Evolution of the electrical installation

Evolution of Electrical Wiring

Paper Insulation (1910).

In this day and age, it's extremely rare to come across paper insulation cabling in a domestic property.

This wiring dates back to WW1 (1914) and as far as I'm aware it was the very first mass-produced wiring to be installed within domestic properties.

This cabling is identified by its paper and oil wrapped outer sheath.

It's a toxic concoction by the way so it should not be touched!

• Lead insulation (1930).

Lead Insulation (1930)

A flat lead sheathed cable containing a rubber inner insulation.

Produced and installed in the 1930s.

Again I am yet to see any of this cabling in actual use.

I have only ever witnessed redundant cabling of this sort hidden under floorboards.

I believe to

my best knowledge that this cabling was only ever used for socket circuits as I have never witnessed it in lofts or in the back of old light switches.

• Vulcanised Indian Rubber (1950).

Also known as 'Vulcanised Rubber Insulated Cable' or a combination of either 'VIR or VRI'. These cables are run as separate individual single wires. They are recognisable as a waxy cotton looking material similar to a shoelace. VIR cables are still very much in use in old buildings. I can even personally hold my hands up and say that I have lived in a property which incorporated them. They are often seen in blocks of flats, run through old imperial sized steel conduits and recessed within the building fabric. Usually, a conduit system enables the prospect of an easy rewire. However with only brittle VIR cables to tie onto and a small 16mm conduit system it is not always possible. I may like to also point out that even when it is possible to pull through new wiring it is not always compliant due to electrical requirements demanding a minimum of 40% free space within cable containment to reduce the build-up of heat.

• Rubber sheath (1960).

A black rubber flat cable. I have heard rumours of this cabling using a similar if not the same material (rubber) as car tyres. The cable was extremely flexible and I have in a few rare cases witnessed the old cable still supplying power to sockets. I can usually expect this when rewiring a home belonging to an elderly customer, or possibly a property who's the previous occupier has just passed and is now being refurbished for new owners. The wallpaper will be the original 1960's loud floral pattern and there will most likely be old lino under the carpet. This cable was one of the first to incorporate an earth (CPC) wire between the live and neutral conductors. Almost like today's twin and earth wiring.

• Grey PVC (1970).

Very common indeed. In fact, it may even be in your home right now. These cables were the first twin and earth cable which incorporated a bare CPC conductor run through the centre of the cable. Although the conductors look like they're made from steel I was educated as per a few older electricians that these are copper conductors coated in a tin alloy to prevent corrosion. These cables can also be located without the earth conductor in many old lighting circuits. If you have ever noticed a green goo (similar to washing up liquid) emerging from any electrical facias you can bet your property incorporates these cables. The green goo phenomenon is caused due to a chemical reaction between the metallic conductors and the cables PVC outer sheath when warm. Thankfully we have rectified this issue in today's PVC cabling.

• White PVC (1980).

These were the cables I installed throughout my apprenticeship. As far as I'm aware they're no different from today's cables apart from colour. The conductors were copper and unlike all previous wiring, they were the first cables to use solid cores for all wiring up to 2.5mm. All previous wiring up to this date used stranded cores. This was the last time we used red and black to identify our live and neutral conductors.

• Grey PVC - harmonised Colours (2004).

To date at last! We are still currently using this cable and even though I have labelled it as 'grey' it can sometimes be seen in very rare occasions as 'white'. The white version is a 'low smoke' version of the cable and is more commonly used in commercial properties and extremely rare in domestic. To harmonise our UK conductor colours with Europe we now use brown and blue as our live and neutral conductor colours. Brown doesn't really shout "danger" like Red did, but if it keeps the cost of cable down by producing it abroad I cannot complain entirely.