Control system for gas burning apparatus

摘要

A control system for a gas burning apparatus having a pilot burner which is initially ignited by electric ignition means upon a need for operation of the apparatus and which in turn ignites a main burner after a flame is established at the pilot burner, the gas flow to the pilot burner being through a first valve and the gas flow to the main burner being through a second valve receiving its gas supply from the first valve. The control system includes flame relay switching means responsive to the presence and absence of flame at the pilot burner and actuated when the control system is initially energized to open the first valve while preventing opening of the second valve and to energize a holding circuit which maintains the first valve open and enables opening of the second valve when the flame relay switching means is subsequently deactuated in response to the establishment of a pilot flame. The control system further includes time delay switching means responsive to the continued absence of pilot flame for a predetermined time interval during a start-up operation or following a loss of pilot flame after start-up to cause closing of the valves. The control system incorporates a fail-safe circuit arrangement so that the gas burning apparatus will be placed in a fail-safe condition in response to the failure of any key component of the control system or the failure of the electric power supply.