Harmonisation, what's it all about?
It is the revision of the conductor colours used in the UK for all electrical wiring operating in the low-voltage range fixed installations. This is all 230V single phase, 415V three phase wiring.

There is a two year changeover period, during which the new or the old coloured cables may be used (between 1st April 2004 and 1st April 2006).

There are some restrictions to be followed during these two years.

  • If you start an installation in the old conductor colour, it must be completed in the same colouration.
  • If new coloured conductor cable is used in a pre-existing installation, clear and visible tags must be applied at all points of cross termination (where both old and new colours are present)
  • With the new coloured conductors, phasing must be tagged appropriately.

What are the colour changes?
For single phase intended cables, 6242Y, 6243Y etc the following changes are occurring

Instead of red (live) and black (neutral) being used with the bare central protective conductor (C.P.C.) acting as the earth conductor the colouration corresponds to flexible cables - already harmonised with Europe - with the live conductor being brown and the neutral conductor being blue.

With three core and earth 6243Y cables, at present you will see red, yellow and blue conductors with a C.P.C. this is changing to brown, black and grey.

For XLPE steel wire armoured (swa) cables, used primarily for three phase distribution the following changes are taking place.

Red, Yellow, Blue were the phase conductors, these are changing to Brown, Black and Grey (or with some cables, Brown, Brown and Brown).

If the swa has a four conductor this will be blue, representing neutral.

If a fifth is present 6945XL, this will be green and yellow to represent an earth conductor.

As SY cables and all ships wiring (658#TQ) have colour free conductors they are not affected by the changes.

Mineral insulated cables will not be affected by the colour changes as their conductors are bare - the sleeving kits for all mineral insulated cables will be revised to suit the new colours.

Below is the colour changes to take place in case they cannot be identified from the images above.

Originally   Revised
RED changes to BROWN
YELLOW changes to BLACK
BLUE changes to GREY
BLACK changes to BLUE

Obvious Problems
There is undoubtedly going to be mistakes made in the industry by electricians making incorrect terminations. At A J Robson (Electrical) Ltd we are enforcing the need for double verification before powering up terminated circuitry and distribution.

The area of most concern is that at present neutral is black and blue is a phase carrying potential. With the new colour scheme the blue is now neutral and black a phase carrying potential.

The possibility of many installations having 415Vac across a 230V system is an almost certainty.

For more information feel free to visit the iee web site for access to the latest amendments to BS7671 relating to the new conductor colours. Go to www.iee.org for more information.