While we tend to use the generic term ‘wiring’ to mean any electrical ‘conduits’, professional electricians make a distinction between the fixed, permanent wiring of electrical circuits, which use cables to carry the current, and portable electrical appliances such as table lamps, which are connected to the fixed wiring by conductors of flexible cord, commonly called flex.
Single-core 6mm sq. cable is used to connect the consumer unit to the earth, and 16mm sq. single-core cable is used to connect the unit to the electricity meter.
Two-Core and Earth Cable
This is the type of cable that runs unseen in your house – under the floors and behind walls. It is used for the fixed wiring of the electrical system in your home. It normally has three conductors: insulated live (red) and insulated neutral (black) plus an earth conductor lying between them. The earth conductor is not usually sheathed – except for the grey or white outer sheath that covers all three – except where it is exposed, such as at a socket outlet in a wall. Here it should be covered with a green and yellow sleeve, which you can buy. Some two-core and earth cables are sheathed in heat-resistant sleeving to safeguard them where extra heat may be generated – such as in enclosed light fittings.
Three-Core and Earth Cable
This type of cable is used in two-way lighting systems – where lights can be switched on and off at different switches. This cable has three insulated conductors – red, blue and yellow – and a bare earth.
A square inside a square printed or moulded onto an appliance means that it has been double insulated so its flex does not require an earth conductor.