Abstract: An automatic fuel ignition system has a spark generator for igniting a pilot burner and two separate pilot flame sensing systems to provide a redundant safety check of flame ignition before the main burner gas is turned on. One sensing system includes a rectifying electrode in the pilot burner flame and a electronic flame sensing circuit responsive to the flame conductivity while the second sensing system includes a flame switch located in the flame and responsive to the heat of the flame.

Abstract: In a thermostat control system including means for modulating the fuel flow to a burner above a predetermined level necessary for combustion, the improvement comprising an ignition circuit adapted to provide a larger fuel flow initially to the burner including in one embodiment a bimetallic switch connected for thermal communication with the burner cavity for completing the circuit of the above thermostat control system after the burner cavity reaches a predetermined temperature.In a second embodiment, a time delay circuit is provided instead of the bimetallic switch, such time delay circuit providing a larger fuel flow to the burner during the ignition time interval.