The TH1120, TH1121, TH1123 and TH1124 series thermostats have two unpolarized wires, eaning that either thermostat wires can be connected to either electrical box wires.
The thermostats of the TH1500 series are equipped with four polarized wires. The wires used to power the thermostat are located in the center and are marked “LINE”. The wires used to connect the heater are positioned at the ends and are labeled “LOAD”.
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