I have a Vokera28 boiler fo about 2.5 years and just recently it has started to over pressurise causing the relief valve to constantly blow off down the side of the house. I have drained the excess pressure off several times but within an hour it is rising again, even without any heating on. I have recharged the expansion vessel with a bike pump to 0.8 bar as given in the fitting instructions, but it is still raising to max pressure within hours.
Any advice gladly accepted.

Chris bowker, June 2008

Thanks for your help. Have fixed the problem now, it was the heat exchanger.

Chris Bowker, July 2008

Chris its me again, if the seal is not leaking u could check the heat exchanger, by isolating the boiler from the water supply (turn off the cold supply tap on RH side and don't use any hot taps until u have checked the pressure) and see if there is any increase in the system pressure over night if thats convienent

RoyT, July 2008

Chris I am almost sure that u will find it is the spindle seal. U can check this by removing the central heating side of the diverter and observe the status of the seal

Roy T, July 2008

Thanks for your help, I have changed the top up tap and non return valve and am certain that no water is passing through here, so it looks like diverter or exchanger plate.

Chris bowker, June 2008

Chris from past experience its possiblly coming through the diveter valve. U will need a service kit and follow service book on removing the diverter valve. Be sure to replace all 'O' rings and apply lubrication to all the rings and spindle

Roy T, June 2008

Chris from past experience its possiblly coming through the diveter valve. U will need a service kit and follow service book on removing the diverter valve. Be sure to replace all 'O' rings and apply lubrication to all the rings and spindle

Roy T, June 2008

must be getting cold supply into heating system possibly from:
filling assembly passing even though it appears off or
plate exchanger pin holed internally.

iain, June 2008