This document provides an example of designing lighting for a classroom and outlines the assumptions and considerations that should be made. It works through calculating the number of fluorescent lamps needed to illuminate a 20m by 15m by 5m classroom with an average illumination of 250 lux. It determines that 34 lamps are needed based on the depreciation factor, maintenance factor, and utilization factor. It then shows the layout, with the lamps arranged in 4 rows of 8 lamps each, spaced 2.5m apart along the length and 3.75m apart along the width. The document provides another homework problem and contact information.

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)