Live earth reverse?

Discussion in 'Electricians' Talk' started by Kaylg, Feb 10, 2019.

  1. Kaylg

    Kaylg New Member


    Our new boiler is temporarily plugged into to a socket circuit whilst we get a fused spur fit. Since running it the circuit has died.

    I've used a lap socket tested and it's reading live earth reverse.

    I've disconnected the circuit right back to the first socket leaving only that on the circuit (no where near the fault socket) but I'm still getting live earth reverse?

    Any tips on where the problem may lie?
  2. eric the fish

    eric the fish Member

    Have you tested the Lap Socket Tester on a "known good circuit"?

    E the F
  3. Kaylg

    Kaylg New Member

    Hi thanks for the reply

    Yes tested on other circuit reads as correct with 2 green lights
  4. 14th edition

    14th edition Well-Known Member

    You need to properly test that circuit! As E the F says above try your tester on a known good circuit....things usually go bang on L>E reverse! Just read your reply above, power off and check that connections are correct in socket, if so ten check in consumer unit with all power off!
  5. Wayners

    Wayners Well-Known Member

    Disconnect everything in the house.. Unplug and pull fuses from fused switchs. Now test a socket .. If good plug in all devices one by one and test each time. Any doubt get a sparks in to look.
  6. Sparkielev

    Sparkielev Well-Known Member

    If it's a TNCS earth system you could possibly get this fault on live neutral reverse turn circuit off test it before removing sockets and check for wrong polarity
  7. unphased

    unphased Screwfix Select

    He's already confirmed polarity on a socket on a different circuit, its not reversed at the origin.

    Its a simple enough fault to locate. Just keep plugging in the socket tester until you find a good one and the fault lies at the next. Probably been done at a single socket. Some designs have all three terminals together and I've found live earth reversed in these before.
  8. Sparkielev

    Sparkielev Well-Known Member

    Which is what I said turn off power and check polarity at sockets , I wasn't saying it was reversed at origin, was pointing out that on TNCS you can get live earth fault when it can be phase and neutral cross polarity at socket
    Last edited: Feb 10, 2019
  9. Bazza

    Bazza Well-Known Member

    Those testers are fine for a quick simple check, but they wont tell you about an earth/neutral reverse.

    @Kaylg you need to use a proper 2-probe voltage tester, or a multimeter to determine what you actually have.
    KIAB and Sparkielev like this.
  10. unphased

    unphased Screwfix Select

    Bazza, he says he's got an L/E reverse as flagged by the socket tester. N/E reverse would trip the RCD (assuming there is one). But the tester also has an N/E reverse function. I don't know how he's come to the conclusion that the 'circuit has died'? The socket tester wouldn't work on a dead circuit! Presumably just the boiler has packed in. They can be sensitive to polarity, he may have blown the boiler PCB. Its not clear, either, whether the circuit he was using for the boiler originally, is a standalone boiler circuit with a socket, or, whether it was another circuit he was using. Nor is it explained why the boiler is waiting for a switched spur to be fitted.Too many unknowns on the original post to draw any conclusion.
  11. KIAB

    KIAB Well-Known Member

    Might also be a replacable fuse on boiler pcb.

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