Electrical wiring systems

Wiring is the system of conductors, switches and fittings used to distribute electric power in a building. Wiring systems are classified by the method of fixing.

1. Cleat wiring

PVC or VIR cables held in porcelain/wooden cleats on the wall. Cheap and temporary; used on construction sites and at exhibitions. Poor appearance and not safe for permanent use.

2. Casing-capping wiring

Cables laid in the grooves of a wooden casing and covered by a capping. Cheap but old-fashioned; a fire risk and affected by moisture and termites; rarely used now.

3. Batten wiring

Sheathed cables (TRS/CTS or PVC-sheathed) are clipped onto teak wood battens fixed to the wall. It looks neat and is cheap, but is poor against moisture and fire; used in dry places.

4. Conduit wiring

Cables drawn inside PVC or GI pipes (conduits).

• Surface conduit: fixed on the wall surface; easy to repair; used in workshops.
• Concealed conduit: buried in the plaster or slab; best appearance, safe against fire, moisture and mechanical damage. Most used in modern buildings, but costly and difficult to alter.

5. Sheathed (TRS/CTS) and lead-sheathed wiring

Cables with a tough-rubber or cab-tyre sheath (TRS/CTS), or with a lead cover, clipped directly to the surface. Resists moisture; used in damp areas; lead-sheathed wiring is costly.

6. Others

Metal-sheathed cable, bus-duct/trunking (large buildings and industry), underground cable.

Comparison: concealed conduit is the safest and neatest, cleat wiring is the cheapest (temporary work), batten is the cheapest permanent system, and conduit/trunking is used in most multistorey buildings.

Systems of distribution: the tree (branch) system and the ring/loop system are the two layouts; the ring system gives better voltage and reliability.