expansion vessel

30 Nov 2004
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United Kingdom
I have a glow worm compact 100e which i am having pressure problems with. I have been told the problem is the expansion vessel. The boiler is only 5 years old and has recently had a new diaphragm fitted on the water side. I replaced the diaphragm and would like to tackle the expansion vessel but i have no info on how to, can anyone help?
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1 is it leaking
2 if the answer to the above is no you can put a replacement vessel on the ststem as long as it has an open path to the boiler ie no valves etc
if the answer is yes then its a boiler off the wall job (corgi) :)
No sign of any leaks.
I found out some info it said"isolate and drain boiler. leave drain open. Test air pressure with tyre gauge? to .75-1 bar if low pump up with foot pump.
If this info is sound adsactly where and how do you test air pressure?
Do you need to remove boiler it sounds simple!!!
there is a valve on the top of the vessel (car tyre type)
use a tyre gauge to check the pressure
after you drain the boiler :)
btw ex vessel is large red disk thing behind boiler
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If u have problems with low pressure are u aware that u have to check/refill the boiler every 3 months with the filling loop. However if u are convinced that the expansion vessel is at fault then the simple way is to refill it with air. Any car foot pump will do. U will require to know how much u r putting in, therefore a pressure gauge is required. So heres what to do. Lower (or drain the boiler only) down to zero, The expansion vessel in most cases is located on the back of the boiler. its normally RED in colour (some later versions are in grey) fit the car foot pump valve to the valve on the expansion vessel. with the boiler drain off still open, re inflate the expansion vessel up to about 1 bar, maintain the air pressure until stable at 1 bar, remove the car foot pump, put back the dust cover, close the boiler drain off valve, refill the boiler to at least 1 to 1.5 bar, don't forget that there is now AIR in the central heating side and when this exits via the auto air vent, the pressure will drop.
the boiler technician
Thanks very much for all the advise. I do appreciate it>
I have found the valve on top of expansion vessel looks similar to a bicycle tyre valve.There is a metal type clamp adjacent to it which is preventing me from getting any leaverage on it, but at least i have found it. Is it possible to, (after i have drained system leaving drain valve open)
to check pressure with a tyre gauge and then pump it up with a bicycle pump stopping occasionaly to check pressure. Also while i am on i have 7 radiators i can only bleed 4 of them with the bleed key the remainder have a plastic shroud with a hole in it preventing the key from fitting is their a reason why?
as long as the press gauge is reading 0 you should be ok
why do you need leverage on the valve :?:
get another key or try to take the plastic off :confused:

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