This document provides information and examples for designing illumination systems. It lists assumptions that should be made, such as depreciation and maintenance factors. An example problem is given to illuminate a 40m x 25m x 6m hall to 90 lux, using metal filament gas lamps. Calculations are shown to determine the number and type of lamps needed based on the space dimensions, illumination level, and utilization factor. For the example, 500W lamps in a 6m x 6m grid layout are determined to be suitable. Instructions are provided for students to solve a similar homework problem.

1. Illumination Based Problems
Vijay Balu Raskar (B.E.Electtrical)

2. NOTE:-
Before Designing assume following things clearly.
Assumptions are required for illumination.
Assume Depreciation Factor = 1.2
Assume Maintenance Factor = 0.8
Utilization Factor = 0.6 to 0.9
Assume illumination is free from glare
Assume illumination is free from dark shadows
Assuming lamps are arranged to give uniform illumination.
Reflective index of wall and ceiling is maximum.
Selecting a fluorescent tube light
Space to height ratio along the length and breadth is less
than or equal to 1.5
Assume Height of mounting of Lamp ( as per area)
Vijay Balu Raskar (B.E.Electtrical)

3. Example -5
• A drawing hall of 40 m × 25 m × 6 m is to
be illuminated with metal filament gas filled
lamps to an average illumination of 90 lm /
m2, on a working plane 1 meter above the
floor. Assume coefficient of utilization of
0.5,depreciation factor of 1.2 and space to
height ratio of 1.2.
Vijay Balu Raskar (B.E.Electtrical)

4. Sr No Size of Lamps (Watts) Luminous
Efficiency
(lm / w)
1 200 16
2 300 18
3 500 20
Estimate suitable number, size and
mounting height of lamps. Sketch spacing
layout.
Vijay Balu Raskar (B.E.Electtrical)

5. Design considerations
• An average illumination of 90 lm / m2. i.e.
90Lux
• Depreciation factor = 1.2 i.e.. Maintenance
factor 0.8
• Space to height ratio = 1.2
• Utilization factor varies from 0.6 to 0.9
here 0.5 (Given)
• Assuming illumination is free from glare
• Assuming illumination is free from dark
Vijay Balu Raskar (B.E.Electtrical)

6. Design considerations
• Assuming lamps are arranged to give
uniform illumination.
• Reflective index of wall and ceiling is
maximum.
• Space to height ratio along the length and
breadth is less than or equal to 1.5
• Selecting a fluorescent tube light
• Selecting utilization factor of 0.86
Vijay Balu Raskar (B.E.Electtrical)

7. Calculation of No. of lamps required for each Type:-
Formula, Gross Lumen Required = A X E X DF
UF
AXEXDF 40 X 25 X 90 X 1 . 2
216000
UF 0 .5 S Size of Luminous Lumen
r Lamps Efficiency
No of lamps required = GLR___ (Watts) (lm / w)
Total Lumen N
For 200W type, o
No of lamps = 216000 1 200 16 200 X 16
3200 = 3200
For 200W type , we required 68 Lamps (app.) 2 300 18 300 X 18
Similarly, = 5400
For 300W type , we required 4 Lamps (app.) 3 500 20 500 X 20
For 500W type , we required 22 Lamps (app.) = 10000
Vijay Balu Raskar (B.E.Electtrical)

8. Given, Space to height ratio is 1.2 and a working
plane 1 meter above the floor i.e Height of
mounting of lamp is (Height – 1) = 5m.
S Ratio = Spacing Between Lamps
H Height of mounting of Lamp
S a
Ratio 1 .2
H 5
a 1 .2 X 5 6
Spacing between the lamps is 6m.
Distance along the length, a = 40/ p = 6m i.e. p = 1 + no of lamps in a row = 6
Distance along the width, b = 25/ q = 6m i.e. q = 1 + no of lamps = 4
No of lamps required = 6 X 4 = 24 lamps required.
Therefore, selecting 500W Vijay Balu Raskar (B.E.Electtrical)

9. Layout
• Taking arrangement as
• No. lamps in one row = 6
• No. of rows = 4
• 2 lamps for black board
• Distance along the length, a = 40/6 = 6.66m
• Distance along the width, b = 25/ 5 = 5m
• Side Length = a / 2 = 6.66 / 2 = 3.33m
• Side Width = b/2 = 25 / 2 = 2.5m
• NOTE:- DRAW LAYOUT
Vijay Balu Raskar (B.E.Electtrical)

10. S Ratio = Spacing Between Lamps
H Height of mounting of Lamp
6 . 66 NOTE:-
Along Length 1 . 332 Given S/H is 1.2
5 And we got less than 1.5.
This is right illumination.
S
Ratio 1 . 332
H
Along Width
5
1
5
S
Ratio 1
H
Vijay Balu Raskar (B.E.Electtrical)

11. HOMW WORK -5
• A drawing hall of 30 m × 15 m × 5 m is to
be illuminated with metal filament gas filled
lamps to an average illumination of 60 lm /
m2, on a working plane 1 meter above the
floor. Assume coefficient of utilization of
0.5,depreciation factor of 1.2 and space to
height ratio of 1.
Vijay Balu Raskar (B.E.Electtrical)

12. Sr No Size of Lamps (Watts) Luminous
Efficiency
(lm / w)
1 300 18
2 400 20
3 600 25
Estimate suitable number, size and
mounting height of lamps. Sketch spacing
layout.
Vijay Balu Raskar (B.E.Electtrical)

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Or
Contact:-
09833066325 Vijay Balu Raskar (B.E.Electtrical)