Expansion vessel stuffed, can I fit an 'external'(?) one?

[micromacromonkey]

Hi all

I believe the expansion vessel on my Baxi combi instant 105e is stuffed (it won't hold pressure when I pump it up - might have been that time I accidentally left the filling loop connected all weekend!), but is it going to be easier to take it off the wall and replace the vessel or fit one somewhere else in-line in the system?

I just spoke to a plumbers merchants and they suggested fitting one elsewhere wasn't a DIY job and I should get a plumber in, as I didn't know the exact capacity of the system. I was wondering how much work this actually entails (considering I fitted the central heating system in the first place a couple of years ago, rewired my house, have done a custom engine transplant on my car etc so I have a fair amount of DIY experience).

There are 7 rads, it's a mid-sized 3 bed terraced house. He said they sell 6 or 8 litre expansion vessels for around 70 quid, prob cheaper than getting the replacement bit from Baxi and less hassle than taking the boiler off the wall again.

cheers

Dan

 

[arfurrrr]

isnt the boiler under gaurantee ? r u sure the bolier isnt losing water out of the PRV?

 

[scatmanjohn]

That model uses a special type of expansion vessel to store hot water for the instant hot water feature.

Ive changed a few and thought it was easy enough (2 hours)

 

[Baxmax]

If you put it on the wall you should be able to remove it.It is a simple job,arm yourself with new washers/seals and go for it.

 

[nickso]

open the pressure relief valve and repressurise the vessel to one bar....you must leave the prv open when you are pumping it up.

check it in the same manner a week later....if its lost pressure then its binned.

you shouldnt be doing gas work by the sounds of it anyway so put a new external expansion vessel on the return pipe near the boiler. if you put the boiler in yourself you naughty boy then putting a new vessel in is going to be easy. 8 litre will do for most houses

 

[Gasguru]

The expansion vessel on the instant is not standard and you can't just replace it with a generic vessel.

The boiler vessel has two connections and is used as a thermal store (you will find it is also insulated).

Have you reduced the system pressure down to zero, pumped the vessel to 0.8 Bar (with boiler pressure gauge still on zero) and then checked if it holds the air pressure (say over a day).

As suggested before you may be loosing water from the PRV if you allowed the water pressure to hit 3 Bar by leaving open the filling loop..

 

[nickso]

hmm i remember now why my english teacher said always read the question twice to make sure you understand it

 

[micromacromonkey]

Thanks for the replies guys. I fitted the boiler myself (almost 3 years ago so no guarantee) but got a corgi friend of a friend who does foreigners to connect up the gas so OK The filling loop incident was v dumb, I had had a minor leak at a rad valve which required me to top up the system every couple of months, then somehow left it on (not fully, but enough pressure to crack open the PRV).

I followed the instructions as per the FAQ, I have a rad off for plastering so just left the valve open so the circuit was open to atmosphere (equivalent to opening PRV?) and pressurised to 0.6 bar approx. It faded away within an hour or so.

The pressure vessel is indeed one unit with the instant storage tank, which is why I am expecting it to cost a lot more than an external one

So, gasguru I definitely need to replace that unit, no chance of a separate one outside the boiler doing? Should I fit a new PRV too in case any gak has got in the current one after it opened? Damn, more expensive than I thought it was going to be. I'm off to Aus to live for a year and am renting the house out so needs to be a proper job.

Recommend a good Baxi bits supplier anyone?

 

[scatmanjohn]

Thinking about it, i can't see any reason why you can't fit an external one.

 

[Gasguru]

In theory an externally plumbed vessel would take care of the expansion volume and the thermal store would function even better (increased volume).

However the diaphragm would be strecthed right over to the air side; whether in time it would break down and bits of diaphragm would get pumped into the plate exchanger. Personally I don't think the diaphragm material is that good to start with.

See what price a new vessel is and go from there.

 

[micromacromonkey]

thanks, I'll see what price I can find on the replacement baxi bit then.

 

[micromacromonkey]

Well the replacement vessel is 52 quid plus the vodka and tonic so I'll take that route I think, much neater than sticking a separate one in. Thanks for everyone's advice.

 

[corgiman]

dont forget you have to take the boiler off the wall to change it

 

[LENABDALE]

Hi might be to late to help but I have just been seen off to the tune of £180 to fit a external vessal assured the vessal was £100 plus the vat
after checking found that Plumb Centre do the 8Ltr Jet Contra-flex 597784/8HT for £37 including vat took the plummer 40 mins to fit to myVokera Linea combi boiler didnt slove the problem still losing pressure
ben under the floor checked all pipe work no leaks. dont see anything cominmg out off the overflow were does the water go to???
Can any body help??

Len

 

[bluefudge11]

my combi boiler expansion vessel is also shot so i want to fit an external one .
The boiler has Pressure Relief Valve, filling loop and gauge so i'm assuming i can just plumb a new vessel in to the CH return without having to use another PRV, gauge and filling loop?

Do i need any seperate isolation or check valves ?

It will be fitted close to the boiler

It is a sealed system - using Baxi 105e combi

Thanks for any advice
BF