Three core and earth carries three insulated line-capable cores plus a bare CPC in one flat grey PVC sheath. Its everyday use is two-way and intermediate lighting switching, where a single run replaces two separate twin and earth cables. Construction, ratings and installation limits are otherwise identical to twin and earth.
Key applications
- Two-way and intermediate lighting switching
- Strapper runs between switch positions
- Small three-phase final circuits in light commercial work
- Control wiring where three conductors and a CPC are needed
- Clipped direct, in trunking or embedded in plaster
Features and benefits
- One cable instead of two for two-way switching, so fewer clips and less drilling
- Factory CPC sized to the standard, removing a separate earth run
- Same clipping and termination practice as twin and earth
- Flat profile suits chasing into plaster
Specification notes and limitations
All three cores are line-coloured under the harmonised scheme: black and grey are line conductors here, not neutral. Where any core is used as a switch wire or as a neutral it must be re-identified at both ends, and particular care is needed on alterations to installations wired in the older red, yellow and blue. The bare CPC needs green-and-yellow sleeving at terminations. As with twin and earth, the 70 °C PVC limit governs derating for thermal insulation and grouping, the cable has no mechanical protection and must not be buried direct in the ground, and the PVC sheath is not suitable for prolonged exposure to sunlight.
