When hot water (dhw) is flowing then the central heating system heats up as well. The Boiler is set to dhw only and the central heating demand light is off. Short term 'solution' has been to turn preheat off and turn all radiators with thermostatic valves off. I guess this is something to do with thebypass valve. The question is what and how to check. Any help appreciated. If I can't fix it myself what sort of cost to repair?

Ken, September 2006

just had the same problem with my baxi. it is the divertor valve. normally gets stuck due to dirt in the pipes. flush the system, repair or replace the diveror valve and then put inhibator in.

It cost me £115 for the part and sorted all the problem.

Steve Mann, November 2006

flow shair valve stuck in open mode.Sprip down valve and free off or fit new flow shair valve

mick., September 2006