Pressure rise on Vokera combi boiler

completely Puzzled · 28 Sep 2005

I have a Vokera Linea 24 combi. Pressure keeps rising within the system ( central heating ) and vents at 3.0 bar. The expansion vessel is good with no leaks of any kind and the filling loop is ok too, all verified by a Vokera engineer. It has been suggested, by engineer, that this 2 year old boiler is not being helped by 19 year radiators, which are more than likely choked beyond repair and therefore restricting water flow and causing the problem. I intend to replace the rads soon. Does anyone have any suggestions and do you think the new rads will cure this, its driving me mad. Please don't mention descaling or flushing, its been done.
Many Thanks

Gasman1015 · 28 Sep 2005

Change the engineer.

No.

kevplumb · 28 Sep 2005

It has been suggested, by engineer, that this 2 year old boiler is not being helped by 19 year radiators, which are more than likely choked beyond repair

that aint gonna rise the pressure
is the loop closed and dissconnected ?

if so prime suspect is the dhw/he

Slugbabydotcom · 29 Sep 2005

completely Puzzled said:
. Please don't mention descaling or flushing, its been done.

Can't see how a pressure rise would warrant the above work.

As gasman1015 says change the engineer double quick

Kev is thinking what I initially thought but if theres 19 rads I'll have a small wager on you needing an additional pressure vessel and the possibility that the one you have isnt as fit as you think it is.

Basically if pressure rise occurs without the boiler being turned on suspect filling loop or secondary heat exchanger otherwise look to PV problems

completely Puzzled · 29 Sep 2005

Thank you kevplumb. i should amend that the rads are 19 years old and there are 8 of them. i guess they could be pretty well gummed up and worth replacing anyway despite using Fernox on a regular basis. However in answer to your thoughts, yes the loop is closed and disconnected, but as soon as heat is required, up goes the temp to 85 deg and she vents at 3.0 bar. normally within 15 minutes or so. ( all rads are hot all over ) And this is from 0.5 bar start. What i have to do is turn the boiler stat down so she doesn't get so hot, which therefore keeps the pressure down too. ( the stat checks out ok ) Domestic hot water is not effected as long as there is enough pressure. What the hell is the dhw/he in plain english please.

breezer · 29 Sep 2005

completely Puzzled said:
What the hell is the dhw/he in plain english please.

Domestic Hot Water Heat Exchanger (amazing what info you can get on here isn't it)

Tinitus · 29 Sep 2005

HI dhw he is the domestic hot water heat exchanger unlikely to be that from what you have said . From info you have gave i would say it has to be the expansion vessal, it needs to be checked for pressure with pressure gauge reading zero

kevplumb · 29 Sep 2005

woah
halt called
is the pressure rising when in use or not

matgasplumb · 29 Sep 2005

pipe to pressure vessel may be blocked - unblock
or
possible leak on schreider valve on pressure vessel
or
calorifier broken down allowing dhw to enter primary water circuit. - replace calorifier.

kevplumb · 29 Sep 2005

pipe to pressure vessel may be blocked - unblock

and if it's rising when not in use

DP · 30 Sep 2005

There is a flexible pipe between the pump and the expansion vessel. It is blocked.

The linea has a three position valve on the cold water connection. System fill is at south point, hot water delivery at north point. Cannot see system pressure rising when the lever in hot water delivery position.

Have in the past had to replace the HWHE. It had failed because the mains pressure was very high. Had to fit a pressure reducing valve as well as replacement HWHE.

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Pressure rise on Vokera combi boiler

breezer

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