Electric power cable colours in the UK
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Always isolate any electrical circuit before working on the circuit.
March 2004 saw amendment 2 to British Standard BS 7671 (Requirements for Electrical Installations). Probably the most significant change introduced for the diyer was the change of colour coding of electric cable. The new coloured cables are referred to as harmonised cables - the colours are harmonised across the EU.
'2 core and earth' cable
Pre March 2004 the UK standard for '2 core and earth' cable used in single phase (i.e. normal household) installation was:
|Earth||Green and Yellow (see note)|
Note: the earth feed is normally bare copper in mains installation cable, the Green and Yellow applies to the coloured sleeving which needs to be fitted where the earth is connected to a fitting or appliance.
Post March 2004 the UK standard was changed to:
|Earth||Green and Yellow (no change)|
You may recognise that this new colour coding is the same as used for appliance flexes in the UK for many years.
'3 core and earth' cable (two way lighting)
Pre March 2004 the UK standard for '3 core and earth' cable used in two way lighting was blue, yellow and red with a bare copper earth.
Post March 2004 the UK standard was changed to Grey, Black and Brown with a bare copper earth.
Why the change ?
As with so very much these days, the change is the result of international standardisation (or harmonisation) with most of Europe already using this colour coding - the new colours are sometimes referred to as 'harmonised'.
How will the change come into effect ?
The new colours came into effect on 1st April 2004, however there was a two year overlap between the old and new colour coding.
Until 31st March 2006, either the old colours or new colours could have been used (but not mixed).
From 1st April 2006, the use of the old colours was no longer permissible in new installations or when making changes.
Where new colour cable are used to extend an existing 'old colour' installation before 1st April 2006, a warning notice (as right) must be fixed at the main distribution or consumer unit of the installation.
The above is our interpretation of the new colour marking rules (together with inputs from some helpful contributors).