How to fit an external expansion vessel ?

[ChrisR]

I don't fit bathrooms.
Didn't know what?

 

[bluefudge11]

Hi
This lively debate is very "interesting" but I am pretty sure my boiler is not an "instant"
It is the 105e CGN 4707508.

so my understanding to date from these posts is:

1) It is possible to fit an XEV - (return side)
2) Secondary PRV would be a good idea but is only effective when boiler isolated and mains pressure gets in to the system via the filling loop valve accidently being opened and the loop connected?
3) The OEM XV fit is 8litre so if I go with a 12l EXV then i should be OK

Isolation valve between vessel and return ( for easy maintenance) debateable

Thanks BF

 

[Agile]

Those are safety requirements:-

Pressure release valve on system!

No isolation valve between system and EXV.

However, if you HAVE fitted a PRV to the system then an isolation valve is unlikely to cause any problem because the system is protected by the PRV. It would just provoke a probably refusal from BG to give cover on your system.

Tony

 

[BigBurner]

Hi
This lively debate is very "interesting" but I am pretty sure my boiler is not an "instant"
It is the 105e CGN 4707508.

so my understanding to date from these posts is:

1) It is possible to fit an XEV - (return side)
2) Secondary PRV would be a good idea but is only effective when boiler isolated and mains pressure gets in to the system via the filling loop valve accidently being opened and the loop connected?
3) The OEM XV fit is 8litre so if I go with a 12l EXV then i should be OK

Isolation valve between vessel and return ( for easy maintenance) debateable

Thanks BF

The isolation valve is strictly not legal as you could isolate a safety device (the vessel), but if tool operated and another PRV fitted then realistically it is fine. Without the valve it means a full drain down and £15 for X-100 if the vessel needs replacing.

 

[bluefudge11]

Firstly - Thanks to all for the advice

I am going to fit 12l external to the 22mm return with PVR (I will buy the vessel"kit" ), I will not use the filling loop.

Final question (I wish!) - Can I mount the vessel upside down? ie valves at the bottom. This would make the pipe work much simpler. I can't think of a reason why not but thought i would ask.
(assuming i have a robust wall fitting of course)

Thanks again
BF

 

[gavinda]

no problem fitting it upside down. and i dont see why you'd need a seperate prv either.just be sure to top up again with some fernox and all shall be well.

 

[bluefudge11]

Thanks Gavinda.
The opinion regarding PRV seems to be divided so for the sake of an extra £10-15 I think i will fit one. I will tee into the external outlet of the existing PRV
If luck is on my side i will be able to mount it very close to existing pipe work and thus should not be too difficult(famous last words )

Thanks
BF

 

[gavinda]

ive fitted many ev's remotely from boilers. never fitted an isolator. just a tee and an adaptor. no reason to suspect that the original prv wont activate should it be reqd. as for the concern of over pressurisation should the boiler be operated with the iso valves shut, weel whoever is gonna operate the boiler that way should be inspecting the system 1st anyway.

 

[bluefudge11]

I tend to agree with you - the likely hood of the existing PRV in the system being over pressurised and isolated "accidently" is pretty unlikely , but like I say, for the sake a few extra squids i will fit one.
i will not fit an isolating valve, can't see much point other than for replacing the vessel at a later date. (i may regret this).
Cheers
BF

 

[Agile]

I dont see any advantage by posting exactly the same question on different forums and getting exactly same answers from mostly the same people.

Wasting peoples time springs to mind!

Tony

 

[bluefudge11]

So every member is a member of every forum - i think not

still not like you to moan

 

[bluefudge11]

another "final" question please

Do I need to set adjust the new vessel dryside pressure to be thasame as the Baxi original
(The new vessel is charged ar 1.5 bar - Baxi vessel is pre charged at 0.5 bar ?

Thanks
BF

 

[Agile]

Most of the professionals are!

The air should be set to 0.9 Bar with system open and the system should then be pressurised to 1.5 Bar.

The air pressure for the Instant is set lower than a normal expansion vessel so that it ends up being mostly full of water when its operating normally.

Shall I copy that answer to the other forum as well?

Tony

 

[bluefudge11]

LOL - no need to post on the other forums unless you feel the urge to.

Thanks for the info
BF