Potterton expansion vessel

22 Mar 2008
Reaction score
United Kingdom
I have a potterton 100 and when pressurised to 1.2 bar as normal when heating is switched on pressure rapidly goes to 3 bar PRV dumps outside. I drained upper system found shraeder type fitting and pressed needle ,air came out no water! there is a flexible pipe running from pump pipe connections to expansion vessel i removed this and cheked it wasn't blocked,replaced it charged up expansion vessel to 1 bar and noticed it dropped to 0.7 bar, pumped back to 1 bar same happened it dropped to 0.7 bar.filled system bled correctly and boiler still the same, overpressure prv dumps. i assume the expansion vessel is no good! I can mount another vessel same capacity right next to boiler but can i just remove flexible pipe on old vessel and connect this to the new vessel alongside the boier and fit new PRV the flexi pipe will reach no problem.
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Right fitted new expansion vessel today pupmped up to 1 bar before filling sytem. bled system vented etc switched on boiler fired up first, time no trvs on rads or room stat. Boiler ran for 15 minutes rads got lovely and hot,Opened hot tap got hot water then cold then hot then boiler tripped out, reset trip switch but boiler wont kick in again on either DHW or heating.. any clues whats wrong? looking for download fault finder from potterton but cant find anything and dont have the original booklets instructions!
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