1) Wiring Basics
• Types of wires:
– Phase (Live - Red/Brown)
– Neutral (Black/Blue)
– Earth (Green/Yellow)
• Proper joints: Straight joint, Tee joint, Western Union joint
• Cable size selection according to load (e.g., 1.5 sqmm for lights, 2.5 sqmm for sockets)
• Use of conduit pipe, bend radius, and cable routing safety
• Switchboard wiring, fan regulator, socket, and lamp connections
2) MCB (Miniature Circuit Breaker)
MCB protects from:
• Overload (too many devices)
• Short circuit (phase touches neutral/earth)
MCB Types:
• B Curve – Home use
• C Curve – Motors & small commercial use
• D Curve – Heavy industrial loads
MCB Rating Examples:
• 6A – Light load circuit
• 10A – Fans & small appliances
• 16A, 20A – Power sockets
3) Circuit & Protection
Common circuits in homes:
• Light Circuit
• Power Circuit (Sockets)
• AC Circuit
• Earthing System
Important protection devices:
• MCB – overload & short circuit
• RCCB/ELCB – protection from electric shock (earth leakage)
• MCB + RCCB = RCBO (combined device)
4) Load Calculation
Calculate wattage of appliances:
Example:
Fan = 70W
LED = 10W
TV = 100W
Total Load = 180W
Current = Load (W) ÷ Voltage (V)
≈ 180 ÷ 230 ≈ 0.8A
Choose wire & MCB higher than calculated current.
5) Layout Understanding
• Read line diagrams
• Phase wire always goes through switches
• Neutral and earth go directly to load
• Know junction box distribution
• Identify loops:
– Switch loop
– Series loop
– Parallel connection (home wiring always parallel)
6) Safety Rules 🛑
• Always switch off MCB before work
• Use tester for checking live wire
• Proper insulation and tight terminals
• Never touch wet surfaces while working
• Good earthing for all metal appliances