Saunier duval isomax, when i run the hot water it works fine for 5 minuits due to it having a storage tank inside when this is used up it starts to run cold when i look at the flame it is verry low its just a level sheet of flame, when i put it just to heating the flame is the same and the heating takes a log time to get hot. I think that over the day when we dont use the hot water the boiler has time very slowly to heat up the small clinder....
Any help thaks

peter k, February 2008

Sounds like the Gas valve requires re-adjusting to the permitted Gas pressure Peter, because the saunier duval has a Fluctuating Gas pressured Valve, setting up the correct pressures on high and low should help your Boiler out! NOTE: This is the basic Problem that could be the problem, so ild start here!

Craig Cross, February 2008