Low Voltage Thermostat Terminal Designations R W System Switching No Fan Switching No Automatic Changeover No Dual Transformer Compatible No Power Method Hardwired Voltage 20 to 30V AC 750mV Compatible No Mounting Vertical Height 4 3/4 in Width 2 7/8 in Depth 1 3/8 in Color White Control Range 50 Degrees to 90 Degrees F Features Mercury Free Integrated thermometer For Use With Gas Oil Forced Warm Air Hot Water Steam or Gravity Includes Hardware