Boiler on the blink, help needed :)

[evesdad]

[quote author=evesdad link=topic=19258.msg222975#msg222975 date=1454098792]
To check if expansion vessel needs re-pressurising top boiler up to just over one bar when the system is cold. Put the heating on and watch the pressure gauge..if the pressure rises over 3bar then the vessel is flat. Pressure relief valves start letting water out of the system at 3 bar, so when the system cools down again water has leaked out of the system so the pressure goes down to zero. The pressure relief pipe should goes to outside so you don't notice any leaks. On your boiler the pressure relief pipe is the one to the left hand side closest to the front of the boiler see if you can find where that goes to and if it has been dripping. Expansion vessels can usually be pumped back up but prv may need replacing.

also if you can get to the expansion vessel  valve undo cap when cold, press valve in to release air and if water comes out its knackered.  I learned that when mine went and as above my system was running passed 3bar which alerted me to the problem
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Doesn't always mean its knackered. If you can still pump the water out of the other side and pump the vessel up to about 0.8 bar you should be ok. You need to have an open end on the system somewhere to pump the water out of the vessel to pressurise it properly.