Geno, I have had one of GE's geospring water heaters long enough
to have the freon leak out twice. A friend of mine put line taps
on the unit and we were able to recharge the system. The
following is my attempt to help some people on a forum that I stumbled
"Bringing up the temperatures on the Geospring to figure superheat is kind of tricky. It is easier to look at the evaporator to "see" what's going on. If the lower tubes are becoming frosted and the higher tubes are dry, your unit is low on freon. If the tubes are sweating, but not all the way up, you are probably leaking some freon and the unit could use a charge. My Geospring seems to like about 40 psi on the low side after the compressor has been running for thirty minutes. At that point, all the tubes on both sides of the evaporator are sweating and the output air is very cold. Check the evaporator now and then to look for these tell tale signs."
I forgot to mention that cleaning the evaporator is imperative to get that "very cold" air. There are several brands of foaming cleaners that combined with soft brushing will do a good job. Several years ago I took a look at my furnace and was surprised to see all the rust accumulating on the sides of the evaporator. Same thing with this heat pump. My approach to arresting this slow deterioration of the metals is to paint some chain saw bar oil on the coil ends of the evaporator. Chain oil has anti-rust properties along with anti-sling to help keep the oil from just flying off, which makes it stick when painted on with a brush.
It has been my experience that any AC system will leak freon over time. Some leak stoppers will help. The EPA is now changing it's mind again about what to use for freon. I believe propane/butane mixtures are the answer. Farmers have known this for a long time. I have not read about any tractor fires attributed to the AC system.
By the way, I am an old man who just turned 70, who likes to trouble shoot.
West Central Minnesota