my central heating combi will not fire when i open hot water tap?

it totally depends on the model boiler you have. It could be a faulty flow switch, faulty diverter valve, faulty pcb, stuck microswitch, internal electrical cable etc. i'm an engineer for Vaillant Group service - largest boiler manufacturer in Europe. best advice... get the manufacturer's engineer in to fix it for you. Most of them do a fixed price including parts. Cheers

Phil
January 2009

have a look on the pressure bar gauge make sure it is above 2 barr if not then you need to top it up by opening the inlet value which should have a silver flexie pipe attached then shut it off when it is 2 barr .should sort it .

chris
January 2009

the most likely cause is the hot water diverter diaphram

tim
January 2009