Wiring Colours

The standard AC mains electrical wiring colours vary between different countries, for example USA wiring colours are different to UK wiring colours, here we look at the different wiring colours used in different countries.

UK Wiring Colours

In the UK the wiring colours are currently, brown, black grey, blue and green / yellow.

UK Single Phase Wiring Colours:

• Line = Brown
• Neutral = Blue
• Earth = Green / Yellow

UK Three Phase Wiring Colours:

• Line L1 = Brown
• Line L2 = Black
• Line L3 = Grey
• Neutral = Blue
• Earth = Green / Yellow

Note: The “Line” conductor might also be referred to as the “Live” or “Hot” conductor depending on the country.

In 2004 the UK wiring regulations changed, the old UK wiring colours before 2004 were as follows,

UK Single Phase Wiring Colours (before 2004):

• Line = Red
• Neutral = Black
• Earth = Green /Yellow

UK Three Phase Wiring Colours (before 2004):

• Line L1 or “R” (red phase) = Red
• Line L2 or “Y” (yellow phase) = Yellow
• Line L3 or “B” (blue phase) = Blue
• Neutral = Black
• Earth = Green / Yellow

As the UK wiring colours have changed great care should be taken before undertaking extension, alteration or repair that all conductors are correctly identified.

Note: Green / Yellow = A single green & yellow stripy conductor, NOT a choice between a single green or single yellow conductor.

USA Wiring Colours

Wiring colours in the United States vary depending on the voltages, they also use a “Hot” wire in some circumstances.

USA Single Phase Wiring Colours (120v, 208v, 240v):

• Line = Black
• Neutral = White
• Earth = Green

USA Three Phase Wiring Colours (120v, 208v, 240v):

• Line L1 = Black
• Line L2 = Red
• Line L3 = Blue
• Neutral = White
• Earth = Green