Pressure Vessel

[waherne]

Hi all,

Just moved into a two storey 1950's house. Second floor rads are frozen while ground floor are roasting. Hot press cyclinder is also hot.

There is a red pressure vessel in the attic. I would think that this needs to be re-pressurised but have no idea how to go about this or what pressure should be set.

Could anyone please help me?

Thanks,

W.

 

[buffy27]

expansion needs to b set a half a bar above system pressure.find system pressure on auto fill maybe.
get a pressure test kit to read expansion pressure. i made one up from a car foot pump.u can add air with a bicycle pump.

 

[HTB]

You would also need to be qualified to work on unvented systems to carry out this work legally.

Without wishing to be rude, if you had done the course you would know the answer, I did the BPEC unvented course some years ag and found it very useful.

My understanding was if you haven't got the qualification you can't work on unvented systems, which is why I paid for and did the course, perhaps I may have got that wrong.

 

[buffy27]

practicle advice is what i try to give .please correct me if i am wrong.always open to criticism.here to learn

 

[HTB]

Buff, pleae let me apologise if that comment seemed snotty, swear it wasn't meant to.

I was just pointing out that pressurised (unvented) systems can cause horrendous injuries if they fail and individuals are exposed to the consequences. The unvented course is very safety orientated, quite rightly so, and goes to great lengths to emphasise the need for appropriate training.

 

[buffy27]

.i agree with strict policies on dangerous probabilities.{oooh that sounds good}.i only carry out work iam 100% certain that i know exactly what iam doing.i should add to the origional question posted that he should seek professional help as this is a pressurised system which has "dangerous probabilities"

 

[Mike Jackson]

Sounds more like a sealed system than an unvented to me. In that case I would check the system pressure and top it up with the filling loop before trying to represurise the expansion vessel.

Mike

 

[stevetheplumber]

You would also need to be qualified to work on unvented systems to carry out this work legally.

Without wishing to be rude, if you had done the course you would know the answer, I did the BPEC unvented course some years ag and found it very useful.

My understanding was if you haven't got the qualification you can't work on unvented systems, which is why I paid for and did the course, perhaps I may have got that wrong.

if like me you did the course years ago and were told it was a one of lifetime thing think again ive just been in formed it has to be renewed ever five years now

 

[unguided1]

Heres why it pays to go on unvented courses YouTube - exploding hot water cylinder myth busters enjoy
Regards
Mike

 

[waherne]

Thanks everyone. Think it's time to call in the professionals.

W.

 

[buffy27]

answer s probably a little hairy / fairy on this particular question. the professional plumbers are all on holidays this week .appologies on behalf of the all knowing ,semi qualified club.

 

[traineedrip]

Sounds more like a sealed system than an unvented to me. In that case I would check the system pressure and top it up with the filling loop before trying to represurise the expansion vessel.

Mike

Mike, shouldnt you drain some water out of a sealed system to give space for the bladder to inflate?

 

[fatoftheland]

If you have the unvented cert, then you repressurise the expansion vessel with zero pressure on the heating. i.e the pressure guage on the heating is at its lowest

 

[traineedrip]

If you have the unvented cert, then you repressurise the expansion vessel with zero pressure on the heating. i.e the pressure guage on the heating is at its lowest

hi mate im currently studing unvented hence the query. if you took the pressure out of the system, so 0 bar.. but still had it full of water and say a half filled expansion vessel bladder.... as you tried to repressurise where would the displaced water go?
wouldnt you pump away seeing the bicycle pump gauge hit the required pressure but in reality the bladders volume is still half filled?

perhaps ive got this wrong? happy to be corrected ... here to learn off you pros

 

[fatoftheland]

There will be no pressure against the air side of the membrane if the boiler guage is at zero (assuming the guage is accurate) This is the only time you should measure and repressurise the air in the expansion vessel. As a quick test if you depress the valve in the vessel and water comes out you can safely assume that the membrane/bladder is split. One more point is that there will be a static pressure in the boiler of 0.1 bat per metre of water above the boiler. 1 bar equals 10 m of water head

 

[Mike Jackson]

Mike, shouldnt you drain some water out of a sealed system to give space for the bladder to inflate?

I meant that the cause was more likely to be lack of pressure in the system than a problem with the pressure vessel.

 

[traineedrip]

There will be no pressure against the air side of the membrane if the boiler guage is at zero (assuming the guage is accurate) This is the only time you should measure and repressurise the air in the expansion vessel. As a quick test if you depress the valve in the vessel and water comes out you can safely assume that the membrane/bladder is split. One more point is that there will be a static pressure in the boiler of 0.1 bat per metre of water above the boiler. 1 bar equals 10 m of water head

thanks. i thought just after id posted it that there would be static pressure from pipes above the boiler. realise also that there is adaquate room otherwise the boiler pressure gauge would rise as you re-charged.

obvious really

I meant that the cause was more likely to be lack of pressure in the system than a problem with the pressure vessel.

Thanks Mike. Realise what you ment now

 

[billybongo]

Out of curiosity what is the difference between unvented and sealed systems , just being nosey

 

[HTB]

Hi steve, I'm on my CCN at the moment back at my old training centre and you are quite correct the Unvented has to be renewed at the 5 year point, there seems to be a question though whether it is 5 years from when the qualification was obtained or 5 years since the new regulation came out, once I know for sure I'll sort it out.

 

[Mike Jackson]

Out of curiosity what is the difference between unvented and sealed systems , just being nosey

When someone says unvented they normally mean an unvented domestic hot water storage system such as a megaflo.

A sealed system is a heating system with a pressure vessel, filling loop and safety discharge valve instead of a header tank with cold feed and open vent.

It can be a bit misleading sometimes as both can have pressure vessels and discharge pipes.

Mike

 

[billybongo]

Thanks for replying Mike , its pretty much what i thought , and like yourself i think its a bit misleading because they are much the same thing . cheers .