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Airlock in Central Heating System, or dodgy radiators?

Discussion in 'Plumbing and Central Heating' started by Gary_M, 1 Feb 2006.

  1. Gary_M

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    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
     
  2. EliteHeat

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    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.
     
  3. Gary_M

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    Thanks for the quick reply.

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

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    I think the level of compensation is judged by the amount you paid for the advice! :D

    Don't worry - your windows will be safe
     
  5. Gary_M

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

    I tried the up-turned cup test, but nothing !! :confused: 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 :eek: 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 :mad: 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
     
  6. Slugbabydotcom

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

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    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?
     
  8. Gary_M

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    Thanks for the advice guys.

    I think I have now sorted the problem.

    There was actually very little pressure in the system :eek: - 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) :oops: :oops: (no comments about 'bl**dy amateurs' please :) )

    Having gone right up to the gauge today, I noticed the 'actual' pointer was sitting almost at zero :rolleyes:

    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 ;)
     

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