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Discuss Literally the most confusing issue ever! in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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JPP

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so.....

I will go over this as briefly as possible....please help!

Bought a house 2 years ago, the day we moved in the pressure dropped on the boiler and it stopped working...did some digging and the sellers (nice people that they were) had hidden the fact there was a leak on the chs....under the floor....the tiled floor....jeeze I hope those lovely people are enjoying their lives right now....! We took 2 floors up, fixed the leak (we hope) and now we find ourselves:

- there is an ufh system to the attic room that comes on, but then stays on and over rides the rest of the chs and keeps that on (we were told it was on its own loop but bought the house in April so it wasn't required) so currently we can't have this on....and concerned this is affecting pressure
- the system pressure drops sporadically, I filled it up the other day as it was under pressure, then Next thing you know it has jumped from 2.5 bar to nearly 4 and volcano status! Blockage maybe?
- concerned the leak under 2 different floors is not sorted
- some rads are patchy heat wise

This is a large chs with 15 rads on, the boiler is quite old but during tests it has found to be in good working order, and has a manga clean on it. Because the system has a variety of diffferent pipes on we have been advised against a power flush...

Please, for the love of hot water god, help us!
 
Your best and easiest option would be to contact a local gas safe engy
 
As above or if money is tight research all parts of the heating system including ufh and controlling different zones but do not go doing anything connected to the boiler other than topping up the pressure when cold.
 
Hi
A competent gas safe engineer will diagnose your problem straight away. But as it's part of the boiler, please call a local one. Won't cost much .
 
Further info....

We have had 3 different gas safe plumbers work on the system all with a different conspiracy theory......we still are no closer to getting it resolved.

It's not the boiler, that is a fact.
 
I've reread your post and you say your boiler is old.
You a
So state it's a sealed system. So has anyone checked th pressure in the expansion vessel? As it's an old boiler , it will be remote from the boiler. The his need checking with your he water side fully drained, best practice, is to remove it completely to check it.
This will cause your increase in pressure.
 
Is there sufficient expansion volume for the size of the system, i.e. if integral to boiler may not be enough on its own to compensate for increased volume when heated and requires additional external expansion vessel. Especially in system with UFH. See this very often.
 
Sorry everyone, there is pretty much an answer to everything, it's just my lack of recall/knowledge that is the problem....

Expansion vessel - this was plumber 1s attempt and he focused on this - no issue

There is sufficient pressure and expansion, this was also checked. We also fitted a new pump to the UFh (didn't work)

There is also an add on tank acting as a back up for hot water - an Alpha Flow smart 50!
 
Checked the filling loop is not letting by and over pressurising the system with subsequent loss of pressure when PRV releases?
 
Vee - not 100% certain on that one but I am 100% certain we investigated the filling loop...

My thoughts, baring in mind I am only a lowly tiler, but I have had 6 months of extreme exposure to chs!! are as follows:
-the ufh system is causing problems with the pressure to the system - because it is a bit of an unknown variable, I am not confident in it...
- there could be a blockage in the system somewhere that is causing pressure issues
- there still could be a leak to sort, but pressure drop is not constant or consistent, so not sure on this

Is there anyway of putting the ufh on its own loop at this stage so it takes that variable out?
 
You should be able to eliminate filling loop by making sure it is disconnected as it should be following top up. Even just a small weep bypassing could interfere.

It should be possible to isolate the UFH by turning off the isolation valves on the manifold. You could also test it for loss using with wet test gauge attached to the drain off provide it had a 3/4 or 1/2” thread. Don’t forget to turn off the controls whilst isolated. UFH should have its own primaries from the boiler via a zone valve.

Check the system for sufficient bypass, particularly if the controls are not wired for boiler interlock, i.e to stop demand when flow is low, as this could also cause symptoms similar to blockage. Also applies to UFH when several loops are closed due to being up to temperature and the tempering valve returning flow straight o the boiler. Distance between manifold and boiler may play a role in this, causing low flow through boiler. Has it an external bypass or only one in the boiler? It may need both.
 
Regarding just the pressure problems you say the expansion vessel was checked but it sounds like it might just not be big enough. This would cause the pressure to go up when the heating is on, more so if the UFH is on as that's even more water to expand, go over 3.5 bar then lose a bit of water every time it does, then be underpressured once it has cooled down.

I think that would be my first thing to look at.
 
Has anyone eliminated loss if after through PRV, after rise in pressure,or, indeed a passing PRV?

I often fit a small party balloon on the PRV outlet, even if I suspect other issues more strongly. Otherwise it is always there as a possibility. It is pretty much a quick, cheap, painless way of completely eliminating.

How old is "old"? Make and Model? Is it a condensing boiler? If so, the HEX could be leaking,and going through to condense. There is an easy test for this, but can sometimes lead to other problems, depending on model
 
I’ve also had a heat exchanger on Ideal Icos that failed in this way, and leaked through condense as firemant describes.
 
Regarding just the pressure problems you say the expansion vessel was checked but it sounds like it might just not be big enough. This would cause the pressure to go up when the heating is on, more so if the UFH is on as that's even more water to expand, go over 3.5 bar then lose a bit of water every time it does, then be underpressured once it has cooled down.

I think that would be my first thing to look at.

The pressure would come back down once the heating goes off though surely? Our pressure has been constant at 4bar for months now

The condense pipe was tested for water passing and nothing is coming out there either!
 
Did you disconnect the filling loop, as previously suggested? Has the vessel pressure been checked. Remember to check it with the boiler depressurised. It's all a stab in the dark not knowing the boiler make and model or whether the vessel is internal or external to boiler. The pressure relief should release at 3 bar. Clearly there is an issue in itself? The lack of info sadly is prohibitive.
 
I'm getting slightly lost on this, is the pressure problem that it's too high or that it's dropping?
 
And to check the expansion vessel is working/sufficiently large enough try this.

-Make sure the heating system is cold, this might take a whole day with the UFH
-Get the pressure to say 1.5 bar, top it up or release some pressure from a drain off valve or bleed vent etc if necessary
-Turn everything heating-wise on, all the rads on full, boiler temperature up and UFH on, room stats up, all that.
-Wait until it gets up to temperature, whilst watching the gauge. If it goes up and up then the vessel has burst/lost it's air/isn't big
enough
 
Also i've just looked up what an Alpha Flow smart 50 is, it seems to be more or less a thermal store, if the mains water coil in that has a hole in it it will be constantly letting mains water into the heating system and overpressurising it.
 
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