Installation Requirements
- Single phase installations used the traditional colours of red and black for the phase and neutral conductors are replaced by the familiar colours of brown and blue (Regulation 514-03-01). A neutral conductor, where identified by colour, must be identified by the colour blue (Regulation 514-04-01). Protective conductors remain green and yellow (Regulation 514-04-02).
- Three phase installations have traditionally used red, yellow and blue for the phase conductors and black for the neutral conductor. These are replaced by the colours of brown, black and grey for the phase conductors and blue for the neutral conductor (Regulations 514-03-01 and 514-04-01). Protective conductors remain green and yellow.
- All installations starting after 31st March 2004 and before 1st April 2006 may be installed in accordance with Amendment No. 2 : 2004 or Amendment No 1 : 2002, in other words they may use the harmonised colours or the old colours but not both.
Extensions, alterations or repairs to existing wiring
- An extension, alteration or repair to an existing single-phase installation should be wired in the colours of brown, blue and green and yellow. If any of these changes are made to an installation that results in both the old and new wiring being present, a warning notice must be affixed at or near the appropriate distribution board or consumer unit (Regulation 514-14-01).
Identification of Conductors
| Function | Alpha Numeric | Colour |
| Protective Conductors | - | Green and Yellow |
| Functional earthing conductor | - | Cream |
| AC Power Circuit(1) | - | - |
| Phase of single-phase circuit | L | Brown |
| Neutral of single or three phase circuit | N | Blue |
| Phase 1 of three-phase circuit | L1 | Brown |
| Phase2 of three-phase circuit | L2 | Black |
| Phase 3 of three-phase circuit | L3 | Grey |
| Two-wire unearthed DC Power Circuit | - | - |
| Two-wire earthed DC Power Circuit | - | - |
| Positive of two-wire circuit | L+ | Brown |
| Negative of two-wire circuit | L- | Grey |
| Positive (of negative earthed) circuit | L+ | Brown |
| Negative (of negative earthed) circuit(2) | M | Blue |
| Positive (of positive earthed) circuit(2) | M | Blue |
| Negative (of positive earthed) circuit | L- | Grey |
| Three-Wire DC Power Circuit | - | - |
| Outer positive of two-wire circuit derived from three-wire system | L+ | Brown |
| Outer negative of two-wire circuit derived from three-wire system | L- | Grey |
| Positive of three-wire circuit | L+ | Brown |
| Mid-wire of three-wire circuit(2)(3) | M | Blue |
| Negative of three-wire circuit | L- | Grey |
| Control circuits, ELV and Other Applications | - | - |
| Phase conductor | L | Brown, Black, Red, Orange, Yellow, Violet, Grey, White, Pink or Turquoise |
| Neutral or mid-wire(4) | N or M | Blue |
(1) Power circuits include lighting circuits.
(2) M identifies either the mid wire of a three wire DC circuit, or the earthed conductor of a two wire earthed dc circuit.
(3) Only the middle wire of three-wire circuits may be earthed.
(4) An earthed PELV conductor is blue.
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