A Ravenheat 820/20 combi boiler, had diverter valve diaphragm replaced last year as it had perished, now occasionally it will only supply cool water either when central heating is on or off. When h/w is coming out cool the burner is lit, the diverter valve appears to be tranferred so where is the heat going?

Walt, February 2006

if the d/valve is ok and the burner is firing for hw-check the hw pipe comming out of the bottom of the boiler next time it happens -if this pipe is roasting and the water out your taps is cool then one of ur mixer taps or shower is faulty-the cold mains is diluting the hw and cooling it down.

stevie, February 2006