I'm writing to find out if there is a valve available to reverse the direction of water (not refrigerant) flow in a ground-source heat pump. I am the son of the owner, an elderly lady whose late husband thought a ground-source heat pump to be wise. This is a bit involved, I regret the length of this post.
History: The unit in question is an old Climate Master 30,000 BTU which has had off and on trouble for years with cooling mode OK, in heating mode the low-pressure protect switch trips after the compressor has run for 10 to 30 seconds. In my absence, several AC techs have attempted to eliminate the fault, none succeeded. In one case I knew no good end would come when the tech disappeared then returned and asked, "Where's the outside unit?". At least once it was given the usual treatment, clean the evaporator, add some gas and collect $$$ to $$$. I don't think any measured the superheat and subcooling.
I was going to do just this today when the root cause finally dawned on me: The water is supplied by a well and controlled by a solenoid valve. It always flows through the coaxial heat exchanger in the same direction. The refrigerant reverses direction when changing from cool to heat. So the water flow is correct for cooling, the coolest incoming water in contact with liquid refrigerant exiting the coil. However, in heat mode the wrong way flow puts water already cold from supplying the latent heat of evaporation in contact with the cold gas exiting, which depresses the suction pressure.
I momentarily corrected the problem by greatly increasing the water flow but there seems to no part that I can find online, essentially a valve which will do for water what the valve inside the heat pump does for the refrigerant. That kind of valve is not suited for water, also the pressure differential would be inadequate to move the piston.
If anyone knows of an elegant solution to this problem, please share. I'm sure this problem is not unique and there's a better answer than four PVC ball valves.
Thank your for your attention,