Electrical Lighting
&
Cable Selection
D.K.Pathirana
Part 1
Finding required number of luminaries
Types of Electrical Lighting
• Ambient lighting
• Task Lighting
• Accent lighting
Ambient lighting
Task lighting
Accent Lighting
Lumen(Luminous flux) [F]
• The lumen is defined such that…
– At frequency of 540×1012 hz, (i.e., at wavelength
λ=555nm) 1 watt of radiant flux (power) will emit
683 lumens of light (luminous flux).
Illuminance (E)
• Defined as the luminous flux (lumens) falling
on a surface per unit area normal to the
surface.
• The unit of illuminance is the Lux
Luminaries
Required no. of Luminaries
E x Lx W
N = _______________________
NL x  x MF x UF x LLD
•
•
•
•
•
•
•
•
•
E= Required Illuminance (Lux level)
L = Room length (m)
W = Room width (m)
NL = Number of lamps in each luminaries
N = Number of luminaries
 = Lamp flux
M = Maintenance factor
UF = Utilization factor
LLD = Lamp Lumen Deterioration factor
Maintanance factor (MF)
• Can be defined as…
Average illuminance on the working plane
after a specified period of use of a lighting
installation to the average illuminance
obtained under the same conditions for a new
installation.
Lamps Lumen Deterioration (LLD)
• Manufacturer data….
• Examples..
Compact fluorescent
Mercury vapor
Metal halide
High pressure sodium
0.85
0.79
0.83
0.91
Reflectance factor
• the fraction of radiant energy that is reflected
from a surface
• Examples- 70% , 0.8, ...
• Here 10 times the reflection factor…..
1.Ceiling
2. Walls
3. Floor\Working plane.
Room Index
K = (LXW)/ [(H1-H0)X(L+W)]
Where,
L
= Room Length (m)
W
= Room Width (m)
H1
= Height of luminaire’s light emitting surface
H0
= Height of the working plan
Utilization factor
Room Index
(K)
Reflectance
873
753
731
551
531
311
0.60
0.39
0.31
0.27
0.29
0.26
0.24
0.80
0.45
0.37
0.32
0.35
0.32
0.29
1.00
0.49
0.42
0.36
0.38
0.36
0.33
1.25
0.53
0.46
0.40
0.42
0.39
0.37
1.50
0.56
0.49
0.42
0.44
0.41
0.39
2.00
0.59
0.53
0.46
0.47
0.45
0.43
2.50
0.61
0.56
0.48
0.49
0.47
0.45
3.00
0.63
0.57
0.49
0.50
0.49
0.47
4.00
0.65
0.60
0.51
0.52
0.51
0.49
5.00
0.66
0.62
0.53
0.53
0.52
0.50
Example for lighting calculation sheet
heigh
Length Width t of
lumin
aries
8.385
7 5.318
6.756
4
4
15.28
67 4.846
4.073
5
3.8
3.366
7 2.312
4.32
4
1.98
3.22
3
3.75
3
3.75
height
Reflec Utiliza Maintan Deterior
of the
Room tion
tion
ance
ation
working
factor
plane
index s
factor factor
factor
1.3016 7 3 1
0.5
967
0.7730
731
0.5
811
1.4718 7 3 1
0.5
214
0.6049
731
0.5
23
3.75
0.4984 7 3 1
1
374
3
0.5430
731
0.5
857
3.75
0.5489
731
0.5
026
0.52
0.85
0.8
0.42
0.85
0.8
0.55
0.85
0.8
0.36
0.85
0.8
0.36
0.36
0.36
0.85
0.85
0.85
Requi Install Lam
red
ed
p
lux
desi
level flux gn
lum
ens
Number Numb Requir
of
er of ed
Total
lumina lumina
lamps in ires
ires
load
each
W
luminaire
5044 335
400 7.01
0
3785 335
400 0.98
0
7.5294
2
038
5.6494
2
001
7922 335
400 9.25
0
2529 335
400 2.97
0
11.825
2
261
3.7750
2
707
0.8
1271 335
400 8.64
0
1.8983
2
051
0.8
5241. 112
150 176
5
4.6588
1
235
0.8
7892. 261
150 157
0
3.0238
1
149
Category of
bulb
8
288
6
216
12
432
4
144
2
LAMP, T8,
1200MM,
72 36W, 3500K
5
FT18W/2G11/
90 830
4
FT36W/2G11/
144 830
1386
Recommended Lighting Levels
Activity
Illumination
(lux, lumen/m2)
Public areas with dark surroundings
20 - 50
Simple orientation for short visits
50 - 100
Working areas where visual tasks are only occasionally performed
100 - 150
Warehouses, Homes, Theaters, Archives
150
Easy Office Work, Classes
250
Normal Office Work, PC Work, Study Library, Groceries, Show
Rooms, Laboratories
500
Supermarkets, Mechanical Workshops, Office Landscapes
750
Normal Drawing Work, Detailed Mechanical Workshops,
Operation Theatres
1,000
Detailed Drawing Work, Very Detailed Mechanical Works
1500 - 2000
Performance of visual tasks of low contrast and very small size for
2000 - 5000
prolonged periods of time
Part 2
Load calculation
• Design power socket outlets….. If not given
• Then analyse….
Load (Amp)
Ground Floor
Quantity
13A Socket Outlets
6
Florecent Fittings 2x36W
Compact lamps (18W)
Compact lamps (36W)
Spot lights
Shaver socket
32
5
4
4
1
10*(1+(6-1)*0.2) 20.000
(36*2*32)/(0.7*230) 14.311
0.559
0.894
0.745
4.000
Basic Lighting Load per
Floor
40.509 Amp.
Per Phase load L-GR
13.503 Amp.
Total load for the new wing = Total load for ground floor+1st
floor+2nd floor……
= 13.503+……+……
=49.29Amp
Total new Load for the
new wing
=49.29 Amp
=(49.29*1.732*
400)/1000
Total KVA
Add 10 % Extra Capacity
Closest Next is
=34.15 KVA
= 37.6 KVA
=
50 KVA
Amp
72.17
Bill Of Quantity (BOQ)
• Example
01 Phillips 20W CFL
warm light
02 Pillips T8
Fluorescent lamp
18W
Quantity Cost
rate(Rs)
40
425
32
600
Total
cost(Rs)
=40*425
=17000
=32*600
=19200
=17000+192
00
=36200
Part 3
Cable selection and Over load
Protection
Basic types of MCB’s
• TYPE B
• TYPE C
• TYPE D
Sizing the cables
• length of the wire
• Check the following inequality
In
It  ___________
Ca Ci Cg Cf
and In  Ib
It = Maximum current capacity of cable for given temp.
Ib = Design current
In = Rated current of the protective device
Ca = Correction factor for ambient temperature.
CI = Correction factor for thermal insulation
Cg = Correction factor for grouping
Cf = Correction factor for semi enclosed fuse.
(for MCBs Cf = 1)
Contd…
• Refer IEE wiring regulation book
• Lesser than 4% voltage drop….
Selecting a protective device
• Nature of the load
• Rated current of the conductor
• Environmental conditions
Contd..
Ib  rated current of protective divice  Iz
•
Where,
Ib = Design service current
Iz = Maximum current carrying capacity of the
conductor
If  1.45 x Iz
•
Where,
Iz = Maximum current carrying capacity of the
conductor
If = Thermal tripping current of MCCB
Single Line Diagram
Questions……
Thank you