Low Voltage Thermostat Terminal Designations B G O R RC W Y System Switching Heat-Cool-Off Fan Switching Auto-On Dual Transformer Compatible Yes 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 1/3 in Color White Control Range 50 Degrees to 90 Degrees F Features Mercury Free For Use With Gas Oil Forced Warm Air Hot Water Steam or Gravity Includes Dealer Logo Pocket