GB1427635A - Burner control apparatus - Google Patents

Abstract

1427635 Combustion control apparatus ELECTRONICS CORP OF AMERICA 1 Nov 1974 [9 Nov 1973] 47425/74 Heading F4T Control apparatus for a burner having flame sensing means, such as a U.V. detector, 68 and means, such as a thermostat, 24 to apply a request signal for burner operation to the control apparatus, comprises a manually resettable burner lock-out switch 108-1 which is normally closed and an actuator 108 therefor, a flame indication circuit 100, responsive to the detector 68 or produce a signal indicative of the flame condition in the combustion chamber and two circuits in parallel for controlling the actuator 108, the first circuit comprising a latchable switch constituted by a SCR 114 with a transistor switch 116 in series and the second circuit comprising two transistor switches 118, 120 in series. The two circuits are coupled by a trigger circuit constituted by a resistor 126 and a feedback circuit consisted by a resistor 122 such that when the switch 118 closes the switch 114 is triggered closed and when said switch 114 closes said switch 118 is triggered to revert back to its normally open state. A control actuator 110 for the contacts 110-1 and a flame-sensing actuator 112 for the contacts 112-1 and 112-2 and controlled by the circuit 100 are also included in the two circuits. Contacts 108-2, 110-1 and 112-1 are normally open and contacts 108-1 and 112-2 are normally closed. A request for operation is signalled by the thermostat 24 and a blower 28 is operated and a switch 36, responsive to air flow, closes. After a delay switch 106 has closed, the actuator 110 closes switch 110-1 to initiate ignition of the pilot fuel. Also the switch 118 is closed and consequentally as explained above, switch 114 is triggered on and latches on, and switch 118 reverts back to its previous state. If a flame is established before the actuator 108 operates switch 108-1 (the delay is caused by a heating circuit which takes 5-30 seconds before reaching a desired operating temperature) actuator 112 switches over contacts 112-1 and 112-2 to ignite the main fuel. At the same time a signal is applied to switch 116 to break the circuit to the actuator 108. Should the fuel fail to ignite, or subsequently goes out, the actuator 108 operates to lock-out the burner control devices and energize an alarm 26. If a flame is present initially switch 120 will be on. This will prevent switch 114 from being switched on and will enable actuator 108 to be energized through switch 118, to operate the lock-out arrangements.