When the heating is on the loop pressure rises and causes the boiler to shut down

I have bled the system and the pump apperas to be OK

Any ideas what it could be

John Payton, September 2007

could be the pressure vessel diaphragm, i had similar problem, the diaphragm had a pin hole in it causing the pressure to rise and dump to outside when the relief valve lifted thus the pressure dropped right off and the flame went out. Try dropping the temp on the control as a short term fix till a repair can be sorted, less heat less pressure build up.I did this and it worked, the repair was not too expensive either.

Andrew, January 2009

I have a Worcester combi-boiler - less than a year old. The thermostat shows the house temperature and a flame is on the display (i.e. showing that the heating should be on). But the heating isn't on. I have reset settings etc. But heating still not on. Any suggestions? It was all working fine til a few days ago.

Liz, December 2008

combi boiler cuts out after 20 seconds

chris, October 2008

the boiler is a 24 cdi series

peter young, April 2008

i have a combi boiler prob the heating works fine the pressure is ok but i have no hot water the boiler is a worcester bosch when you turn the tap on the light to indicate the hot water is working is not coming on can any one help

peter young, April 2008

depends what boiler it is

hi-spec plumbing, September 2007