3/.029 lighting cable damage

O

oldman2

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• 12 Aug 2008

• #1

I expect most have seen it all before, but here goes again.

I just rewired the lighting circuits in a 1962 house, the original 3/.029 cable had been drawn through holes bored in the joists that were slightly too small for 2 cables or should I say the sparks had drawn one in and then forced the other through with a bit of speed. Result is that the insulation gets very hot and melts on the static cable.

View media item 3763 View media item 3764 View media item 3765
There was another with a bare neutral but I mislaid the sample.

These cables had been working fine tucked away in the holes in the joists

 

S

sparkybird

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• 13 Aug 2008

• #2

wow! Thats remined me, musts check out the grouping factor table...

Presumably IR fault caused you to search them out?

 

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oldman2

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• 13 Aug 2008

• #3

Nope, lived here many yrs and never had any trouble with the circuit. It was a routine rewire and as I was removing as much old stuff as possible for the tot box it came to light then so to speak

 

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jason1958

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• 13 Aug 2008

• #4

Unusual to see it on PVC - very clumsy install.

More common to see it on modern LSOH.
LSOH sheath will abrade like cheese if dragged against another sheath.

 

K

kai

• 13 Aug 2008

• #5

Presume the old cable was not earthed, being from 1962, so no earth fault to blow the fuse or trip the RCD out.

 

ColJack

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• 14 Aug 2008

• #6

there would be no fautl to speak of..

the only section shown with exposed copper is the live..

the cable dragged over it would not be adraded at the point of contact since it's constantly being pulled past it..
so the other cable touching it will still be insulated..

 

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oldman2

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• 14 Aug 2008

• #7

Yes, no faults as there were no cases where both conductors were bare and even if both were it would be unlucky for them to short against each other with another cable alongside acting as an insulator.

Still I have not seen many like that before, he must have been in a real hurry