oversizing expansion

[Killy Bing]

out of interest does over sizing an expansion vessel cause issues ? tell me oh wise ones

 

[kimbo]

No. Only costs more to buy

 

[oz-plumber]

I am skeptical about answering this question.

I don't consider myself wise... and maybe out of my depth.

Therefor.. I would 'assume' the answer to be 'No'

But don't take my word for it....

 

[mountainman]

No. Only costs more to buy

Agreed!

 

[Centralheatking]

I have not thought about this before - so it is a really good question. My design company
is mostly arranged around pressure systems.

I think that it is quite possible - but will reply after I have checked this out

Centralheatking (API 2006) etc

out of interest does over sizing an expansion vessel cause issues ? tell me oh wise ones

 

[Hybrid]

Oversizing will cause less wear on the EV and cause less pressure rise in the system when heated. If you see a pressure gauge rise rapidly and high on heating the EV is under sized.
EV loosing pressure or the membrane perishing is probably the most common fault I see.

 

[Killy Bing]

the reason I ask I always size a system and put the equivalent size expansion vessel in for that + a size up and I don't include the expansion vessel in the boiler, I see that as an extra. I had a little disagreement with another engineer over this his argument was it causes the prv to fail. I naturally being my angry short self called him a tool

 

[Centralheatking]

A heavily oversized exp vessel could i suppose prevent the sealed system
reaching operating pressure - what do u think ? CHK

 

[AWheating]

its operating pressure is set at standing.

 

[Ray Stafford]

An EV should be sized to cope with the expansion within normal operating parameters. After that, it should blow off, creating nuisance and drawing attention to a potential system fault.

If you oversize the EV, then its additional capacity may mask another problem, which may then persist longer than it ought, causing damage elsewhere? Sounds convincing, but I have no idea whether its true.


On the other hand, as a supplier of EVs, you buy 'em as big as you like. The bigger the better. Can I interest sir in the "Dominator 2000" model, with added ribbing for extra sensitivity?

 

[zzzjim]

Oversize EV too much and you get a Bigger puddle if it leaks ?

(Less wear and tear = less future proffit -vs- Reliable reptutation )

 

[Billy Bob Bob]

over-sizing the EV causes no issues,cost between a 10-12L is not much,most 24kw,s will be 8L,most 30kw,s will be 10L,a 12L allows for extra rads that mystic meg might have added if she was a plumber or wizard or something

 

[tamz]

I naturally being my angry short self called him a tool

Quite rightly so and i hope you added the appropriate emphatic adjective :smile:

 

[DaveTidy]

It doesn't make any difference having a larger expansion vessel, it's initial pressure is set at cold and the EV's job is solely to take up expansion.

Other safety valves have their own setting so aren't affected by anything but their own characteristics.

Diaphragms generally fail due to water contaminents causing perishing, not usually low or high pressure.

It's no difference to fitting an enlarged header tank, as long as it takes up the expansion of the system water, the system will operate correctly.

Now how high should the open vent be above the water level per kw input, there's a question, have some of that!

 

[Killy Bing]

oh a little advantage of oversizing expansion.
more water content to fill rads while refilling the system !!!

 

[TBServices]

the reason I ask I always size a system and put the equivalent size expansion vessel in for that + a size up and I don't include the expansion vessel in the boiler, I see that as an extra. I had a little disagreement with another engineer over this his argument was it causes the prv to fail. I naturally being my angry short self called him a tool

You're over thinking it. Why would you waste time and money doing that on every install unless you know the vessel inside the boiler is too small?

 

[Killy Bing]

i would prefer to go back and service it and not have a completely flat vessel and a dripping prv
i noticed that was usually the case during my apprenticeship on places we hadn't fitted an extra one
it's just become part of what i personally want on my work

 

[TBServices]

Honestly I've never been back to one of my installs with PRV or expansion problems.

If your employer was repeatedly getting these issues, it was for other reasons. Not everyone wants an expansion vessel on the wall. The beauty of the combi (for the customer) is the lack of space they require.

 

[zzzjim]

.................l unless you know the vessel inside the boiler is too small?

Do customers crank up Flow temperatures (then forget to wind down when it warms up)
Do manufacturers actually do big enough internal EVs when they cost money ?
( are internal EVs fitted in sensible places , designed cleverly )

 

[Killy Bing]

Honestly I've never been back to one of my installs with PRV or expansion problems.

If your employer was repeatedly getting these issues, it was for other reasons. Not everyone wants an expansion vessel on the wall. The beauty of the combi (for the customer) is the lack of space they require.

oh i fully agree, i only fit them if its in a dedicated cupboard ,by a cylinder or can be hidden away.

however what does urk me is i keep going to expansion vessel's on flexi's !!!

 

[TBServices]

Do customers crank up Flow temperatures (then forget to wind down when it warms up)
Do manufacturers actually do big enough internal EVs when they cost money ?
( are internal EVs fitted in sensible places , designed cleverly )

No. Don't see your point there tbh, return temp is the nigh on the same inside the boiler as it is a metre away.
Yes. And if not THEN you fit an extra.
Not always, but then if the EV on your boiler of choice is in a stupid place, that's your own fault for fitting a ****e boiler lol. If it fails THEN you fit an external one.

 

[zzzjim]

My flow temp reference is about average water temperature ,when biggest quantity is hot .(If that ever happens with trv's , and zone valves these days.)
Sorry just over thinking !

 

[TBServices]

At least you admit it jim

 

[Killy Bing]

i'll happily admit im over engineering
however i can see less wear and tear?