I have a Baxi Duo-Tec Combi HE A boiler. Its normal operation is fine but even when not in use for long periods the pump comes on and off. In fact it seems to come on for 10 minutes duration during every 20 minutes (24 hours a day). Is this a fault with the boiler, and which component would be a likely culprit? Many thanks.

Tom, May 2010

Further update - I've had another look inside the boiler and one of the electrical plugs wasn't very firmly attached. I have secured it and so far it's cured all the problems we were having.

It was the plug that goes to control the 3-way selector valve, the '3' end of the multi-plug had partially come away.

Thanks

Tom, June 2010

Hi Ian

Thanks for your prompt reply! Indeed the CH light is often illuminated while the pump pumps (although this is not always the case). This despite having all the stats on the radiators turned off and the CH timer turned off. Although the demand light is on, the burner never comes on to actually heat anything.

Incidentally the central heating timer is a wireless Potterton one - I've tried removing the batteries / renewing the batteries to no effect.

Everything was installed in late 2008 (new build property). Many thanks, Tom.

Tom, May 2010

look to see if there is a demand light on with no demand. i.e. heating off and no taps running. there are lights to either side of the temperature display, if either is lit then the boiler thinks there is a demand, so if the heating light is on i'd guess at a faulty timer or wiring fault. if the hot water light is on then you either have a dripping tap / shower or the flow sensor is stuck on. if no demand lights but pump still running then i'd guess at a faulty pcb but never seen this fault myself so difficult to tell. remember the pump will continue to run for a short time after each demand.
hope that helps.

Ian, May 2010