Wiring Systems
This domain tests the choice and installation of wiring systems: cleat, casing-and-capping, batten, conduit, concealed conduit and surface conduit. The exam checks compliance with standard wiring practice, correct cable selection, subcircuit division, colour coding and protective-device coordination.
Core rules
- IS 732 gives the code of practice for electrical wiring installations. The Indian Electricity Rules cover safety of supply and installation.
- Final circuits are divided by load: lighting circuits are commonly 6 A, power circuits 16 A, and fixed high-load appliances get dedicated circuits.
- Conduit wiring protects conductors from mechanical damage and allows rewiring. Concealed conduit must be installed with proper boxes and pull wires before plastering.
- Live conductors are switched, not the neutral. Every socket outlet must have a protective earth connection unless it is double-insulated and specifically permitted.
- Cable size is selected for current-carrying capacity, voltage drop and fault protection, not only for mechanical strength.
Worked example
A lighting subcircuit has 10 lamps of 60 W each on 230 V. Total load = 600 W. Current = 600/230 = 2.61 A. A 6 A MCB and 1.5 mm² copper cable are adequate for this small lighting load, provided voltage drop and derating are acceptable. A 16 A MCB would not protect the 1.5 mm² cable as intended.
Traps
Do not switch the neutral instead of the live. Do not omit earth continuity to metal enclosures. Do not mix lighting and heavy power loads on one undersized circuit. Do not select cable only by mechanical size.