I am having some work done at home and have noticed this 'greening' of the power cables. The cable that is green is from the original build in 1977 and the other that are still white is when the extension was built in 1990. The green deposit has an oily consistency, any ideas what causes it. I have also noticed it on the old wiring in the power sockets.

http://www.locostbuilders.co.uk/photos.php?action=showphoto&photo=Dscn0574_1.jpg

Looks like verdigris (copper oxide). The wires are copper so kind of makes sense.

Haven't seen it happen before though!!! Must mean the copper wire is oxidising and the oxide leaching out into the covering.

Never seen that before! Odd it's just that one cable..

It's not damp on the cable??

Dan

It's the insulation degrading

The PVC splits into the dry plastic and the oil.

http://static.schneider-electric.us/docs/Circuit%20Protection/Miniature%20Circuit%20Breakers/0110DB0301.pdf

If the wire is in situ, it probably won't short out, but if it gets knocked the insulation can just crumble away and expose the copper!

I'd recommend getting it replaced.

Mike

What Mike said...possibly a bad batch of wire at the time by the sounds of it. PVC shouldn't degrade that quickly - most household wiring lasts 50+ years.

David

Is there a makers name and other info on the cable , as over the years lots of cable has been imported fom Asia, you can usualy tell it by the conductor covering as they are all white with a top colour added blue brown etc, i used to use loads of it as it was all one could get at certain times, ( it was rubbish to strip) many contractors bought it from Wicks around here as it was a lot cheaper than there usual wholeseller .

Mike

The discolouration appears to be nearer the junction boxes. I suggest you have a look in the jb to check that there is no local overheating which may have caused the sheath to start decomposing.
If the gunge cleans off and the cable is not brittle or degraded then you should be OK.

Of course it could be just where you have sneezed.

Have you had any polystyrene near that cable?
Polystyrene will leech the oil from the PVC, and then the insulation goes brittle and falls away becoming dangerous.

We has to sheath all our cables on out boat where they passed through the Polystyrene insulation sheets.

Heard about it, but not seen it before.