Hướng dẫn màu dây điện

How this is calculated#

The tool answers two questions. The first is what colour each conductor should be. The second is what a conductor of a given colour can be, when you find one on site.

For fixed installation wiring the tool reads the wiring rules' table of conductor colours. Protective earth and equipotential bonding conductors are green/yellow. A neutral is black or light blue, except in a New Zealand domestic installation, where it is black only. An active may be any colour other than green, yellow, green/yellow, black or light blue. The table's notes recommend red or brown for a single‑phase active, and red, white or blue for the actives of a multiphase circuit. The tool shows those as recommendations, beside the rule.

An older installation may carry colours from a previous edition. A bare or green earthing or bonding conductor may stay, and so may a yellow live conductor. New terminations on them take sleeving: green/yellow on the earth, white on the yellow active.

For flexible cords the tool reads the in-service testing standard. Its colour table gives the international scheme and the superseded one, which older and imported cord sets still use. A second table gives the cores of each modern cord, single phase or three phase, Class I or Class II, with or without a neutral.

To identify a colour, the tool checks every row of both standards and lists each function the colour can carry, and where.

Worked examples#

• A New Zealand house. The recommended active is red or brown, the neutral black, and the protective earth and bonding green/yellow.
• An Australian three‑phase board. The recommended actives are red, white or blue, the neutral black or light blue, and the earth and bonding green/yellow.
• A five-core cord. The phases are brown, black and grey, the neutral blue, and the earth green/yellow.
• A yellow conductor in an older house. It can only be an active from a previous edition. Treat it as live and sleeve it white at a new termination.
• A black conductor on site. Neutral or active: a neutral in fixed wiring and in a superseded cord, a phase in a modern three‑phase cord.

Limits#

A colour says what a conductor should be, not what it is: prove it by test before work. The tool does not cover the special applications of Cl 3.8.3, such as numbered cores, or the internal wiring of equipment. It does not set a phase order for red, white and blue, because the table sets none.

See also: Wire colours in NZ and Australia, old and new, Reading the wiring in an older house and Test and Tag.