The Homemade Heat Pump Manifesto

[BradC]

Originally Posted by randen

Maybe the little 2 ton may have done the job. A little more refrigerant charge and antifreeze might have done it. Oh well. The joys of hacking.

So as you draw heat from the water, you are unable to keep enough heat feeding the refrigerant to prevent the SST from dropping below the freezing point of water. You have a couple of options. Increase your evaporator surface area and/or water flow rate. Change the freezing point of the water. Prevent your SST from dropping that low.

The third is probably your cheapest option. You have several ways of doing this. They will all reduce the system mass flow. You can slow the compressor, increase condensation temperature or look at an evaporator pressure regulator.

If your compressor will sustain it, an EPR will prevent your evaporation temperature falling below that of the freezing point of water. Do that and you prevent ice buildup. The SST at the compressor will continue to drop until the system mass flow equalizes. Same end result as increasing condensation temperature in that you reduce overall COP, but it will absolutely prevent your evaporator icing up under high load conditions.

You only need the EPR set about 1 degree north of freezing. Ice crystals just won't form if your pipes never drop to or below freezing.