Cable - Old Cable Colours And The New Harmonised Cable Colours
All new electric cable installations must use the new harmonised colours.
On 31st March 2004 the IEE published Amendments No2 to BS 7671:2001 (the IEE Wiring Regulations) which specify the required core colours for cables used in all new fixed wiring electrical installations in the UK. The new colour scheme was nicknamed ‘harmonised’ colouring as it made UK electrical installations more similar to those used in mainland Europe.
What changes have been made to the colour identification of conductors?
Fixed wiring in installations no longer use red and black colouring for the phase and neutral conductors of single-phase circuits. Instead, brown is used for the phase conductor and blue for the neutral conductor. However, the green and yellow colours traditionally used for protective conductors have not changed colour. These new colours have already been used in appliance flexible cables and cords in the UK for the past few decades.
For conductors in three-phase circuits, the harmonised colours are brown, black and grey with a blue neutral conductor. This replaces the red, yellow, blue and black colours used previously. Again, the green and yellow used to indicate a protective conductor has not changed.
Why were these colour changes necessary?
A few decades ago the UK agreed to adopt the colour blue for neutral conductors as was the norm in mainland Europe. However, no changes were made to the colour identification used for non-flexible cables that were used in fixed wiring.
In 1999 however, it became evident that a new European Standard would require the colour blue, rather than black, to be used to identify the neutral conductor on fixed wiring throughout Europe. The BSI and IEE joined, forming a committee responsible for the technical content of the Wiring Regulations (BS 7671) and established a Working Group to consider what position the UK should adopt with regards to changing their wiring colours for fixed wiring. The Working Group came to the conclusion that the UK had to adopt the same colours as were being used in the rest of Europe i.e. blue for neutral and brown for the phase conductor of single-phase circuits, plus black for one of the other phases of a multi-phase circuit. The Group also proposed using grey to distinguish between the phases of a three-phase circuit.
These recommendations formed the basis of a UK proposal that the CENELEC countries accepted almost unanimously. Europe now has the opportunity to fully harmonise the colour identification system not only for non-flexible cables for fixed wiring, but also for flexible cables and cords and distribution cables.
Where can I find more details and guidance on the harmonised colours?
Amendment No2 to BS 7671: Requirements for Electrical Installations has been issued, including a new appendix that provides advice on marking the interface between the old and new colours and also gives general guidance on the various colour options that may be used for line conductors (not neutral or protective ones)
What is the most significant safety issue?
There is the risk of confusing the blue for neutral conductors and black for at least one phase conductor in a multi-phase circuit with the old black neutral conductor and blue phase conductor in existing three-phased distribution circuits. However, other European countries have successfully managed radical colour changes so the risk is not considered to be a large one. The UK public are also already familiar with the blue neutral and brown phase colours used for domestic appliances.