When I turn on the hot water tap at the sink, the boiler fires up but shuts off after 5 seconds. It does the same from cold or when central heating is on. System pressure is at about 2 Bar.
Hot water Pressure and flow at sink when tap opened is a bit low. Mains pressure on cold side is good. any ideas?

Peter Butler, May 2008

either the inline filter on the water main into the boiler is blocked (should be cleaned every service interval), you dhw thermister has gone faulty, or the plate to plate heatexchanger has become partially blocked and may need replacing........try the filter first...a common problem

T, May 2008