Patent GB-651949-A (GB)
Title: Improvements in or relating to the control and operation of oil burners
IPC: F23N5/20
Filed: 1948-11-05
Abstract: 651,949. Automatic temperature control systems. KEMP, R. Nov. 5, 1948, No. 28813. [Class 38 (iv)] [Also in Group XI] A control system for an oil burning installation comprises electromagnetically actuated condition responsive valve mechanism for automatically varying the rate of flow of oil to the burner, an electrically driven blower for supplying air to said burner, and means for varying the speed of said blower and thereby the amount of air fed to such burner in conformity with automatic variations in the setting of said valve mechanism. An oil burner 1, Fig. 2, for a water heating system (not shown), has a single jet 2 supplied with oil through a pipe 3 and with air by a blower 6 through a duct 5 and perforations 4, an air vent 7 normally closed by a cap 8 being provided for emergency operation in the event of failure of the motor. Oil is supplied to a manually operable valve 9 in the pipe 3 either through electromagnetically operable valves 12, 13 or through electromagnetically operable valve 12 and manually operable valve 14, or, in the event of electric supply failure, through a manually operable valve 11. Across supply mains 15, Fig. 1, are connected (a) the blower motor 6 in series with variable resistances 19, 20 ; (b) the operating coil 13a of the valve 13, in series with a thermostatic switch 22 adapted to open when the water temperature rises above a pre-selected valve, and in parallel with the operating coil of a relay 21 which when energized closes contacts to short circuit the resistance 20, and (c) the operating coil 12a of the valve 12 in series with a thermostatic switch 18 which is adapted to open when the temperature of the burner flue falls below a pre-selected valve. In starting the apparatus the main switch 16 is closed and the valves 12, 14 are partly opened by hand. The thermostatic switch 22 being closed the coil 13a will be energized to open the valve 13, and the relay 21 will be energized to short-circuit the resistance 20 so that blower motor 6 is run at high speed to supply air at a high rate. The desired size of flame is selected by adjustment of the valve 9 and the variable resistance 19 ; and when the flue warms sufficiently to close the switch 18 the solenoid 12a is energized to open the valve 12 fully. When the water temperature is sufficiently high to open the switch 22 the solenoid 13a and the relay 21 are de-energized so that the valve 13 closes to reduce the oil supply to that controlled by adjustment of the valve 14, and the air supply is reduced by the placing in circuit of the resistance 20. Should the water temperature fall sufficiently to close the switch 22 the energization of the coil 13a and the relay 21 results in increased fuel and air supplies. Should the flue temperature fall sufficiently to open the switch 18, e.g. in the event of flame failure, the coil 12a is de-energized to close the valve 12 and to cut off the oil supply completely. At the same time a switch 12b is closed to connect a battery 23 with an alarm 24 which may be disconnected when desired by a switch 25. In a modified circuit the relay 21 is omitted, the switch 22 being directly in parallel with the resistance 20 whilst the solenoid 13a is in parallel with the resistance 19 and the blower motor 6 in series. The solenoid 13a is then such that the current therethrough when the switch 22 is open is insufficient to maintain the valve 13 open. Alternatively the switch 22 may be placed in parallel with the resistance 20, and the solenoid 13a in parallel with either the resistance 19 alone or the motor 6 alone. A further modified circuit is described in which the switch 22 and the solenoid 13a, connected in series, are placed in parallel with the resistance 20. The Provisional Specification describes control means for a burner comprising a main jet and a pilot jet, the main jet being controlled by a thermostatic switch which opens an electromagnetic valve to allow fuel to the main jet at the same time as it short-circuits a resistance in series with the blower motor, and the pilot jet being controlled by a second thermostatic switch, the arrangement being such that when the fuel supply to the pilot jet is cut off that to the main jet is also automatically cut off.