What systems is this thermostat compatible with, and what systems will it NOT work with?
This thermostat works with common 24-volt systems such as forced air, hydronic, heat pump, oil, gas, and electric. It will NOT work with millivolt systems such as a gas fireplace, or with 120/240 volt systems such as baseboard electric heat. (Page 4)
From the official Honeywell RET97B5D100 Home Programmable Thermostat manual, page 4
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