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2 Radiators not getting hot

Discussion in 'Plumbing and Central Heating' started by WLF85, 17 Oct 2016.

  1. gigz

    gigz

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    He may well have but if they're even a slight bit closed its a restriction. Plus they might not be suitable for heating systems (but they might be)
     
  2. WLF85

    WLF85

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    I'm starting to think there might be a fundamental design flaw with this setup.

    If you look at my picture in the first post, the problematic radiators are connected to a section where the return runs down through the left hand pipe with the isolation valve, into the plastic elbow join and along the horizontal pipe until it reaches the main return pipe going into the boiler.

    I've already mentioned how most of the pipework in this section remains cold, however this evening I noticed that the horizontal return pipe after the elbow join is hot.

    I'm assuming that hot water that should be returning to the boiler is being incorrectly partially diverted into that return pipe where it meets the resistance of the flow and then gets stuck.

    Does that make any sense at all?

    Thanks again
     
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  4. WLF85

    WLF85

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    OK ignore my rambles above.

    Obviously the reason return water is diverting into that pipe is because there is no flow pressure coming from it because there is a block somewhere. I would say there's a good chance it is indeed the isolation valve on the return pipe because the horizontal pipe is full of hot water until the isolation valve, which has cold water above it.

    As you told me.

    Thanks! :)
     
  5. phod

    phod

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    1. make sure motorised valve to downstairs zone is latched open.
    2. fully close TRVs and lockshields on both rads.
    3. open TRV on rad1
    4. bleed out a pint or 2 of water.
    5. close TRV on rad1 and open lockshield on rad1
    6. bleed out a pint or 2 of water
    7. repeat for rad2 with rad1s valves closed.
    8. repressurise at filling loop as needed when bleeding.

    This checks that water is flowing through both those 22mm flow and return pipes and isnt airlocked / blocked.
    Its possible just the bleeding on its own moves the airlock on its own.
    If water doesnt easily bleed out when you are doing this you need someone to go back to the filling loop and pulse it on/off then on/off again repeatedly in the hope you can push the airlock / blockage through to that open bleed screw. Be armed with a bucket at the bleed screw listening for water and then air to hopefully come rushing through. Its sometimes best to completely remove the whole bleed screw during this process and turn off the flow via that one open rad valve once the airlock/blockage is starting to move (can be quite noisy/violent when it does go).

    Im not sure why your magnaclean is below (ie not in the circuit of) both the upstairs and downstairs rad returns. Is it connected into the cylinder return only? You really want it somewhere in the main circuit so that whatever zone is used the water flows through it.
     
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  7. WLF85

    WLF85

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    Just to report back, I parked this for a few weeks to work on other projects, and a few days ago the radiators randomly started to work.

    I have no idea what happened. I'm assuming there was a blockage which became dislodged.

    Thanks a lot for all your advice, I'll be sure to revisit the advice when the problem comes back.
     
  8. DIYnot Local

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