Wiring Materials, Conductors and Accessories
This domain covers what you actually fix on a wall or inside a panel: wires, cables, conduit, boxes, switches and sockets, and the rules for choosing them.
Systems and materials
- Wires are single-core; cables are multicore with an overall sheath. PVC-insulated copper conductors to IS 694 are standard; sizes 1.0, 1.5, 2.5, 4 and 6 mm² cover most lighting and power points.
- Wiring systems: cleat (temporary), batten, casing-and-capping (quick surface work), conduit surface and concealed (permanent, rewirable), cable tray and trunking in industry.
- PVC conduit suits general and damp locations; GI conduit gives mechanical strength and heat resistance but must be earthed.
Selection rules
- Conduit fill should not exceed about 40% of internal area so cables can be drawn in without damage.
- Keep lighting and power sub-circuits separate: a light circuit commonly carries up to 800 W over about 10 points, while a 16 A circuit feeds geysers, air-conditioners and kitchen loads.
- Switchboards are usually fixed about 1.2–1.3 m above floor level; light points around 2.25 m.
- Use 6 A accessories for lighting and 16 A for power; never plug a 16 A appliance into a 6 A socket.
- Match every accessory to the cable and load: ceiling rose, batten holder, modular switch, 3-pin socket with earth, DP MCB in the distribution board.
Worked example
A 2 kW, 230 V geyser draws 8.7 A. A 1.5 mm² copper PVC cable in conduit is rated around 14 A, so it carries the current, but on a 15 m run with grouping derating the voltage drop pushes the choice to 2.5 mm². The circuit is protected by a 16 A MCB, controlled by a 20 A DP switch, and uses a 2.5 mm² earth conductor.
Traps
- Selecting cable by current rating alone, ignoring voltage drop and derating.
- No earth continuity to metal conduit and boxes.
- Concealed joints buried in conduit or plaster.
- Mixing accessory ratings and cable sizes so the socket is the weakest link.