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 0.85 Mercury vapor 0.79 Metal halide 0.83 High pressure sodium 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 sheetLength Width

height of

height of the Room

Reflection

Utilization

Maintanance

Deterioration

Required

Installed

Lamp

Number of

Number of

Required Total Category of

luminaries

working plane index

factors factor factor factor

lux level flux

design lamps in

luminaires

luminaires load bulb

lumens

each luminaire

W

8.3857 5.318 3 0.5

1.3016967

7 3 10.52 0.85 0.8 400

50447.01

3350 2

7.5294038 8 288

LAMP, T8, 1200MM, 36W, 3500K

6.7564 4 3.75 0.5

0.7730811 7 3 1 0.42 0.85 0.8 400

37850.98

3350 2

5.6494001 6 216

15.2867 4.846 3 0.5

1.4718214

7 3 10.55 0.85 0.8 400

79229.25

3350 2

11.825261 12 432

4.0735 3.8 3.75 0.5

0.604923 7 3 1 0.36 0.85 0.8 400

25292.97

3350 2

3.7750707 4 144

3.3667 2.312 3.75 1

0.4984374

7 3 10.36 0.85 0.8 400

12718.64

3350 2

1.8983051 2 72

4.32 1.98 3 0.50.5430

8577 3 1

0.36 0.85 0.8 1505241.

176112

5 14.6588

235 5 90FT18W/2G11/830

4 3.22 3.75 0.50.5489

0267 3 1

0.36 0.85 0.8 1507892.

157261

0 13.0238

149 4 144FT36W/2G11/830

1386

Recommended Lighting LevelsActivity Illumination

(lux, lumen/m2)Public areas with dark surroundings 20 - 50Simple 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 prolonged periods of time 2000 - 5000

Load calculation

Part 2

• Design power socket outlets….. If not given• Then analyse….

Ground Floor QuantityLoad (Amp)

13A Socket Outlets 6 10*(1+(6-1)*0.2) 20.000

Florecent Fittings 2x36W 32 (36*2*32)/(0.7*230) 14.311Compact lamps (18W) 5 0.559Compact lamps (36W) 4 0.894Spot lights 4 0.745Shaver socket 1 4.000

Basic Lighting Load per Floor 40.509 Amp.

Per Phase load L-GR 13.503 Amp.

Total new Load for the new wing =49.29 Amp

Total KVA

=(49.29*1.732*400)/1000

=34.15 KVAAdd 10 % Extra Capacity = 37.6 KVA

AmpClosest Next is = 50 KVA 72.17

Total load for the new wing = Total load for ground floor+1st floor+2nd floor……

= 13.503+……+……

=49.29Amp

Bill Of Quantity (BOQ)• Example

Quantity Cost rate(Rs)

Total cost(Rs)

01 Phillips 20W CFL warm light

40 425 =40*425=17000

02 Pillips T8 Fluorescent lamp 18W

32 600 =32*600=19200

=17000+19200=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 ___________ and In Ib

Ca Ci Cg Cf

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