Flat twin and earth is the default fixed-wiring cable for domestic and light commercial circuits in the UK. Two PVC-insulated cores run side by side with a bare circuit protective conductor between them, the whole lot held in a flat grey PVC sheath. It is intended for clipping direct, running in trunking or burying under plaster in dry or damp premises where the risk of mechanical damage is low.
Key applications
- Lighting circuits and socket-outlet ring or radial finals
- Cooker, shower and immersion heater circuits
- Submains between distribution boards inside a building
- Clipped direct to joists, battens and surfaces
- Drawn into trunking, conduit or ducting
- Buried in plaster behind capping or conduit
Features and benefits
- Flat section sits tight to the surface and takes cable clips cleanly
- Factory-fitted CPC means no separate earth wire to pull in
- Solid conductors up to 2.5 mm² terminate quickly and hold shape
- Stocked by every UK wholesaler, so replacement and extension work is straightforward
- Readily available with BASEC approval
Specification notes and limitations
The CPC is bare, so green-and-yellow sleeving has to be fitted at every termination and joint. The 70 °C PVC limit is the binding constraint: ratings must be reduced where the cable is surrounded by thermal insulation or grouped with others, and the installation method has to be matched to the correct BS 7671 rating table rather than assumed. There is no armour and no mechanical protection, so the cable must not be buried direct in the ground, and where it is run in a wall it needs mechanical protection or the depth and RCD provisions of BS 7671. PVC is not UV-stable and should not be left exposed to sunlight on an external surface. Avoid routing against flues, hot pipework or inside luminaires where the conductor could exceed 70 °C, and do not pull the cable in below about 0 °C, as cold PVC cracks.
