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Tracing a faulty cable

Discussion in 'Electrics UK' started by Steve412L, 9 Mar 2021.

  1. Steve412L

    Steve412L

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    Hi all, I have a problem with upstairs power sockets (upstairs and downstairs lighting and downstairs sockets are all ok) The fuse for the upstairs just trips out and wont re-set. There is a dead short on the circuit somewhere....we have had problems with a mouse between the floor and ceiling and I suspect it has chewed through the cable insulation causing the short. Is there any way of tracing which part of the circuit has the problem section of cable without having to take up all of the floorboards rather than just the affected bit?
     
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  3. EFLImpudence

    EFLImpudence

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    Firstly: Is the tripping device an MCB or RCBO? Picture if you are not sure - just copy and paste.
     
  4. narkeybee

    narkeybee

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    Is it a ring final or a radial?
    how many sockets are involved?
    Have you got a test meter?
    you will need to split the circuit and test between the conductors.
     
  5. AndyPRK

    AndyPRK

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    If its a 32A ring its good news.
    Hopefully there are no USB scckets upstairs

    DIsconnect the wires from the CU. Prove you can see the fault with a normal electric meter on continuity (need to understand which 2 or the 3 wires are shorted or low resistance)
    Then roughtly half way round the circuit (guess) split the circuit.
    See which side the fault is on.
    Keep splitting it down until you find the cable and disconnect it.
    Then fit a 20 MCB to the CU and connect it back up
     
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  6. Steve412L

    Steve412L

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    Thanks all...here is a pic of the tripped fuse
     

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  8. EFLImpudence

    EFLImpudence

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    Ok, that suggests there is a fault, either with the device because it has been supplying more than 16A for items plugged in - not really likely for upstairs circuit, OR

    there is a fault between L & N or L & E which should be detectable with the meter using the method suggested above.


    You could investigate the outside sockets first. Has anything happened out there?
     
  9. Steve412L

    Steve412L

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    Ok, so if I get a reading showing continuity between L & E or L & N on any particular length of cable, that shows the short yes?
     
  10. EFLImpudence

    EFLImpudence

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    Yes - as long as you have not overlooked something plugged in somewhere.
     
  11. Steve412L

    Steve412L

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    Ok cheers I'll try that over the weekend. Thanks for the info.
     
  12. crystal ball

    crystal ball

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    Just spent 2 hours tracing a fault in a holiday home, DB was very precisely labelled, kitchen far wall, dishwasher, 2 x sockets, split the ring and traced the fault to the return leg back to the DB, pulled kickboards off as the cabling was under the units, all good, found the fault on towel rail in the bathroom above, all the other heaters are wired individually except that one
     
  13. DIYnot Local

    DIYnot Local

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