| 摘要 |
<p>A circuit (10) for delaying the firing of a boiler for a domestic water central heating system is connected between the boiler thermostat and a fuel control valve of the boiler fuel control system. In operation, when the boiler water temperature drops below the preset thermostat temperature level and the thermostat is tripped to fire the boiler, the firing signal from the thermostat is intercepted by the circuit (10) and is used to trigger a delay circuit (28) which subsequently fires the boiler after a delay of 5 or ten minutes selected by switch 38. Once the boiler water has been heated to the required temperature the boiler is switched off, as normal. A delay of one second can be selected when testing the circuit 10. <IMAGE></p> |
