Every cable can safely carry only so much current. When an appliance draws more than the cable is made for, the copper heats up, the insulation softens and, over time, it can melt or start a fire. Choosing the right size from the start is cheaper than rewiring later.
Common sizes in a house
- 1.5mm for lighting circuits.
- 2.5mm for socket circuits (the everyday 13A sockets).
- 4mm to 6mm for heavy loads such as water heaters, cookers and air conditioners.
- 10mm and above for the main supply into the consumer unit, as your electrician advises.
Things that change the size
Long runs lose voltage, so a long cable to an outside building may need the next size up. Cables bunched together or buried in insulation also run hotter. Always match the cable to the breaker that protects it.
Buy genuine copper
Cheap cable often has less copper than its label says, so it behaves like a thinner cable. Buy from a supplier you trust and check the markings on the sheath. If you are not sure, tell us what you are wiring and we will help you choose. For the installation itself, use a qualified electrician.
Tell us what you are working on
We will suggest the right items and give you a price.
