The most fundamental factor in selecting cable size (measured in square millimetres (mm²) of cross-sectional area) is the expected load current. As current flows through a conductor (typically copper or aluminium), resistance generates heat. If a cable is too small for the load—for example, using 1.0 mm² cable for a 20-amp power circuit—the conductor will overheat. This heat degrades the insulation (usually PVC or XLPE), potentially leading to a short circuit or fire.
The Science and Regulation of Electrical Cable Sizing in Australia electrical cable size australia
The primary document governing cable selection in Australia is the Australian/New Zealand Standard for Wiring Rules (AS/NZS 3000). This mandatory standard provides the tables and methodologies electricians must use. Unlike some countries that rely on "rule of thumb," Australia mandates a rigorous calculation process. The standard works in conjunction with AS/NZS 3008.1.1, which provides the specific current-carrying capacity tables for cables. Compliance with these standards is legally required under the National Construction Code (NCC) and various state electrical safety acts. The most fundamental factor in selecting cable size