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O/T - central heating & boiler question - help would be greatly appreciated



Goldstone1976

We Got Calde in!!
Helpful Moderator
NSC Patreon
Apr 30, 2013
13,765
Herts
Good morning gentlefolk who support the Albion. I wonder if some expert might be able to assist me...

I'm at my mother's this morning, trying to understand the central heating system she has in place and trying to fix a problem. The problem I'm trying to fix is that the bathroom radiator keeps filling with air (a radiator full every 2 weeks). This radiator (which she describes as the "master") is the only one without a TRV, and is closest to the boiler (a combi Worcester Highflow 400 Electronic). There is absolutely no sign of any water leaking out of the system anywhere, but I accept that water must be coming out somewhere as air is getting in (unless the whole system was full of air and air bubbles are moving round the radiators and pipes until they get to the bathroom radiator??)

The thing that I don't understand is that that there is a flexible pipe linking two pipes coming out of the boiler. This flexible pipe has an inline (two actually, but I think one is just for redundancy) valve. The flexible pipe seems to connect the mains cold water pipe to one that is integral to the heating (or hot water?) loop. The valves were closed when I first started looking at the system. In order to bleed the radiator, I needed to open the valves (to allow water into the system to replace the air I was bleeding out, I presume). Should these valves be open or closed during normal operation?

many thanks for any help you might be able to offer on either question!
 


knocky1

Well-known member
Jan 20, 2010
12,948
Closed. Otherwise you are constantly filling the system and will over pressurise.Did you bleed with heating on? You should.
Is the rad the highest in the building? The leak could then be elsewhere and air makes it's way up??

Only guesswork on my part.
 


Goldstone1976

We Got Calde in!!
Helpful Moderator
NSC Patreon
Apr 30, 2013
13,765
Herts
Closed. Otherwise you are constantly filling the system and will over pressurise.Did you bleed with heating on? You should.
Is the rad the highest in the building? The leak could then be elsewhere and air makes it's way up??

Only guesswork on my part.

I bled with the heating off, but will change that habit. Rad is equal highest (with one other), so you could be right. Thanks for confirming the valves s/be closed. Hmmm - so, it's pretty certain that there's a leak somewhere then. Bugger. I have no idea where from. Time for a plumber? But - will they be any more able to find a leak than me?.

thanks for the help...
 




knocky1

Well-known member
Jan 20, 2010
12,948
Check you haven't overfilled the system by reading the pressure dial on the boiler before putting on heating.

That leads to a possible answer, by the way, the pressure relief valve may be leaking and that would be outside the house. But it's time for my inner cowboy to retire.
 




Soulman

New member
Oct 22, 2012
10,966
Sompting
Obviously being a sparks best to leave it to the experts on here, however, surely if your system had a leak then the pressure would drop and you would keep having to use the expansion loop to get the pressure up to about 1.5. The boiler would shut down if the pressure dropped. I take it the boiler has not been shutting down? or has it.
 


Goldstone1976

We Got Calde in!!
Helpful Moderator
NSC Patreon
Apr 30, 2013
13,765
Herts
Check you haven't overfilled the system by reading the pressure dial on the boiler before putting on heating.

That leads to a possible answer, by the way, the pressure relief valve may be leaking and that would be outside the house. But it's time for my inner cowboy to retire.

There's a pressure dial/gauge on the boiler?! Not obvious where it is - I'll dig out the manual and check the pressure. I'll also see if I can find the pressure relief valve! Thank you, Mr Cowboy...
 


Goldstone1976

We Got Calde in!!
Helpful Moderator
NSC Patreon
Apr 30, 2013
13,765
Herts
Obviously being a sparks best to leave it to the experts on here, however, surely if your system had a leak then the pressure would drop and you would keep having to use the expansion loop to get the pressure up to about 1.5. The boiler would shut down if the pressure dropped. I take it the boiler has not been shutting down? or has it.

Boiler has never shut down. I've been having to bleed said bathroom rad for about two months though. Seems like I need to find a pressure gauge...!
 




Goldstone1976

We Got Calde in!!
Helpful Moderator
NSC Patreon
Apr 30, 2013
13,765
Herts
Ah ha. Front panel of boiler removed. "Maximum heating system pressure 2.5 bar"; pressure gauge = 3.2 bar. Now to find out how to reduce pressure!
 


knocky1

Well-known member
Jan 20, 2010
12,948
On lowest radiator should be a drainage wot sit but could be messy. You could bleed it out of any rad. OR turn the heating on and it will come out the PRV, not recommended.

If the heating is off that pressure will increase when the water heats up.
 


Soulman

New member
Oct 22, 2012
10,966
Sompting
Boiler has never shut down. I've been having to bleed said bathroom rad for about two months though. Seems like I need to find a pressure gauge...!

Well, wait for the experts to come on but normally on the boiler there is a gauge, and a green section, if the needle is in this section then your pressure is correct and presumably only drops when you are bleeding the system, which i would assume means you do not have a leak. Have you tried bleeding all the rads, making sure that each time the pressure is correct, otherwise if the pressure has dropped then you are unlikely to be bleeding it properly.
 




Westdene Seagull

aka Cap'n Carl Firecrotch
NSC Patreon
Oct 27, 2003
20,938
The arse end of Hangleton
Ah ha. Front panel of boiler removed. "Maximum heating system pressure 2.5 bar"; pressure gauge = 3.2 bar. Now to find out how to reduce pressure!

Be careful, you need to be Gas Safe registered to do that !
 


Soulman

New member
Oct 22, 2012
10,966
Sompting
Ah ha. Front panel of boiler removed. "Maximum heating system pressure 2.5 bar"; pressure gauge = 3.2 bar. Now to find out how to reduce pressure!

Bleed the problem radiator until the pressure on the boiler drops to the correct level, maybe helpful to have someone at the boiler to tell you when the pressure has reached the correct level.
 


Mr Bridger

Sound of the suburbs
Feb 25, 2013
4,408
Earth
Filling loop should be disconnected until you need to fill up the system. Otherwise it can be left on and let water into the system and alternatively if the check valve fails, central heating fluids can back flow into the potable water supply.
Rad in bathroom won't have TRV and probably used as a bypass which means if heating is on and all other rads shut down it has somewhere to circulate.
The drop in pressure constantly could be due to faulty expansion vessel and air will collect in the highest point, I assume it's a towel rad?
You can repressurise the expansion tank but may need replacing if membrane split.

Ring a plumber....
 




Goldstone1976

We Got Calde in!!
Helpful Moderator
NSC Patreon
Apr 30, 2013
13,765
Herts
Ok guys. Found the pressure relief valve knob. Turned it and watched pressure drop til it hit 1.8 bar, when I turned it back off.
(Which is where the manually moveable red needle is turned to - which I'm guessing is the correct pressure). So far, so good. Unfortunately, the pressure just kept on going down, and bottomed out at 0.2 bar, even though the valve was off. So, I repressurised to 2 bar. And watched it drop to 0.2 bar. Rinse and repeat 5 times.

Hmmm.

Plumber called.

thank you for all the helpful suggestions and support. Gotta love NSC at times like this :thumbsup:
 


jon12345

New member
Jul 22, 2014
119
Bleed a radiator allowing water to release until the gauge on the boiler is 1 bar when cold ( Boiler not on and radiators cold) You might need some old towels and do it in a room with lino, not your best carpet.

Use the boiler as normal and bleed the bathroom rad when needed and top the water to 1 bar when cold after bleeding.

hard to be sure without seeing/hearing the system run. But my guess would be it needs flushing. Probably a build up of muck in the system.


Screen shot 2015-05-24 at 12.37.24.png
 


Mr Bridger

Sound of the suburbs
Feb 25, 2013
4,408
Earth
Ok guys. Found the pressure relief valve knob. Turned it and watched pressure drop til it hit 1.8 bar, when I turned it back off.
(Which is where the manually moveable red needle is turned to - which I'm guessing is the correct pressure). So far, so good. Unfortunately, the pressure just kept on going down, and bottomed out at 0.2 bar, even though the valve was off. So, I repressurised to 2 bar. And watched it drop to 0.2 bar. Rinse and repeat 5 times.

Hmmm.

Plumber called.

thank you for all the helpful suggestions and support. Gotta love NSC at times like this :thumbsup:

Faulty expansion vessel
 


Rowdey

Well-known member
Jul 7, 2003
2,529
Herne Hill
Or now he's used the PRV, that is letting by (even more than before..)

Goldstone1976 - Is the PRV (the open pipe to outside) dripping after you have released pressure from it ?
 




BN9 BHA

DOCKERS
NSC Patreon
Jul 14, 2013
21,451
Newhaven
Closed. Otherwise you are constantly filling the system and will over pressurise.Did you bleed with heating on? You should.
Is the rad the highest in the building? The leak could then be elsewhere and air makes it's way up??

Only guesswork on my part.

Unless I have read this wrong, are you advising to bleed the rads with the heating on ?
 





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