Down to the final plumbing of the newly installed radiant floor heat. There are two zones each about 12k btus. The plan is to install a buffer tank and feed the floors from the tank and have the w2w heat exchanger keep the tank warm. This should help prevent short cycling of the heat pump. Starting the circulators for the floors is done with thermo couples embedded in the floors hooked to a thermostat and then wired to a zone controller. The problem I'm having it figuring out how to monitor the tank temperature and have the heat pump come on and warm up the tank. There are some storage tanks that have thermocouple in the them and then a simple thermostat would work. The Rheem marathon tank is the preferred storage tank, but they don't seem to have thermocouples in them. Any recommendations as to how to manage the heat pump or any other feedback would be appreciated. A little extra information, the loop field is 4 350' deep vertical holes creating a close loop. There are 3 water 2 air heat exchanges currently on the loop field. By late February when the loop is least efficient the inlet water temperature is about 55 degrees and the outlet water temperature is about 42 degrees with all heat pumps running the maximum. This installation has been running for 8 years without any trouble. The radiant floor heat is in rooms already heated my the forced hot air and won't be an additional load.
The absolute basic control for a boiler (or w-w heat pump) is an aquastat. The complexity goes up from there though. I would start with something that has outdoor reset on it (Tekmar, HBX, Honeywell, ...)
