Glow worm pressure loss

[mtaylor]

Hello.
I have a glow worm 24 ci combi boiler with a low pressure problem. The heating system occasionally needed toping up especially when system was cold.
Recently I took a radiator of to do some work in the kitchen. put it back on again and bled the system thoroughly. the system was constantly loosing pressure. saw that pressure relief valve had blown. also noted that the pressure went very high over 3 bar when system was hot then went right down to below 0.5 when cold. Know i need a new pressure relief valve and also want to check expansion vessel pressure which i learnt from another post.
Does anyone know the best way to do this on a 24 ci looks quite inaccesable. Manual just talks about removing boiler from wall for expansion vessel replacement. Do i have to do this just to check the pressure!?
Any info gratefully recieved M

 

[Soggy_weetabix]

fit a new expansion vessel to system externally. Treat it like a sealed system.

A rad could take up expansion in the meantime.

David

 

[mtaylor]

Hi david thanks for your reply. How does rad take up expansion ? Buy draining an upstairs rad? how much water should be taken out.
Is there a particular external expansion vessel to be recomended or size
cheers Mike

 

[BOB..DOLE]

you can get to the test valve from the top of the boiler and should be 0.5

 

[mutantgoat]

Press relief valve blown? they are sprung should reset. is there water coming out of the valve exit pipe [usually outside the house] when valve is closed - just a drip every so often in enough. Then you can remove and dismantle-looks like a tap inside with a large rubber washer/diaphragm which forms a seal both the washer and the seat may have scale deposits descale and put back. The diaphragm may be punctured and/or the seat may damaged by scale. Best to replace before looking elsewhere

 

[gasgeezer]

A very common fault on this boiler is the flexi exp. tube blocking preventing the exp. vess. from working gives the same symptom of failed exp. vess.It has been mentioned numerous times on this forum and should be checked.

 

[mtaylor]

i know this is probably to late but thanks everyone for your help it worked!