Discussion in 'Electricians' Talk' started by dvddvd, Dec 6, 2021.

  1. dvddvd

    dvddvd Well-Known Member

    I have a 4mm cable from my main consumer unit to my garage. It runs from one side of the house to the other through the loft space, to a garage style consumer unit.

    I was using a 550 watt pillar drill in my garage and the power went off.

    I checked the MCB on the garage consumer unit and all was ok, but no voltage and nothing tripped.

    I checked the MCB on the main consumer unit and that was fine.

    There is voltage from the main consumer MCB and using a NCV along the cable I get a reading and suddenly it stops?

    Seems strange that theres a break in the cable all of a sudden? It's never been touched or damaged ?
  2. Bogle Crag

    Bogle Crag Screwfix Select

    It can happen when a cable is flexing for a considerable time, the cores can break with no outside signs, I have only seen it on smaller cables ??
  3. DaveF

    DaveF Active Member

    I have seen this on a smaller cable but never on a 4mm. The cable is internally damaged and just blows like a fuse without leaving any outward sign of an issue. And it particularly happens with motors since they have a high inrush current. But 4mm? I would be tempted to just isolate and test the cable.
  4. Tony Goddard

    Tony Goddard Screwfix Select

    This happens a lot on vacuum cleaners where the cable flexes too and fro where it enters the machine, suddenly the cleaner is dead, simply from a core breaking.

    Never seen it on fixed wiring, and 4mm would be rather too robust to break without flexing. The non contact pens are not that reliable, you really need to test using a voltage tester at the garage CU, it could be an MCB that has failed, or loose connection in your garage end wiring.
  5. Bogle Crag

    Bogle Crag Screwfix Select

    Is the cable swinging free or securely clipped?
  6. dvddvd

    dvddvd Well-Known Member

    thanks the cable is fixed to the wall. I tested the part in the loft and all seemed ok. So its somewhere it goes down the wall.

    I've ordered some new 6mm so will replace it all

  7. dvddvd

    dvddvd Well-Known Member

    I did test with a voltage meter at the garage CU and there was nothing.

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