirLoopHVAC:UnitarySystem objects for single-stage ASHP.

https://bigladdersoftware.com/epx/doc...

This object includes the thermal and electric output variables.

Seems weird that UnitaryHeatPump:AirToAir doesn't. Did you check the object description for clues?

sashadf1 gravatar image sashadf1  ( 2021-07-30 13:19:02 -0500 )edit

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answered 2021-08-16 06:31:35 -0500

MPK gravatar image

I found the solution: Since this is a compound model, more output values can be pulled directly from its sub-components:

image description

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answered 2021-07-30 14:51:42 -0500

sashadf1 gravatar image

If you want to model a Multispeed or Variable Speed ASHP, you can configure AirLoopHVAC:UnitarySystem with Coil:Cooling:DX:MultiSpeed/VariableSpeed and Coil:Heating:DX:MultiSpeed/VariableSpeed.

https://bigladdersoftware.com/epx/doc...

"This system is unique in that it can accommodate all fan and coil types whereas other system types are specific to the type of fan and coil available for simulation."

"Links to the fan, cooling coil, heating coil and reheat coil specifications are provided in the unitary system input data syntax."

Select the heating coil object type here: https://bigladdersoftware.com/epx/doc...

select from: - Coil:Heating:DX:MultiSpeed or - Coil:Heating:DX:VariableSpeed depending on your application.

Similarly, select the cooling coil object type here: https://bigladdersoftware.com/epx/doc...

In the Unitary System Outputs, you can see that thermal load variables like Unitary System Total Heating Rate, Unitary System Total Cooling Rate, and Unitary System Electricity Rate are available.

https://bigladdersoftware.com/epx/doc...

If you use multispeed coils, you need to add this object.

https://bigladdersoftware.com/epx/doc...

"correct specification of the heat/cool unitary system requires specification of the following objects in addition to the unitary system object":

Fan (Fan:OnOff or Fan:ConstantVolume)

Cooling coil

Heating coil

Reheat coil

Direct air unit (AirTerminal:SingleDuct:ConstantVolume:NoReheat) for each zone served by the unitary system when used in an air loop.

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Asked: 2021-07-30 03:21:04 -0500

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Last updated: Aug 16