--- title: "General electrical rules for installation and wiring" subject: "Industrial Power Distribution and Illumination" chapter: 1 key: "semester_6/industrial_power_distribution_and_illumination:electrical-rules-installation" source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/electrical-rules-installation site: BCT Engineering --- # General electrical rules for installation and wiring Industrial Power Distribution and Illumination · Chapter 1: Introduction - Asked in: 2077 Chaitra, 4 marks; 2073 Bhadra, 4 marks; 2072 Asoj, 4 marks (asked 3 times) - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/electrical-rules-installation - Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-1 ## Question Write down general electrical rules related to electrical installation. ## Short answer All materials must be rated and approved. Switches and fuses go in the phase conductor only. Every installation needs a main switch, proper earthing, and circuit protection (MCB/RCCB). Lighting and power circuits are separate. Standard colour codes and clearances must be followed. Testing (insulation, earth, polarity) is mandatory before energising, and work must be done by licensed persons. ## Answer Electrical installations must follow the rules of the regulator and the standards of good practice. In Nepal these come from the **Electricity Regulations, 2050**, NEA's connection requirements and **NBC 207** (Nepal National Building Code, electrical design), which are largely based on the Indian Electricity Rules 1956 and IS 732. The main general rules are: 1. **Approved materials:** all wires, cables, switches and fittings must meet the relevant standard (NS/IS/IEC) and be rated for the circuit voltage and current. 2. **Switches and fuses in the phase conductor:** single-pole switches, fuses and MCBs go in the phase (live) wire only, never in the neutral, so that opening the switch makes the equipment dead. 3. **Main switch and cut-out:** every consumer installation must have a main switch (or MCB/MCCB) and a cut-out near the point of supply, easy to reach and clearly marked. 4. **Earthing:** the metal body of every appliance, the conduit, metal enclosures and the neutral of the supply transformer must be properly earthed. Earth resistance is kept low (about 1 Ω for large substations, a few ohms for installations). Three-pin sockets must have the earth pin connected. 5. **Protection of every circuit:** each sub-circuit is protected by a fuse/MCB rated for the cable. Earth-leakage protection (RCCB/ELCB) is used where shock risk is high (wet areas, sockets). 6. **Separate circuits:** lighting and power circuits are kept separate. A lighting sub-circuit normally has no more than about 10 points or 800 W; a power sub-circuit has no more than 2 power sockets (about 3 kW). 7. **Polarity and colour code:** phases R-Y-B (red, yellow, blue), neutral black and earth green (or green/yellow) must be used consistently. 8. **Clearances:** overhead lines and service mains must keep minimum clearances from ground, buildings and other lines as given in the regulations. 9. **Mechanical protection:** cables are run in conduit, trunking or trays, or are armoured, where they may be damaged. 10. **Danger notices:** HV equipment and substations must carry danger boards in Nepali and English. 11. **Testing before energising:** insulation resistance, earth continuity, polarity and earth resistance tests must be done and the results recorded before the supply is connected. Insulation resistance must not be less than the value required by IS 732/regulations (about 1 MΩ for new LV wiring). 12. **Licensed persons:** design, installation and testing must be done or supervised by a licensed electrician/engineer. 13. **Accessibility:** distribution boards and switchgear must be accessible, with enough working space in front, and not placed in wet or hazardous locations. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. In which conductor should single-pole switches and fuses be placed? A. The neutral conductor only B. Both phase and earth C. The earth conductor D. The phase (live) conductor only Answer: D. With the switch in the phase wire, opening it makes the equipment dead; a neutral switch leaves it live. (Key point: Switch in phase) 2. Which parts must be earthed in an installation? A. Only the phase wire of each circuit B. Only plastic fittings C. Metal bodies of appliances, conduits, enclosures and the transformer neutral D. Only the lamp holders Answer: C. Non-current-carrying metal parts and the supply neutral are earthed with low resistance for safety. (Key point: Earthing rule) 3. What must be done before the supply is connected to a new installation? A. Only a visual check of the wiring B. Insulation resistance, earth continuity, polarity and earth resistance tests with results recorded C. Connect the load and watch for tripping D. Test only after the first month of use Answer: B. Tests are done while the system is dead and recorded before energising. (Key point: Testing before energising) 4. What is the rule about lighting and power sub-circuits? A. They are kept separate, with limits such as about 10 points or 800 W per lighting circuit B. They are always combined on one circuit C. Lighting circuits may carry up to 10 kW D. Only power circuits need protection Answer: A. Lighting and power circuits are separate, and each has a limit on points or load. (Key point: Circuit separation) ## Related in Industrial Power Distribution and Illumination - [Complying with electrical rules and standards](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aimportance-rules-standards-compliance) — Industrial Power Distribution and Illumination, chapter 1 - [Types of electrical installation](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aelectrical-installation-types) — Industrial Power Distribution and Illumination, chapter 5, asked 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 - [Electrical installation in a factory](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aexplain-electrical-installation-factory) — Industrial Power Distribution and Illumination, chapter 5 - [Requirements and installation of factory lighting](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Afactory-lighting-installation-types) — Industrial Power Distribution and Illumination, chapter 7 - [Purposes of emergency lighting installation](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aemergency-lighting-purposes) — Industrial Power Distribution and Illumination, chapter 9 ## Related in other subjects - [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 - [General safety rules in a machine workshop](https://www.bctengineer.com/question.md?key=semester_2%2Fworkshop_technology%3Aworkshop-safety-rules) — Workshop Technology, chapter 1