--- title: "Hall 16 × 12 m LED lighting" subject: "Industrial Power Distribution and Illumination" chapter: 7 key: "semester_6/industrial_power_distribution_and_illumination:hall-16x12-led" source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/hall-16x12-led site: BCT Engineering --- # Hall 16 × 12 m LED lighting Industrial Power Distribution and Illumination · Chapter 7: Illumination Design Principles - Asked in: 2075 Bhadra, 8 marks - Video: [ILLUMINATION ENGINEERING - PART - 11 - LUMEN OR FLUX METHOD OF CALCULATION AND THREE PROBLEMS](https://www.youtube.com/watch?v=mB573i9S39A) — zenmurali Sachithanandam - 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/hall-16x12-led - Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-7 ## Question A hall of size 16 m× 12 m is to be illuminated by 55 watt LED lamp. Inside the hall, an average illumination of 300 lumen/m² is to be provided on the working plane. The walls and ceiling are brightly painted. Calculate the no. of luminaries required to be fitted in the hall. Draw lay-out diagram showing arrangement of luminaries, switches and distribution board. Decide the light sub-circuits if the supply is 400 V, 3-phase 4 wire system. Assume value for utilization and maintenance factor are 0.8 and 0.8 respectively, the lamp efficiency is 90 lumen/watt. ## Short answer Mounting height 3 m. N = (300 ×192) / (4950 ×0.64) =20 luminaires in a5 ×4 grid. Distribution board: 6 A TPN MCB incomer, 25 A RCCB, three 6 A SP lighting circuits. ## Answer **Given:** hall 16 m × 12 m, E = 300 lm/m², 55 W LED at 90 lm/W, UF = 0.8, MF = 0.8, supply 400 V, 3-phase, 4-wire. **Assumptions:** mounting height 3 m above working plane, SHR ≤ 1.5, pf 0.9. #### Number of luminaires Lumen method: N = (E × A) / (φ × UF × MF), where φ is the output of one luminaire. ```text Area A = 16 × 12 = 192 m² φ per luminaire = 55 W × 90 lm/W = 4950 lm Total lumens = E × A / (UF × MF) = 300 × 192 / (0.8 × 0.8) = 90000 lm N = 90000 / 4950 = 18.18 ``` Rounding up and fitting a regular grid: **5 × 4 = 20 luminaires** (5 along the 16 m side, 4 along the 12 m side). #### Arrangement and spacing ```text Spacing along length = 16/5 = 3.2 m Spacing along width = 12/4 = 3 m End spacing (to wall) = half of these Max spacing = SHR × Hm = 1.5 × 3 = 4.5 m 3.2 m and 3 m ≤ 4.5 m → OK Actual E = 20 × 4950 × 0.8 × 0.8 / 192 = 330 lux (≥ 300 lux required) ``` #### Layout diagram ```text Plan 16 m × 12 m (letter = phase of lamp circuit) +-----------+ | R R R R R | | Y Y Y R R | | Y Y Y Y B | | B B B B B | +-----------+ [DB] [SB] <- entrance: DB and switch board S S S S ... one switch per sub-circuit ``` Each light sub-circuit is controlled by one 6 A one-way switch; all switches are grouped on a switch board (SB) next to the entrance, and the DB is mounted beside it. #### Sub-circuits Rule (IS 732 / NEA practice): a light sub-circuit carries at most 10 points and 800 W. Here one luminaire is 55 W, so up to 10 luminaires per sub-circuit. Number of circuits is made a multiple of 3 for phase balance. | Circuit | Luminaires | Load (W) | Current (A) | Phase | MCB | |---|---|---|---|---|---| | L1 | 7 | 385 | 1.86 | R | 6 A | | L2 | 7 | 385 | 1.86 | Y | 6 A | | L3 | 6 | 330 | 1.59 | B | 6 A | #### Distribution board design | Phase | Circuits | Load (W) | Current (A) | |---|---|---|---| | R | L1 | 385 | 1.86 | | Y | L2 | 385 | 1.86 | | B | L3 | 330 | 1.59 | ```text Total connected load = 1100 W (lighting) Most loaded phase = 385 W Iph = 385 / (230 × 0.9) = 1.86 A Main MCB ≥ 1.25 × 1.86 = 2.32 A → 6 A TPN MCB ``` **DB specification:** 4-way-per-phase TPN DB (12 ways in all, spares included) with 6 A TPN MCB as incomer, 25 A 4-pole RCCB (100 mA) for earth-leakage protection, 6 A SP MCBs (B-curve) for light circuits. Incoming cable: 4-core 1.5 mm² Cu PVC (rating 21 A ≥ 6 A), plus earth continuity conductor. ```text 3-phase, 400/230 V, 4-wire supply | [Energy meter] | [6 A TPN MCB] | [25 A 4P RCCB] | ==R====Y====B====N== busbars | | | | | L1 L2 L3 ... ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is the light output of one 55 W LED at 90 lm/W? A. 55 lm B. 990 lm C. 4950 lm D. 49500 lm Answer: C. phi = 55 x 90 = 4950 lm. (Key point: Luminaire output) 2. Total lumens 90000 and 4950 lm per luminaire give 18.18. What is fitted? A. 18 luminaires, rounded down B. 20 luminaires in a 5 x 4 grid (rounded up) C. 100 luminaires D. 12 luminaires Answer: B. Rounding up to a regular grid gives 5 x 4 = 20, and actual E is 330 lux, above 300 lux required. (Key point: Number of luminaires) 3. How are the 20 luminaires split between sub-circuits? A. All on one circuit of 20 B. 7, 7 and 6 on phases R, Y and B C. 10 on R only and 10 on Y only D. One per circuit Answer: B. One circuit allows at most 10 points, and three circuits balance the phases: 7, 7 and 6 luminaires. (Key point: Sub-circuits and phases) ## Close variants set in other exams - [Factory hall 15 × 12 m metal halide lighting](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Afactory-hall-metal-halide) — Industrial Power Distribution and Illumination, chapter 7, asked 4× - [Factory hall 55.75 m × 40.25 m LED lighting](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Afactory-hall-led-55x40) — Industrial Power Distribution and Illumination, chapter 7, asked 4× - [Production room 27 × 45 m twin 36 W tubes](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aproduction-room-27x45) — Industrial Power Distribution and Illumination, chapter 7, asked 4× ## Related in Industrial Power Distribution and Illumination - [Industrial shop 30 × 25 m LED lighting](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aindustrial-shop-30x25-led) — Industrial Power Distribution and Illumination, chapter 7 - [Industry room 30 × 20 m LED lighting and DB](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aindustry-room-30x20-led) — Industrial Power Distribution and Illumination, chapter 7, asked 2× - [Conference hall 2×36 W CFL lighting](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aconference-hall-cfl) — Industrial Power Distribution and Illumination, chapter 7 - [Drawing hall 40 × 25 × 6 m, 250 lux LED](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Adrawing-hall-40x25-250lux) — Industrial Power Distribution and Illumination, chapter 7, asked 3× - [Drawing hall 40 × 20 × 6 m lighting design](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Adrawing-hall-40x20-led) — Industrial Power Distribution and Illumination, chapter 7, asked 2× - [Workshop hall lighting and power distribution](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aworkshop-hall-lighting-power) — Industrial Power Distribution and Illumination, chapter 7