If you are rewiring a light fitting and not sure what cable to choose, start off with the **Voltage** the fitting is operating at and the total number of **Watts** that will be drawn (e.g. quantity of lamps x their wattage). This will enable you to work out the **Amps** drawn by the fitting and therefore the **cable conductor size** that will be required.

Current Ratings for Flexible Cables

Conductor Size, sq mm | Max Current, amp |

0.50 | 3 |

0.75 | 6 |

1.00 | 10 |

1.50 | 15 |

To calculate the Current (in Amps) drawn by a particular lamp, or any other appliance, divide the Power (in Watts) by the Voltage (in Volts).

Examples:

Example 1: A mains-powered (240V) heater rated at 3000W draws a current of 3000 divided by 240, which equals 12.5 Amp. From the table above, it will need 1.5 sq mm flex.

Example 2: A mains-powered (240V) light bulb rated at 100W draws a current of 100 divided by 240, which equals 0.4 Amp. It will need 0.5 sq mm flex.

Example 3: A 12V circuit of 20 LED bulbs, each rated at 3W, draws a current of 20 multiplied by 3 divided by 12, which equals 5 Amp. From the table above, it will need 0.75 sq mm flex.