Department store 36 × 15 m LED panel lighting

Given: store 36 m × 15 m, 45 W LED panel giving 4800 lm, Hm = 3 m, E = 200 lux, CU = 0.8, MF = 0.8, supply 400 V, 3-phase, 50 Hz. Assumptions: SHR ≤ 1.5 (so spacing ≤ 4.5 m); 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        = 36 × 15 = 540 m²
φ per luminaire = 4800 lm
Total lumens  = E × A / (UF × MF)
              = 200 × 540 / (0.8 × 0.8)
              = 168750 lm
N             = 168750 / 4800 = 35.16

Rounding up and fitting a regular grid: 9 × 4 = 36 luminaires (9 along the 36 m side, 4 along the 15 m side).

Arrangement and spacing

Spacing along length = 36/9 = 4 m
Spacing along width  = 15/4 = 3.75 m
End spacing (to wall) = half of these
Max spacing = SHR × Hm = 1.5 × 3 = 4.5 m
4 m and 3.75 m ≤ 4.5 m  → OK
Actual E = 36 × 4800 × 0.8 × 0.8 / 540
         = 204.8 lux (≥ 200 lux required)

Layout diagram

Plan 36 m × 15 m (letter = phase of lamp circuit)
+-------------------+
| R R R R R R Y Y Y |
| B B B B B B Y Y Y |
| R R R R R R Y Y Y |
| B B B B B B Y Y Y |
+-------------------+
[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 = 1620 W light + 12000 W power = 13620 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
  |    |    |    |    |
  L1   L2   L3   P1   P2  ...