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Modeling heated floor with hot water from condenser side of water cooled VRF

asked 2019-05-14 16:30:08 -0500

Hi,

A similar question was asked previously but the answer is not 100% clear to me and also the setting of my model is slightly different. My question below:

I am trying to model a radiant heated floor system in EnergyPlus that gets hot water from a plate heat-exchanger that in turn gets its hot water on the supply side from the condenser side of a water-cooled VRF system. The heated floors are not being used to meet the heating loads of the space but are only being provided for occupant comfort as this is being designed for a spa area. Based on the responses to this, this and this, the condenser side of the water-cooled VRF system should be modeled as a plant loop which makes sense. However, I am not sure about including the radiant heated floor to this plant loop as "ZoneHVAC:LowTemperatureRadiant:VariableFlow" would need to be on the plant supply-side but this component cannot be included in the plant equipment list. I would really appreciate it if someone can suggest a work-around to model this scenario?

Thanks!

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answered 2019-05-14 23:08:14 -0500

Hi, the "ZoneHVAC:LowTemperatureRadiant:VariableFlow" can only be on a ZoneEquipmentList so it will need to be controlled to some degree based on loads. How is the real system controlled?

This object will also need to be on a branch, and this brand put on a plant loop. If the radiant floors are served by the condenser water only, then you can try putting the branch on that loop (along with the cooling tower if there is one). This is essentially a way for the VRF to reject heat back into the zone instead of outdoors. I've never tried this so lets us know how it works out.

As for controls, as I mentioned you'll need to control it for loads in some way. Maybe you could try limiting its capacity to a small value and have the main heating system take up the rest of the load?

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Thanks for looking into it @Matt Doiron , my confusion is about setting up the condenser side loop. According to the previous questions, my understanding is that it needs to be set as a plant loop in EnergyPlus. Based on the actual system set up, the radiant panels would need to be on the supply side of this loop but since this cannot be done in E+, I am wondering if there is an alternative way to set up this loop. The radiant panels themselves are being controlled to maintain a constant surface temperature of 76F.

rsunnam gravatar imagersunnam ( 2019-05-15 12:00:41 -0500 )edit

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Asked: 2019-05-14 16:30:08 -0500

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Last updated: May 14