The latest changes to cable core colours were reflected in Amendment No 2, 2004 of BS 7671:2001, published on 31 March 2004.
Harmonisation of cable colours from March 2004
Amendment No 2, 2004 of BS 7671:2001, Requirements for Electrical Installations (the 'IEE Wiring Regulations'), formally published on 31 March 2004, states the new (harmonised) colours and includes guidance for alterations and additions to installations wired in the old cable colours.
The new (harmonised) colour cables may be used on site from 31 March 2004. New installations or alterations to existing installations may use either new or old colours, but not both, from 31 March 2004 until 31 March 2006. Only the new colours may be used after 31 March 2006. For more details see the information sources and directions to links below.
Q1. What are the changes that are proposed for the colour identification of conductors?
For the fixed wiring of an installation, it is proposed to replace the traditional colours of red and black for the phase and neutral conductors of single-phase circuits 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.
Q2. Why are the changes for conductor colour identification necessary?
The United Kingdom agreed some 28 years ago to adopt the colour blue for neutral conductors, and has since used harmonised (brown/blue/green-and-yellow) colours 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, while 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/Institution of Engineering and Technology 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 fewest 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.
Q3. How were the changes implemented?
The changes were included in Amendment No 2 to BS 7671:2001 Requirements for Electrical Installations. To assist with the implementation of the new colours for fixed wiring, the amendment included a new appendix to BS 7671 providing advice on marking at the interface between the old and new colours, and general guidance on the extended range of colours that may be used for line (not neutral or protective) conductors.
Q4. When did the changes come into effect?
BS 7671 permitted the use of the new conductor colours for fixed wiring commencing on site from 1 April 2004. Continued use of the old colours was permitted until 1 April 2006, after which time only the use of the new colours was permissible. During the two year transition period, it was permissible to use either the new or old colours, but not a combination of both in the same installation work.
Q5. To minimise the number of new installations that will have mixed (old and new) colours, was it permissible to use conductors with the new colours as soon as they become available, perhaps before BS 7671 was amended?
If a designer or other person responsible for specifying an installation decided to use the new cable colours in advance of the amendment to BS 7671, it was necessary for that person to record on the Electrical Installation Certificate for that installation a departure from the requirements of BS 7671, confirming that the same degree of safety has been provided as that afforded by compliance with the Regulations. Regulations 120-02-01 and 511-01-02 refer.
However, as some of the proposed requirements, including the marking of cables at terminations, were yet to be agreed, it may have been impracticable for specifiers to provide the required confirmation until such time as all the installation requirements had been firmly established by publication of the amendment to BS 7671. Use of the new colours before all the related safety requirements had been established and communicated to the industry might be considered inadvisable.
Q6. What is the most significant safety issue?
The change in the United Kingdom 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 is already familiar with a blue neutral and brown phase in the leads of their domestic appliances.