Expansion vessel question....

[Gunslinger]

ok, this is on my Ideal Classic Combi NF80 boiler, recently had someone out to replace the diverter valve for me, thats all done and working, but he advised me that it seems the expansion vessel is full of water and should be replaced.

now, before i go blindly and buy a replacement, i have a couple of questions...

1. the expansion vessel works by having a build up of compressed air pumped into it, and the diaphragm inside separates the air from the water in the system..... correct ? (i know thats a basic description) ... is it possible that it needs the air side recharging ?

2. is there any point looking to see if it's repairable or is it a case of simply getting a new one.

3. what are the side affects of running the boiler with the vessel in this state ? - like should i turn it off until i can get a replacement ?

4. is the switching of the expansion vessel something i can do myself without too much trouble ?


TIA

 

[GasMan1965]

If you press the pin in on the valve which is the same as a car wheel valve and water comes out then it needs replacing ,, if no water then repump to manufacturers spec !!

 

[Gunslinger]

thank you, that is a nice easy test even i can get right, i will check it tomorrow.... dont know why i didnt think of that, over thinking the problem i guess and missed the obvious !

 

[petit_pablo]

Did he say why he thought the expansion vessel needed changing? Is the pressure too high?
The expansion vessels braided hose on these block up V easily. We have a few on contract that are prone to blocking up

 

[Agile]

Follow the FAQ on this site to try to repressurise the EXV.

If it has failed then you need a CORGI to remove and refit the flue if that has to be moved to change the EXV.

Its usually possible to fit an external EXV which is far easier and cheaper.

Tony

 

[breezer]

IF your expansion vessel is kaput, its easier to install a new additional one than try to get the old one out.

 

[petit_pablo]

Follow the FAQ on this site to try to repressurise the EXV.

If it has failed then you need a CORGI to remove and refit the flue if that has to be moved to change the EXV.

Its usually possible to fit an external EXV which is far easier and cheaper.

Tony

The classic combi exp vess is at the front of the boiler on top i believe

 

[WDIK]

FAQ No7

 

[Gunslinger]

quick answers to the questions asked then i will go look at the FAQ as i obviously missed something in there !

1. to replace the diverter valve on this boiler you must move the expansion vessel out of the way
2. yes it is connected via a braided hose
3. one screw in the frame it sits in is all that is used to grip the lip and hold it in place
4. yes it is mounted at the front and at the top, and has a small support bracket on it which you use to mount it elsewhere out of the way when working on the other parts of the boiler - so no need to disturb the flue at all.
5. i believe he based his initial thoughts on the weight of it when he moved it, although i did not ask - he's the qualified one with the experience ... he did tap it / knock on it ... so i assume that when its full of water it will be like tapping on a drum full of water in that it will be different if its empty.
6. pressure on the gauge at the front is varying a bit, it was up fairly high (3+ bar) with no release from the relief valve yet, however after bleeding the radiators this came down to about 2 1/2 bar when hot and in use, but when cool it's dropping off to nearer 1/2 bar (i did open up the fill valve to increase the static pressure to 1 bar which i believe is the minimum)

ok, any more info i can give just ask...... and yes, if anyone is interested, the system seems to be working fine, had the diverter valve not gone, i probably would not even know about this issue !

 

[WDIK]

dont bleed radiators at the moment its the only expansion room you have at the moment

 

[Agile]

Follow the FAQ repressurisation procedure and then tell us what the effect is.

Tony

 

[Gunslinger]

ok, no bleeding the rads - got it

and i've got a copy of that section from the FAQ, and will go through it tomorrow

thanks for the very speedy replies much appreciated

 

[petit_pablo]

Im laying my money on a blocked expansion vessel hose still. These boilers were a horrendous idea

 

[Gunslinger]

i will check that after the pressure vessel checks (if i get water out of the fill valve i'll have to change it and will change the hose too at the same time)

but your experience and advice is appreciated, i would not have thought about the hose until much later, if at all

 

[Agile]

If the hose was blocked then the EXV would pump up with air very quickly, just a few strokes of the foot pump.

If the hose is OK then it will take about 15-30 strokes!

Tony