Dates for different electrical cable types

[Caecilius]

I'm doing some building and renovation work on a commercial property, and it's got a number of generations of electrical wiring.

Is there any guide as to the approximate dates when the various types of cable would have been used? This is mainly for my own interest, as I'm getting an electrician to test and rewire as necessary.

I've seen the following, in what I think is oldest to newest:

1. Rubber covered single cables in black metal trunking. No earth wire, so presumably the trunking was used as earth.

1. Grey T&E cable. Not the new grey T&E, because some of it goes to old round three-pin sockets, and the earth wires are joined by twisting them together which doesn't look like modern practice to me.

2. White T&E cable. Looks like the most recent to me.

Everything is using the old red/black colour scheme.

Does anyone know the date ranges when these types of cables were used?

[Nightjar]

Except in some specialised applications, such as heat resisting butyl rubber leading to immersion heaters, rubber insulation is probably at least half a century old and probably more. It should be considered to bedangerous and in urgent need of replacement.

Could be anything from c 1950s to fairly recent. I still have reel or two of grey sheath red and black cable around somewhere. BS 546 round pin sockets went out of general use in the 1960s, but could be much later, particularly if the desire was to match existing sockets elsewhere in the building. On balance through, probably several decades old.

Not easy to say as grey and white sheath were both available as alternative options for a long time.

Unless 1 and 2 are only used in very limited areas, it would probably be best simply to remove everything and rewire. Otherwise, with this sort of mix and age, there is a risk that what looks like modern wiring is simply an extension onto a much older and unsafe cable. A rewire also allows you to match the installation to modern needs.

Colin Bignell

[Andy Wade]

As posted previously:

Lead sheathed cables: pre-1948.

Tough rubber (TRS): 1945-1962.

Capothene and Ashothene Sheathed Cables: 1952-1960.

PVC/PVC cables without cpc (lighting): 1955-1966.

Imperial cables PVC: 1955-1971.

2.5mm PVC/PVC with 1mm cpc: 1971-1981.

Black earth conductors: pre-1966.

Green protective sleeving: pre-1966.

Absence of main equipotential bonding conductors: pre-1966.

2.5mm main equipotential bonding conductors - small installations: 1971-1972. 6mm main equipotential bonding conductors - small installations: 1966-1983. 10mm main equipotential bonding conductors - small installations: post-1983.

Twin twisted flexible cords: pre-1977.

Fault voltage operated circuit breakers: pre-1981.

Accessories mounted on wooden blocks: pre-1966.

Non-13A socket-outlets pre-1955.

Double-pole fused switchgear on AC installations: pre-1955.

Others might may have other recollections. I appreciate that some things were being used some time after the dates e.g. 15amp sockets.

[1] Original source here: (edited for typography by the present author).

[Caecilius]

Yes, it's probably going to be a complete rewire. I'm more interested in the dates to understand some history of the building rather than in an attempt to retain old and marginal wiring.

[Caecilius]

Thanks for that. Very useful.

[Tabby]

[js.b1]

Does Capothene look like polythene, semi-translucent, waxy surface, if overheated tends to go from red to brown and suffers cracking around its circumference on bends?

From a known 1951 build:

Power...

- Tinned strand copper, +/- CPC, rubber insulation, TRS sheath

- Bare strand copper, + CPC, PVC insulation, PVC sheath, green pthalate goo!

Ground Lights...

- Bare solid copper, - CPC, waxy semi-translucent insulation, waxy light grey plastic sheath

Master Bed Lights...

- Tinned strand copper, + CPC in green!, waxy semi-translucent insulation, black plastic sheath

- That green is throughout the length of the cable, I stripped back

12" of the other end Lights...

- Stranded tinned copper, - CPC, waxy semi-translucent insulation, waxy light grey plastic sheath

Clocks...

- Bare solid copper, + CPC, waxy semi-translucent insulation, waxy light grey plastic sheath (BICC)

House build 1951, cables provided by head EE of LEB who also worked at BICC (relative). A note with the deeds states the police attended site due to theft of materials, including reels of cable - so only the clocks and not the downstairs lights (concrete floor) got CPC (FTE).

The oddball was that black cable, the green is continuous, but live - intended for a switch by the bed which was never integrated (pullswitch had been left wired to it in the loft). Lead cable cleats everywhere, except for a "builders cable" which was cutoff singles fitted by bending a masonry nail over them.

[ARWadsworth]

Andy, the Tough Rubber Cable is mentioned in a 1931 book that I have. It also refers to it as "maconite" cable. Is this the same thing as Capothene and Ashothene Sheathed Cables.

See my posts on the ""Non-Association" Cable " thread to see a couple of scans about old cables from this book. I have never had the pleasure of installing such cables but I am interested in them.

Cheers

[Dave Osborne]

Do you want this ticket for your collection, then? I'm happy to pop it in the post.

DaveyOz

[ARWadsworth]

I have one somewhere. Dunno where it is at the moment.

[chris French]

What about the pre war rubber(?) stuff such as was in our old house?

Semi detached in Leeds, built by 1938 going by the documentation and the news papers lining the loft. Singles in small diameter steel conduit, AFAICT installed at construction. (sounds similar to the OP's stuff)

Insulation was falling off, it went very rapidly when I discovered exposed cables in the loft which had been joined to a plastic choc block connector happily sparking away..........

[Nightjar]

I was involved in starting up and running the Seeboard Electricity Museum, now incorporated into the Chalk Pits Museum, and we had some exhibits with rubber insulated wiring that pre-dated the Great War.

Colin Bignell

[Tabby]

Any piccies of such historic bits would be great for the wiki :)

NT

[Nightjar]

We never even got around to cataloguing everything before I left Seeboard. The collection came in from Electricity Boards across the country and rapidly filled a small generating station. It is much better laid out in The Chalk Pits Museum, but they only show a fraction of the collection.

Colin Bignell

[Huge]

On 2010-11-04, Nightjar

[Terry Casey]

I'm sure I remember this being referred to as slit conduit because, I assume, of the longitudinal slit along the conduit.

[ARWadsworth]

You old git, so does

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[Dave Osborne]

Huh, no pictures of nipples. Boooring!

[John MacLeod]

A general truth. But there's rubber and rubber. And even when it isn't butyl rubber it's not necessarily true that it's going to be either perished and dangerous. In one installation I've inspected quite a few cable ends of rubber cables wired directly into tubular convector heaters c 1955 and all were perfect. Not hardened or perished in any way. Top-quality installation using what was obviously top-quality cable. And I've no intention of replacing it unless forced to :-)

John

[John MacLeod]