Although cable and flex may look similar they are used for different purposes. Cable is used for wiring electrical circuits while flex is used to connect electric appliances and lamps to electric circuits. Both consist of a protective PVC sheath that holds a number of cores (the metal conductors that carry the electric current). Each core will have a colour coded PVC cover (although the earth core in electric cable is often bare requiring yellow-and-green sleeving to be fitted).
If the cable has four cores (used for two-way switching) the colour coding will be:
*Any or all may be live.
New two-core-and-earth.
New three-core-and-earth.
If the old cable has four cores as used for two-way switching, the colour coding will be red, yellow, blue (any or all may be live) and a bare earth wire.
Old two-core-and-earth.
Old three-core-and-earth.
Cable comes in different sizes and is classified by the area of the cross-section of the cores and can range from 1mm2 to 10mm2. The size of the cable you require depends on the current supplied by the circuit. Below is a list of common cable sizes and what they are used for. If you are not sure what size of cable you need, seek advice from a professional electrician.
2.5mm2
4mm2
6mm2
10mm2
1mm2
As mentioned above flex also comprises PVC sheathing that protects colour-coded insulated conductors or cores. The PVC sheath of standard flex can be damaged if it comes into contact with a hot surface, there fore portable appliances that produce high levels of heat such as an electric iron or toaster, may well be fitted with rubber sheathing heat-resistant up to 85°C or a braided flex.
The cores in three-core electric flex are colour coded as below:
The cores in two-core electric flex are colour coded as below:
Three-core flex.
Two-core flex.
For non-metal light fittings and double insulated appliances such as some power tools.
Use for all appliances that need to be earthed.
There is also 1.5mm2 heat resistant flex for use with immersion heaters.