First off boiler is working OK, however the system pressure is fluctuating.

When cold/ambient pressure is approx 0.8bar, fires up OK then pressure rises to +3.5bar (safety valve doesn't lift), then settles down to about 1.4bar.

Have bled the system so no air trapped and there's no leaks.

I'm thinking the pressure sensor is U/S or on the way out, any other alternative suggestions gratefully received.

Can anyone point me in the direction of on-line spares for this boiler or a compatible manufacturer.

Dick Sibo, December 2009

sounds like the pressure vessel has either no air in and/or the pipework going to the vessel is blocked. boiler spares in stockport cheshire are very good stockists and usefull for advice too. check for water coming out of pressure relief valve pipework outside when heating is on. also water when you heat it up expands, but on a normal combi system the rise should be up to 1 bar from cold. any more than that the expansion vessel charge/pipework is most likely

pete, December 2009

alot of these where supplied by the plumbcenter

Flux, December 2009

0.8 bar is about borderline for safety shutdown on these.set it to 1.1 bar cold and try it.the bar rate does rise during the heating process.

Flux, December 2009