Patent GB-778205-A (GB)
Title: Control system for fuel burners
Inventor: THOMPSON THOMAS RICHARD
IPC: F23N5/20
Filed: 1954-01-18
Abstract: 778,205. Controlling burners. CLYDE FUEL SYSTEMS, Ltd., and SUNVIC CONTROLS, Ltd. April 18, 1955 [Jan. 18, 1954], No. 1372/54. Class 75(1)  An electrical control system for a fuel burner comprises a time delay switch 1, Fig. 1, incorporating lock-out mechanism adapted for manual re-setting, at least one motor 5 adapted to operate at least one fuel burner, a fluestat 7 having a hot and cold setting corresponding to the conditions in the burner flue, a master relay 3 controlled by the fluestat to provide in the cold setting thereof a path for current to a fuel igniter and for energizing the motor by way of the time delay switch and to provide in the hot setting of the fluestat a path for current to the motor by-passing the time delay switch which is then de-energized and means for delaying operation of the motor until a predetermined interval of time after the igniter is energized. The operation of the motor is delayed by a hot wire vacuum switch 4 having an operating winding 11. The time delay switch 1 incorporates a heating winding 9 and a bi-metallic element 14 which in cold condition causes a contact arm 15 attached thereto to engage a fixed contact arm 16. The master relay 3 comprises a winding 12 and two movable arms 17, 21 each coacting with two contacts 10, 18 and 20, 24. The fluestat 7 comprises a movable arm 23 coacting with a hot contact 22 and a cold contact 26. The igniter is energized by a transformer 8. The burner is put into operation by closing a master switch (not shown) and current passes through a pressure or temperature sensitive switch 6 to the closed time delay switch 1. From arm 16 thereof current passes to the ignition transformer 8 via contact 20 and arm 21 of the master relay 3, and to heating winding 9 of the time delay switch 1 and then to operating winding 11 of the motor delaying switch 4 through contact 10 and arm 17 of the master relay 3. The igniter is immediately energized and after a time the motor delaying switch 4 becomes conducting and energizes the motor to supply the burner. The temperature in the burner flue then rises and the movable arm 23 moves from the cold contact 26 to the hot contact 22 to energize the winding 12 of the master relay, 3. The movable arms 17, 21 then change their contacts so that the heater winding 9 and the ignition transformer 8 are deenergized but the operating winding 11 of the motor delaying switch 4 is maintained energized through the contact 18 and a resistance 19 (preferably of the same value as the heating resistance 9) connected to a terminal 25 of the motor. This is the normal operating condition. If the burner fails to ignite the fluestat arm 23 remains in contact with the cold contact 26 and consequently the master relay does not break the supply circuit to the heating winding 9 of the time delay switch 1. Eventually therefore the bimetallic element 14 moves the arm 15 away from the arm 16 to de-energize the igniter and the motor and to energize a warning lamp 13. In the circuit shown in Fig. 2 the master relay comprises two relays 42, 43, the first relay 42 having a movable arm 44 for energizing the igniter transformer 56 and a further movable arm 45 which energizes delay switches 57 58 for the motor 59 in series with the heating coil 35 of the time delay switch 32 when the relay is de-energized and alternatively in series with a resistance 54 when the relay is energized, the second relay 43 having a winding 50 which is energized through the cold contact 39 of the fluestat 37 to close contacts 51, 53 to connect the movable arm 38 of the fluestat directly to the time delay switch 32 so that when the fluestat arm engages the hot contact 40 the winding 43A of the first relay 42 is energized. A thermostat sensitive to the temperature of the fuel oil may be inserted between the cold contact 39 of the fluestat and the time delay switch 32, and a further thermostat controlling a boiler may be connected between the point 55 common to the relay windings 43A, 50 and the ignition transformer 56 and the neutral N of the electric supply.