MICC pyro wiring question

Nov 13, 2005 4 Replies
A

I have a mid 60's flat and a light in one of the rooms suddenly stopped working a while ago. I swapped the bulb and checked the connections at the switch and ceiling rose. All connections seemed ok but the light still did not work. The switch worked fine with a multimeter continuity test. There did not seem to be any voltage at the wires going into the switch though.



A couple of times the light has just flickered on and then off for a second or so before staying off again.



I have been told that the wiring from the fusebox is "pyro" mineral insulated copper cable (MICC) which I am not familiar with. I had borrowed a tool to detect metal/voltage in walls but due to the copper coating of the wires I don't expect it will be much use...?



So, a couple of questions...


- What is the most likely cause of intermittent failure with this type of wiring?



- Is there any way to determine where the problem might be, without physically digging out the wiring from walls/floor/ceiling?



Thanks for any help, Andrew



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C

On 13 Nov 2005 09:14:21 -0800,it is alleged that "Andrew" spake thusly in uk.d-i-y:

It would still detect it as metal, and depending on sensitivity it may pick up that 'buzzing' from the mains earth.

Intermittent is VERY unusual with this type of cable, the insulation absorbs moisture, if you get a fault in the cable it usually goes to a low insulation value which then deteriorates until the cable physically bursts or short circuits. Intermittent faults are more likely to be at some other termination in the circuit.

Not that I know of.

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D

It's *very* unlikely to be the cable. So check connections carefully. And it's possible to be a feed from another part of the circuit that has failed rather than just those in the room.

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H

Andrew has brought this to us :

It is a copper outer, therefore a metal detector should be able to trace it.

Least likely the pyro. Check out other causes first. If it really is the pyro, then the most likely cause will be a broken wire - where it emerges from the outer, at the termination, within the black sleave.

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A

Depends if you are talking about the product, or one of the manufacturers.

or Mineral Insulated Copper Clad/Covered

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