GB1064945A - Improvements in fuel burner control systems - Google Patents

Abstract

1,064,945. Controlling burners. HONEYWELL Inc. Sept. 18, 1963 [Sept. 20, 1962], No. 36801/63. Heading F4T. [Also in Division G1] A control apparatus for a burner installation having multiple main fuel burners 11, 12, 13, 14 comprises a separate flame detector 30, 31, 32, 33 for each burner adapted to control a main valve 15 supplying fuel to all the main burners and a neon indicator 42, 43, 44, 45 associated with each flame detector and adapted to be energized when its flame detector indicates a failure of its flame, the the neon indicators being mutually interconnected so that while any one is energized the others are disabled, i.e. they cannot be energized. The energized neon indicator indicates which burner or its flame detector has caused the main valve to close. The flame detectors may be photocells or flame rods 25, 26, 27, 28. The neon indicators 42 . . . 45 are energized by a D.C. voltage provided at terminals 40, 41 by a secondary winding 38 of a transformer 37 in conjunction with a doubler rectification system, and the circuit to each neon indicator includes a switch 55 or 58 or 61 or 65 controlled by a relay 50 or 51 or 52 or 53 energized by its flame detector 30 or 31 or 32 or 33. If any flame relay, say 50, drops out switch 55 closes and neon indicator 42 lights up and the current therethrough causes most of the D.C. voltage at terminals 40, 41 to be dropped across a resistor 104 and consequently the voltage across the other neon indicators is insufficient to fire them when their switches 58, 61, 65 subsequently close. The apparatus also includes two cycling relays 88, 89 the latter operating a switch 97 connecting all the flame detectors to earth 34 and thus simulating cyclically no flame conditions at the burners whilst the burners are burning. The cycling stops in the event of flame failure at any burner or a fault producing a wrong response by a flame detector. Upon initial application of voltage to line conductors 35, 36 cycling relay 89 is energized through switches 54, 57; 60, 64 of the flame relays to close switch 97 to place the flame detectors 30 . . . S3 in a condition to detect the burner flames. This is a standby position. On a demand for heat, a control 68 closes and energizes a relay 75 which energizes a pilot valve 29 supplying pilot burners 16. . . 19 and an ignition transformer 24. The detectors detect the pilot flames and energize the flame relays 50 . . . 53 and consequently cycling relay 88 is energized through switches 56, 59, 63, 66 of the flame relays and opens switch 91 in a holding circuit for the other cycling relay 89 which is thus de-energized with consequent opening of the switch 97 and closure of a switch 95 in a holding circuit for the relay 88. The flame relays 50 . . . 53 then drop out due to the simulated no-flame condition but the relay 88 remains energized through its holding circuit. However, when all the flame relays 50 . . . 53 have dropped out the relay 89 is energized and breaks the holding circuit for the relay 88 at switch 95. The cycle is then repeated. If no flame exists at any burner the corresponding flame relay is not energized and consequently one of the switches 56, 59, 63, 64 fails to close. The relay 88 is not therefore energized and the cycling of the relays stops. The continued cycling of the relays 88, 89 is effective to energize a further relay 90 from a capacitor charge and discharge circuit comprising a half-wave rectifier and a capacitor 140 which is charged and discharged alternately by switches 92, 94 of the cycling relay 88, the discharge charging a further capacitor 141 across the relay 90. Energization of the relay 90 is effective to energize a master flame relay 80 which controls the ignition transformer 24, the pilot valve 29, a bi-metal safety cutout 72 heated by a resistance 71 and a further relay 46 which controls the main valve 15 and transfers the control of the pilot valve 29 to the master flame relay 80. If therefore the cycling of the relays 88, 89 stops due to flame failure or a fault in the flame detector the master flame relay 90 is de-energized and the pilot and main valves are closed.