More Valliant Ecotec problems...F.22

[Hack]

We have an ecotec plus 831 that recently has been giving us problems.
We had an F.75 error in Dec and replaced the pressure sensor but the engineer who came out thought there may be a problem with the expansion vessel. Since then it has been working ok but this morning we had an F.22 (dry fire) error. Pressure on the manometer was down and I didn't think to record the digital readout.
I switched the boiler off and filled it a little so that pressure was just over 1 bar and switched the boiler back on. All seemed to be ok but then pressure rose to over 3 bar (on the manometer it was as far in the red as possible.) I switched the boiler off again and checked the pressure relief discharge pipe and it was discharging a little. Again I didn't think to check the digital sensor. I came back to it later after the pressure had dropped and switched boiler on but left CH off. Pressure was stable at 1.1 bar.
I switched the CH back on again and it took a while to rise to 2.1 bar but then rose v quickly to 3 bar so switched boiler off again and drained a bit out using the pressure relief valve/ flap on the right hand side of the boiler. Am currently monitoring the pressure - at present @ 1.8 bar/ halfway in the grey after switching boiler back on and CH on.
What could be causing this problem? Could the expansion vessel be the problem? I don't really know anything about boilers other than the problems we've had so please don't get too technical!
Thanks for any help.
Rob

 

[Deleted member 105431]

The expansion vessel has lost it's charge. Read the FAQ'S.

 

[Hack]

Thanks for the tip. Don't have a pump that fits or a guage - thought about getting one today in case it was that. Oh well, better invest in that for the next time. Think for the moment will call out an engineer but one question...as the sensor failed in Dec, the pressure was checked I think then. Should it have dropped so quickly or could that indicate a further problem?
Also, would you know where the drain cock is on an ecotec + 831? Had look at the manual but can't figure it out

 

[Hack]

I've had a look at the expansion vessel and when I take the cap off the valve, there's a slight hissing noise coming from the valve which seems to indicate a leak. This can't be normal can it? I imagine when the cap goes back on it bocks the leak but the cap's not going to be airtight.

 

[gas4you]

No there shouldn't be any hissing from the valve. Get your self a cheap pump and pressure gauge and test it.

You may find that pressing the pin in a few times lets the valve re-seat, but I doubt it