UK Old cable in dwelling light circuit

RealNetworks · Aug 5, 2022

We are currently renovating an old house after recently moving in. Whilst purchasing the property we received written assurances that the original 1920/30s wiring had been fully upgraded and subsequently tested.

After removing all of the downstairs ceilings, it is clear than new electric 2.5m2 and 1.5m2 cable/wiring has been installed, however there would appear to be an old and rather thick set brown fabric cable routing upstairs. Using a ‘non touch’ volt tester I was able to identify that the cable was live and part of the house light circuit. (The full house is on a single ring light circuit is, not ideal but it works). I noticed that this old cable routes into a round, brown junction box with the lid missing. The cable would seem to be an old 2 core cable with no earth present. Both cores are large ‘silver’ cables with several strands twisted together. I’m no electrician and therefore will refrain from touching it or proding around, however I would be grateful if someone would kindly advise if this cable should be changed, or indeed what it is. Everything works as it should, I’m just concerned that if we install new ceilings and it then needs to be replaced. The house is an old property and uses a TT system setup which I believe was upgraded with the installation of the EV charging unit. Any advice would be very much appreciated.

littlespark · Aug 5, 2022

Best course of action is get it replaced now, to ensure there is an earth present… done by a professional so you get the test certificates.

Whether there’s any comeback on the fact it was supposed to already have been rewired…. I don’t know.

When was it supposed to be rewired? If it was pre 1980’s, it possibly needs done again… just for increasing number of sockets more than anything.

Brown/blue colours are post 2007 and will be fine.

davesparks · Aug 5, 2022

That looks like a bit of VIR which is in surprisingly good condition if it is. As far as I know it shouldn't ever have been installed outside of conduit if it is VIR as its the equivalent of modern singles.

A non-contact voltage detector does not prove that it is live, it shows that it might be live. Likewise they do not prove that something is dead, they prove that it might be dead.
A disconnected cable sat next to a live cable will often cause a non-contact voltage detector to light up due to the capacitive coupling effect.

Does that cable actually connect to any of the new wiring?
If you've only found one end of it so far I'd suggest trying to carefully trace it to find the other end and see if it is connected.

Or else call an electrician to test it and see what's going on.

RealNetworks · Aug 5, 2022

littlespark said:
Best course of action is get it replaced now, to ensure there is an earth present… done by a professional so you get the test certificates.

Whether there’s any comeback on the fact it was supposed to already have been rewired…. I don’t know.

When was it supposed to be rewired? If it was pre 1980’s, it possibly needs done again… just for increasing number of sockets more than anything.

Brown/blue colours are post 2007 and will be fine.

To be honest I tend to agree with you. I’ve traced the cable from the consumer unit right up to the loft. From there it feed into a junction box. Each wire from the junction box there after is subsequently 1.5m2 twin & Earth. What’s the point of the subsequent wire having an earth when the main feed doesn’t…it just makes no sense to me. I suspect the electrician who rewired the house found it too much trouble to re-routes a new main feed wire from the CU up into the loft for the lighting circuit. He then replaced the more accessible/visible wire. The out of sight mentally I guess - how sad! Hey ho. The rewiring was done in 2006. I completely agree however, the best thing to do is call an electrician to look at and ensure it is safe to use. as when I’ve traced the cable I found a junction box extending said wire. The condition mortified me. Can a professional electrician explain how this wast picked up on a test. I’ve attached a picture below.

RealNetworks · Aug 5, 2022

This is a picture of what I discovered.

RealNetworks · Aug 5, 2022

davesparks said:
That looks like a bit of VIR which is in surprisingly good condition if it is. As far as I know it shouldn't ever have been installed outside of conduit if it is VIR as its the equivalent of modern singles.

A non-contact voltage detector does not prove that it is live, it shows that it might be live. Likewise they do not prove that something is dead, they prove that it might be dead.
A disconnected cable sat next to a live cable will often cause a non-contact voltage detector to light up due to the capacitive coupling effect.

Does that cable actually connect to any of the new wiring?
If you've only found one end of it so far I'd suggest trying to carefully trace it to find the other end and see if it is connected.

Or else call an electrician to test it and see what's going on.

I completely agree and understand that, but it is a useful tool for quickly providing a rudimentary reference point. The cable was live until I isolated the light circuit, and then live again. I’m just a little confused how live and neutral is identifiable without any markings. To be honest, the safest thing to do is have a electrician inspect the electrics in it entirety,

westward10 · Aug 5, 2022

As above a volt stick is wholly unreliable. The fact it goes off when the circuit is isolated is no guarantee it is still live so it needs verifying with an appropriate voltage indicator.

RealNetworks · Aug 5, 2022

westward10 said:
As above a volt stick is wholly unreliable. The fact it goes off when the circuit is isolated is no guarantee it is still live so it needs verifying with an appropriate voltage indicator.

I agree, I’m not implying it is 100% reliable. I’m simply explaining it was indicated. I’ve got my old Fluke 1653 multifunction tester I will use to determine any certainty.

davesparks · Aug 5, 2022

RealNetworks said:
This is a picture of what I discovered.

That's not regular VIR then, that's something I've not seen before. It appears to be a coaxial 2 core cable with cotton tape and rubber insulation and a woven sheath.
@Lucien Nunes may be able to shed some light on what it is.

So to answer your question of how the cores are identified it is their physical position within the cable, the centre core will most like be live and the outer conductor neutral (may have been neutral/earth combined originally)

RealNetworks · Aug 5, 2022

davesparks said:
That's not regular VIR then, that's something I've not seen before. It appears to be a coaxial 2 core cable with cotton tape and rubber insulation and a woven sheath.
@Lucien Nunes may be able to shed some light on what it is.

So to answer your question of how the cores are identified it is their physical position within the cable, the centre core will most like be live and the outer conductor neutral (may have been neutral/earth combined originally)

Reply, many thanks for the detailed response

7029 dave · Aug 5, 2022

I have not seen that type of VIR. Is this cable still in service (live), if yes then I advise the circuit/ circuits need rewiring.

timhoward · Aug 5, 2022

It reminds me a little bit of this photo, described on a USA wiki as "fabric- and rubber-insulated multi-strand electrical wire."

I'm not 100% sure it's the same though.
While it would be interesting to know what it is, whatever it is it pretty clearly shouldn't be in service.

At a minimum the CU end of this needs a good look at, some tests need doing at the junction box you found, and the lighting circuit downstream of it needs testing for the presence of a CPC and absence of any other supply.

Quite aside from any issues from the elderly cable, if there are any metal lights or switches then there is a pressing safety issue if the lighting circuit isn't earthed. It might be that the subsequent T+E has an earth connection from another circuit. (This is permitted by the regs if sized correctly)

But really it needs someone to take a good look at it, soon.
It might be worth sharing (vaguely) what area you are from as there may be a forum member nearby that can help you.

RealNetworks · Aug 5, 2022

Thanks everyone. I can’t disagree with anyones comments and or advice, it’s been very helpful.

It’s certainly an interesting one. Every other wire on this circuit is 1.5m2. I’ve also notice this wire connects to a 1.5m2 wire before entering the CU. Effectively, the electrician has installed new wire either side what would’ve been a complicated run of wiring from downstairs up through to the loft.

telectrix · Aug 5, 2022

@OP. ifyou post your rough location, 1 of us may be close enough to have a quick look and advise.

RealNetworks · Aug 5, 2022

telectrix said:
@OP. ifyou post your rough location, 1 of us may be close enough to have a quick look and advise.

Excellent idea. Northumberland.
To be honest, I think the whole property requires a complete rewiring. Whilst my background is a Network Engineer and I’m quite happy doing small electrical jobs and understand the logic and principles involved. However under no circumstances, is it ever good idea for a DIY or amateur to consider replacing cables or messing around in the CU. Others may disagree, but quite frankly is the risk worth it? I don’t think so. It’s important to understand what installation you have and how it works, but leave the doing it to professionals.

westward10 · Aug 5, 2022

It is two core it is just that the red insulation has all but gone but you can just still see it. It is more like PBJ that that was normally single core meter tails.

RealNetworks · Aug 5, 2022

westward10 said:
It is two core it is just that the red insulation has all but gone but you can just still see it. It is more like PBJ that that was normally single core meter tails.

How would they’ve earthed the circuit as there is no cpc present. I think moving forward the sensible thing to do is have a EICR done. In the meantime for peace of mind, whilst I don’t like meddling with mains electric, I’m competent enough to use my Fluke multifunction tester to do some rudimentary testing. Therefore I will do a r1, r2 + rm and Zs and Ze as I’m not convinced about the external cpc. I will report back.

littlespark · Aug 5, 2022

They may have borrowed a cpc from another circuit…. Upstairs sockets or whatever…

It needs replaced anyway.

I’m close to Northumberland…. But only the top bit.

RealNetworks · Aug 5, 2022

Just a quick note. As I really don’t recognise this cable, I’m wondering do any of these old fabric cables contain asbestos in their inner insulation?

westward10 · Aug 5, 2022

Not likely to contain asbestos and it may not even be live a voltage indicator will quickly prove this.

UK Old cable in dwelling light circuit

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