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Old 02-25-16, 12:07 PM   #211
jeff5may
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Whoo! What an added wrench thrown into the works with the DHW option!

OK, so with the previous design considerations, you have a lineset running into your equipment closet that is being used as-is right now. The air handler has its own metering device indoors connected the coil with a check valve. Due to site constraints, it was decided not to mess with existing runs of water or refrigerant lines. All the mods can be done outdoors, where the outdoor unit sits. You also have your DX loop and compressor for the HPWH situated right next to where the HVAC unit is now.

As far as DHW being generated off of the GSHP, the simplest and most reliable method would be a desuperheater HX in between the compressor discharge and the reversing valve. That way, it is always heating, regardless of mode, without extra components. The main issue with this approach is now you have two heating loops that have to run through the water heater. It doesn't matter whether you use a refrigerant-to-water exchanger at the GSHP or at the tank, you would still have to run some sort of piping to the tank.This translates to heat loss of some sort.

Also, the little DX rig seems to be serving you well in its current configuration. The added water heating loop would definitely have an effect on that system, and would vary between heating and cooling modes of the GSHP. Also translates to heat loss somewhere.

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