Combi boiler pressure variation too great

The boiler is a Worcester Bosch 28 CDi, about seven years old.
At installation I was told the pressure should be about 1 Bar when off and about 2 Bar when running.
I recently bled the radiators and re-pressured the boiler and now the pressure range seems too great: 0.5 Bar when off; 2.6 Bar when on.
What needs to be done? What are possible causes?
--
Chris

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On 27/11/2010 05:17, Chris wrote:

If you're sure there's no air in your system, then I'd suggest the expansion vessel in the boiler has lost its pressure? - would need repressurising or probably replacing
David
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Chris wrote:

Might be an idea to check that out with WB themselves?

AFAIK and IANAHE is there not an 'over' pressure valve that dumps any excess pressure? Again, could you check with WB to find out at what pressure that opens at?
--
Dave - The Medway Handyman
www.medwayhandyman.co.uk
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Are you talking about the pressure relief valve ?
I think it opens at 2-2.5 bar (it will be in the manual which came with the boiler
Sounds like the pressure vessel (big orange / red pancake thing) which is attached to the mounting frame on the boiler. Pain in the arse to get at on this boiler - easiest solution is to add an extra pressure vessel somewhere else inconspicuous in the heating circuit
google "expansion vessel" plenty of links
prolly something about it written by Ed in the FAQs (www.uk-diy.org will take you there)
--
geoff

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