Conference hall 2×36 W CFL lighting

Given: hall 40 m × 20 m × 5.5 m, 2 × 36 W CFL set (72 W per set) at 60 lm/W, E = 108 lm/m², 3-phase 4-wire supply. Assumptions: UF and MF not given, so UF = 0.6 (medium-light room surfaces) and MF = 0.8 (clean room); working plane 0.8 m and sets suspended 0.5 m below ceiling → Hm = 5.5 − 0.5 − 0.8 = 4.2 m; SHR ≤ 1.5; 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 × 20 = 800 m²
φ per luminaire = 72 W × 60 lm/W = 4320 lm
Total lumens  = E × A / (UF × MF)
              = 108 × 800 / (0.6 × 0.8)
              = 180000 lm
N             = 180000 / 4320 = 41.67

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 × 4.2 = 6.3 m
4.44 m and 4 m ≤ 6.3 m  → OK
Actual E = 45 × 4320 × 0.6 × 0.8 / 800
         = 116.6 lux (≥ 108 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 72 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 = 3240 W light + 12000 W power = 15240 W
Most loaded phase    = 5080 W
Iph = 5080 / (230 × 0.9) = 24.54 A
Main MCB ≥ 1.25 × 24.54 = 30.68 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  ...