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Electric underfloor heating tripping

Discussion in 'Electrics UK' started by kashcheema, 4 Jul 2021.

  1. kashcheema

    kashcheema

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    Hi all, I had porcelain tiles put down in March and my electrician has only had time recently to wire up the underfloor heating. The thermostat is a Devi touch, with multiple mats and using a double pole fused spur. The thermostat recognises that the floor temp is 21.7 degrees celsius but the moment I try and increase it by even 0.5 of a degree it trips my new consumer unit after a few minutes. Below is a link to the video showing what happens. I am a complete novice and I notice the red light on the smart meter flashes like crazy when I turn the temp up, what does this red light signify? I have spoken to my electrician and said he will come down to take a look but is busy for a couple of weeks and wanted to see if I could resolve this myself:


    Any help would be appreciated.
     
    Last edited by a moderator: 4 Jul 2021
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  3. flameport

    flameport

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    The red light indicates the amount of electricity being used, faster flashes = more used and therefore more cost.

    Depends on what's tripping as to what the problem is, it's either an overload due to incorrect installation or an RCD tripping because the element(s) have been damaged.
    There is no video.
     
  4. JohnD

    JohnD

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    incorrectly wired, or nail through a cable. Turn it off, remove the fuse in the FCU, do not touch it, call a competent electrician.
     
  5. kashcheema

    kashcheema

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  6. flameport

    flameport

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    What's shown in the video is entirely normal - with the heating turned on, more power is used and the light on the meter flashes more quickly.
    It will do the same for any added load such as a kettle.

    Please add a photo or the 'new consumer unit' and a clear image of exactly what is tripping.
     
  7. kashcheema

    kashcheema

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    Thank you. Please find attached photos as discussed of the unit and I have circled the MCB which trips. The value on there is B20 if that helps.

    And you are correct, I just turned the kettle on and it blinks just as fast as in the video.
     

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  8. davelx

    davelx

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    What is the power rating of the UFH in kW?
     
  9. flameport

    flameport

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    That device tripping after a few minutes is due to overload, so either the heating is a lot more than 20A, or it also supplies something else and the total of that and the heating together is over 20A.
     
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  11. kashcheema

    kashcheema

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    The power rating is unknown as the tiler is how i say, not being cooperative.

    What can be done due to the overload then please? It only supplies the heating to the UFH.
     
  12. JohnD

    JohnD

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    what I said.
     
  13. Taylortwocities

    Taylortwocities

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    You need to know the number of mats and the power rating of each mat. Didn’t the supplier give you any paperwork?
    Then we could make a guess at the total load.

    Devi mats are typically 150W/m², so measure what sort of area we are talking about and can make a guessy calculation.

    Of course, there could just be a short circuit somewhere.
     
  14. fezster

    fezster

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    Do you know what brand of ufh was installed? What is the area?

    Mats are normally 150-200W/sqm. You can then deduce what the max current drawn will be and if the mcb is suitably rated.

    Its also possible to check the resistance of the mat with the circuit and thermostat disconnected - this may tell you whether there is any damage or a short circuit.

    You need an electrician who knows how electric ufh works if you're not able to do any of this yourself.
     
  15. kashcheema

    kashcheema

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    Hi guys, so my electrician came round just now (he didn't charge me for it), and he realised that that MCB was too low and changed it for a 32A MCB. We switched the UFH onto 25 degrees and it's slowly increasing and is currently at 24.5. Thankfully it hasn't tripped and the floor is heating up nicely. He also tested all the mat wiring to ensure none had failed and they all tested out fine. So i think the error was the low amp MCB.
     
  16. securespark

    securespark

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    I smell a large long-tailed rodent.

    UFH is usually supplied locally by a FCU.

    Unless you have a ring final feeding multiple UFH set-ups or a 4 Milli radial, you should not need a 32A breaker.

    How many UFH systems have you got installed?
     
  17. kashcheema

    kashcheema

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    I have one system with 5 mats covering about 60sqm
     
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