Harmonising cable colours

For the last 28 years, the UK has used the colour blue for neutral conductors and harmonised brown, blue, green and yellow colours for the identification of the cores of flexible cables and cords. This is set to change.

The IEE Wiring Regulations (Requirements for Electrical Installations) BS 7671, which for some time has been based on a common European standard document, is harmonising with CENELEC (the European Committee for Electrical Standardisation). The international harmonisation of cable colours was not considered to be a viable option, so the planned harmonisation applies only to Europe.

Why make the changes?
The UK had previously agreed with CENELEC and IEC to the harmonisation of the colours for flexible cables. However, no similar agreement was reached for non-flexible cables used for fixed wiring. This resulted in the UK becoming out of step with the rest of Europe, where most countries were standardising on blue for the neutral conductor, with brown or black phase conductors.

The divergence between the UK and Europe was compounded by the new European Standard EN 60466: 2000. This requires the use of the colour blue for the neutral conductors of fixed wiring throughout Europe.

A Working Group to consider the position that the UK should take on colour harmonisation was set up by the BSI/IEE committee responsible for the technical content of BS 7671. The Group concluded that the UK would have to agree to use the colour blue for the neutral conductor and brown for the phase conductor of single-phase circuits. Also, due to widespread European adoption, black would have to be used for one of the other phases of a multi-phase circuit.

In addition, the Working Group proposed that for a three-phase circuit the colour grey be used. This would enable phase colours to be identified without any ambiguities.

The recommendations of the Working Group formed the basis of a UK proposal. This was accepted by CENELEC as the best way forward to provide a pan-European, harmonised, colour identification system for flexible and non-flexible cables and cords and power distribution cables.

The standard changes
The amendment introducing the harmonised colours is BS 7671: 2001 Requirements for electrical installations, Amendment 2. It is due to be published on 31 March 2004.

Under the amendment, the harmonised colours can be optionally used from 1 April 2004 and must be used from 1 April 2006. Installations starting on site prior to 1 April 2006 can be started and completed in pre-harmonised colours. However, pre-harmonised and harmonised colours should not be mixed. A new installation started during the two-year transitional period should be in either one set of colours or the other.

It is not all black and white. Or in this case blue, brown, black and grey. The new harmonised system does allow other colours to be used in particular circumstances. For example, in Pyro or multi-cored armoured cables, BS 7671 allows identification by colour lettering or numbering. Thus, colours could be numbered one to seven or they can be lettered L1, L2, L3, N, E etc.

For phase conductors in special and control applications cables can be brown, black, red, orange, yellow, violet, grey, white, pink or turquoise. No other markings will be required. If these colours are used for ac power circuits the markings of BS 7671 table 51 should be applied at terminations. But under the new BS EN standard, harmonised two, three, four and five-core cables will only be available in the brown phases or brown, black, grey, all with blue neutrals and green/yellow circuit protective conductors (cpcs).

The new amendment requires that termination over markings is applied “except where there is no possibility of confusion” at interfaces, ie the joint between pre-harmonised and harmonised cables. In practice, the installer will need to take a view on this, but Appendix 7 of Amendment 2 suggests that no marking is required for most single-phase, correctly coloured, interfaces.

For three-phase, the appendix suggests applying L1, L2, L3 and N. The Appendix places the responsibility with the installer, who if uncomfortable with interpretation, is recommended to always apply the interface marking in three-phase installations.

This is an important development and change for fixed wiring. The main safety concern is the role reversal of the colours blue and black: these are changing from phase and neutral to neutral and phase. This may lead to confusion and possible accidents if electrical operatives and personnel are unaware of the changes.

It is therefore essential that the new cable colours and requirements of the IEE Wiring Regulations Amendment 2 of BS 7671:2001 are communicated and promoted to the electrical contracting industry.

The Electrical Contractors’ Association will be playing a major role in the promotion of the forthcoming colour changes. It advises contractors to ensure that all operatives are aware of the changes and that toolbox talks are provided. Contractors are also advised to plan ahead, liaise with their cable suppliers and pre-order stocks of the new harmonised cables if necessary.