GB1503307A - Gas burner controls - Google Patents

Abstract

1503307 Gas burner control system UNITED GAS INDUSTRIES Ltd 4 Nov 1975 [5 Nov 1974] 47782/74 Heading F4T A gas burner control system comprises a manually-operable multi-position switch which in a first position connects an electricaly operated pilot valve 12 in parallel with a spark generator 20 to allow them to be operated together by an iginition switch 21, and in a second position connects a circuit to open a main gas valve 11, the system also comprising a switching device (e.g. thyristor 24) actuated by a flame sensing device 22 and connected in series with the switch. In both the first and second positions, switch S1 is closed, supplying power to transformer 13, to supply the valve and ignition control circuits, and also to clock motor 14 and, via speed reducing circuit 17, to fans 15 and 16. When switch S2 is in the first position (as shown) and the ignition switch 21 is pressed the pilot valve 12 is opened and the spark generator 20 is operated; if a flame is sensed the thyristor 24 conducts so that when the switch 21 is released the pilot valve remains open but a reverse bias is applied to a diode in the spark generator which becomes inoperative; or there may be a further switch or a further position of the multi-poisition switch in which the spark generator is non-operative. If no flame is sensed then the pilot valve will close when the switch 21 is released, and this will be indicated by the extinction of neon bulb 25. When the switch 52 is in a second position, main valve 11 is connected through a series of devices C (such as switches controlled by the clock motor 14 or by thermostats) so that if they are all in compliance (and the thyristor 24 is conducting) the main valve is opened. There may be several operating positions of the multiposition switch, correponding to different conditions of the devices C; there is also an off position in which the switch S1 is open.