Drawing hall 40 × 25 × 6 m, 90 lm/m² LED

Given: hall 40 m × 25 m × 6 m, E = 90 lm/m² on a plane 1 m above floor, CU = 0.8, depreciation factor 1.2, SHR = 1.2, 45 W LED at 90 lm/W, 3-phase 4-wire supply. Assumptions: luminaires mounted on the ceiling, so Hm = 6 − 1 = 5 m; pf 0.9; 12 power sockets of 16 A (1 kW each).

Number of luminaires

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

Area A        = 40 × 25 = 1000 m²
φ per luminaire = 45 W × 90 lm/W = 4050 lm
MF            = 1/DF = 1/1.2 = 0.833
Total lumens  = E × A × DF / UF
              = 90 × 1000 × 1.2 / 0.8
              = 135000 lm
N             = 135000 / 4050 = 33.33

Rounding up and fitting a regular grid: 7 × 5 = 35 luminaires (7 along the 40 m side, 5 along the 25 m side).

Arrangement and spacing

Spacing along length = 40/7 = 5.71 m
Spacing along width  = 25/5 = 5 m
End spacing (to wall) = half of these
Max spacing = SHR × Hm = 1.2 × 5 = 6 m
5.71 m and 5 m ≤ 6 m  → OK
Actual E = 35 × 4050 × 0.8 × 0.833 / 1000
         = 94.5 lux (≥ 90 lux required)

Here the spacing limit (SHR 1.2) decides the grid: 34 lamps are needed for lux, and 7 × 5 = 35 just satisfies spacing ≤ 6 m. If the lamps were suspended 1 m (Hm = 4 m), spacing ≤ 4.8 m would need a 9 × 6 = 54 grid, so ceiling mounting is chosen.

Layout diagram

Plan 40 m × 25 m (letter = phase of lamp circuit)
+---------------+
| R R R R R R Y |
| B B Y Y Y Y Y |
| B B B B R R R |
| Y Y Y Y R R R |
| Y Y 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 45 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 = 1575 W light + 12000 W power = 13575 W
Most loaded phase    = 4540 W
Iph = 4540 / (230 × 0.9) = 21.93 A
Main MCB ≥ 1.25 × 21.93 = 27.42 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
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  L1   L2   L3   P1   P2  ...