Burnt cable

[DonDonson]

Hi, does anyone know why this cable has burnt out? It's the supply to a 8kw shower, I could smell a bit of burning lately and when I've looked in the switch I found this, I'm sure the cables are about 6mm, the red and black is the cable from the board and the brown and blue go to the shower.
It's been in now for about two years and the shower gets used daily.
I thought it might be because both live wires were touching and got hot??
Before the comments come about getting an electrician I've already sorted one that's coming to look at it but wanted a bit of info first.

Thanks.

Untitled

• DonDonson
• 3 Dec 2013
• 1

 

[viewer]

Probably poor connections. The ends of the cables look rather poorly prepared as well; maybe even a missing strand. If the electrician finds other damage it is probably a good idea to fit 10mm cable even if keeping the same shower.

 

[Jackrae]

Highly probable that the switch contacts have been "sparking" and heat has passed back into the cable and melted the insulation. You'll need a new switch and a sparky to sort out the damaged cable ends.

 

[RF Lighting]

Duff connection to the switch.

 

[PrenticeBoyofDerry]

Looks like VIR cable and should be replaced!

 

[DonDonson]

What's VIR cable?

 

[PrenticeBoyofDerry]

Vulcanised Indian Rubber, when this is found, the condition of the cables insulation has usually degraded to a state were it is unsafe and requires rewiring.
Does your installation run through conduit or is this cable(red/black) sheathed in cloth?

Rubber Insulation:
For many years wiring cables were insulated with vulcanised natural rubber (VIR). Much cable of this type is still in service, although it is many years since it was last manufactured. Since the insulation is organic, it is subject to the normal ageing process, becoming hard and brittle. In this condition it will continue to give satisfactory service unless it is disturbed, when the rubber cracks and loses its insulating properties. It is advisable that wiring of this type which is still in service should be replaced by a more modern cable.

But it could be the burning of the cable that is making it look like VIR, as the conductors look burnt, it is hard to identify the conductor type, VIR is usually silver in colour.

 

[DonDonson]

I'm sure I know what cable you mean, and it's not that, the cable is not that old even though the supply is the old black and red. It does seem more probable that the connections were not in tight enough.

 

[PrenticeBoyofDerry]

It does seem more probable that the connections were not in tight enough.

I have no doubt that is the issue, but now the cable has burnt and damaged the insulation, the conductor will need taking back to bright copper and the insulation back to where it is no longer damaged and brittle.