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Flood lighting design and luminaire selection

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.

Explain the design procedure for flood lighting system and selection of luminaries for it.

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.
   Building face
 ┌───────────────┐
 │  overlapping  │
 │    beams      │
 └───────────────┘
     \  |  /
      \ | /   distance ≈ 0.7–1 × H
       [P P P]  projectors

Selection of luminaires (projectors)

  1. Beam spread:
Beam classSpreadUse
Narrow12°–25°Long throw > 70 m, tall towers
Medium25°–40°Throw 30–70 m, facades
Wide> 40°Short throw < 30 m, yards
  1. Lamp type: LED, metal-halide (good colour), HPSV (high efficacy, yellow), halogen (low efficacy, being phased out).
  2. Efficacy and life – lower running and replacement cost.
  3. Colour rendering and colour temperature to suit the surface (warm light for brick, cool light for stone/glass).
  4. Beam factor – proportion of lamp lumens inside the beam.
  5. Ingress protection (IP65 or more), corrosion-resistant housing, toughened glass.
  6. Mounting and aiming facility (adjustable brackets, aiming scale).
  7. Glare control – visors and louvres.
  8. Cost and maintenance – ease of lamp replacement and cleaning.

✓ Answer checked by Claude Opus 5.5 (high effort)

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