The hot water microswitch on the diverter valve may be faulty keeping the boiler on. Put the selector switch on hot water only and if the boiler fires up with no hot water taps running replace the microswitch. The diverter and microswitch is at the bottom left hand side behind the control panel.
Ian.
May 2007
You may be running the system too high. How often does it cut off? It could be several things. Poor circulation, partial blockage in a heat exchanger, burner pressure too high. Does it do it more on heating or hot water or same on both? How long has it been happening?
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