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New copper light fitting to old wiring (no earth)

Discussion in 'Electrics UK' started by Crediblehippo, 11 Aug 2021.

  1. thomp1983

    thomp1983

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    As Keith said but instead of a long piece of wire you can just use an extension lead if you've got a decent sized one, obviously check earth between the extension and the socket your using first before any other testing
     
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  3. bernardgreen

    bernardgreen

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    Before testing for continuity do a voltage check (250 Volt AC range ). Any reading above 10 Volts would suggest the Earth is not connected.

    This way you reduce the risk of putting 230 Volts onto the Ohms range of the meter and damaging the meter.
     
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  4. thomp1983

    thomp1983

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    Double post of my message above
     
  5. Harry Bloomfield

    Harry Bloomfield

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    Just to qualify that test - It will only confirm if you have some sort of earth at the light, it will not confirm how good it is or whether it is up to an acceptable standard. An Earth Loop Tester is needed to do it properly.
     
  6. ericmark

    ericmark

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    I am afraid we are all guilty of on occasions failing to test, we know we should, and I remember with some water damage the electrician sent by insurance company did test, although he did not record the results.

    But where everything seems to be done correctly, I am sure many assume that earth wire is connected to earth, until some one gets a tingle, and I remember trying to trace a loss of earth connections in a house on the Falklands and in the end came to the conclusion there was some junction in the loft and no access to the loft.

    So it is down to risk assessment. Or are you willing to take a chance that the earth is connected?

    Basic to methods, one is with a low ohm meter, the idea is at least 200 mA is run through the earth wire, and in real terms a 12 volt battery and a head light bulb will show if the earth is good enough to trip an RCD, the earth could be 100Ω and the RCD would still trip, but with a B6 MCB the B means 5 times for the magnetic bit, so 5 x 6 = 30 amp, ohms law 230/30 = 7.6Ω add 5% for safety so 7.28Ω and the question is how would you measure that?

    It can be done, but not easy.
     
  7. plugwash

    plugwash

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    Personally I think not testing the earth at all because you can't do an ideal test is a severe case of letting the perfect be the enemy of the good.
     
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  9. markyd1

    markyd1

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    Get somebody who knows what they are doing
     
  10. Keithmac

    Keithmac

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    Of you've got continuity between the lighting and socket earths how slim is the possibly they aren't connected at the Consumer Unit, absolutely miniscule I'd say.
     
  11. Harry Bloomfield

    Harry Bloomfield

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    There is a reason why an Earth Loop Tester was invented, to ensure the connections are sound.
     
  12. Colin Brenton

    Colin Brenton

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    You could combine the method above with a voltage reading at the socket between live and earth... ;)
     
  13. securespark

    securespark

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    But in the absence of that tester, the tests described here will at least confirm a connection which is more than a lot of DIYers do.
     
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