I have a potterton performa 28i combination boiler less than 5 yrs old. Worked fine until few months ago. Called in plumber as boiler was losing pressure and hot water running hot/cold. We have had the safety valve, expansion vessel, domestic hot water heat exchanger, pcb board and micro switches ALL replaced at great expense. Pressure now OK hot water problem is worse than ever - burner kicks in but only lasts about 20 seconds then goes out, if lucky we can get lukewarm water before goes cold again. AT WITS END!!

Amanda, April 2007

HAVE YOU GOT A THERMOSTATIC SHOWER the worst one is the bar type with thermostat at the end try or recessed try to isolate the cold to the shower as sometimes mains water can push into the hot side cooling the hot water from the combi the boiler will think its hot enough,
one other to try is when every thing is cold to just put on the hot water for 10 mins then go and check the nearest radiator if ist warm the diverter valve is passing

RAY, April 2007