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.
2. 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.
3. 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?
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.
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 :-)
If it is wired directly into heaters, then it ought to be a heat
resisting rubber. The most likely is butyl rubber, which has been around
since the 1930s. All the heat resisting rubbers are also highly
resistant to aging so, as you say, the general rule does not apply.
However, the cost makes it extremely improbably that anyone is going to
use butyl rubber for a complete installation.
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:
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.
 Original source here:
(edited for typography by the present author).
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:
- Tinned strand copper, +/- CPC, rubber insulation, TRS sheath
- Bare strand copper, + CPC, PVC insulation, PVC sheath, green
- 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
- Stranded tinned copper, - CPC, waxy semi-translucent insulation,
waxy light grey plastic sheath
- 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
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.
<SNIP very good info>
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.
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..........
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.
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
And I thought the collection of spark plugs at the Shuttleworth Collection
was geeky... :o)
(No offence - I learned years ago not to take the piss out of other people's
hobbies - I'm sure mine seem equally as bizarre to them!)
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