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How to calculate the number of luminaires

Basic data

Room:

  • length – а;
  • width – b;
  • height – h;
  • reflection coefficients of the ceiling, walls and floors.
Luminaires:
  • coefficient use of luminaires;
  • estimated height (distance between the luminaire and the working surface).
Lamps:
  • lamp type;
  • power.
 
Norms: 
  • required illumination.

The calculation of luminous flux:

Supporting materials:

  • Table of coefficients of use
  • Table of reflection of coefficients
  • Table of recommended levels of illumination
  • Table of initial  luminous flux of fluorescent lamps

Calculation formulas:

  • Definition square room: S = a × b .
  • Definition of index room: φ = S / ( h - Кs ) * ( a + b ).
  • Definition coefficients use the lighting system for tables the various series fixtures from the values of reflection coefficients and the index premises.
  • Definition the required number of fixtures:  N = ( E * S) / ( U * n * Fl *  Кs )
Е – required horizontal illuminance, lx.
S – coefficient square room, sq.m.
Кs – safety factor   (Кs  = 0,8)
U – coefficient of use the lighting system.
Fl – luminous flux of a lamp, lux.
n - number of lamps in one fixture.

 

Example calculation:

Office, light ceilings, light walls, gray carpet. Baseline data: room a = 9 m, b = 6 m, h = 3,2 m. Lamp LPO 12-2 × 40-904, fluorescent lamp 36 W, in a single lamp 2 lamps, F = 2850 lm (production PHILIPS) . The norm of the E = 500 lux at 0.8 m above the floor. The safety factor Ks = 0,8. The reflection coefficient of the ceiling - 0,5, walls - 0,5, sex - 0,3.


 Calculation:

  1. define square room: S = a × b = 6 × 9 = 54 m2
  2. define the index room: φ = S / (h - Ks) * (a + b) = 54 / (3,2 - 0,8) * ( 9 +6) = 1,5
  3. determine coefficient of use the lighting system, based on the reflection coefficient and the index space U = 0,51
  4. determine the required number of Lamp: N = (E * S) / (U * n * Fl * Ks) = (500 * 54) / (0.51 * 2 * 2850 * 0.8) = 11.6
  5. accepted 12 fixtures.
     
 

Table for calculating of illumination

 
ceiling
0,8
0,7
0,7
0,5
0,5
0,5
Wall
0,5
0,5
0,3
0,5
0,3
0,3
floor
0,3
0,3
0,3
0,3
0,3
0,1
0,60
0,33
0,32
0,25
0,3
0,24
0,24
0,80
0,41
0,39
0,32
0,36
0,3
0,29
1,00
0,47
0,45
0,38
0,42
0,35
0,34
1,25
0,53
0,51
0,44
0,47
0,41
0,39
1,50
0,58
0,55
0,48
0,51
0,45
0,43
2,00
0,65
0,62
0,56
0,57
0,52
0,49
2,50
0,7
0,67
0,61
0,61
0,56
0,53
3,00
0,64
0,71
0,65
0,64
0,6
0,56
4,00
0,79
0,75
0,7
0,68
0,64
0,6
5,00
0,83
0,78
0,74
0,71
0,68
0,62
 

Table of reflection of coefficients

 
The plane made of materials with high reflectivity
0,8
The plane with a white surface
0,7
The plane with a bright surface
0,5
The plane with the gray surface
0,3
The plane with a dark surface
0,1

 Table illumination levels for certain types of premises
 
Name of premises
The estimated plane
Illumination in lux
1
Offices and other operating room
Horizontal 0.8 m from the floor
 500
2
Design, engineering and drawing office
H 0,8
 500
3
Reading Rooms
H 0,8
300 
4
Room with a PC
H 0,8
400
5
Meeting rooms and boardrooms
H 0,8
 200
6
Laboratories
H 0,8
400
7
Classrooms, auditoriums, classrooms
H 0,8
400 
8
Blackboard education institutions
Vertical 1.5 m from the floor
 500
9
Classrooms and teachers rooms
H 0,8
 300
10
Gyms
on floor
200 
11
Bedrooms kindergartens
on floor
150 
12
Foster, locker rooms, gaming, dining kindergartens
on floor
200 
13
Showrooms
H 0,8
200 
14
Trading rooms of grocery stores
H 0,8
400 
15
Salesrooms other stores
H 0,8
300
16
Offices of physicians
H 0,8
300 
17
Hairdressers
H 0,8
400 
18
Lobbies and public buildings wardrobe
on floor
150 
19
Lobbies and wardrobes of industrial buildings
on floor
75 
20
Staircases industrial buildings
on floor
100 
21
Staircases of residential buildings
on floor
10 
22
Operating rooms, box office premises
H 0,8
400 
23
Hotel rooms
H 0,8
100 
24
Washing, cleaning, smoking
on floor
75 
25
Showers
on floor
50 
26
Corridors and passages in public buildings
on floor
75 
27
Corridors and aisles of residential buildings
on floor
20 

 

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