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Wiring Regulations: Harmonised Cable Colours
For many years, the UK has used the familiar Red / Yellow / Blue colour system to identify the three phases found in an electrical installation. However, it has been proposed that this system be changed in order to bring the UK in to line with a new European Standard.
This page, based on a document from the IEE, aims to summarise the proposals and explain why the changes have been deemed necessary.
Why the changes?
The United Kingdom agreed some 28 years ago to adopt the colour blue for neutral conductors, and has since used harmonised colours (brown/blue/green-and-yellow) for the identification of the cores of flexible cables and flexible cords but, at that time, no move was made towards such harmonisation for non-flexible cables used for fixed wiring. Unfortunately, whilst the United Kingdom was contemplating such change, much of the rest of Europe was standardising on blue for neutral, with brown and/or black phases.
When it became evident in 1999 that, within a few years, a new European Standard would require the use of the colour blue (rather than black) for the neutral conductor of fixed wiring throughout Europe, it became necessary for the United Kingdom to address the cable colour issue with some urgency. The joint BSI/IEE committee now responsible for the technical content of the Wiring Regulations (BS 7671) established a Working Group to consider the position the United Kingdom should take with respect to the harmonisation of the colours of the conductors of non-flexible cables for fixed wiring.
The Working Group concluded that the United Kingdom had no realistic option but to agree to use the colour blue for the neutral, and brown for the phase conductor of single-phase circuits. It also concluded that, due to the widespread adoption in the rest of Europe, the United Kingdom would have to accept black for one of the other phases of a multi-phase circuit. The Working Group also considered that there was a need to be able to distinguish between the phases of a three-phase circuit and decided to propose the colour grey for one of the phases, because, of the very few remaining pan-European colour options, this seemed to have the least disadvantages.
The Working Group’s recommendations subsequently formed the basis of a United Kingdom proposal which was accepted by the CENELEC countries 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.
What are the changes?
For the fixed wiring of a single-phase installation, it is proposed to replace the traditional colours of red and black for the phase and neutral conductors with brown for the phase conductor and blue for the neutral conductor. The green-and-yellow bi-colour identification of protective conductors will continue unchanged. The proposed colour identification will be familiar, having been used in appliance flexible cables and cords in the United Kingdom for the past 28 years.
The proposed colours for the conductors of three-phase circuits are brown, black and grey with a blue neutral conductor, in place of the traditional red, yellow and blue with a black neutral. Again, the bi-colour green-and-yellow marking of protective conductors will remain unchanged.
The proposed change will implement the use of the core colours introduced in the revision of European Harmonisation document HD 308: Identification of cores in cables and flexible cords, and to align with BS EN 60446: 2000 Basic and safety principles for the man-machine interface - identification of conductors by colours or numerals.
When will the changes come into effect?
If the proposals are accepted, the amendment to BS 7671 will permit use of the new conductor colours for fixed wiring commencing on site from 1 April 2004. Continued use of the old colours would be permitted until 1 April 2006, after which time only the use of the new colours would be permissible. During the two year transition period, it would be permissible to use either the new or old colours, but not a combination of both in the same installation work.
What is the most significant safety issue?
The proposed change in the UK to adopt blue for neutral conductor and at least one black for a phase conductor in a multi-phase circuit could, if not properly addressed, introduce the possibility of confusion with the black neutral conductor and blue phase conductor in existing three-phase distribution circuits. However, it is generally considered that the risk is a manageable one. It is acknowledged that other European countries have reportedly made radical changes in their conductor colour identification systems without immoderate safety ramifications. The public in the United Kingdom are already familiar with a blue neutral and brown phase in the leads of their domestic appliances.
See also:
- Go back
- Other electrical reference information
- Main Technical Reference index
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