UK cable colours: old and new
UK fixed wiring changed to harmonised European colours in 2004. Line went from red to brown and neutral from black to blue. Old colours were allowed for new work until 2006, so you'll still meet both in older homes.
Single phase
| Conductor | Old colour (before 2004) | New colour |
|---|---|---|
| Line (L) | Red | Brown |
| Neutral (N) | Black | Blue |
| Protective conductor (CPC) | Green and yellow | Green and yellow (no change) |
Three phase
| Conductor | Old colour | New colour |
|---|---|---|
| L1 | Red | Brown |
| L2 | Yellow | Black |
| L3 | Blue | Grey |
| Neutral (N) | Black | Blue |
| Protective conductor (CPC) | Green and yellow | Green and yellow (no change) |
Watch out
- Black means two different things. In old wiring black is the neutral; in new three-phase wiring black is L2, a line. Never assume: identify every conductor and test it.
- Blue changed too. Old three-phase L3 was blue; in new wiring blue is the neutral.
- Switch wires. Where the blue core of a cable is used as a line conductor, such as a switch wire, it must be identified as line with brown sleeving or tape (or marked L) at its terminations.
Mixed old and new colours
When new wiring is added to an installation wired in the old colours, a caution notice goes on or near the consumer unit or distribution board. The wording is:
CAUTION: This installation has wiring colours to two versions of BS 7671. Great care should be taken before undertaking extension, alteration or repair that all conductors are correctly identified.
Dates
The new colours could be used from April 2004. From April 2006, only the new colours are allowed in new work.
Colours help identify conductors, but they don't prove anything. Always test before you touch. Check against your copy of BS 7671. See also the safe isolation trainer.