No problem on hot water. C/htg does not cut in if temp lights display a high temp. To get the boiler running for c/htg I have to switch off, run a hot tap to reduce the shown temp then switch to c'htg + hot water mode. The c/htg then cuts in. If the c/htg temp control is turned down for slightly warmer weather the c/htg wil spontaneously cut out (anything from 1 to 4 times daily) but the red temp lights climb 60/80 deg after the c/htg has failed. The boiler will not reignite until the temp has been reduced as above.

When restarting as above, there is a cavitating sound from the boiler unit as though there is a lot of air in there somewhere.

The problem is more pronounced when the hot water pre-heat is on; therefore I'm running it as a straight 105 at the moment and getting overheated on warmer days (but not so warm I can turn the heating off!) Two engineers can find not fault and it's a bit embarrassing. HELP!!!!

Any suggestions greatly appreciated. Roy

Roy Fearn, December 2005

your exspansion vessel at the back of the boiler could be split inside

jon leighton, December 2007

just mike again after reding your problem again this sounds like your diverter valve could jamming especially if the problem occurs often in the morning

mike, December 2005

this problem could be be a lazy or seized pump the way to check it is to remove the big silver screw in the front of the pump and run central heating you should be able to see the spindle spin inside ,hold a small bowl under the pump whilst you do this to catch any spills if it isnt spinning using a flat headed screw driver spin the spindle back and forth then replace the silver screw, also ensure you have enough pressure in the heating system displayed on the front of the boiler if not top it up using your filling loop, if pump still isn't running you need to check you have power there if there is power and pump isnt running new pump is required after checking these and still can't find fault post another thread to mike

mike, December 2005