Patent ID: 8899971

Claim:
A dual fuel vent free gas heater comprising: a gas burner adapted to receive one of a first type of gas or of a second type of gas, a first pilot burner located adjacent the gas burner and intended to receive the first type of gas, a second pilot burner located adjacent the gas burner intended to receive the second type of gas, a normally closed control valve comprising an actuator and adapted to open upon a predetermined electrical voltage being applied to the actuator, the control valve situated to permit either the first type of gas or the second type of gas to flow through the control valve toward the gas burner when the control valve is in the open position, a first temperature sensor located adjacent the first pilot burner, a second temperature sensor located adjacent the second pilot burner, and a normally closed thermal switch coupled to the first temperature sensor and not to the second temperature sensor and located in an electrical flow path between a voltage source and the control valve actuator, the thermal switch configured to open when the temperature detected by the first temperature sensor exceeds a predetermined temperature indicative that the second type of gas is being delivered to the first pilot burner.