'DE-NEUTRALISING' BLACK
Under the new legislation colours for fixed wiring introduced by Amendment 2 to BS7671, black is now used to identify a phase conductor, not a neutral conductor, in new installation work.
for all single-phase applications, it is required use cables marked for such use, that is with brown, blue and green-yellow cores.
Breaking the black/neutral association
Where three-core cables, marked in the new three-phase colours are used for single-phase applications, it is proposed that, as a convention, the black core is used for the protective conductor, the brown for the phase conductor and the grey for neutral. This convention is intended to break the association between black and neutral. It would mean that the black core would normally be over-marked green-yellow, and the grey core over-marked blue or N. The brown core would not need additional marking.
Street Lighting
The Institute of Lighting Engineers (ILE) intends to introduce such a convention where SWA cables with brown, black and grey cores are used for street lighting applications, the black core being used as a circuit protective conductor in parallel with the amouring to maximize circuit lengths.
Fire Alarm Systems
Applying the same convention to a flat three-core fire alarm interlink cable, the grey would be over-marked as the neutral and the black interlink over-marked brown.
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