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Tracking HPWH Performance

asked 2020-10-05 11:42:55 -0600

DW gravatar image

updated 2021-10-11 08:53:12 -0600

I am trying to model a Heat Pump Water Heater in OS 2.9.1

I keep seeing high peak electrical use in my model from water heating systems. When I try to track the HPWH performance by exporting the variables for heating rate and electrical energy, I am seeing a COP of only 1. If I use the default settings when I first add a HPWH to the zone, all I see is the gas energy at 80% efficiency. I assume that these are only tracking the tank supplemental heating - not the HPWH DX heating coil. When I track heating coil variables, I do not see the HPWH coil. Is only the tank functioning?

How do I export the HPWH coil electrical inputs and heating rate so I can verify that my COP of 3+ is actually being modeled and figure out what proportion of my heating is coming from the tank heater vs the HP coil?

I used the same method shown here to set up my HPWH:

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answered 2021-10-11 10:17:48 -0600

The documentation appears to be incorrect; the output variables are "Cooling Coil Foo", not "Heating Coil Foo". We've been using "Cooling Coil Water Heating Electricity Energy" in our modeling workflow to successfully get the energy use.

Interestingly, note that the description of the Coil:WaterHeating objects all say:

From the air-side heat transfer perspective, the water-heater receives heating energy from air. Thus it is considered as a cooling coil, and the output variable names are using “Cooling Coil”.

But then the output variables in the documentation don't reflect that statement.

So it looks like the output variables for Coil:WaterHeating:AirToWaterHeatPump:VariableSpeed are correctly labeled as "Cooling Coil" while Coil:WaterHeating:AirToWaterHeatPump:Pumped and Coil:WaterHeating:AirToWaterHeatPump:Wrapped are incorrectly labeled in the documentation.

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answered 2021-10-10 21:54:14 -0600

chriswmackey gravatar image

I have the same question. From this section of the Input/Output reference, it seems that we should be able to request the "Heating Coil Water Heating Electricity Energy" whenever there's a Coil:WaterHeating:AirToWaterHeatPump:Pumped in the model. But it's not available for some reason when the heating coil is a part of the heat pump water heater. I opened an issue on the EnergyPlus GitHub with a sample IDF file and, hopefully, we can get confirmation if this is the expected behavior.

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Asked: 2020-10-05 11:42:55 -0600

Seen: 210 times

Last updated: Oct 11 '21