Raventheat 820/20 External Expanssion Vessel

Hi I have a revenheat 820/20 and its internal expansion tank has failed. Does anyone have instructions on how to fit an external one and what size to buy. I have tried to get a plumber to do it but can not get one for months. i have been told that it is not a hard job

8 litre expansion vessel, bracket to fit against wall (unless you want it sitting on shelf/floor), connect to return pipe using normal tube/fittings. I generally us a flexible connector like those for taps, although they're not rated for the highest CH temperatures. Expansion vessel has male ¾" thread, but the rest of the connection to the return pipe does not need to be that size - I've even used microbore.

I think the instrs are on the Ravers site??

the size of the vessel depends on how many rads you have i.e. how much water is in your system.
For an average 9 rad system an 18 ltr vessel should be ok. Last time i did one they were about £60 and come with full instructions.
If the SRV is ok on the boiler then you just have to connest it to either the flow or return, preferrably close to the boiler.

BTW, who said the pressure vessel was kapputt?

Its such a difficult job re-charging the vessel on the 820 (and impossible if no LHS clearance) it is often simpler to install an 8 litre vessel underneath.

If the filling link is underneath its easy to stick in a tee off the return connection. I use 3/4 to 1/2 flexible hoses specifically designed for heating pressure/temps.

Vessel and bracket should be around £20.00

Had British Gas out for a Gas safty test as the house id going to be rented out and they said it was broken.

When the boiler heat up and the water presure increases the overflow starts to leak and the boiler looses presure

By the way how do you drain down the boiler to fit it and how do you refill it

Thanks for your advise

You can only tell if the vessel is "broken" by re-charging it with air - this has evidently not yet been done by BG. If it holds pressure ie air doesn't leak out of the seam or through a holed diaghram and there isn't excessive water coming out of the valve the vessel is normally OK.

Problem is access to the schrader valve is very limited and its often easier to fit an additional vessel than to attempt to re-pressurise the existing one.

The boiler would be drained with the safety valve, auto air vent and safety valve replaced, and the vessel tee'd into the filling loop conection.

Some of this work involves opening up the combustion chamber and therfore really Corgi teritory. The whole job including safety checks should take no more than an hour.

Pre-charge on new vessel must be checked before installation - from the factory they are often charged with sky high pressures.