Any central heating experts about??

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Jukie

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I find I have to regularly bleed three of my radiators when the heating is on.

Before I call out a plumber, any ideas where the air might be getting in or what the problem might be?

Whatever it is, it's not something I'll be tackling myself - floods and/or gas explosions spring to mind!!!

TIA, David.
 
What kind of system do you have, a system boiler with a header tank or a sealed combi boiler system.?
 
What sort of system do you have? Open vented, sealed / pressurised?

How old is the system? Corrosion, through lack of inhibitor, can lead to gas being generated.
 
Just a wee aside - you should bleed your radiators with the central heating turned OFF, not ON.

Try that, then switch the heating on, see if it makes any difference. If not, it sounds like you have an air lock, not difficult to fix if you know what you're doing! SHouldn't be too expensive.
 
you might have a small leak in the system i know you can get a sealer a bit like radweld i used it in my inlaws combi & it did work just put it in one off the rads easy to do
 
I had air intake via a corroded ' spindle assembly ' on a rad valve. Replaced the valve and was ok. I believe too high a pump setting can also cause air getting into the system through venting too much.

You can also buy ' automatic ' bleed valves that replace the bleed screw which vent automatically. Not the ideal solutiuon but might help. However, if the bleed screws are ' inset ' rather than being flush with the end of the rad, then the length of the automatic bleed valve may not be long enough to fit.

John
 
It could be one or more of a number of things. If your system is a an open vent (usually non combination boiler) :-

If the pump is on the return side of the system then, when its running, the system pressure is less than atmospheric and air can enter via old seals around, (typically), radiator valves etc then gather at the tops of the radiators.

If the pump is on the flow side of the system it could be pumping over into the header tank in the loft which will cause aeration and therefore air seperation in the system.

It might well not be air at all and it could be hydrogen. How old is the system?, has it ever been dosed with inhibitors? or has it been flushed or cleaned? If its old and a small amount of air has entered somehow at some point, (as above), then you have the mixture of air+water+steel=corrosion which manifests itself has hydrogen gathering at the tops of radiators.

There is a very old trick to verify this but its risky and you must know what you are doing?, all I will say is it involves a match or a lighter ;) ok if you have been brought up in gas/plumbing industry but otherwise......

Hope that helps? Its always hard to diagnose from a distance.

Cheers.

Portzy
CORGI No 302827;)
 
One further thing. If its a sealed system - normally fitted with a pressure vessel at a high point (usually red in colour) and fitted with a small pressure gauge. Make sure that the vessel is running at its proper working pressure otherwise air can get in the system. There is normally a small hand valve near the vessels inlet connection which you can open and close to increase the pressure in vessel. The pressure gauge is USUALLY marked with the correct operating pressure range. Make sure its within the range indicated, and if low, open the valve to increase to working pressure. Close the valve when its reached its working pressure.
Over a period of time (say 3-4 years) the pressure in the system will drop because of numerous things and you do very occasionally need to repressurise the system to keep it all working as it should. If the pressure in vessel is allowed to get too low, air can be sucked into the system caused problems which you describe. Check the pressure gauge and see.
 
If your system is open vented, it may be full of sludge (iron oxide), best think to do would be get it powerflushed, and have a magnaclean filter fitted (Adey solutions) or at a lesser cost, have any blockages removed and fit a magnaclean.
 
Also scale buildup in the heat exchanger leading to "kettling" (localised boiling) which releases oxygen. Descalant, flush, then inibitor will do the trick if that's the case.

Do you have a dial or high/low switch for the boiler water temp (not the hot water temp), try turning this down to see if it makes a difference (less chance of kettling if water is not as hot in the first place).
 
i would say portzy's hit the nail on the head as im corgi registered aswell
wont be scale its a common misconseption it will be hydrogen id imagine caused by iron oxide - air ingress ( red water) or magnatite which is chemical caused by lack of inhibitor and reaction of all the different metals ( black water ) . but i would be surprised is poor system design is at fault ---- i see it every day. do you have any slight leaks any where? is the system sealed? portzy will vouch i image , blue tooth / telephone diagnostics are a mare...........
 
i would say portzy's hit the nail on the head as im corgi registered aswell
wont be scale its a common misconseption it will be hydrogen id imagine caused by iron oxide - air ingress ( red water) or magnatite which is chemical caused by lack of inhibitor and reaction of all the different metals ( black water ) . but i would be surprised is poor system design is at fault ---- i see it every day. do you have any slight leaks any where? is the system sealed? portzy will vouch i image , blue tooth / telephone diagnostics are a mare...........
Yep - porty's points are the most likely (I was just adding an alternative)
 
Thanks to all replies so far.

Sorry for not adding additional info before now. Night shifts are the devil's work!!!

I've a combi-boiler, no water tank. Boiler is not yet a year old (December 07) and I don't believe the problem existed from day 1 of the new boiler but I can't remember when I first noticed it.

When the boiler was put in, a radiator was replaced in the bathroom. Inhibitor was used put into the system with the new boiler. As for the rest of the system, I've no idea how old it is. Not aware of any leaks, all rads bar the new one have thermostatic valves on them.
 
Last edited:
Thanks to all replies so far.

Sorry for not adding additional info before now. Night shifts are the devil's work!!!

I've a combi-boiler, no water tank. Boiler is not yet a year old (December 07) and I don't believe the problem existed from day 1 of the new boiler but I can't remember when I first noticed it.

When the boiler was put in, a radiator was replaced in the bathroom. Inhibitor was used put into the system with the new boiler. As for the rest of the system, I've no idea how old it is. Not aware of any leaks, all rads bar the new one have thermostatic valves on them.

In that case it does look or rather sound like hydrogen production. With a combi (no tanks) the system is sealed and always under a pressure of about 0.75 to 1.0 bar (cold) so what would normally be the usual suspects for air entrainment would manifest themselves as definate leaks.

If no leaks are apparent (you would be losing pressure and the boiler would fail safe?) then the system is producing the gas which is being confused as air.

Unless your engineer can spot something else than I would:-

1. Have it powerflushed or a good long winded and thorough manual flush.
2. Fill up and vent adding a litre of Sentinel X300 (cleanser)
3. Leave that in for a few weeks, about four, and use the heating frequently.
4. Drain off completely and hot flush out, completly, 3 to 4 times.
5. Fill up and vent adding 1 litre each of Sentinel X100 & X200 (inhibitors).

See how that goes.

HTH.

Portzy.
 
In that case it does look or rather sound like hydrogen production. With a combi (no tanks) the system is sealed and always under a pressure of about 0.75 to 1.0 bar (cold) so what would normally be the usual suspects for air entrainment would manifest themselves as definate leaks.

If no leaks are apparent (you would be losing pressure and the boiler would fail safe?) then the system is producing the gas which is being confused as air.

Unless your engineer can spot something else than I would:-

1. Have it powerflushed or a good long winded and thorough manual flush.
2. Fill up and vent adding a litre of Sentinel X300 (cleanser)
3. Leave that in for a few weeks, about four, and use the heating frequently.
4. Drain off completely and hot flush out, completly, 3 to 4 times.
5. Fill up and vent adding 1 litre each of Sentinel X100 & X200 (inhibitors).

See how that goes.

HTH.

Portzy.

Cheers, Poetzy.

Could these steps be undertaken by a total novice, i.e. me? 'Cause I wouldn't know where to start!

I suspect I'm best off getting an expert! lol

David.
 
Cheers, Poetzy.

Could these steps be undertaken by a total novice, i.e. me? 'Cause I wouldn't know where to start!

I suspect I'm best off getting an expert! lol

David.

A competent handy person or DIY'er? I would say yes but, with the utmost respect, not really a "total novice". There are a few diy websites around that guide you through draining off and re-filling heating systems so have a read and see what you think.

All the best.

Portzy.
 

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