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 installed a temperature sensor on the water outlet pipe of the heat pump. I used an inexpensive indoor outdoor
thermometer ($15) with an outdoor probe taped to the water out pipe on the heat pump.
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.