Duel Fuel Thermostats


Feb 21, 2017
I have a Tarm Solo Plus 40 MK II, with an 800 gallon thermal storage tank. For heat this is tied to my Train 5 ton heat pump. I have a heat exchanger in the air handler for the house heat, which is tied into the hot water heater. This is back up / secondary heat to my primary Train Heat Pump. Currently have a plain-Jane Honeywell thermostat, no frills, Wifi enabled.

I would like to put some type of sensor in the thermal storage tank, if the temperature is above 130 degrees, the thermostat calling for heat would run the fan only. If the temperature was below 130 degrees in the thermal storage tank but the outside temps were above 28 degrees the system would run as a heat pump, and if the temps were below 130 in the thermal storage tanks but the outside temps were below 28 degrees the electric heat strips would assist the heat pump.

Any suggestions on why thermostat might meat these requirements?

I've had 4 different HVAC guys give me there opinion. The only common thread was having two separate thermostats and managing them individually.

Bad LP

Minister of Fire
Nov 28, 2014
Northern Maine
Priority switching with an aquastat.