faulty expansion vessel

[paddyhyland]

Hi all, attempting my first post so please go easy on me. I was wondering if someone could help me concerning a problem with my boiler? I had a worcester bosch junior 28i (non condensing) combi boiler fitted in 2004, which is now over pressurizing and then stops working, displaying warning lights. I have had the problem identified to the expansion vessel, proved by water escaping from the schroeder valve. I have been quoted £1700 to replace the boiler or £500 to fit a new expansion vessel as the boiler has to come off the wall, which unfortunately isn't an option at the moment . I would really appreciate some clarification or a heads up on the following:-

I intend to fit a secondary expansion vessel and am concerned about what size vessel would I need? Screwfix are selling a 18 litre Comap EV for £24, would this be compatible? What pressure would this need to be charged to, don't seem to be able to find any info in the installation manual?
I also intend to fit the vessel teeing off the filling loop to the CH return, again is this a good call?
Lastly can I leave the original EV in place and most importantly would the PRV still work?

I am happy enough to drain the system,pump etc down and feel this is a job I could complete but need some reassurance before I have a go, also with 3 young children in the house is this a project that could legally be tackled by myself? If not how much would a qualified person roughly charge to undertake such a job? Hope this all makes sense?

 

[matt1e]

quick answer to all your questions is yes, the size of your vessel is mostly dependent on the water content of the system,off hand I'm not sure of the size fitted to your boiler but it will probs be around 8 litre or so, it certainly wont be 18, so the 18 litre will be fine (too big is fine/better, too small is not) you will also be ok fitting a 12 litre
Fit it on the return adjacent to the boiler and as for pre-charge, regardless of the size of vessel you fi,t make it 0.2 of a bar less than the system
ie if the system is pressurised to 1 bar then charge the vessel to 0.8 (easier to do before fitting it)

Matt

 

[ianmcd]

Get another heating engineer in you are being ripped off, if it is just the schraeder valve the tool to remove and replace is about £7 with 3 shraeder valve inserts from Halfords, 18L external expansion vessel more than enough and can go anywhere on the return pipework , it will come pre charged but should be checked before fitting and it will have the pressure stamped on it , it comes charged with Nitrogen but you can top up the pressure just using a normal car footpump with a guage, I would get a decent engineer to check your existing expansion vessel it probably just needs recharged , you could do it your self check out the Wiki on here and it will tell you how to

 

[matt1e]

Ian its not the Valve that's goosed it's the bladder, as the way I read it there is water spurting out when tho op depresses said valve,
the Op could add some air into the vessel as a temp fix but then it will slowly dissolve into the system water which is undesirable

Matt

 

[ianmcd]

Mattie well if it is the bladder that is goosed then the OP would never be able to add air into the vessel as it would just go straight into the system water, it wasnt me that said the schraeder was faulty it was the OP, have only ever seen one schraeder leaking but have been at the back of around 20 engineers quoting a new expansion vessel needed when they just didnt know how to properly recharge an expansion vessel or check for a blocked communication hose, just because some condensation comes out of a schreader valve when the valve is depressed doesnt mean that the bladder has gone

 

[paddyhyland]

thanks for your input,very much appreciated.
Just to give an overall picture of what is happening with the boiler at the moment.

The pressure never remains on a stable 1 bar even when topped up and will raise to 3 bar+ when the heating is on which results in a trickle from the overflow pipe via the PRV. Just of late the heating warning light has starting flashing and the heating will stop, although will start after a reset and pressure drops. Even if I 'top' the system up to 1 or 1.2 bar it will drop even when cold?
The schrader valve when pressed does release some water, which sort of confirms that the EV is shot, so the heating engineer stated. Although reading up on the FAQ's I'm now thinking maybe the PRV maybe unseated and dropping pressure, maybe why the pressure is dropping when cold.

I am happy to fit a secondary EV now you guys have reassured me the 18 litre unit is not overkill but any more input would be great. Sort of lost faith in gas safety/heating engineers as they seem intent on doom and gloom and raping your wallet(hope that doesn't insult or offend the good guys out there)

Just also like to add what a great web site and look forward trying to help anyone out with regards to electrics (approved), access control, alarms and cctv.

 

[ALEC1]

well it also depends where the schrader valve is top side or bottom..I know of vessels that discharge about a tea cupful of water from a valve at the bottom with the bladder intact, but the side and top ones never do unless the bladder is shot..

If the PRV is dischargng, then that will probably need replacing too...

as for the £500 what does that include... it can all get very involved... I came accross one where a filling loop was letting by..so that was the underlying fault that caused around that sort of cost of damage... in my case that took out an electrinic pessure sensor too...ok in central london that is unmitigated aggravation for the long suffering heating technician...