Electrical Installations: Basic Wiring and Safety — CSEC Building Technology
This topic covers the basics of electrical circuits in buildings and the safety practices that protect users.
Basic circuits
- An electric current flows only in a complete (closed) circuit with a source of supply.
- Conductors are covered with insulation (usually PVC) to prevent short circuits and shock.
The three conductors
- Live — carries the supply (brown; older systems red).
- Neutral — completes the circuit (blue; older black).
- Earth — the safety wire (green and yellow) that conducts fault current safely to ground, protecting against electric shock.
A switch is connected in the live conductor so the appliance is fully isolated when off.
Protection devices
- A fuse or circuit breaker automatically breaks the circuit if too much current flows, preventing overheating and fire.
- An overloaded circuit overheats conductors, which is a fire risk.
Safety practices
- Always switch off and isolate the supply before working on a circuit.
- Confirm the circuit is dead before touching it.
- Use the correct insulation and properly rated cables and devices.
Exam tips
- Current flows only in a complete circuit.
- Wires: live (brown), neutral (blue), earth (green/yellow) for safety.
- A fuse/circuit breaker protects against overload (fire).
- Always isolate the supply before working on a circuit.