--- title: "Safety precautions in electrical works" subject: "Building Technology" chapter: 12 key: "semester_6/building_technology:electrical-safety" source: https://www.bctengineer.com/q/semester_6/building_technology/electrical-safety site: BCT Engineering --- # Safety precautions in electrical works Building Technology · Chapter 12: Other services in building - Asked in: 2080 Chaitra, 4 marks; 2078 Poush, 4 marks; 2066 Bhadra (old course), 4 marks (asked 3 times) - Video: [Electrical Safety Basic Training for Non-Electricians | Schneider Electric](https://www.youtube.com/watch?v=ggJo6m8NZtA) — Schneider Electric - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/building_technology/electrical-safety - Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-12 ## Question Explain the safety precautions to be taken during electrification (electrical wiring works) of a building. ## Short answer Earthing all metal parts (resistance <5 ohm) and using MCB, ELCB/RCD (30 mA) prevent shock and fire. Switches and fuses connect only the phase; wires must be properly sized, insulated, and kept from water and heat. Work only when supply is off, using insulated tools, and test insulation regularly. ## Answer Electricity can cause shock, burns and fire, so every stage of the electrification of a building must follow safety rules (Nepal Electricity Act / Regulations, NBC 207 and IS 732). #### Safety precautions - **Earthing:** connect all metal parts of appliances and the DB to earth (earth pit with a GI plate/pipe, resistance less than 5 ohm for buildings) to avoid shock. - **Protective devices:** fuses, MCB, MCCB and ELCB/RCD (30 mA) to cut the supply on overload, short circuit and leakage; a lightning arrester on the roof. - **Proper materials:** use standard-quality wires, switches and fittings of the correct current rating, and the proper conductor size for the load. - **Switch only the live (phase) wire:** switches and fuses on the phase; neutral kept solid; use 3-pin plugs. - **Insulation and joints:** all joints properly made and insulated; no bare wire; use junction boxes. - **Avoid overloading:** do not connect many appliances to one socket; use separate circuits for heavy loads (AC, geyser). - **Safe location:** keep wiring away from water pipes, gas lines and hot surfaces; place sockets and switches out of reach of children and away from bathrooms (or use waterproof types), at sufficient height. - **During work:** switch off the main supply before repair; use insulated tools, rubber gloves and mats, and "danger/men at work" notices; avoid working in wet conditions; employ qualified electricians only. - **Fire precautions:** keep extinguishers (CO2/dry powder) nearby; never use water on an electrical fire. - **Testing and maintenance:** test insulation resistance (megger) and earth continuity after installation and periodically. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why are metal parts earthed? A. To avoid shock by providing a path for fault current to earth B. To increase voltage C. To save energy D. To make wires thicker Answer: A. Earthing (resistance less than 5 ohm) prevents shock. (Key point: Earthing) 2. Where should switches and fuses be placed? A. On the live (phase) wire B. On the neutral wire C. On the earth wire D. Anywhere Answer: A. Placing on phase ensures the equipment is dead when off. (Key point: Switch position) 3. What is the role of an ELCB/RCD (30 mA)? A. Increase current B. Cut supply on earth leakage C. Measure insulation D. Limit voltage drop Answer: B. It trips on small leakage currents. (Key point: ELCB) 4. What should never be used on an electrical fire? A. CO2 extinguisher B. Dry powder C. Water D. Switching off main supply Answer: C. Water conducts electricity; use CO2 or dry powder. (Key point: Fire) ## Related in Building Technology - [Electrical services principles, wiring, safety](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aelectrical-principles-wiring-safety) — Building Technology, chapter 12 - [Electrical wiring systems](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aelectrical-wiring-systems) — Building Technology, chapter 12, asked 3× - [Fundamental requirements of electrical wiring](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aelectrical-wiring-requirements) — Building Technology, chapter 12 - [Electrification system and fire protection](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aelectrification-fire) — Building Technology, chapter 12 ## Related in other subjects - [General electrical rules for installation and wiring](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aelectrical-rules-installation) — Industrial Power Distribution and Illumination, chapter 1, asked 3× - [Short note: Electrical safety rules](https://www.bctengineer.com/question.md?key=semester_1%2Fbasic_electrical_and_electronics_engineering%3Ashort-note-electrical-safety-rules) — Basic Electrical and Electronics Engineering, chapter 4, asked 2× - [Basic electrical safety rules and regulations](https://www.bctengineer.com/question.md?key=semester_8%2Fhigh_voltage_engineering%3Aelectrical-safety-rules) — High Voltage Engineering, chapter 2 - [Planning electrical installation of industrial building](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aplanning-industrial-installation) — Industrial Power Distribution and Illumination, chapter 5