My Honeywell thermostat just broke. I want to get a new one and install it myself but I don't know whether to get a 24V model or a 120-240v model. There is no indication of this on the one I have. How do I tell?
How thick are the wires connected to the thermostat?
24V wiring will be small gauge, usually 22-18 AWG. It's commonly used for forced air, hot water, and similar systems.
120/240V thermostats will typically use 14-10 AWG, and are commonly used for electric baseboard heaters.