can a good plumber explain this

C

chippyno

New Member
potterton powermax 150ltr

pressure dropping over 1 day

all pipes are in the ceiling space between upstairs and downstairs , no leaks are obvious.

replaced expansion vessel.

checked flexi hose to primary expansion vessel in the boiler.

replaced prv.

any ideas of the cause , when boiler on with ufh and rads pressure often between 1.5 - 3 bar

prv works at about 3.2bar , but it dont get to this , ive manually added more pressure to check.

I am pretty handy at most things , but am lost at this

any help most welcome.:):);)
 
any ideas of the cause , when boiler on with ufh and rads pressure often between 1.5 - 3 bar =======

if its rising that amount the ex v is undersized

and if the leak is not obvious the boiler is a good place to start looking
 
I had a leak on my combi once. Twas the compression joint where the ch pipes came out of the boiler. Leak was so slow that the leak was evaporating as it leaked. Only found it when the ch had been off during the summer months (week).
 
v.

Carnt believe you Leaky,its a like for like exp vessel,if its under sized the pressure will increase. Its got fuckall to do with a pressure drop. That is a leak. ***
 
Shooorly an undersized expansion vessel will allow the pressure to increase to where excess stuff is ejected via the PRV - so when the system cools down again - voilà - low pressure?

Place a container under the PRV discharge pipe and see if anything comes oot.
 
there is no prv leak .

but it seems to be that when the rad circuit is on the pressure rises to just under 3 bar then when the rads curcit goes off it drops to just under 1 bar then it drops gradually then it locks out.

how long would it take for a leak to show on a pb ceiling ?

all rads hot top to bottom ....im lost
 
Dear OP,


You change various parts, without reason but a good guess
You never say you check/test the parts
Repeat steps above, presumably charging each time.

Cowwwwwwwwwwwwwww-boyyyyyyyyyyyyyyy.

It's quite obvious that if the pressure increases to "just under" 3 bar - a standard for sealed central heating systems, that there's a PRV pi$$in somewhere. At an outside chance there is a leak under pressure but unlikely.

Sounds like an undersized exp vesssel and water out of the PRV. Who cares if you've replaced the original like for like. Does that mean it's the correct size.

Next time pretend you're a DIYer rather than a cowboy/thief. We might take pity on you.
 
Ouch, (Imran), quite a volley there.

From the symptoms described I would say there is a definite leak and it will be on a rad valve!

You need to take off the plastic caps and inspect all rads on full burn. The water can be leaking and evaporating before you find it coming through your ceiling.
 
Have you checked the auto air vent it is on top of boiler right hand side has a plastic cap on top of it but this should be slackend off but if this is passing it could be your problem
 
what pressure are you putting in the system when its cold ? try dropping the water pressure and checking the exp vessel pressure , should be around 10psi , then repressure
 
Imran says "Sounds like an undersized exp vesssel and water out of the PRV. Who cares if you've replaced the original like for like. Does that mean it's the correct size.
" So the manufacturer has undersized the exp vessel? I don't think so matey. unless you know different?????
 
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