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Underfloor heating not circulating!

Discussion in 'Plumbing and Central Heating' started by Rob broom, 17 Nov 2020.

  1. Rob broom

    Rob broom

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    Hi!
    Hopefully somebody will be willing to help me with this issue?

    I have bought and installed a underfloor heating system.

    I have followed all of the instructions on installing and priming it and I am satisfied that I have done a good job!

    however, the system does not seam to circulate!

    I have 2 zones, both with two “loops”
    So, I have a 4 way manifold.

    With everything switched on and working, the flow through the indicators is really low, at around 0.5LPM. That’s with the flow valves fully open! Doesn’t seal enough to me.

    however, if I open the drain valve on the return manifold and let the water escape into a bucket, the flow rates immediately shoot up to 2 or 3 LPM.

    it seams to me like the mixer valve isn’t letting the water return from the lower manifold. It’s almost as is there is a blockage!

    It was all new equipment and I filled the whole system with clean water.

    Any suggestions from anyone please?!?

    thanks
     
  2. CBW

    CBW

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    Check for a kink in the pipe, or a restriction somewhere
     
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  4. Rob broom

    Rob broom

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    Thanks for that.

    I had those thoughts?

    But I’m confident that the pipes are all good cuz as I say, when the system is running and I let the water out of the drain tap, the flow indicators go high and everything flows perfectly

    I have been manually opening and shutting each zone with the screw caps to find the issue. I can open all four loops together or isolate it down to just one and It makes no difference to the outcome. The flow rate is poor! But if I let it drain into a bucket, they are brilliant.

    It just seams like the mixer valve won’t let it go back!

    or the pump is weak?

    The pump is a GRUNDFOS UPM3 Auto.
    it has loads of settings like proportional pressure, constant pressure and constant curve!

    I haven’t touched it, but It’s currently on proportional pressure 3.

    Anyone know if there is a better setting to get the pump to push and work harder?!

    thanks
     
  5. CBW

    CBW

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    Have you disconnected the mixer valve, checking for debris?
     
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  7. Rob broom

    Rob broom

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    Hi!

    yep, that was the first thing I did!

    All clear!

    right....... I think I have found the answer to the problem!

    I just played with the motor settings and put it on “Constant curve - max” and the flow indicators have shot up!

    so, it’s a pump setting issue!

    should I leave it on this setting?

    Or which one of the other 11 settings is best?

    thabks
     
  8. DIYnot Local

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