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Joiner drilled through cable

Discussion in 'Electrics UK' started by Bob49, 20 Jan 2020.

  1. Bob49

    Bob49

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    Hello,

    Eight years ago we had an extension built. While fitting a kitchen unit the joiner drilled through a cable, one of the RCDs tripped and half of the electrics went off.

    Luckily the electrician was on site. He had a look at the damage, said it was just nicked, flipped the RCD back on and work carried on. No attempt was made to repair the cable or re-plaster the inspection hole he made. The joiner just hung the kitchen unit over the damaged area of plaster.

    At the time I didn't give it much thought because there was so much else going. This was minor to the other issues we were facing.

    But now I have started to have a nagging doubt about it. I can't see how the RCD was tripped without some damage occurring to the cable. It can't can it?

    So either:

    1) One or more of the conductors is completely cut through and I have two radials.

    2) No conductor is damaged but some of the copper is exposed.

    3) One or more of the conductors have reduced copper and the circuit is not up to spec.

    After the extension was finished another electrician did a test of all the new circuits and the new consumer unit and filled in a NICEIC certificate for building control. I have a copy of this certificate.

    The certificate gives a separate resistance reading for the three cores of the cable in question. So according to this all three cores have continuity. Also from the L & N readings I have calculated using 7.32mΩ per meter the length of the cable. This also seems about right.

    So unless the other electrician falsified the results (they did know each other) then I can rule out number 1).

    So that leaves 2) or 3), so how much of an issue is exposed conductor? Conductors are exposed in the socket outlets after all.

    Also this circuit has a washing machine and tumble dyer on it, so quite a high load.

    So what to do? Take down the kitchen unit and examine it myself? Get a qualified electrician to do a continuity/insulation test?

    Or am I worrying for nothing?

    Thanks,

    Bob
     
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  3. EFLImpudence

    EFLImpudence

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    Tests will not show anything if none of the conductors was actually broken.

    If that is the case, looking is the only way to know for sure.
     
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  4. Bob49

    Bob49

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    Thanks, so for the Rcd to trip then the drill bit must have touched one of the conductors? There is no other way the Rcd could have tripped In this situation?
     
  5. EFLImpudence

    EFLImpudence

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    One or two of the conductors, yes. No other way.

    It could have been a pointed drill bit that just made a little hole - or not.
     
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  6. EFLImpudence

    EFLImpudence

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    I would have thought the electrician would have repaired it seeing as it was not his fault and if not associated with the joiner.
     
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  7. Bob49

    Bob49

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    Thanks, so I guess I either trust the electrician that said it's just nicked and nothing needs doing or I investigate further.

    But what's the consequences of exposed but undamaged conductors?

    Bob
     
  8. sparkwright

    sparkwright

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    Is it easy to take the wall unit down?

    It's the only real way to see what happened.
     
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  9. Bob49

    Bob49

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    It's doable, I guess It's the only way to know.
     
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  11. Bob49

    Bob49

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    He was really annoyed by it but said nothing needed doing. He was one of the better contractors and I was happy at the time.
     
  12. EFLImpudence

    EFLImpudence

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    To know for certain - yes.
     
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  13. sparkymarka

    sparkymarka

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    And after 8 years .... ? Your now worried about it !
     
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  14. Bob49

    Bob49

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    I was falling asleep a few months ago and a thought entered my head that surely the cable is damaged if the Rcd tripped. Before that I had forgotten about it.
     
  15. sparkwright

    sparkwright

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    A lot of bad connections, faults etc can go unnoticed for years and years. They need addressing though.
     
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  16. bernardgreen

    bernardgreen

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    There is a small chance that a screw put into that hole may be in contact with a Live conductor and this would be a hazard if anyone touched that screw head. ( to get serious shock the person would have to be also touching something conected to Earth
     
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  17. Risteard

    Risteard

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    The cable is clearly damaged and should be either repaired or replaced. Whilst it may not reveal itself during testing, this does not mean that it's not potentially dangerous.

    Also, the NICEIC contractor is prohibited from issuing certification for jobs which he did not supervise during the erection of the installation. He is not permitted to issue a certificate for someone else's job, so the certificate you have received is invalid, null and void. He should have been reported to the NICEIC for breach of the Rules of Enrolment (or rules of registration if he is one of these so-called "Domestic Installers" as opposed to the proper scheme, which is the Approved Contractor scheme).
     
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