Cables & Wiring
Open wiring consists of single-core insulated conductors that operate at not more than 250 V to earth. However, this is not a recommended installation method for new installations. Open wiring can still be seen in older buildings and homes.
Screened single-core co-axial communication cable, sometimes referred to as the aerial wire, has a single copper strand insulated by thick plastic and surrounded by foil and screen wire. It is commonly used to connect an aerial to the TV.
Surfix or norsk cable
Popular cables used for domestic wiring applications are available in either flat or round and are commonly referred to as “twin and earth”. They have two single copper strands insulated with PVC and a bare single copper earth wire. Norsk cable has the earth wire between the two strands. Round surfix cable has an extra strand of PVC material embedded to maintain its “roundness”. Surfix cable also has an outer foil shield to prevent induction. It is sold in a variety of sizes. Norsk cable is available in black or white whereas round Surfix is always white.
Flex or ripcord
A twin-stranded wire is normally used for bells, lamps and the wiring of alarm systems. It does not have an earth wire. For some ripcords, the outside of one strand is marked with either a ridge or a different colour to identify which is to be used for the positive (live), and which for the negative (neutral) side. However, most ripcords have a red and white satin insert in one strand for this purpose.
Cabtyre – three core
The most popular cable of all. It is extensively used for extension leads and supply cables to appliances. It is sold in a variety of sizes and colours.
Cabtyre – twin core
Mostly used for lamps and other appliances that do not have to be earthed, it is sold in different sizes and colours.
The most popular cable of all. It is extensively used for extensions and supply cables to appliances. It is sold in a variety of sizes and colours.
Used for the internal wiring of buildings. It is sold in a variety of thicknesses and colours and typically a seven strand core. The earth wire is always bare.
Armoured cable is normally used to transfer power either underground or overhead. The construction is normally the inner cores (which are multi strand) being individually sheathed, then covered by an initial overall plastic sheath, followed by the protective wire armour with a final outer sheath to hold it all together. The inner cores may number two, three or four depending upon the application. The wire protective armour should always be earthed at the supply end to ensure that it cannot become live if the cable is severed or a fault should develop within the cable.
Information supplied by Buildaid Publishing.