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Heating Pressure Loss #1627950
15/12/2018 10:04
15/12/2018 10:04
Joined: Mar 2006
Posts: 8,852
Cambridge & Cotswolds
M
MeanRedSpider Offline OP
Je suis un Coupé
MeanRedSpider  Offline OP
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M

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Cambridge & Cotswolds
I’m losing pressure in my heating system but, confusingly, it seems to mostly happen overnight. I can’t figure out what’s going on. The system is currently pretty butchered because of house work but I can’t find a leak anywhere and I drop from 2 bar to 0.8 bar overnight.

I can only think of two things:
1. It’s a boiler issue that’s internal and the leak occurs when it’s off duty.
2. It’s in the hot water circuit and the pressure drops only when hot water heating occurs (this one doesn’t really make sense as the systems are common on the return)

Any ideas?

Re: Heating Pressure Loss [Re: MeanRedSpider] #1627954
15/12/2018 11:20
15/12/2018 11:20
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Jim_Clennell Offline
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Jim_Clennell  Offline
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I'll ask Stepson Senior (plumber/heating engineer)...

Re: Heating Pressure Loss [Re: MeanRedSpider] #1627955
15/12/2018 12:05
15/12/2018 12:05
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Cambridge & Cotswolds
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MeanRedSpider Offline OP
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Cambridge & Cotswolds
Thanks, Jim! I’m a bit baffled by the symptoms

Re: Heating Pressure Loss [Re: MeanRedSpider] #1627957
15/12/2018 12:18
15/12/2018 12:18
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Jim_Clennell Offline
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The response was that it could be the expansion vessel. He says check any vents (probably to exterior) as it could be the pressure relief valve.

Re: Heating Pressure Loss [Re: MeanRedSpider] #1627958
15/12/2018 12:32
15/12/2018 12:32
Joined: Jun 2006
Posts: 5,244
Watford, Herts.
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Hyperlink Offline
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Watford, Herts.
Is the system fully bled - you could be seeing a pressure change as any trapped air expands or contracts as it heats/cools?

Re: Heating Pressure Loss [Re: Jim_Clennell] #1627959
15/12/2018 12:33
15/12/2018 12:33
Joined: Mar 2006
Posts: 8,852
Cambridge & Cotswolds
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MeanRedSpider Offline OP
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Joined: Mar 2006
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Cambridge & Cotswolds
Originally Posted By Jim_Clennell
The response was that it could be the expansion vessel. He says check any vents (probably to exterior) as it could be the pressure relief valve.


Cool - will look. Thank him, please (and you too, Jim)

Re: Heating Pressure Loss [Re: Hyperlink] #1627960
15/12/2018 12:36
15/12/2018 12:36
Joined: Mar 2006
Posts: 8,852
Cambridge & Cotswolds
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MeanRedSpider Offline OP
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Cambridge & Cotswolds
Originally Posted By Hyperlink
Is the system fully bled - you could be seeing a pressure change as any trapped air expands or contracts as it heats/cools?



I don’t know if totally bled though I’ve topped it up loads of times thinking that this may be what it is - but, if anything, the problem is getting worse - the reverse to what you’d expect if it was air

Re: Heating Pressure Loss [Re: MeanRedSpider] #1627962
15/12/2018 14:08
15/12/2018 14:08
Joined: Aug 2009
Posts: 6,192
Bristol, UK
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Hovedan Offline
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Bristol, UK
Watching. Mine does EXACTLY the same. Have consulted Dr Google and pressure relief valve seems to be high on the list.

Thing I have, is pressure is 1.5 bar when the boiler is operating, then when the system is off and cold it sits at 0.5 bar in the red. Switch it on and it rises to 1.5 when going.

I should only be concerned what the pressure is when it's on, is my line of thought?

This strangely feels like an oil pressure conversation!!

Re: Heating Pressure Loss [Re: MeanRedSpider] #1627968
15/12/2018 15:43
15/12/2018 15:43
Joined: Dec 2005
Posts: 21,070
Chertsey in the Thames
bockers Offline
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All this does sound like the expansion vessel is broken. It's like the lung of the system keeping everything at a regular pressure if it fails the pressure will rise when hot and the relief valve will blow then when cold it will be under pressure.

Re: Heating Pressure Loss [Re: MeanRedSpider] #1627969
15/12/2018 16:11
15/12/2018 16:11
Joined: Mar 2006
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Cambridge & Cotswolds
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MeanRedSpider Offline OP
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Cambridge & Cotswolds
Except the pressure never gets very high and hardly fluctuates - 2.4 bar max - which is below the 3 bar gauge “red line” (the boiler’s gauge goes up to 6 bar). I also expect to see steam rising somewhere in this cold weather if the hot water was venting.

I’ll ask the builder’s heating guy to take a look at it when he’s doing the underfloor heating connections.

Re: Heating Pressure Loss [Re: MeanRedSpider] #1627972
15/12/2018 17:45
15/12/2018 17:45
Joined: Dec 2005
Posts: 33,522
Berlin
barnacle Offline
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Berlin
I chased a similar problem for weeks and didn't find a hint until I chanced to wonder why there were water marks on the coupe... the manifold in the room above the garage had a pinhole leak and the gap below the floorboards had two inches of water sitting in it.


[Linked Image]
Don't get no respect! Coupe Fiat 1994-2000 - an owner's guide <-- clicky!
Re: Heating Pressure Loss [Re: MeanRedSpider] #1627973
15/12/2018 19:35
15/12/2018 19:35
Joined: Oct 2008
Posts: 6,783
In the coupe.
magooagain Offline
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In the coupe.
Loss of pressure normally points to a leak somewhere. And shows more when the system is heating and pumps are running.

A small leak will show a lot of pressure loss over 24hours.



Re: Heating Pressure Loss [Re: magooagain] #1627989
16/12/2018 22:39
16/12/2018 22:39
Joined: Dec 2005
Posts: 19,937
North wales
pinin_prestatyn Offline
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North wales
Another vote for the expansion ‘bladder’. A friend had the same issue.



Coopless!
Re: Heating Pressure Loss [Re: MeanRedSpider] #1627993
17/12/2018 06:38
17/12/2018 06:38
Joined: Jul 2012
Posts: 1,650
Dark side of the Moon
H_R Offline
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Dark side of the Moon
Have you checked the pressure relief valve in case its draining into a hidden drain
And normal domestic combi boilers only need to be about .8 bar if you are topping up to 2.4 im not supprised its dropping pressure when it cools down as it will certainly vent as it expands then be less when cold

Re: Heating Pressure Loss [Re: MeanRedSpider] #1627994
17/12/2018 06:53
17/12/2018 06:53
Joined: Mar 2006
Posts: 8,852
Cambridge & Cotswolds
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MeanRedSpider Offline OP
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Posts: 8,852
Cambridge & Cotswolds
It’s a big, f-off, Boulter oil-fired boiler that basically cuts out at 1 bar or less. The mid-point of the “green” zone on the pressure gauge is 2 bar.

Anyhow, I think I’ve found the problem - or, more accurately, Mrs MRS did. Visiting the “building site” that serves as my home, she asked Charlie why his bedroom carpet was wet. He said he’d been wondering about that...! Clearly, a first from Cambridge doesn’t mean you have a brain.

I’ve tightened the offending joint and hopefully that’s it solved. The first floor level at Charlie’s part of the house is 8” concrete slab hence no sign below and it was under his desk.

Thanks for the suggestions - as usual, it’s the simple answer - compounded by the chaos that my home currently is. Waiting on windows that, in true Grand Designs style, are months late.

Re: Heating Pressure Loss [Re: MeanRedSpider] #1627995
17/12/2018 06:55
17/12/2018 06:55
Joined: Dec 2005
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Jim_Clennell Offline
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Sounds like a nightmare, but also very exciting!

Re: Heating Pressure Loss [Re: Jim_Clennell] #1628005
17/12/2018 15:52
17/12/2018 15:52
Joined: Mar 2006
Posts: 8,852
Cambridge & Cotswolds
M
MeanRedSpider Offline OP
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Joined: Mar 2006
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Cambridge & Cotswolds
Kinda got here

click to enlarge

Re: Heating Pressure Loss [Re: MeanRedSpider] #1628006
17/12/2018 17:21
17/12/2018 17:21
Joined: Aug 2017
Posts: 338
Camberley, Surrey
J
jonnyboy54321 Offline
Making a profit
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Joined: Aug 2017
Posts: 338
Camberley, Surrey
Originally Posted By MeanRedSpider
Kinda got here

click to enlarge


I remember those days all too well ooo
click to enlarge


Always seem to have too many 20VT's to count......

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