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HeatPumpPlantLoopEIRHeating Not Heating

asked 2021-04-27 20:42:32 -0500

mldichter gravatar image

updated 2021-04-28 07:21:16 -0500

I have an HeatPumpPlantLoopEIRHeating that I'm trying to use as a air to water source heat pump to replace a natural gas boiler in a plantloop. The problem is the plantloop flow is almost always zero water flow with thousands or unmet heating hours. It just isn't turning on.

To test, I took the same file, replaced my realistic air to water source heat pump curves with constant 1 curves, which did not work either. I'm using look tables to model a particular piece of equipment, so thought that might cause a problem.

Then I changed the HeatPumpPlantLoopEIRHeating into a Boiler:HotWater, which did work. That leads me to believe I have the plantloop pump setup wrong or something.

Here are the zipped files in a google drive link if anyone is kind enough to help out.

If I can't get the HeatPumpPlantLoopEIRHeating object working, I'll try using EMS to control a District Heating object instead. A bit of a kluge, but it should work.

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@Aaron Boranian Are you familiar with the health of the HeatPumpPlantLoopEIRHeating object? You are my first best hope from answering this question. https://unmethours.com/question/45283...

mldichter gravatar image mldichter  ( 2021-04-27 20:46:21 -0500 )edit

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answered 2021-04-30 14:27:37 -0500

updated 2021-04-30 14:28:32 -0500

HeatPump:PlantLoop:EIR:Heating is a new object and unfortunately autosizing does not work for the Load Side Reference Flow Rate or Reference Capacity fields. Fortunately, you have developed the same model but served by a boiler, so you can simply use the sizing capacity and flow rate from that model and input those hard sizes into your heat pump model.

So change this object to:

HeatPump:PlantLoop:EIR:Heating,
    Heat Pump Boiler,        !- Name
    Boiler Inlet Node,       !- Load Side Inlet Node Name
    Boiler Outlet Node,      !- Load Side Outlet Node Name
    AirSource,               !- Condenser Type
    Heat Pump Boiler Air Inlet Node,  !- Source Side Inlet Node Name
    Heat Pump Boiler Air Outlet Node,  !- Source Side Outlet Node Name
    ,                        !- Companion Heat Pump Name
    0.0255,                !- Load Side Reference Flow Rate {m3/s}
    autosize,                       !- Source Side Reference Flow Rate {m3/s}
    757742,                !- Reference Capacity {W}
    3.122627907,             !- Reference Coefficient of Performance {W/W}
    ,                        !- Sizing Factor
    HPBoilerCapCurveFuncTemp,!- Capacity Modifier Function of Temperature Curve Name
    HPBoilerEIRCurveFuncTemp,!- Electric Input to Output Ratio Modifier Function of Temp
    HPBoilerEIRCurveFuncPLR; !- Electric Input to Output Ratio Modifier Function of PLR

We are working towards fixing this bug so hopefully it will not be an issue by the next release.

Btw, your models are mislabeled:

  • natural gas boiler.idf: actually uses HeatPump:PlantLoop:EIR:Heating with real curves

  • air to water heat pump boiler with real curves.idf: actually uses Boiler:HotWater

  • air to water heat pump boiler with 1 curves: this is labeled correctly

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For other who find this post. Energyplus developers are working on improving this object and may be fully functional in the version of EnergyPlus released in Sept/Oct 2021.

mldichter gravatar image mldichter  ( 2021-05-05 16:57:22 -0500 )edit
0

answered 2021-04-30 16:37:05 -0500

For this project we are modeling a large office with VAV hydronic reheat with heat supplied by a conventional boiler, a condensing boiler, or an air to water heat pump. We intentionally used very low supply water temperature for the heat pump to achieve a high heat pump COP and therefore also a low delta T, based on conversations with Taylor Engineering about some of their recent designs. The conventional boiler uses a supply water temperature setpoint of 160F and delta T (LWT-EWT) of 40F. The condensing boiler uses a supply water temperature setpoint of 140F and delta T (LWT-EWT) of 30F. The heat pump uses a supply water temperature setpoint of 115F and delta T (LWT-EWT) of 13F. We had planned to use autosizing for the hydronic supply loop flow rate to account for the differences in water loop flow rate required. Is there a quick way to get the autosizing to work? Alternatively, we could multiply the water loop flow rate for the conventional boiler by the ratio of the delta T to estimate the new target water loop flow rate.

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@davidvernon this is more of a comment or follow-up question than a new answer. Unfortunately, comments have a character limit that your post exceeds. Would you mind reposting this as multiple comments under Eric's answer above?

Aaron Boranian gravatar image Aaron Boranian  ( 2021-05-02 12:14:23 -0500 )edit

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Asked: 2021-04-27 20:42:32 -0500

Seen: 61 times

Last updated: May 05