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Some radiators get hot others don’t. Any advice?

Discussion in 'Plumbing and Central Heating' started by bob2015, 13 Jan 2015.

  1. bob2015

    bob2015

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    OK let me just set the scene. I brought a house recently and I am still settling in. One of the things I am trying to get my head round is the central heating. Due to the age of the house I don’t think the house had central heating when built so must have been added since. The house has a relatively new combi boiler with sealed central heating system. Over the years the house has been modified a few times where radiators must have been moved. I have been having an issue that only half the radiators in the house are getting hot the others are only getting mildly warm.

    I firstly checked the radiators were all bled of air and there was good pressure in the system. All of which were fine.

    Ok so thought the issue was because the system just needed balancing, which I tried to do, by closing the valves on the hot radiators slightly and opening the valves on the cold radiators…….. However I got to the stage where the ‘hot radiators’ were completely closed (so now cold) and I only had one of the ‘cold’ radiators fully opened all the rest closed but I was then getting no flow at all around the central heating system, the boiler was still going. I confirmed the no flow by feeling the pipes directly under the boiler which were cold, I then opened a ‘hot’ radiator and instantly the pipes under the boiler were very hot. I carried this same experiment out on a few of the other ‘cold’ radiators with the exact same results.

    So at this point I knew it must be due to either at blockage or airlock somewhere in the pipework. So I thought I could confirm this by flushing the system through by opening a drain valve on one of the cold radiators and opening the filling loop simultaneously. I got really good flow out the drain valve so I closed it all up and re added some inhibitor (as I think I completely drained the system in the end). But I realised that this doesn’t prove anything as the water could easily be travelling a different path to the drain valve such as up the return or through another radiator or something, but after re adding the inhibitor, I don’t want to carry out any more similar experiments.

    I was convinced that it was an issue with an airlock until a few days ago when a hot radiator (which are still only slightly open but very hot) started making an annoying nose so I fully opened it then all of a sudden it became obvious that one of the ‘cold’ radiators was suddenly red hot!. So I am now confused as the radiators I am referring to are on opposite corners of the house. I thought at first that somebody must have plumbed these radiators up in series, but surly this is unlikely when the radiators are on opposite corners of the house isn’t it?

    So I was just wondering does anybody have any suggestions as to what is happening here and if it was ever acceptable to plumb radiators in series?
     
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  3. Agile

    Agile

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    Unlikely but you cannot assume anything!

    If you are lucky they may just need balancing.

    If anything is blocked then you should have already read about the bucket test in the FAQ here.

    Tony
     
  4. bob2015

    bob2015

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    Thanks for the reply.

    I have done some more test and I can now definitely say that when I shut off this one special radiator half the radiators go stone cold. If I then open the radiator all the cold radiators come back to life.

    I can't see the pipes as they are chased into the wall, but there is enoght free pipe for me to create a bypass pipe under the radiator some day but I think I will just live with having to keep the radiator open for the time being.
     
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