Great update, guy!
Looks like your one ton unit may be similar to my 3/4 ton McQuay unit which was also from a boiler/chiller former life.
I was completely unfamilar with these types but found mine has only small differences with the geothermal varients which mcquay also makes.
Mine had a ntc temp sensor in the leaving water line which , in heat mode, sent the unit into compressor shutoff and elec heat when that temp dropped to 55f and kept it there til the loop water temp came back to 65 or so. Apparently the unit software is written to trigger it then.
I managed to hang a potentiometer in parrallel with the ntc sensor to fool it into thinking it was warmer and have my leaving water temps down to about 42f. I did this by decreasing the pot gradually so not to freeze the evsp but now am running into a low temp cutout triggered by another sensor on the evap refrigerant line itself which happens at about the 42f lwt mark.
So i have to measure what suction line temp thats happening at and see if its safe to "fool" that one too!
Did you have those problems with your unit? I understand they are made to operate with about 70f water winter and summer but i'm pretty sure that with mine and with the exception of softwate/firmware, they are the same as the geo units?
There are bunches of the boiler/chiller types available cheap from hospital, hotel, etc remodel jobs.
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