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Voltage difference

Discussion in 'Electrics UK' started by jq1805, 22 Oct 2020.

  1. jq1805

    jq1805

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    I've recently installed a stud wall and extended the existing wiring for two double sockets by using a block connector and single cable. Does anyone know why one socket would show 240v and the other show 208v please?

    Thanks.
     
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  3. endecotp

    endecotp

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    How are you measuring that?

    Do the sockets seem to work?
     
  4. jq1805

    jq1805

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    With a multimeter.

    The 240v socket does, the 208v socket doesn't.
     
  5. plugwash

    plugwash

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    You most likely have a bad connection somewhere.
     
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  6. JohnW2

    JohnW2

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    What is the voltage between L and earth on the "208V socket"?

    Kind Regards, John
     
  7. jq1805

    jq1805

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    Thanks John.

    It's 241v
     
  8. terryplumb

    terryplumb

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    Is the circuit a ring final ? If so how have you connected the two sockets with a single cable ?
     
  9. JohnW2

    JohnW2

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    Thanks. That strongly suggests that plugwash was right, and that there is a loose/poor connection on the NEUTRAL at that socket.

    Kind Regards, John
     
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  11. SimonH2

    SimonH2

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    Sounds like you have a bad connection - it's got a high, but not "infinite", resistance. So when testing with your high impedance voltmeter, you get a reading, but as soon as you apply a load, all the voltage disappears across the high resistance joint. This is the reason why we do certain tests to check work, using equipment that puts a reasonable amount of current through a circuit.
    From the way your original post is worded, it sounds like you have done a non-compliant alteration, and quite possibly created a dangerous situation.
     
  12. jq1805

    jq1805

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    Thanks very much John, very much appreciated. I'll have a look in the morning.

    Regards.

    John.
     
  13. JohnW2

    JohnW2

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    I agree with your conclusion (as I said, it sounds like a poor connection of the neutral at the one socket).

    However, as for testing, I suspect that even if someone had just installed an entire sockets circuit, they would probably not "...do certain tests to check work, using equipment that puts a reasonable amount of current through a circuit" at every socket on the circuit, would they? (and, if they didn't, they probably wouldn't detect a problem such as we are postulating in the OP's case at just one socket)

    Kind Regards, John
     
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  14. SimonH2

    SimonH2

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    You would as a minimum do L-N and L-E loop tests either around the ring or to every end of a radial (i.e. every branch). If not then you have not adequately tested the circuit. In addition, you would do polarity checks at every socket/outlet - otherwise you risk missing a miswire of the kind that comes up regularly (Birakos Enterprises Limited). And the loop tests would be done with something more than the micro amps a multimeter would put through the circuit.
    So while a bad neutral connection could be missed, it would be unlikely - you would need the terminal of a socket to be loose, but the wires to be in good contact.
     
  15. ericmark

    ericmark

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    My guess one reading line - neutral the other reading line - earth, lets see if right.
     
  16. JohnW2

    JohnW2

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    That's not my understand - which is that one was reading 240V L-N (and 'working') and the other reading 208V L-N (and 'not working) but (following my question) the latter reading 240 L-E ...

    ... from which I concluded that it's probably a dodgy N connection at the second (208V L-N, with high impedance meter, 'not working') socket.

    Kind Regards, John
     
  17. ericmark

    ericmark

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    Easy to check, measure L - N and L - E at both sockets.
     
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