GB1470524A - Water boilers - Google Patents

Abstract

1470524 Boiler feedwater control W M STILL & SONS Ltd 8 Aug 1974 [9 Aug 1973] 37743/73 Heading F4A A hot water boiler feedwater inlet valve is connected to respond to a boiler water level sensor defining a preset level and a boiler pressure switch which responds to two preset pressure values; the inlet valve being opened if the water is below said preset level and the pressure has reached the upper preset value, the valve being closed when the pressure reaches the lower preset value regardless of water level, and the boiler heating means (which may be an electric heating element, a gas heater or a steam heating supply) being connected to be turned on when the pressure reaches the low value. In the embodiment shown in Fig. 1 the boiler 2 is provided with two probes 4 which respond to a low water level so as, when both uncovered, to close via an electronic control circuit 6 a relay 16 thus energizing the boiler heating means 28 and connecting one side of the solenoid of a water inlet valve 30 to an electric supply, the other side of the valve solenoid being connected to the other pole of the supply via boiler pressure switch 32 which acts to open the valve if the pressure reaches the higher of two preset pressure values, say 4¢ p.s.i., and closes the valve when the pressure falls to a lower preset value, say 2¢ p.s.i. When the water level rises to cover both probes 4 the boiler heating means is switched off and the valve 30 is closed. Thereafter the pressure switch 32 acts via 36, 38 to turn the heating means only on and off depending on whether the low or high pressure value is reached. In the embodiment shown in Fig. 2 only the pressure switch 32 controls the heating means 28. In both embodiments the automatic arrangements described above can be overriden at 12 to allow the boiler to be initially filled up to the desired level. The boiler may produce steam in addition to hot water.