Wiring Systems
What the domain tests
Wiring Systems tests how cables are run and protected in buildings: cleat, casing-and-capping, conduit, concealed and batten wiring, plus colour code, conductor size and basic load selection.
Core rules
- Choose the wiring system for the location: PVC conduit concealed in walls, surface conduit in workshops, casing-and-capping for light domestic runs, and armoured cable where mechanical damage is likely.
- Indian practice uses phase red/yellow/blue, neutral black, and earth green for three-phase; single-phase often uses red or brown as phase, black or blue as neutral, and green as earth. Always follow the installation’s labelling.
- The earth conductor must be continuous and connected to the earth pin; it must never carry load current.
- Switch the phase, not the neutral. Use proper junction boxes; avoid joints inside conduit.
- Cable size depends on current, voltage drop, grouping and ambient temperature, not just on the appliance wattage.
Worked example
A 2 kW heater at 230 V takes I = 2,000/230 ≈ 8.7 A. A 1.5 mm² copper conductor in conduit can typically carry more than this, so it is adequate for current, but a long run may still fail on voltage drop. The reasoning must check both current-carrying capacity and voltage drop-not just “1.5 mm² looks big enough.”
Traps
Do not connect the earth wire to a fuse or switch. Do not switch the neutral and leave the phase live at the appliance. Do not run extra load on an old circuit without checking cable size and protection. Do not make concealed joints without accessible boxes.