Spotters' guide to early plastic-insulated lighting cables

We recently had a thread or two about some cables that were almost certainly tinned copper, but people continued to suspect they were aluminium because they were solid core, not stranded, i.e. from the metric cable era when copper was invariably plain. In fact, the smallest tinned-copper lighting cable in general use in the imperial era was solid-core; read on for an explanation...

In the era of imperial cable sizes, domestic lighting circuits were usually wired with one of two sizes - 1/.044 i.e. one strand of 0.044 inches diameter hence a solid conductor, or 3/.029, i.e. a stranded one. 1/.044 is almost exactly 1.0mm² so the two cannot be told apart by measuring the conductor. There was no equivalent to 1.5mm² but 3/.029 at 1.28mm² was the usual 'next size up', also preferred for all 'high class' work regardless of loading because a stranded conductor was more flexible and thought to make better terminations. Next up was 3/.036 at nearly 2.0mm² but this is rarely seen in domestic wiring.

Sheathed flat-twin, twin-and-earth and their triple equivlalents were around long before plastic insulation. All had existed in rubber insulated and tough-rubber sheathed since the inter-war years, all of which have tinned-copper conductors because this was necessary to stop them reacting with the sulphur in the rubber. It was not customary to run an earth on a lighting circuit unless the wiring system required it (e.g. lead-sheathed, or singles in conduit) so the smaller sizes of flat insulated-and-sheathed rubber cables were more often without an earth.

Plastic insulation was actually being made before WW2 but didn't find a market until afterwards. When it began to take over from rubber, twin cables were often insulated with polyethylene, not PVC, just like modern XLPE SWA. It can be distinguished by its glossy, waxy appearance, often slightly translucent, and a waxy smell when heated in a flame. The cable sheath was invariably PVC though. I am not sure what influenced the the selection of PE vs. PVC over the years, although at first PVC was found to be a poorer insulator than natural rubber (which is still true - rubber ages badly, but when new is a superb insulator). Although plain copper in contact with PE and most PVC is fine, tinned conductors were still standard, probably because people expected it for corrosion-resistance at the terminations, and because rubber cables being produced alongside required it. As the s rolled into the s, various permutations emerged. Some imperial cables were made with plain copper, rubber cable manufacture having ended.

In a typical early plastic insulated lighting circuit, one might still find PE-insulated PVC sheathed 1/.044 both with and without an earth, the earthed variety looking rather like 1.0mm² T+E but in fact an imperial cable that could be 70 years old. The distinguishing features will be the glossy insulation (although not the sheath) and the tinned copper conductors. The sheath may be thinner than on a metric cable and may have stiffened slightly with age although the insulation will be fine.

The first pic shows two early examples of 1/.044 from the 50's, PE-insulated and PVC sheathed, without earth and with. The end-view of the stripped-off sheath shows the typical webs of plastic between the cores and the overall thinner profile compared to 1.0mm². Next are two samples of 3/.029; the top one is of similar age and material to the 1/.044, below which is a PVC-insulated and sheathed type by Rists, with plain copper conductors, that probably dates from near the end of imperial cable manufacture. The enlarged pic gives a clearer view of the difference between the early PE and late PVC insulations.




None of these cables would give me any cause for concern in themselves, their IR was measuring as good as new until recently removed and they may have many decades of useful life left. But where they are found, there may be non-MF joint boxes hidden away that have not been touched for over half a century, and that is more of an issue.

We recently had a thread or two about some cables that were almost certainly tinned copper, but people continued to suspect they were aluminium because they were solid core, not stranded, i.e. from the metric cable era when copper was invariably plain. In fact, the smallest tinned-copper lighting cable in general use in the imperial era was solid-core; read on for an explanation...

In the era of imperial cable sizes, domestic lighting circuits were usually wired with one of two sizes - 1/.044 i.e. one strand of 0.044 inches diameter hence a solid conductor, or 3/.029, i.e. a stranded one. 1/.044 is almost exactly 1.0mm² so the two cannot be told apart by measuring the conductor. There was no equivalent to 1.5mm² but 3/.029 at 1.28mm² was the usual 'next size up', also preferred for all 'high class' work regardless of loading because a stranded conductor was more flexible and thought to make better terminations. Next up was 3/.036 at nearly 2.0mm² but this is rarely seen in domestic wiring.

Sheathed flat-twin, twin-and-earth and their triple equivlalents were around long before plastic insulation. All had existed in rubber insulated and tough-rubber sheathed since the inter-war years, all of which have tinned-copper conductors because this was necessary to stop them reacting with the sulphur in the rubber. It was not customary to run an earth on a lighting circuit unless the wiring system required it (e.g. lead-sheathed, or singles in conduit) so the smaller sizes of flat insulated-and-sheathed rubber cables were more often without an earth.

Plastic insulation was actually being made before WW2 but didn't find a market until afterwards. When it began to take over from rubber, twin cables were often insulated with polyethylene, not PVC, just like modern XLPE SWA. It can be distinguished by its glossy, waxy appearance, often slightly translucent, and a waxy smell when heated in a flame. The cable sheath was invariably PVC though. I am not sure what influenced the the selection of PE vs. PVC over the years, although at first PVC was found to be a poorer insulator than natural rubber (which is still true - rubber ages badly, but when new is a superb insulator). Although plain copper in contact with PE and most PVC is fine, tinned conductors were still standard, probably because people expected it for corrosion-resistance at the terminations, and because rubber cables being produced alongside required it. As the s rolled into the s, various permutations emerged. Some imperial cables were made with plain copper, rubber cable manufacture having ended.

In a typical early plastic insulated lighting circuit, one might still find PE-insulated PVC sheathed 1/.044 both with and without an earth, the earthed variety looking rather like 1.0mm² T+E but in fact an imperial cable that could be 70 years old. The distinguishing features will be the glossy insulation (although not the sheath) and the tinned copper conductors. The sheath may be thinner than on a metric cable and may have stiffened slightly with age although the insulation will be fine.

The first pic shows two early examples of 1/.044 from the 50's, PE-insulated and PVC sheathed, without earth and with. The end-view of the stripped-off sheath shows the typical webs of plastic between the cores and the overall thinner profile compared to 1.0mm². Next are two samples of 3/.029; the top one is of similar age and material to the 1/.044, below which is a PVC-insulated and sheathed type by Rists, with plain copper conductors, that probably dates from near the end of imperial cable manufacture. The enlarged pic gives a clearer view of the difference between the early PE and late PVC insulations.

View attachment
View attachment

None of these cables would give me any cause for concern in themselves, their IR was measuring as good as new until recently removed and they may have many decades of useful life left. But where they are found, there may be non-MF joint boxes hidden away that have not been touched for over half a century, and that is more of an issue.

We recently had a thread or two about some cables that were almost certainly tinned copper, but people continued to suspect they were aluminium because they were solid core, not stranded, i.e. from the metric cable era when copper was invariably plain. In fact, the smallest tinned-copper lighting cable in general use in the imperial era was solid-core; read on for an explanation...

In the era of imperial cable sizes, domestic lighting circuits were usually wired with one of two sizes - 1/.044 i.e. one strand of 0.044 inches diameter hence a solid conductor, or 3/.029, i.e. a stranded one. 1/.044 is almost exactly 1.0mm² so the two cannot be told apart by measuring the conductor. There was no equivalent to 1.5mm² but 3/.029 at 1.28mm² was the usual 'next size up', also preferred for all 'high class' work regardless of loading because a stranded conductor was more flexible and thought to make better terminations. Next up was 3/.036 at nearly 2.0mm² but this is rarely seen in domestic wiring.

Sheathed flat-twin, twin-and-earth and their triple equivlalents were around long before plastic insulation. All had existed in rubber insulated and tough-rubber sheathed since the inter-war years, all of which have tinned-copper conductors because this was necessary to stop them reacting with the sulphur in the rubber. It was not customary to run an earth on a lighting circuit unless the wiring system required it (e.g. lead-sheathed, or singles in conduit) so the smaller sizes of flat insulated-and-sheathed rubber cables were more often without an earth.

Plastic insulation was actually being made before WW2 but didn't find a market until afterwards. When it began to take over from rubber, twin cables were often insulated with polyethylene, not PVC, just like modern XLPE SWA. It can be distinguished by its glossy, waxy appearance, often slightly translucent, and a waxy smell when heated in a flame. The cable sheath was invariably PVC though. I am not sure what influenced the the selection of PE vs. PVC over the years, although at first PVC was found to be a poorer insulator than natural rubber (which is still true - rubber ages badly, but when new is a superb insulator). Although plain copper in contact with PE and most PVC is fine, tinned conductors were still standard, probably because people expected it for corrosion-resistance at the terminations, and because rubber cables being produced alongside required it. As the s rolled into the s, various permutations emerged. Some imperial cables were made with plain copper, rubber cable manufacture having ended.

In a typical early plastic insulated lighting circuit, one might still find PE-insulated PVC sheathed 1/.044 both with and without an earth, the earthed variety looking rather like 1.0mm² T+E but in fact an imperial cable that could be 70 years old. The distinguishing features will be the glossy insulation (although not the sheath) and the tinned copper conductors. The sheath may be thinner than on a metric cable and may have stiffened slightly with age although the insulation will be fine.

The first pic shows two early examples of 1/.044 from the 50's, PE-insulated and PVC sheathed, without earth and with. The end-view of the stripped-off sheath shows the typical webs of plastic between the cores and the overall thinner profile compared to 1.0mm². Next are two samples of 3/.029; the top one is of similar age and material to the 1/.044, below which is a PVC-insulated and sheathed type by Rists, with plain copper conductors, that probably dates from near the end of imperial cable manufacture. The enlarged pic gives a clearer view of the difference between the early PE and late PVC insulations.

View attachment
View attachment

None of these cables would give me any cause for concern in themselves, their IR was measuring as good as new until recently removed and they may have many decades of useful life left. But where they are found, there may be non-MF joint boxes hidden away that have not been touched for over half a century, and that is more of an issue.

Thanks for this Lucien Happy days for some of us, earth cable was never insulated either, bare copper mostly 7/029 if I recall correctly, which when surface run you had to use staples, no not in dispensers
Sore pinkies and a hammer, albeit a small hammer was the choice of most Sparkies back in the 60s. Spent many a happy hour searching in the Electricians old Army bag for these staples often ending up with them stuck under my nails, or in my fingers.

Two common types of cable jacket materials used in industrial applications are PVC and PUR. Both of these materials are flexible and durable thermoplastics, materials which melt at extremely high temperatures and become solid again when cooled. Even though they are both plastics, their differing physical properties imbues them with unique abilities. These abilities make PVC cables and PUR cables suited for use in different types of environments.

Tongda contains other products and information you need, so please check it out.

Polyvinyl chloride, or PVC, is a widely used, general-purpose cable jacket material due to its versatility and low cost. PVC cables can resist heat, oils, moisture, and abrasions, but are especially resistant to common cleaning chemicals. Polyurethane, known as PUR, is also good for oil, moisture, and abrasion resistance, but does not have the same heat resistance qualities as PVC. However, PUR cables are stronger and more flexible. 

PVC cable jackets are inherently flame- and heat-resistant, owing to their chemical makeup. They can also resist oils, acids, abrasions, sunlight, salt water, ozone, oxidation, and moisture, and a PVC cable with an IP69K rating means it is sealed against the ingress of water even during washdown. This makes them an excellent choice for most chemical washdown applications in the food industry and beverage industry. Because PVC is a blend of materials and can vary from manufacturer to manufacturer, its properties can be adjusted and tailored for specific applications and conditions. PVC cable jackets have good-to-excellent resistance to common cleaning solvents including, but not limited to:

• sodium hypochlorite
• sodium hydroxide
• potassium hydroxide
• peracetic acid
• hydrogen peroxide
• quaternary ammonium compounds

You will find PVC cable jackets in other applications across many different industries, including packaging and assembly lines, lighting, and medical manufacturing.

When choosing a cable jacket material, it is also important to consider the concentration of chemicals, temperature of the process, and the duration and frequency of exposure since these factors can impact the suitability of PVC for these applications. For example, though PVC has some resistance to oils, other materials such as PUR offer improved oil resistance, making PVC less suited for automotive and machine tool industries.

For more PVC Insulated Cablesinformation, please contact us. We will provide professional answers.

In addition to cleaning chemical resistance, PVC cables are typically more rigid than other types of cables. This makes them suitable for use in applications where they will be exposed to high temperature, high pressure washdown. The rigidity of the PVC sheathing protects the cable from damage and extends the life of the cable. However, the rigidity of PVC cables can be a disadvantage in freezer applications, where low temperatures can cause the material to crack if the cables are being flexed. 

Like PVC, PUR is a thermoplastic material used for cable jackets. However, the chemical composition of polyurethane is noticeably different than that of polyvinyl chloride. Despite not having the natural fire resistance of PVC, PUR does not contain halogens like PVC does and will not emit toxic fumes if exposed to fire. It also creates little smoke. This makes PUR the preferred material in the European Union because EU regulations required “low/no smoke, low/no halogen” properties to be identified on the cable jacket. In case of an incident, fewer halogens will be released into the air.

PUR cables have a high tensile strength and are resistant to UV light, water, tears, and abrasions. They are also resistant to weld slag, cutting fluids, oils, solvents, and other harsh chemicals, making them a good choice for many automotive manufacturing, stamping, and machining applications.

One standout feature of PUR cables is their flexibility and small bend radius. This makes them ideal for applications where connections move or bend frequently, such as robotic applications. Many PUR cables can maintain flexibility even in low temperatures. Besides robotics, PUR cables’ flexibility lends itself to use in paint facilities, medical applications, and other applications with constant movement.

Are you interested in learning more about Flexible Control Cable? Contact us today to secure an expert consultation!