Pressure Drop on boiler

[Jeffcarrier]

Hello Plumbers Forum,
My Boiler is a Glow-Worm 30 cxi Condensing Combination Boiler. It was installed in 2005.
The boiler pressure normally - that is when the central is not on, is between 1.0 and 1.6 bar.
In the last few days it dropped to 0.8 bar. I adjusted the supply and it went up very quickly to 2.0 bar.
The following day it had dropped to 0.8 bar.
Can anyone help me solve this problem.
Thanks - Jeffcarrier

 

[Tamdowie2112]

hi its looks like it could be your expansion vessal on the boiler need recharged.

 

[Simon F]

hello Jeff, what pressure is it reading when the ch is fully up to temperature?
Has there been any leaking from the pressure relief valve?

 

[M12 OKEH]

Jeff - try the following:

(i)Pressurise your system to 1 bar when cold
(ii)Secure a plastic bag (without holes) around the discharge pipe from the pressure relief valve of the boiler (the copper pipe that passes through the wall to outside)
(iii)Fire up your boiler on heating. Watch the pressure gauge of the boiler. Does it rise to over 3 bar? Is there water in the plastic bag?

If the pressure climbed to over 3 bar and there's water in the plastic bag, then the expansion vessel requires recharging or it's failed completely.

The manufacturer's instructions will advise on the pressure that the vessel should be pumped up to. If there's water coming out of the Schrader valve, then the vessel has failed. Simple job to replace the expansion vessel on this boiler because it's not fitted at the rear of the boiler.