The heat pump manual has a wiring diagram for different thermostats. I found it odd that wiring for the circulator pump was not mentioned in the manual. The heat pump utilizes a 230 volt relay switch to turn on the heat pump. I connected the circulator to one branch of this relay. I later installed a bypass switch where the circulator could be left on continuously. I also installed a high temperature cutoff switch above the heat pump for safety.

I placed insulation around the temperature probe so room heat won’t effect the temperature reading. I’ve found this is the best indicator of how much more heat I can get from the heat pump. If the outlet water temperature goes below 35F, then continued use of the heat pump could freeze the coil. At these times I would turn off the heat pump and wait for the temperature to go back up to ground temperature. I shouldn’t have to be so cautious about this when I install the higher horsepower, higher flow pump.