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Live/earth reverse problem

Discussion in 'Electrics UK' started by dja69, 9 Aug 2014.

  1. dja69

    dja69

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    Hi I have run a 3 core 10mm armoured cable from my consumer box in my house to my log cabin. I have connected all the cables correctly. In the cabin lights don't work and the sockets when I plug in a tester say I have a live/ earth reverse problem. Does anyone know how I can sort this fault out. Many thanks.
     
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  3. westie101

    westie101

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    Use a correct test lamp not one of these as they can be unreliable.
    we've seen similar with a missing earth & a neutral/earth fault on the wiring
     
  4. AndyPRK

    AndyPRK

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    What wire colours have you used for what at each end
     
  5. Lectrician

    Lectrician

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    Sounds like lack of earth. Perhaps not in your cable, but in the installation you have connected to.

    What happens with the plug in tester at the supply end?
     
  6. AndyPRK

    AndyPRK

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    He says his light doesn't work, so don't think it's a lack if earth.
     
  7. bernardgreen

    bernardgreen

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    the lights do not work and the tester indicates reversal of Live and Earth

    Maybe the Live and Earth are reversed in which case the installation is dangerous and could result in exposed metal of an appliance plugged in at the cabin being Live. That could result in a severe if not fatal electric shock .
     
  8. RF Lighting

    RF Lighting

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    Obviously not :rolleyes:


    It's an open circuit neutral. With a load across line and neutral the two wires are at the same potential, but both different potential to earth, so the tester thinks it's a line and earth reversal.
     
  9. flameport

    flameport

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    That is obviously not the case.

    If the plug in 'tester' is the only testing equipment you have, then you should not be installing new circuits to cabins or anywhere else.
     
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  11. JohnW2

    JohnW2

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    I think you need to explain that a bit, at least for me!

    Kind Regards, John
     
  12. AndyPRK

    AndyPRK

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    I'm sure he owns a kettle !
     
  13. RF Lighting

    RF Lighting

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    With a load connected across line and neutral, but the neutral is open circuit, the neutral will rise to the same potential as the line. The same as how you can get a shock from a lighting circuit with a borrowed neutral.

    The earth remains at earth potential, while line and neutral are now both at line potential.

    To show a line and earth reversal the tester expects 230V between transposed line and transposed earth, and also transposed line (in the earth position) and neutral. The exact same pattern of potentials as an open circuit neutral with neutral feedback.

    Hope that makes some sort of sense!
     
  14. JohnW2

    JohnW2

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    Exactly. However, when you wrote:
    ...you appeared (at least to me) to be suggesting that although L & N would be at the same potential (line potential), the L and N would be at different potentials to earth - which would obviously not make any sense.
    Indeed so - as you say, the tester sees identical potential differences with a L-E reversal and a 'broken neutral' (but only of there is an L-N load downstream of the neutral break).

    Kind Regards, John
     
  15. RF Lighting

    RF Lighting

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    Sorry perhaps not the clearest way of wording things! I was meaning both l&n have a pd to earth, where as normally only line would have.
     
  16. JohnW2

    JohnW2

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    Indeed - but as I've just added in my edit above, the tester will only see a broken neutral as an L-E reverse IF there is an L-N load downstream of the discontinuity in the neutral. In the absence of such a load, it will correctly report the 'no neutral' fault.

    Kind Regards, John
     
  17. JohnW2

    JohnW2

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    FWIW, although the above is quite clear from a theoretical point-of-view, I'm a great believer in the 'confirmatory experiment', so I've just done it.

    A Martindale plug-in tester does, indeed, correctly report a missing/broken neutral as such, provided that there is no load connected to the neutral downstream of the discontinuity (a load upstream of that point obviously makes no difference). However, when one connects a load (L-N) downstream of the discontinuity/break in the neutral, then, as expected, the tester reports it as an L-E reversal.

    Kind Regards, John
     
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