GB1017356A - Improvements in or relating to fuel burner control systems - Google Patents

Abstract

1,017,356. Burner control systems. HONEYWELL Inc. June 17, 1964 [June 17, 1963], No. 25132/64. Heading F4T. An electrical control apparatus for a fuel burner has a bridge circuit comprising resistors 21, 23 the primary 22 of an ignition transformer, and a fuel valve 11 closed when de-energized. On starting the flame detector switch 14 is closed and current flows from the supply 30 through switch 14, the primary winding 22 of the ignition transformer, the closed switch 19 of the safety cut-out, the zone thermostat 10 to the other supply line 31 to cause sparking at the ignition transformer and consequent lighting of the burner. A circuit is also established from 30 through the flame detector switch 14 through the heater 18 of the safety cut-out, leads 35, 34, through the fuel-valve 11, switch 19, thermostat 10 to the supply line 31, thus opening the fuel valve 11 to allow fuel to reach the burner. If the burner ignites the flame detector switch 14 opens and resistor 21 is brought into circuit to reduce current through the ignition transformer to a value which does not allow sparking. Also, the terminals 26, 27 reach similar potentials and current no longer flows through the heater 18, the reduced current necessary to hold the fuel valve 11 open flows to the terminal 25 through the resistor 23 from the line 30. Should ignition not take place, the switch 14 will remain closed and the heater 18 will remain in circuit thereby heating the bimetal 17 in the out-out 16, to open the contact 19 and cut off the fuel valve and ignition transformer from the supply. Under these conditions contact 20 is made establishing a circuit through the limiting resistor 40 and the thermostat 10 to the supply to maintain the cut-out condition until the thermostat switch 10 is manually open long enough for the bi-metal 17 to cool.