black rubber

[marsaday]

our new house was wired on the black rubber, but had been teed into with modern wiring. is this bad practice? it has all been changed now.

the lighting system was left alone. it was done on 1mm cable with an external earth. is this ok?

 

[holmslaw]

..

 

[marsaday]

i have had it checked and the power has been renewed. lightening was ok, but we didnt touch that. i just wondered what people thought of 1mm lightening with external earth.

 

[RF Lighting]

It sounds oh so very very wrong.

 

[marsaday]

it may sound wrong, but what is the reason for it being wrong.

 

[Taylortwocities]

Because the earth should be an integral conductor within the cable. It is called the Circuit Protective Conductor.(CPC)

Its there to ensure that severe damage to the cable will cause the protective device to disconnect the supply (because the supply will short to earth.)

 

[coylumbridge]

Our house also had twin core rubber with external earth in multi core as part of the installation - think this was from the 1950's. Some of the insulation was perished, couldn't be sure about earth continuity etc. It has all now been replaced.

 

[JohnD]

when I was rummaging under the floor of an old house recently, I found the disused 1920's electric circuit (in slip-joint conduit used as earth) and, where a rubber cable emerged and went off for a socket, a separate bare earth wire had been clamped to the conduit to go with it. Took me a while to puzzle out why they used a separate earth. I suppose they didn't have T&E or 3-core. Inside the conduit is rubber singles.

The conduit is disused but, thinking about it, I may as well bond it to the bonded copper pipes under the same floor.

Wall conduit to some light switches is heavy screwed gas-barrel, I have worked out that this would have been something to do with the even-older Gas Light installation.

 

[plugwash]

Because the earth should be an integral conductor within the cable. It is called the Circuit Protective Conductor.(CPC)

Its there to ensure that severe damage to the cable will cause the protective device to disconnect the supply (because the supply will short to earth.)

That is the reason for the earthed outer layer in swa/concentric/pyro/split con but T&E in no way gaurantees that damage will cause a short.

IIRC it is acceptable to use a seperate CPC but it has to follow the same route as the cable it is acting as a CPC for and I think there may be a minimum of 4mm for earths that aren't part of a sheathed cable and aren't in conduit (I know that is the rule used for bathroom bonding, not sure if it is more general). By the time you have done that it is just as easy and probablly just as cheap to rewire the circuit with modern cable.

 

[securespark]

Advice I have been given is that if the external cpc follows the same path as the other conductors, is connected back to the origin of the supply and each point in the circuit has a sound earth connection, that is acceptable.

However, this method indicates your installation is probably due for renewal.

EDIT: Too slow again...

As for the black rubber, that is well past its sell-by.

If you have to replace that, you may as well replace the whole lot.

 

[marsaday]

thanks all. so what i have learned is that my lighting circuit is fine and not wrong. the external earth is sheathed and follows the path of the lightening cable.

the black rubber power circuit has been replaced with new circuits.

 

[RF Lighting]

Please can we have some photos?

 

[JohnD]

Please can we have some photos?

not one of my interests, but hey, it takes all sorts

View media item 1680

 

[Steve]

thanks all. so what i have learned is that my lighting circuit is fine and not wrong.

If you learnt that, you havent been reading this topic.

Your lighting (not lightening) circuit is potentially unsafe since it is wired in black VIR cable. If it was my house, I'd turn off the power to that circuit until it was replaced. But thats just me being careful, since I wouldnt want my house to burn down etc. Its up to you.