International standard IEC 60446 Basic and safety principles for man-machine interface, marking and identification - Identification of equipment terminals, conductor terminations and conductors defines basic safety principles for identifying electrical conductors by colours or numerals, for example in electricity distribution wiring. The standard has been withdrawn; the fourth edition (IEC 60446:2007) was merged in 2010 into the fifth edition of IEC 60445 along with the fourth edition, IEC 60445:2006.
The standard permits the following colours for identifying conductors:
- black, brown, red, orange, yellow, green, blue, violet, grey, white, pink, and turquoise.
(The colours green and yellow on their own are only permitted where confusion with the colouring of the green/yellow protective conductor is unlikely. Combinations of the above colours are permitted, but green and yellow should not be used in any of these combinations other than as green/yellow for the protective conductor.)
Use of colours
Neutral or mid-point conductor
If a circuit includes a neutral or midpoint conductor, then it should be identified by a
AC phase conductors
The preferred colours for AC phase conductors are:
The colour combination
Protective earth and neutral (PEN) conductor
Insulated PEN conductors (combined protective earth + neutral in TN–C systems) should be marked:
green/yellow along their entire length with light blue markings at their ends,
light blue along their entire length with green/yellow markings at the ends.
The cable must have a cross section of 16 mm2 (5 AWG) or greater.
United States, Canada and Japan
The three countries United States, Canada and Japan are mentioned in a note in the standard for using different colours:
white or natural gray for mid-wire or neutral conductor (instead of light blue) green for the protective conductor (instead of green/yellow)
British Standard BS 7671:2001 Amendment No 2:2004 adopted the IEC 60446 colours for fixed wiring in the United Kingdom , with the extension that
Where conductors are in addition identified by letters and numbers, then:
- letters to be used come from Latin character set,
- numbers must be written in Arabic numerals, digits 6 and 9 must be underlined (6 and 9),
- and a few symbols like + and − can be used.
Green-and-yellow conductors must not be marked.
Examples: L1, L2, L3, N, L+, L−, M, 35, 16
- "Archived copy" (PDF). Archived from the original on 12 April 2017. Retrieved 2016-01-25.CS1 maint: archived copy as title (link) CS1 maint: BOT: original-url status unknown (link)
- IEC 60446:2007: Basic and safety principles for man-machine interface, marking and identification – Identification of conductors by colours or numerals, International Electrotechnical Commission, Geneva.
- IEC 60445:2010: Basic and safety principles for man-machine interface, marking and identification - Identification of equipment terminals, conductor terminations and conductors, International Electrotechnical Commission, Geneva.
- Paul Cook: Harmonised colours and alphanumeric marking. IEE Wiring Matters, Spring 2006.
- "IEC 60446" at International Electrotechnical Commission