Patent ID: 6908300

Claim:
A control circuit for shutting off a fuel-fired appliance burner having a thermocouple voltage that enables a gas valve solenoid to supply fuel to the appliance burner, the control circuit comprising: a power source for powering the control circuit; a fuse that is connected in series with the gas valve solenoid of the appliance in a manner such that the thermocouple voltage to the gas valve solenoid is interrupted when the fuse opens to cause the flow of gas to the burner to be shut off; a switching means for switching power from the power source to the fuse to cause the fuse to open; a sensor capable of detecting the presence of flammable vapor, where the sensor responsively changes in resistance as the concentration of flammable vapor changes; and a voltage divider circuit comprising a resistor and the sensor, the voltage divider circuit having a voltage potential between the resistor and the sensor that controls activation of the switching means, wherein the detection of flammable vapors by the sensor causes the voltage potential of the voltage divider to activate the switching means and open the fuse to cause the flow of gas to the burner to be shut-off.