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water-to-air DOAS w/ water-to-water radiant?

asked 2016-04-04 16:49:31 -0600

umop-3pisdn gravatar image

updated 2016-04-05 09:48:40 -0600

I am trying to model a building that is served by radiant panels and a DOAS (in OpenStudio 1.11, with E+ 8.4 in the back). The CHW/HW for the radiant panels is provided by a water-to-water heat pump. The DOAS has a water-to-air heat pump (with a HW reheat coil tied to the radiant HW loop). Both heat pumps are tied to a condenser loop that rejects/extracts heats from a nearby river via a heat exchanger (the daily/monthly/weekly avg temps of which are known). Both heat pumps also have a waterside economizer, so that the condenser water can be used when there's a call for cooling and the loop is cold enough.

I am a little lost as to how to set up the water-to-air heat pump as a component within the air loop; the only option i can see is to put a water-to-air heat pump within a zone as terminal equipment... is there any way of implementing such a device on the air loop level?

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Please tag this question and remember to always tag your questions with a specific software and/or engine if you have one in mind. Here I'm assuming you're using EnergyPlus but it's not crystal clear.

Julien Marrec gravatar imageJulien Marrec ( 2016-04-05 02:49:22 -0600 )edit

done! using OpenStudio 1.11 running EnergyPlus 8.4.

umop-3pisdn gravatar imageumop-3pisdn ( 2016-04-05 10:11:02 -0600 )edit

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answered 2016-04-05 02:48:06 -0600

updated 2016-04-05 02:50:18 -0600

For the water-to-air heat pump, you need to use coils of the type WaterToAirHeatPump.

Depending on your project, you need to use:

These coils can live in a ZoneHVAC:WaterToAirHeatPump or in a AirLoopHVAC:UnitarySystem. The documentation is pretty obscure about this fact, but this question - Using Coil:Cooling:WaterToAirHeatPump:EquationFit - confirms that fact.

So in your case, you need to use the AirLoopHVAC:UnitarySystem, and place that on your DOAS AirLoopHVAC loop. The UnitarySystem is a bit weird in the sense that you can choose or not to package the fan in there or not...

In OpenStudio, you might get into a problem if you put everything (cooling coil, heating coil, fan) in the same unitary system because you won't be able, without an E+ measure, to add the required setpoint manager on the outlet of each coil. See these two questions for more information:

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Thank you for the reply Julien! This is very helpful. I have created the water-to-air heat pump and linked it to a plant loop that features a OS:PlantComponent:TemperatureSource and OS:HeatExchanger:FluidToFluid on the condenser loop to represent the river water source.

Two follow up questions:

1) is it possible to change the water-to-air HP's reheat coil from electric to hot water?

2) when i place an OS:HeatPump:WaterToWater:EquationFit component to provide the hot and chilled water for the radiant panels, i am unable to link them to the same condenser plant loop. is this possible in OS?

umop-3pisdn gravatar imageumop-3pisdn ( 2016-04-05 10:20:57 -0600 )edit

You need to create a unitary hvac from scratch using the API.

Julien Marrec gravatar imageJulien Marrec ( 2016-04-05 10:55:05 -0600 )edit

Julien, have you been able to do this?

jmoody gravatar imagejmoody ( 2018-02-09 14:09:50 -0600 )edit
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answered 2016-10-24 12:57:42 -0600

DW gravatar image

After attempting to do this several times in OpenStudio, I have found it easier to set up this type of HVAC in EnergyPlus. As Julien Marrec noted, I created a unitary system with the object: "AirLoopHVAC:UnitaryHeatPump:WaterToAir" to serve several zones with the same coils.

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Asked: 2016-04-04 16:49:31 -0600

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Last updated: Oct 24 '16