Installation, Maintenance and Safety Practices
Installation, Maintenance and Safety Practices is examined through site preparation, protective-device selection, earthing, maintenance and safe working procedures.
What the exam tests
Questions test cable and protective-device selection, earthing, preventive maintenance, fault isolation and electrical safety. Safety-practice questions include shock response, PPE, lockout/tagout and safe disposal of electronic waste.
Core rules
- Select cable by current-carrying capacity, derating and voltage drop; keep drop within about 5% for a typical installation. Protect with an MCB/fuse rated above normal load but below cable capacity.
- Earth is a separate safety conductor; never use neutral as earth. Earth resistance should be as low as practicable (commonly ≤5 Ω for domestic installations), tested with an earth tester.
- RCD/ELCB with 30 mA sensitivity protects people; MCB protects cable against overload/short circuit. Both are not interchangeable.
- Isolation procedure: notify, switch off, lock/tag, prove tester on a known live source, test dead, discharge capacitors, then work. Use insulated tools and PPE.
- ESD: wrist strap and grounded mat when handling PCBs; store ICs in conductive foam.
Worked example
A 2 kW appliance runs on 230 V. Load current = 2000/230 = 8.7 A. A 10 A MCB is appropriate for the load, but the cable must carry 8.7 A after derating; a 1.5 mm² copper conductor is typically adequate for this current in a short run, while a long run needs a voltage-drop check. The reasoning is: calculate current, choose protection above load, then verify cable capacity and drop - not just match the plug rating.
Traps that cost marks
Choosing an MCB from appliance wattage alone; using earth wire as a current-carrying conductor; testing for dead with an unproven tester; working live because it is only low voltage; ignoring capacitor discharge in power supplies; skipping the voltage-drop check on long cable runs.