Illumination Examples Sides 5 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 = 0.6 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 -4
• An illumination of 75 Lux is required on
working plane in a big hall of (40 m (L) X
15 m (b)). The lamps to be hung 4 m
above the work bench.
Assuming a suitable space height ratio, a
utilization factor of 0.5, a lamp efficiency of
14 lumens per Watt and candle power
depreciation of 20 %, Estimate the no.
rating and disposition of lamps.

4. Design considerations
• Illumination required is = 75 lux.
• Candle power depreciation + Depreciation
Factor = 1
• Depreciation Factor = 1 - Candle power
depreciation
= 1- 0.2
= 0.8

5. 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
A×E
Gross Lumenn required =
M.F × U.F.
(40 15) 75
=
0.5 0.8
= 112500
Gross Lumen
Total Wattage required=
Lumen Efficiency
112500
=
14
= 8036 Watts
8036
So, No. of lamps of 200 W each = 40
200
40 lamps in 4 rows each having 10 lamps can be used.

6. Layout
• 200W Lamp selected.
• Taking arrangement as
• No. lamps in one row = 10
• No. of rows = 4
• 2 lamps for black board
• Distance along the length, a = 40/10 = 4m
• Distance along the width, b = 15/ 10 = 1.5m
• Side Length = a / 2 = 4 / 2 = 2m
• Side Width = b/2 = 1.5 / 2 = 0.75m
• NOTE:- Draw a layout

7. S Ratio = Spacing Between Lamps
H Height of mounting of Lamp
Along Length 4
1
4
S
Ratio 1
H
Along Width 1 .5
0.375
4
S
Ratio 0.375
H
Vijay Balu Raskar (B.E.Electtrical)

8. HOME WORK-4
• An illumination of 95 Lux is required on
working plane in a big hall of (26 m (L) X
30 m (b)). The lamps to be hung 5 m
above the work bench.
Assuming a suitable space height ratio, a
utilization factor of 0.5, a lamp efficiency of
14 lumens per Watt and candle power
depreciation of 18 %, Estimate the no.
rating and disposition of lamps.

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