--- title: "Flood lighting design and luminaire selection" subject: "Industrial Power Distribution and Illumination" chapter: 8 key: "semester_6/industrial_power_distribution_and_illumination:flood-design-luminaire-selection" source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/flood-design-luminaire-selection site: BCT Engineering --- # Flood lighting design and luminaire selection Industrial Power Distribution and Illumination · Chapter 8: Outdoor Lighting Design - Asked in: 2071 Bhadra, 8 marks - Video: [ILLUMINATION ENGINEERING - PART -12 - FLOOD LIGHTING - IMPORTANT TERMS & PRBOLEMS](https://www.youtube.com/watch?v=xOpYxgnD9kg) — 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/flood-design-luminaire-selection - Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-8 ## Question Explain the design procedure for flood lighting system and selection of luminaries for it. ## Short answer Floodlight design: choose E, area A, projectors at distance ~0.7‑1× height, beam spread via θ = 2 tan⁻¹(half‑size/distance), total lumens = E×A×DF×WLF/CU, N = F/(W×efficacy). Luminaire selection factors: beam spread class, lamp type/efficacy, IP rating, glare control, colour rendering, mounting and cost. ## Answer Floodlighting is the lighting of large surfaces (building facades, monuments, yards, stadiums) by **projectors** that concentrate the light into a controlled beam. Its design consists of finding the lumens, choosing suitable luminaires (projectors) and arranging them. #### Design procedure 1. **Study the object and site:** dimensions, shape, material, colour and reflection factor; brightness of surroundings; viewing direction. 2. **Choose illumination level (E):** e.g. light-coloured stone in dark area 50–100 lux; dark brick in bright city area 200–300 lux. 3. **Area to be illuminated:** A = length × height. 4. **Location of projectors:** - On the ground in front, at a distance of about 0.7–1 × height of building; - Or on nearby poles/roofs; or on the building itself (for tall buildings). - They must be hidden from viewers and must not dazzle traffic. 5. **Beam spread:** found from the distance and the size to be covered, θ = 2 tan⁻¹(half-size / distance). 6. **Select factors:** CU or beam factor, depreciation factor, waste light factor. 7. **Total lumens:** F = E × A × DF × WLF / CU. 8. **Lamps:** select type and wattage; N = F / (W × efficacy). 9. **Aim and arrange:** overlap beams by about 10–20% for uniformity; trial aiming at night. 10. **Electrical design:** circuits, cables, control by timer/photocell, protection. ```text Building face ┌───────────────┐ │ overlapping │ │ beams │ └───────────────┘ \ | / \ | / distance ≈ 0.7–1 × H [P P P] projectors ``` #### Selection of luminaires (projectors) 1. **Beam spread:** | Beam class | Spread | Use | |---|---|---| | Narrow | 12°–25° | Long throw > 70 m, tall towers | | Medium | 25°–40° | Throw 30–70 m, facades | | Wide | > 40° | Short throw < 30 m, yards | 2. **Lamp type:** LED, metal-halide (good colour), HPSV (high efficacy, yellow), halogen (low efficacy, being phased out). 3. **Efficacy and life** – lower running and replacement cost. 4. **Colour rendering and colour temperature** to suit the surface (warm light for brick, cool light for stone/glass). 5. **Beam factor** – proportion of lamp lumens inside the beam. 6. **Ingress protection (IP65 or more)**, corrosion-resistant housing, toughened glass. 7. **Mounting and aiming facility** (adjustable brackets, aiming scale). 8. **Glare control** – visors and louvres. 9. **Cost and maintenance** – ease of lamp replacement and cleaning. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Where are projectors normally placed relative to a building? A. About 0.7-1 times the building height away, hidden from viewers and not dazzling traffic B. Directly touching the wall C. At least 5 times the building height away D. Anywhere, as location does not matter Answer: A. Typical distance is 0.7-1 x height, out of view and without glaring traffic. (Key point: Projector location) 2. Which beam class suits a long throw over 70 m or tall towers? A. Wide (over 40 degrees) B. Medium (25-40 degrees) C. Narrow (12-25 degrees) D. Any beam, equally Answer: C. Narrow beams for long throws; medium for 30-70 m; wide for under 30 m. (Key point: Beam spread classes) 3. How should the beams be arranged for uniform lighting? A. Keep beams strictly separate B. Overlap beams by about 10-20% and trial-aim at night C. Overlap beams completely D. Aim all projectors at one point Answer: B. Slight overlap evens out the illumination. (Key point: Aiming for uniformity) 4. Which feature is a correct luminaire selection criterion for outdoor projectors? A. Lowest possible efficacy B. Open housing for easy cooling C. Fixed mounting with no aiming D. IP65 or higher ingress protection with adjustable aiming and glare control Answer: D. Outdoor projectors need weather protection, aiming facility and glare control visors/louvres. 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