Combi-boiler woes.

Hi All. I replaced the presure relief valve on my combi last night. Bled the boiler but thesystem pressure goes right up. Is this purely down to air in the system (rads etc) expanding ?
Should I bleed upstairs first or downstairs and work up?
Cheers Pete
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Pet wrote:

Downstairs first. If the pressure goes way up when the system warms up it could be your expansion vessel is kaput.
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Off the top of my head, some of the following could be causes:
1. Leaking mains pressure heat exchanger (a) Within combi (b) Heatbank plate exchanger (c) Unvented cylinder indirect coil
2. Filling loop left connected.
3. Broken, uncharged or missing expansion vessel.
4. Broken pressure gauge.
5. Misunderstanding how system works (1 bar cold, but up to 2 bar when system heats up, depending on size of system, temperature rise and size of expansion vessel).
Christian.
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Did you bleed the air from your expansion vessel valve by any chance ?
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tarquinlinbin wrote:

You cruel person!
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wrote:

wouldnt be the first time and not only by DIYers either,even alleged CORGI men do it..but then a lot of them dont even test for soundness these days,or tightness come to that!
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tarquinlinbin wrote:

I surely hope not.
(Its a Valiant BTW)
I bled the valve at the top of the spirally tube that goes round the hot bit and the 2 walves eiter side (inlet + Outlet)
Tried the radiators, but no air was anywhere to be seen.
Seems OK today, I guess I had the cold pressure too high, which on start up was getting up to nearly 2.5 bar where the valve got sticky.
Lowering the pressure to about 0.9 bar, it goes up to about 2, then as the rad's shut down on 'stats, it seems to settle at about 1.5
I did notice however, when it was going right up in pressure and leaking, there were drips running from the bottom of one of the 2 flat(ish) cylinder tank type things (up the back next to the wall)
Hope my technical descriptions make sense.
:)
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Your expansion vessel is either broken, underinflated or undersized. You could benefit from ensuring that it is topped up. If this doesn't reduce the high pressure spike, consider fitting an additional unit.

I will hazard a guess that the flatish cylinder tank type thing is an expansion vessel. (I may be wrong). Releasing water in the way you suggest would be indicative that it may be blown, which would explain the excessive pressure rise.
Christian.
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Christian McArdle wrote:

Thanks for your advice Christian, How/where would I look at topping it up,

Ah. Sounds like a big job, as I presume the boiler will have to come off the wall.
As long as I run it at the current pressure, and it doesn't peak to "leaking" pressure, I presume I can get away without replacing it untill spring, or is it likeley to deteriorate rapidly?
Thanks for your help.
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You'll need to post the make and model of your boiler, so that the flat cylinders can hopefully be properly identified by someone with some specific product knowledge (which won't be me!). Better still would be if you could also take a photograph and put it on the web with a link. (Don't attempt to post a photo direct to the group).
Christian.
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Christian McArdle wrote:

Excellent idea. I'll take some snaps later tonight and post links in the next few days.
Cheers Pete
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On Mon, 10 Nov 2003 09:02:02 +0000, Christian McArdle wrote:

More info in FAQ below.
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Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
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Ed Sirett wrote:

Thanks Ed. That cleared up a lot of queries. Cheers Pete
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