Illumination Examples Sides 2 out of 8

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 = 0.5 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 -1
• A classroom measuring (20 m (L) X 15 m
(b) X 5 m (h) is to be illuminated.
a. State the design considerations for the
lightening of above class room
b. Calculate the no. of lamps required.
c. Draw the lighting layout.
Vijay Balu Raskar (B.E.Electtrical)

4. Design considerations
• Assuming an average illumination of 250
lux.
• Assuming depreciation factor = 1.2 i.e..
Maintenance factor 0.8
• Utilization factor varies from 0.6 to 0.9
• Assuming illumination is free from glare
• Assuming illumination is free from dark
shadows.
Vijay Balu Raskar (B.E.Electtrical)

5. 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)

6. Calculation of No. of lamps required
• From Table on Lamp Data, for the Fluorescent
lamp selecting wattage of 36 (82/84/86) with Lumen
output = 3250 (As per your data sheet)
A × E
N o . o f lam p s =
F lu x /fittin g × M .F × U .F .
(2 0 15) 250
=
3250 0 .8 0 .8 6
= 3 3 .5 4
= 3 4 lam p s
Vijay Balu Raskar (B.E.Electtrical)
S o , to tal n o . o f lam p s req u ired are = 3 4

7. Calculation for Layout
• Taking arrangement as
• No. lamps in one row = 8
• No. of rows = 4
• 2 lamps for black board
• Distance along the length, a = 20/8 = 2.5m
• Distance along the width, b = 15/ 4 =
3.75m
• Side Length = a / 2 = 2.5 / 2 = 1.25m
• Side Width = b/2 = 3.75 / 2 = 1.875m
Vijay Balu Raskar (B.E.Electtrical)

8. Layout
Vijay Balu Raskar (B.E.Electtrical)

9. S Ratio = Spacing Between Lamps
H Height of mounting of Lamp
Along Length 2 .5
0 . 625
4
S
Ratio 0 . 625
H
Along Width
3 . 75
0 . 9375
4
S
Ratio 0 . 9375
H
Vijay Balu Raskar (B.E.Electtrical)

10. Home Work -1
• A classroom measuring (30 m (L) X 20 m
(b) X 6 m (h) is to be illuminated.
a. State the design considerations for the
lightening of above class room
b. Calculate the no. of lamps required.
c. Draw the lighting layout.
Vijay Balu Raskar (B.E.Electtrical)

11. E-mail if any queries:-
student5147@yahoo.com
Or
Contact:-
09833066325 Vijay Balu Raskar (B.E.Electtrical)