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Radiator Circulation

Discussion in 'Plumbing and Central Heating' started by Bon, 14 Mar 2020.

  1. Bon

    Bon

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    Good evening all,

    I'm mid-way through a project which has involved moving 2 radiators and branching off one of these to install a new radiator.

    I did all the first-fixing a while ago (drained down, made break-ins etc...) and today I have drained down again and made the final connections.

    I refilled the system (adding inhibitor), bled, topped up and fired everything up.

    The 2 radiators that consist of one that I've moved and the new one don't seem to be getting any heat circulating. The other radiator I moved is fine and the rest of the house is toasty.

    They bled fine and have water at them, but they're not heating up.

    My initial thought was that the branching (10mm tee off a 10mm pipe) was too small and the pump wasn't able to circulate. So, I isolated one and turned the pump up to max speed and took the dog for a walk. I've just got back and it's still stone cold.

    SO far I've thought;

    1 - Blockage - But it filled up OK
    2 - Crossed flow/return - The TRVs are bi-directional so this shouldn't make a difference
    3 - 10mm pipe serving 2 rads is too small - Need to get out my sizing tables, BUT would have thought they would at least get some heat to them
    4 - Too much resistance - Isolated one rad completely and turned the pump up
    5 - TRV stuck - I've taken the heads of and manually worked the valves and left them both (and the LSV fully open)

    Tomorrow (when I'm full of the enthusiasm of a new day) I'm going to try shutting all of the other rads on the zone downstairs to see if it's a balancing issue.

    Would any of you lovely people care to make any suggestions as to anything else to try?

    Many thanks!
     
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  3. denso13

    denso13

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    That's what I would suggest first.
     
  4. gasbanni

    gasbanni

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    Make sure the lockshields opposite the trv's are both open ( full anti clockwise from above ) ! That's the first thing to do.

    Turning all the other rads off but leaving these two on and putting the heating on you'll see within seconds if it's a balancing issue.

    Do this whist your there .....the dog can wait !
     
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  5. gasbanni

    gasbanni

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    Water coming out if the bleed valve can still occur even if you've crossed the flow and return pipework.

    If your heating circuit isn't zoned in other words when the heating is on all the rads get hot, turn off every rad except one of the rads that doesn't heat up.

    Stay by the boiler whilst all the rads except one are closed and turn the heating on, if the boiler starts to overheat or complain (kettling/ banging) turn it off.
    Then open the other closed rad and turn off the one that was on .......see what happens ......might be airlocked.

    You can always remove the bleed screw housing on the rad, screw in a 1/2" male x 15mm compression put in a few inches of 15mm copper put a hose on it jubilee clipped then to out side, open the filling loop then open in turn the lockshield or trv individually in turn you would expect water to flow in either direction, you might need to do this on each rad.....it should at least reveal the problem.
     
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  6. DP

    DP

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    Forget thee radiator, is the pipe/ valve heating.
    10mm is for single radiator connection, branch is bad move
     
  7. Bon

    Bon

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    Thanks for all the help guys. I’ve managed to get some heat round now!!

    Increased pump speed, and did some more bleeding and now it’s toasty-warm!!

    Cheers again for the advice!!
     
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  8. DIYnot Local

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