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Airlock in Central Heating System, or dodgy radiators?


 
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Gary_M

from United Kingdom

Joined: 01 Feb 2006
Posts: 1138
Location: Moray,
United Kingdom

PostPosted: Wed Feb 01, 2006 8:22 pm Reply with quote

Hi,

I would appreciate your advice regarding an issue I am having with one of my radiators.

Symptoms

    Radiator is requiring bleeding approx. once per week

    When the central heating 'kicks in' I can hear water bubbling in this radiator - almost as if the radiator is empty and it is filling up when the pump starts


I am not sure which position this radiator is within the system. I am guessing that it is the second one from the pump (5 radiators in total).

I have bled them all, as well as the system, but the problem keeps returning. There is no evidence of water escaping from this radiator, and the joints seem ok. There is no problem with the other radiators. The system is 'sealed' and hasn't lost any pressure. This radiator was removed recently and cleaned out and I was wondering if it is possible that this could have caused an air lock in the pipes between this radiator and the one before it? I have not been in this house for long, so I don't know the situation prior to the radiator being removed.

Any advice would be much appreciated. Also, how could I check if there is an airlock in the pipes, and more importantly, how can I get rid of this?

Thanks,

Gary
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EliteHeat

from United Kingdom

Joined: 28 Jan 2006
Posts: 1094
Location: London,
United Kingdom
Thanked: 2 times

PostPosted: Wed Feb 01, 2006 8:25 pm Reply with quote

Contaminated system producing hydrogen in the rads. Check it out by catching some gas in an upturned cup and then trying to ignite it. If it pops then you have a slowly dissolving system - treat it to a powerflush and a dose of inhibitor.
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Gary_M

from United Kingdom

Joined: 01 Feb 2006
Posts: 1138
Location: Moray,
United Kingdom

PostPosted: Wed Feb 01, 2006 8:32 pm Reply with quote

Thanks for the quick reply.

I'll get onto that tomorrow. Do you offer compensation if I blow my cup to pieces? icon_lol.gif
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EliteHeat

from United Kingdom

Joined: 28 Jan 2006
Posts: 1094
Location: London,
United Kingdom
Thanked: 2 times

PostPosted: Wed Feb 01, 2006 8:39 pm Reply with quote

I think the level of compensation is judged by the amount you paid for the advice! icon_biggrin.gif

Don't worry - your windows will be safe
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Gary_M

from United Kingdom

Joined: 01 Feb 2006
Posts: 1138
Location: Moray,
United Kingdom

PostPosted: Fri Feb 03, 2006 1:22 am Reply with quote

The plot thickens..............

I tried the up-turned cup test, but nothing !! icon_confused.gif There was quite a bit of air came out but no ignition, so I am guessing that it isn't a system deterioration. To be sure, I did it on several occasions with the same result.

I did notice something strange though - when I bled the 'suspect' radiator, it maintained a uniform heat, but one of the other radiators went cold at the top icon_eek.gif To my knowledge, the initial radiator that was causing the problem (the one I bled) was the second in line from the boiler, and the radiator that has gone cold at the top was the last in line (with two others in between). There was no effect on the other radiators and they always seem to be working fine - no air escaping when bleeding.

The pressure reading on the system is about 1.1bar - which is what it has always been.

I then tried to bleed the 'cold radiator'. Some air escaped, but not much, and it heated up again - BUT the other one went cold at the top icon_mad.gif I did notice that when I was bleeding this the 'noise' of the water circulating around the system changed for about 1 minute, then returned to its usual sound.

Any suggestions?

Thanks
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Slugbabydotcom

from United Kingdom

Joined: 10 Mar 2005
Posts: 3509
Location: Middlesbrough,
United Kingdom
Thanked: 83 times

PostPosted: Fri Feb 03, 2006 1:38 am Reply with quote

Turn your boiler stat down a bit then run it for a while and see if the problem eases.
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Softus

from United Kingdom

Joined: 21 Oct 2004
Posts: 19558
Location: United Kingdom
Thanked: 9 times

PostPosted: Fri Feb 03, 2006 8:08 am Reply with quote

I have a hunch that your pressure gauge isn't working, because it's very unusual not to have to repressurise after venting.

You said that it always reads 1.1 bar. If you turn off the boiler to make sure it doesn't fire, and that the pump doesn't pump, and then vent from one rad until nothing whatsoever comes out, does the gauge then drop to zero?
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Gary_M

from United Kingdom

Joined: 01 Feb 2006
Posts: 1138
Location: Moray,
United Kingdom

PostPosted: Fri Feb 03, 2006 12:23 pm Reply with quote

Thanks for the advice guys.

I think I have now sorted the problem.

There was actually very little pressure in the system icon_eek.gif - the last few times I was checking the pressure, I had just popped my head into the loft to look at the gauge - I have been looking at the 'moveable' pointer (the one you can set as a guide to maximum/ideal pressure) icon_redface.gif icon_redface.gif (no comments about 'bl**dy amateurs' please icon_smile.gif )

Having gone right up to the gauge today, I noticed the 'actual' pointer was sitting almost at zero icon_rolleyes.gif

I have re-pressurised the system, and had it running now for a couple of hours. All seems fine, but I'll keep an eye on things over the next few weeks.

Thanks again for all your advice icon_wink.gif
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