Drawing hall 40 × 20 × 6 m lighting design

Given: hall 40 m × 20 m × 6 m, E = 150 lm/m² on a working plane 1 m above floor, CU = 0.8, depreciation factor 1.2, 40 W LED panel at 100 lm/W (the question's "metal filament" lamp is replaced by this LED panel as stated). Assumptions: luminaires suspended 1 m below the 6 m ceiling, i.e. at 5 m above floor, so mounting height above working plane Hm = 5 − 1 = 4 m; SHR ≤ 1.5; pf 0.9; 12 power sockets of 16 A (1 kW each) along the walls.

Number of luminaires

Lumen method: N = (E × A) / (φ × UF × MF), where φ is the output of one luminaire.

Area A        = 40 × 20 = 800 m²
φ per luminaire = 40 W × 100 lm/W = 4000 lm
MF            = 1/DF = 1/1.2 = 0.833
Total lumens  = E × A × DF / UF
              = 150 × 800 × 1.2 / 0.8
              = 180000 lm
N             = 180000 / 4000 = 45

Rounding up and fitting a regular grid: 9 × 5 = 45 luminaires (9 along the 40 m side, 5 along the 20 m side).

Arrangement and spacing

Spacing along length = 40/9 = 4.44 m
Spacing along width  = 20/5 = 4 m
End spacing (to wall) = half of these
Max spacing = SHR × Hm = 1.5 × 4 = 6 m
4.44 m and 4 m ≤ 6 m  → OK
Actual E = 45 × 4000 × 0.8 × 0.833 / 800
         = 150 lux (≥ 150 lux required)

Layout diagram

Plan 40 m × 20 m (letter = phase of lamp circuit)
+-------------------+
| R R R R R R R R Y |
| B B Y Y Y Y Y Y Y |
| B B B B B B R R R |
| Y Y Y Y Y R R R R |
| Y Y B 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. Power sockets (16 A, 3-pin, with earth) are placed along the walls at about 1 m height, spaced roughly evenly.

Sub-circuits

Rule (IS 732 / NEA practice): a light sub-circuit carries at most 10 points and 800 W. Here one luminaire is 40 W, so up to 10 luminaires per sub-circuit. Number of circuits is made a multiple of 3 for phase balance.

Power sub-circuits (assumed): 12 sockets of 16 A, each taken as 1 kW, at most 2 sockets per power sub-circuit (IS 732), 2.5 mm² Cu wire, 20 A MCB.

Distribution board design

Connected load = 1800 W light + 12000 W power = 13800 W
Most loaded phase    = 4600 W
Iph = 4600 / (230 × 0.9) = 22.22 A
Main MCB ≥ 1.25 × 22.22 = 27.78 A → 32 A TPN MCB

DB specification: 6-way-per-phase TPN DB (18 ways in all, spares included) with 32 A TPN MCB as incomer, 40 A 4-pole RCCB (100 mA) for earth-leakage protection, 6 A SP MCBs (B-curve) for light circuits and 20 A SP MCBs for power circuits. Incoming cable: 4-core 6 mm² Cu PVC (rating 45 A ≥ 32 A), plus earth continuity conductor.

3-phase, 400/230 V, 4-wire supply
        |
   [Energy meter]
        |
   [32 A TPN MCB]
        |
   [40 A 4P RCCB]
        |
==R====Y====B====N== busbars
  |    |    |    |    |
  L1   L2   L3   P1   P2  ...

Result: 45 LED panels of 40 W each, mounted at 5 m above floor (Hm = 4 m) in a 9 × 5 grid.