Low Voltage Thermostat Terminal Designations R W System Switching No Fan Switching No Automatic Changeover No Dual Transformer Compatible No Power Method Hardwired Voltage 24V AC 750mV Compatible Yes Mounting Horizontal Height 3 1/4 in Width 3 1/16 in Depth 1 1/8 in Color White Control Range 50 Degrees to 90 Degrees F Features Mercury Free For Use With (250-750 Millivolt and 30V AC) Heat Only System Gas Oil