The burners won't ignite when CH is selected, the demand light comes on but no ignition. When CH is turned off and the hot water tap turned on the burners light and stay on until the tap is closed.

When the burners have lit for the HW, if I turn the CH on the burners go out.

Keith G, January 2010

Thanks for your quick response Ian. I'm actually not using the timer, so must suspect the CH pump. I tried it again this morning and the CH side has fired up, so the fault is intermittent and therefore probably very difficult to diagnose.

Keith G, January 2010

may be a faulty timer or faulty pump. twin pumps on this boiler, one for heating and another for water.

Ian, January 2010