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Discuss Identifying ring main cables without a socket in the DIY Electrical Forum area at ElectrciansForums.co.uk.

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  1. David_l
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    David_l New EF Member

    Location:
    Scotland
    Hi, to give you a quick break down of my situation. I have a converted bungalow that has several generations of wiring and I'm currently trying to add an additional socket (via a junction box) to be located in a loft onto a ring main.

    Thankfully in my loft I have plenty of 2.5mm twin and earth running in there, however I'm unsure of which is the ring main. My question is, Is there a way to identify cables externally without breaking into the cable or having a socket to use a voltmeter since all the cable disappears under the floor boards. Essentially I just have a middle of a cable and I was going to switch each ring off at the circuit breaker and see which cable dies and label them up, however after searching online a clamp meter looks like it might work, is this the right way of thinking or is the only way to cut into them when their dead?

    Now I have thought about the possibility of them being spurs but I would check the ring continuity once I have cut into the cable but at least this would help me in knowing which cable to trace.

    Thanks in advanced (and a air high five)
    David
     
  2. buzzlightyear
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    buzzlightyear Electrician's Arms

    Location:
    star command
    are you a spark!
     
  3. spinlondon
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    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    Simplest method would be to obtain a non-contact voltage tester. Check the cable is live first, then turn off a circuit and check the cable again. Repeat until circuit is identified.
     
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  4. davesparks
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    davesparks Trusted Advisor

    Location:
    guildford
    A clamp meter won't work.
     
    • Agree Agree x 3
  5. buzzlightyear
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    buzzlightyear Electrician's Arms

    Location:
    star command
    or employ a local spark to do the job for you .without you damaging yourself or burning your property down.
     
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  6. Dannyg8810
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    Dannyg8810 Electrician's Arms

    Location:
    Leeds
    Non contact volt meter should indicate the cable from the circuit you wish to spur from,make sure you test said circuit before hand to ensure it's a ring final circuit first!!
     
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  7. buzzlightyear
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    buzzlightyear Electrician's Arms

    Location:
    star command
    by finding the right cable and isolating that ring. when using the non contact volt meter
    mark the cable with tape .for the spur for your loft .
     
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    • Creative Creative x 1
  8. David_l
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    David_l New EF Member

    Location:
    Scotland
    Wow thanks for the quick reply you all get a air high five! A non contact voltage tester is exactly what I'm looking for, I'll be using this as just the very beginning of my search since I want to use this to see which cable to start to follow rather than getting half way round the house only to find it's the wrong one. Once I find out which one it is I'll trace it and check its continuity making sure it's definitely a ring main before adding the socket.

    Thanks again guys!
    D.
     
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  9. buzzlightyear
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    buzzlightyear Electrician's Arms

    Location:
    star command
    yeah, likes would be nice if not put some monies in the tip jar. upload_2017-7-27_21-58-44.png I forgot he is in Scotland, short arms and long pockets .
     
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    Last edited: Jul 27, 2017
  10. davesparks
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    davesparks Trusted Advisor

    Location:
    guildford
    But remember that such devices are not reliable and can indicate that a cable is dead when it is in fact live.
    Do not ever trust them as a means of proving that anything is safe to work on, always use an approved voltage indicator in accordance with gs38 and established safe isolation procedures.

    A mistake in this could cost you your life in a very quick but painful fashion.
     
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  11. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    Agreed I use them a lot on EICRs but I wouldn't put my life on one as they can be deceptive with bunched cables.
     
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  12. Pete999
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    Pete999 Trusted Advisor

    Top Poster Of Month

    Location:
    Northampton
    Ring Main no it's a Ring Final Circuit Oh and get an Electrician in you could be adding a new socket to an already spurred one, don't rely on a non contact tester , many an accident has happened using those things, OK in the right hand but not for a DIYer imo
     
  13. HandySparks
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    HandySparks Trusted Advisor

    Location:
    Hampshire
    Business Name:
    Neish Electrical Services
    Care to describe a few that you know the details of?
     
  14. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    i can. i trod on mine, foot rolled off, fell over, broke me fag and spilt me ale.
     
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  15. Pete999
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    Pete999 Trusted Advisor

    Top Poster Of Month

    Location:
    Northampton
    Tragic occurrence Tel, Tragic.
     
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  16. HandySparks
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    HandySparks Trusted Advisor

    Location:
    Hampshire
    Business Name:
    Neish Electrical Services
    So, that's a no then.
     
  17. davesparks
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    davesparks Trusted Advisor

    Location:
    guildford
    Personally I have only had the one accident with one, and that was enough to teach me never to trust one. I was using one to test a T&E, the tester showed that it was live, I operated the mcb and the tester went off, I tried the tester on another cable and it was still working so I cut the cable with a loud bang and a flash.
    I still got the pair of cutters with the holes in them somewhere, and have never trusted one of those testers since then.

    I do own one and use it for a basic means of identification, but never trust it for a definite test.
     
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  18. Wilko
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    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Similarly, I used one to help identify the live cable in a loose bundle. But I didn't feel I got a conclusive result with it and resisted the temptation to destroy a set of cutters, for once :rolleyes:
     
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  19. littlespark
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    littlespark Regular EF Member

    Location:
    Scottish Borders
    Question to OP: Why are you installing a socket in the loftspace? if its just for a light, would it be easier to find a supply from the lighting circuit?
     
  20. Strima
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    Strima Electrician's Arms

    Location:
    St Neots
    Those non-contact testers are only good for three things.
    1. Cable tracing for fault finding followed up with a contact tester.
    2. Stabbing holes in plasterboard.
    3. Stirring your tea. Remember to remove plaster dust first...
     
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