Quote:
Originally Posted by randen
I had thought about building a double compressor GSHP but the complexity seamed to make it a lofty dream. I had two compressors in captivity but again the further I had looked into it it got difficult. If I was to build another GSHP I would use a 3 phase compressor and moderate the speed with a VFD. This would provide a nice soft start and you could slow it for a reduced out-put. Even still a plain single phase GSHP is pretty efficient. It starts with no load and I'm not really convinced if slowing the compressor and reducing the heat out-put when a temperature set point is reached would save a noticable amount of energy.
Randen
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There is a real dearth of comps with EVI or liquid injection or VFDs in our market so I was only able to find some sanyo or other Japanese comps but they are also smaller and not so suitable for our heat loads. If you ever looked inside a Mitsi or Daiken, the level of complexity is astounding. I will be putting a VFD on a standard copeland R410A comp. There are some inverter controls available for single phase, IIRC, depending on needed current draw but you have to be very careful with oil return to the comp, slow speeds can be a problem.