by the question:
.. you ran air-to-refrigerant AND water-to-refrigerant concurrently in parallel?
Yes
Did you notice any "hunting" as has been suggested is the behavior of non-identical evaporators in a previous post?
Previous post mentioned 'hunting' for a system without 2 separate TXV, I had 2 separate TXV
Also, are you saying the air-to-refrigerant side shut down when it frosted up?
Yes, since that evap could boil off less refrigerant, the txv on that evap closed down
Was the water-to-refrigerant being drawn on the whole time?
This was a system I built over 30 years ago, but recall I had a tsat that turned on the water when air tem was 50F or below.
Now, having said that, the system I have now operates with 2 separate compressors, which provides redundancy in case of one system failure.
The compressor failed when I was out of town, and DW had a hard time keeping warm, so figured to have 2 separate systems.
What I have now is I replaced the 4t compressor in my air-air HP with a 2T compressor. COP increased from about 3 to 4.5 or so at 40F.
Built the 5T GSHP described in you epic thread as a stand alone system. Above 40F the 2T air-air operates and never freezes with the oversize evap as the coil temp only goes down to 32.1F. The 2T air-air is able to heat the 5300 sq ft house OK at 40F outside.
At 40F outdoor temp, and outdoor thermostat switches over to the GSHP by way of a few custom relay and FET circuits. The air-air HP blower operates for both systems, but at different speeds.
It is all also intertied with the fireplace, which has water wall pipes and 2 old car air conditioner condensers in the ductwork and a hot water circulating pump. When there is a hot enough fire, the HPs are locked out.
May have time later in the week to copy the control schematic and post in a separate thread.
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