Wiring Systems
What this domain tests
Wiring Systems covers selection and layout of cleat, casing-capping, batten, surface conduit, concealed conduit and CTS wiring, plus control circuits such as one-way, two-way and godown wiring. The exam looks for safe switching, correct conductor identification and adequate support.
Core rules
- In a lamp circuit, the phase conductor goes to the switch and the neutral to the lamp holder; never switch the neutral.
- Conductors must be protected by conduit or casing where required; conduit fill should leave room for heat dissipation and pulling.
- Use a separate earth continuity conductor; do not use conduit or a metal box as the only earth path unless the design permits it.
- Two-way switching uses two two-way switches with strapping wires; godown wiring uses multi-position switches so one lamp can be controlled from several points.
Worked example
A 230 V corridor has six 20 W LED lamps. Total load = 120 W, current = 120/230 = 0.52 A. A 6 A lighting circuit is ample, but the switch must be rated for the load and the circuit must have a 6 A MCB. For a 30 m run, check voltage drop; at 0.52 A the drop is negligible, so the limiting factor is mechanical strength and code minimum size, not heating.
Traps that cost marks
Putting the switch in the neutral, using earth wire as a neutral, mixing phase and neutral in looping, ignoring box depth when many wires enter, and failing to test polarity and earth continuity after wiring.