According to BS 7671, we have to use brown colour for phase wire and blue colour for neutral in a single phase circuit. Answer 'Phases' are not identified in three-phase systems.

The use of grey as neutral, rather than black, comes from the old traditional re-use of three phase colours for single phase, when it was Red (live) yellow (or white) an s Earth, and Blue as neutral So, Phase 1> L Phase 2> E Phase 3> N If you then keep this with the new colours ,well, now phase …

In the old IEC color code, all the lines in three phase supply are either brown or black. Indeed, all of the relavent tables in BS 7671 (The 17th Ed Regs), are now calculated to 230 V. Examples of this can be seen in the Maximum Earth Fault Loop Impedance Tables in Chapter 41.

What are the current UK electrical wiring colours? 2.1 Single-phase installation. Any electronic wiring in a UK home features three colours of wiring which are used for three different functions: Blue This is the neutral wire. Phase 2 is powering units 2,5,8,11 and phase 3 the other units. An addition or an alteration made to a single-phase installation need not be marked at the interface provided that: i) the old cables are correctly identified by the colour red for line and black for neutral, and ii) the new cables are correctly identified by the colour brown for … Hence, the new color code is introduced. The UK changed colour codes three decades after most other European countries, as in 1977 the change of neutral and phase colours was not considered safe by the IEE. United Kingdom had its own color code until 2004. There are actually 12 units and phase 1 from the cabinet is powering units 1,4,7,10.

UK started using the IEC code from March, 2014. But from March, 2004, the UK started following the IEC color code.

If we have to wire single phase circuits from a 3 phase distribution board in a building, is it illegal to use wire colours brown, black and grey for the single phase circuits to distinguish between the 3 phases. This is new equipment just waiting to be installed.

This created a lot of problem. Green & Yellow; This is the earth wire.

We are now 'harmonised' with Europe and theoretically the voltages in the UK are 230 V single phase and 400 V 3 Phase. Brown This is the live wire.
Colours, letters, or numerals are used to identify lines.

A 17th edition guy has specified that we can use the 3 phase colours to wire the units. Blue, previously used as a phase colour, is now the colour for neutral.