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Ministry of High Education

El-Shorouk Academy

High Institute of Engineering

Electrical Power and Machines Department

DESIGN OF ELECTRICAL DISTRIBUTION

SYSTEM FORRESEDENTIAL AREASThis thesis is submitted as a partial fulfilment of the requirements for the

Bachelor of Science Degree in Electrical Engineering

Supervised by

Assoc. Prof. Dr. Amged El Wakeel

Prepared by

Abdalla Tallat Tolba. Osama Abd El Mohsen Osman.

Abd El shafi Abdalla Bakr. Maisara Neyazy Abd El Sattar.

Ahmed Maged Ezzat. Mhdi Mohamed Emam.

Ahmed Mamdouh Abd El Mongy. Mohamed Abd El Aziz El Komy.

Ahmed Moatamed Saied. Mohamed Taha Abdalla.

Ahmed Mohamed Abd El Hamed. Mostafa Mohamed Abdo El Soaud.Ahmed Younis Younis. Wael Mohamed El Hady.

Ahmed Zakaria Shokry. Wael Mohamed Sbak.

Amr Baiomy Saied. Walied Ali Khatab.

Amr Mohsen Gemei. Yaser Ragaey Mohamed.

El Sayed Mohamed Baraka.

Gaber Abd El Latif Gaber.

Hani Abd El Hamed Soliman.

Ibrahim Mohamed Kutp.

Islam Gaber Abd El Wahab.

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ABSTRACT

In parallel to the increasing in population size, the requirement of new

residential buildings becomes vital particularly in crowded areas. In developing

countries such as Egypt, construction of residential buildings is being carried out

as part of strategic development programs. It is expected that residential buildings

should provide a safety and comfort and maximize the degree of resident

satisfaction within reasonable cost.

Residential buildings can encompass everything from a single apartment

or single-family dwelling unit to an apartment building with two hundred units.

Although residential designs vary greatly, there are considerations that must be

taken into account regardless of the size of the project. Location, materials,

safety, energy and cost are just a few of the things that should be kept in mind

during design stage. A good residence design shall take into consideration the

overall "streetscape" as well as the needs of individual occupants.

From above, it is clear that comprehensive and cohesive design

methodology for residential building including outlets distribution, load

estimation, branch circuit design, cable sizing, and switchboard design is a

difficult and specialised task. Comprehensive design is usually achieved through

a step-by-step procedure and design checks. Although, electrical Egyptian code

does cover residential building design, it does not ban the using of other

national/international codes. This enables us searching in different national codes

in order to achieve proper design.In this project, constructional features of residential buildings are

explained in detail to explore their effects on indoor and outdoor lighting

schemes, elevator design, cable selection and protection system. Different design

methodologies have been applied throughout the work; however the design by

synthesis is applied for the most of the work including indoor and outdoor design.

Also different codes and regulation have been applied such as NEC, BS, Egyptian

Electrical code and IEE regulations.

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TABLE OF CONTENTS

ABSTRACT.............................................................................................................. IIIACKNOWLEDGEMENT............................................................................................. IVTABLE OF CONTENTS............................................................................................... V

LIST OF FIGURES...................................................................................................... XLIST OF TABLES...................................................................................................... XI

CHAPTER 1 INTRODUCTION.......................................................................................1

1.1 General ....................................................................................................................1

1.2 Dwelling or Residential areas design .....................................................................1

1.3 Project Objectives ..................................................................................................2

1.4 Outline .....................................................................................................................2

CHAPTER 2 ILLUMINATION SYSTEMS.........................................................................4

2.1 Indoor lighting ........................................................................................................4

2.1.1 Introduction ...................................................................................................4

2.1.2 Basic Definitions ...........................................................................................4

2.1.3 Types of lamps ..............................................................................................6

2.1.4 Designing of the lighting scheme ...............................................................11

2.1.5 method of calculations ................................................................................12

2.2 Street lighting: .......................................................................................................17

2.2.1 Introduction: ................................................................................................17

2.2.2 Arrangement of luminaries .........................................................................17

Street lighting arrangements...............................................................................18

Curves 19

2.2.3 Choose of lamps for street lighting .............................................................20

2.2.6 Calculation of street lighting: ...................................................................20

2.2.4 llumination level for street for lighting and mounting height of lamps .....21

2.2.5 Methods of streets lighting design ..............................................................22

2.3 Comparison between good and bad design of outdoor lighting .......................... 22

2.3.1 Bad Lighting design Examples ...................................................................23

2.3.2 Good Lighting design Examples ...............................................................24

CHAPTER 3 BRANCH CIRCUIT DESIGN.......................................................................26

3.1 Introduction ...........................................................................................................26

3.2 General ..................................................................................................................26

3.2.1 The definition of branch circuit ..................................................................27

3.2.2 General purposes of branch circuit: ............................................................27

3.2.3 Individual branch circuit: ............................................................................27

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3.2.4 Multi wire branch circuit : ..........................................................................27

3.2.5 Rating of branch circuit: .............................................................................27

3.2.6 The electrical requirements for place have equipment or devices: ............28

3.2.7 Ungrounded conductors: .............................................................................29

3.3 Lighting branch circuit: ........................................................................................30

3.3.1 The electrical applications of different voltages: ......................................30

3.3.2 Continuous and non-continuous loads: .....................................................31

3.3.3 The ground fault circuit interrupter protection for personnel: ..................33

3.3.4 Storage or equipment: ................................................................................33

3.3.5 Other than dwelling units: ...........................................................................33

3.3.6 Lighting outlets required: ...........................................................................33

3.3.7 15-and 20- ampere branch-circuit: ...........................................................34

3.3.8 30-ampere branch circuits: ........................................................................34

3.3.9 Required outlets ........................................................................................34

3.3.10 Dwelling unit receptacle outlets: ............................................................35

3.3.11 40 and 50 Ampere branch circuit: ..........................................................35

3.3.12 Branch circuits larger than 50 amperes: .................................................35

3.4 Receptacles ............................................................................................................35

3.4.1 Single Receptacle on an Individual Branch Circuit: ..................................35

3.4.2 Total Cord-and-Plug-Connected Load: ......................................................35

3.4.3 Receptacle Ratings ......................................................................................36

3.4.4 Branch-Circuit Requirements Summary ...............................................36

3.4.5 Dwelling Unit Receptacle Outlets ..............................................................37

3.4.6 Spacing ........................................................................................................38

3.4.7 Wall Space ..................................................................................................383.4.8 Floor Receptacles ........................................................................................38

3.4.9 Bathrooms ...................................................................................................39

3.4.10 Hallways ...................................................................................................40

3.4.11 Heating, Air-Conditioning, and Refrigeration Equipment Outlet ..........40

3.4.12 Receptacle Outlets ...................................................................................40

3.4.13 Small Appliance Circuit Load .................................................................42

3.4.14 Appliance Load Dwelling Unit(s) ......................................................42

3.4.15 Heating and Air-Conditioning Load ........................................................43

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3.5 Motor Branch Circuit Design ...............................................................................44

3.5.1 Motor Overload protection .........................................................................45

3.5.2 Motor Branch-Circuit Short-Circuit and Ground-Fault Protection ...........46

3.6 Components of low voltage distribution system ..................................................49

3.6.1 Distribution transformer .............................................................................50

3.6.2 Distribution boxe (Pillar) ............................................................................50

3.6.3 Building box (coffree) ................................................................................51

CHAPTER 4 CABLE SIZING AND PANELBOARDE DESIGN............................................52

4.1 Introduction ...........................................................................................................52

4.2 Under Ground Cables ...........................................................................................52

4.2.1 Introduction .................................................................................................52

4.2.2 Basic definition ...........................................................................................53

4.2.3 Main Requirements OF Cable ....................................................................55

4.2.4 General construction of cables ....................................................................55

4.2.5 Type and classification of cables ................................................................62

4.2.6 Method of laying under ground cables ......................................................64

4.2.7 Method of laying under ground cable in special location ..........................65

4.2.8 Cable Sizing ................................................................................................66

4.2.9 Voltage drop calculation: ............................................................................69

4.2.10 Calculation of short circuit current ..........................................................70

4.3 Panelboards and power factor improvement ........................................................70

4.3.1 Panel boards ................................................................................................70

The selection of circuit breaker is based on: ......................................................76

4.3.2 Power Factor Improvement ........................................................................76

CHAPTER 5 GROUNDING AND STANDBY SYSTEMS....................................................78

5.1 Introduction ...........................................................................................................78

5.2 The main objectives of the grounding are to: .......................................................78

5.3 The qualities of a good grounding system are: ....................................................78

5.4 System Grounding: ...............................................................................................78

5.5 IEC nomenclature: ................................................................................................79

5.5.1 TN network: ................................................................................................80

5.5.2 TN-S: ...........................................................................................................81

5.5.3 TN-C: ..........................................................................................................815.5.4 TN-C-S grounding system: .........................................................................82

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5.5.5 TT network: ...............................................................................................83

5.5.6 IT network: ..................................................................................................83

5.5.7 Example of The Various Earthing Systems Included In The Same

Installation :: .........................................................................................................84

5.6 Earth Conductors: .................................................................................................84

5.6.1 Conductor sizing : .......................................................................................85

5.7 Earth Electrodes: ...................................................................................................86

5.7.1 Rod Electrode: .............................................................................................87

5.7.2 Plates: ..........................................................................................................88

5.7.3 Earth Plates (courtesy A N Wallis and Co): ...............................................88

5.8 Earth Resistivity and Design of Driven Grounding: ............................................88

5.8.1 Calculation Procedure: ................................................................................88

5.9 Lightning Protection .............................................................................................92

5.9.1 Introduction: ................................................................................................92

5.9.2 Risk Assessment: ........................................................................................93

5.9.3 Components of the Lightning Protection System: .....................................94

5.9.4 Air terminations: .........................................................................................94

5.9.5 Down leads and bonding conductors: .........................................................95

5.9.6 Earth termination: .......................................................................................95

5.9.7 Electrical Safety in the Workplace: ............................................................95

5.9.8 Ten Golden Rules: ......................................................................................95

5.10 Emergency and standby systems .......................................................................97

5.10.1 Introduction ...............................................................................................97

5.10.2 Definitions ................................................................................................97

5.10.3 Main idea ...................................................................................................975.10.4 Tests and Maintenance ..............................................................................98

5.10.5 Capacity .....................................................................................................99

5.10.6 Generator Set .............................................................................................99

5.10.7 Precautions should be made before using emergency and standby

systems 100

CHAPTER 6 HELIOPOLIS SPORTING CLUB HOUSING PROJECT CASE STUDY..............103

6.1 General ...............................................................................................................103

6.2 Models A and B .................................................................................................105

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6.2.1 Model A description ................................................................................105

6.2.2 Model A, flat type1( 145 m2): ..................................................................105

6.2.3 Model A, flat type2( 120 m2): ................................................................107

6.2.4 Model A, Riser and feeder calculations: ..................................................108

6.2.5 Elevator calculations .................................................................................109

6.2.6 Calculation of the main feeder for model A: ...........................................110

6.3 Models C and D .................................................................................................112

6.3.1 Model C, flat type1( 115 m2): ..................................................................112

6.3.2 Model C, flat type2( 145 m2): ..................................................................114

6.3.3 Model C, Riser and feeder calculations: ...................................................115

6.4 Outdoor lighting .................................................................................................118

6.4.1 Lighting Pillars calculations: ....................................................................118

6.5 Transformer Calculations ...................................................................................119

6.5.1 Transformer sizing ....................................................................................119

6.5.2 Short circuit calculation ...........................................................................128

6.6 Summary .............................................................................................................130

CHAPTER 7 CONCLUSIONS..................................................................................... 131

7.1 General ................................................................................................................131

7.2 Conclusions ........................................................................................................131

APPENDIX A: LUMINAIRES DATA........................................................................ 133APPENDIX B: CABLES DATA.................................................................................142

APPENDIX C GROUNDING DATA...........................................................................148

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LIST OF FIGURES

Figure 2-1 Filament Lamp...............................................................................................6Figure 2-2 Fluorescent lamps............................................................................................9

Figure 2-3 OSRAM clear Mercury vapour lamp HQA 80 Watt............................10Figure 2-4 OSRAM colour corrected Mercury vapour lamp HQL 80........................................11

Figure 2-5 Single sided arrangement................................................................................18Figure 2-6 Staggered arrangement....................................................................................18Figure 2-7 Opposite arrangement.....................................................................................19

Figure 2-8 Middle arrangement.......................................................................................19Figure 2-9 Bad street lighting design.................................................................................23

Figure 2-10 Bad canopy lighting design.............................................................................24Figure 2-11 Good street lighting design.............................................................................24

Figure 2-12 Good canopy lighting design...........................................................................25Figure 3-13 Branch circuit layout.....................................................................................27

Figure 3-14 Combination receptacle.................................................................................28Figure 3-15 Combination receptacle and switch...................................................................29

Figure 3-16 Multiconductor armoured cable.......................................................................29 Figure 3-17 Branch circuit panelboard...............................................................................30Figure 3-18 Street-tunnel lighting....................................................................................31

Figure 3-19 Continuous load branch circuit........................................................................32Figure 3-20 Dwelling unit receptacle outlets.......................................................................37

Figure 3-21 Wall space.................................................................................................38Figure 3-22 General load branch circuit.............................................................................39

Figure 3-23 Receptacle outlets........................................................................................41Figure 3-24 Receptacle branch circuit...............................................................................42

Figure 3-25 A main distribution center supplying individual branch..........................................48Figure 3-26 A feeder supplying individual branch circuits to each motor.....................................48

Figure 3-27 A 20-ampere branch circuit supplying lighting, small motors, and appliances...............49Figure 3-28 A motor branch circuit showing the essential parts................................................49

Figure 4-29 Hand hole enclosure.....................................................................................55Figure 4-30 construction of cable.....................................................................................56

Figure 4-31 Aluminium cable.........................................................................................57Figure 4-32 Copper cable..................................................................57

Figure 4-33 Insulation materials................................................................58Figure 4-34 Single core cable..........................................................................................63

Figure 4-35 Multicore cable...........................................................................................63Figure 4-36 Direct laying method....................................................................................65

Figure 4-37 Road crossing.............................................................................................65Figure 4-38 In tunnel....................................................................................................66

Figure 4-39 A panelboard with main circuit breaker disconnect, suitable for use as service equipment.. .72

Figure 4-40 An arrangement of three individual lighting and appliance branch circuit panelboards with

main overcurrent protection remote from the panelboards.......................................................73Figure 4-41 Circuitry for a 200-ampere (left) and a 150-ampere (right) split-bus panelboard............73

Figure 5-42 TN system.................................................................................................80Figure 5-43 TN-S system...............................................................................................81

.Figure 5-44 TN-C system.............................................................................................82Figure 5-45 TN-C-S system............................................................................................82

Figure 5-46 TT system..................................................................................................83Figure 5-47 IT...........................................................................................................84

Figure 6-48 Landscape of the buildings area.....................................................................103Figure 6-49 Picture for the entire buildings.......................................................................104

Figure 6-50 single line diagram for x-Floor of model A.......................................................106Figure 6-51 single line diagram of the ground floor in model A.............................................108

Figure 6-52 MDB for buildings of model A......................................................................111 Figure 6-53 single line diagram of ground floor of model C..................................................113Figure 6-54 single line diagram of x- floors of model C.......................................................115

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Figure 6-55 MDB of buildings of model C.......................................................................118

LIST OF TABLES

Table 2-1 Main characteristics of incandescent lamp...............................................................7Table 2-2 Advantages and Disadvantages of Fluorescent Lamps.................................................9

Table 2-3 VA per square meter [NEC]..............................................................................13Table 2-4 Utilization factor table.....................................................................................17

Table 2-5 Arrangement of Luminaires...............................................................................17Table 2-6 Primary initial design.......................................................................................21

Table 3-7 Maximum Cord-and-Plug-Connected Load to Receptacle..........................................35Table 3-8 Receptacle Ratings for Various Size Circuits..........................................................36

Table 3-9 Summary of Branch-Circuit Requirements............................................................36Table 3-10 Motor overload protection...............................................................................45

Table 3-11 Motor overload relay protection........................................................................45Table 3-12 Motor thermal protector..................................................................................45

Table 3-13 motor branch circuit short-circuit and ground-fault protection...................................47Table 4-14 Comparison between Copper and Aluminium materials...........................................56

Table 4-15 the main properties of insulating material............................................................59Table 4-16 Ambient temperature (A)................................................................................69

Table 5-17 IEC nomenclature.........................................................................................79Table 5-18 IEC nomenclature.........................................................................................79

Table 5-19 Three variants of TN systems...........................................................................80Table 5-20 Formulas for Calculation of Resistances to grounding.............................................89

Table 5-21 Resistivity of Different Soils............................................................................90Table 5-22 Effect of Moisture Content on Resistivity of Soil...................................................91

Table 5-23 Effect of Temperature on Resistivity of Sandy Loan, 15.2 Percent Moisture................91Table 6-24 loads in VA of flat 145 m2 , model A...............................................................105Table 6-25 loads in VA of flat 120 m2 , model A...............................................................107

Table 6-26 Total VA connected to the feeder of buildings of model A......................................110Table 6-27 Loads in VA of flat 115 m2 , model C..............................................................112

Table 6-28 Loads in VA of flat design 145 m2, model C......................................................114Table 6-29 total VA connected to the feeder of model C.......................................................116

Table 6-30 Actual design of street lighting.......................................................................118 Table 6-31 Available Short Circuit Current for Transformers.................................................129Table 6-32 Short circuit calculation for AL cables..............................................................129

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Table 6-33 Short circuit calculation for CU cables..............................................................129

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Chapter 1 Introduction

CHAPTER 1 INTRODUCTION

General

The distribution of electrical energy on a consumers premises begins at

the supply intake position. The latter can take many forms depending on the type

of premises from the simple single phase arrangement in domestic premises to a

large private substation supplying an industrial complex. Whatever the size of the

installation, however certain basic requirements statutory and otherwise must be

satisfied. The main function of any internal distribution system is to divide and

subdivide the total load at the consumers terminal into small individual loads,each of which is protected and controlled by suitable rated protective devices and

switches.

1.2 Dwelling or Residential areas design

Dwelling Unit is a single unit, providing complete and independent living

facilities for one or more persons, including permanent provisions for living,

sleeping, cooking and sanitation. Dwelling unit could be One-Family which is a

building that consists solely of one dwelling unit or a Multifamily which is a

building that contains two, three or more dwelling units.

In residential areas planning, careful consideration needs to be given to the

spatial quality of layouts. Roads and buildings must be designed and located to

ensure that the scale of space between buildings is related to the pedestrian, i.e.

on a human scale and not large nor impersonal. In mixed development schemes,

open spaces should be illuminated and related to building height to provide

variety and interest and careful thought given to its intended function.

This project will focus in the electrical distribution system design for

residential areas. This will cover not only the indoor or interior design of the

building but also the outdoor design. The outdoor design includes, the design of

street lighting, outdoor pillars and electrical transformers sizing.

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1.3 Project Objectives

Generally, the main objective of designing an electrical distribution system for

any application is to achieve the consumer requirements in acceptableengineering way. The design procedure itself contains the following tasks:

Determining

the correct size of cables.

Choosing the

suitable capacity for switchgear system.

Deducing the

current rating of overcurrent devices.

So, in order to achieve these tasks, there are many considerations must be taken

into account as:

Subdivision

and number of circuits needed.

Nature and

type of electrical loads.

Normal

current of protective devices.

Different cable

derating factors.

Necessary

design checks such as voltage drop and short circuit calculation.

1.4 Outline

The thesis is structured into seven chapters and three appendixes as follows:

Chapter 1: general, objectives, and thesis outline are described.

Chapter 2:presents a detailed design of lighting scheme including indoor

lighting, street lighting, and comparison between good and bad design.

Chapter 3: explains the load estimation and design of lighting branch circuit,

receptacles, and motors branch circuit.

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Chapter 4: in this chapter cable sizing and panelboard design are detailed for

comprehensive design.

Chapter 5: covers the grounding and standby systems which are required for safe

and reliable operation of any electrical system design.

Chapter 6: discusses the capabilities of the proposed design procedure by

deigning a real case study.

Chapter 7: summarises the work and highlights the main conclusions.

Appendix A: includes the main luminaires data required for lighting calculation.

Appendix B: includes the main cables data required for branch circuit and cable

sizing.

Appendix C: contains main important grounding data.

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Chapter 2 Illumination Systems

CHAPTER 2 ILLUMINATION SYSTEMS

2.1 Indoor lighting

2.1.1 Introduction

Light is the prime factor in the human life as all activities of human beings Ultimately

depend upon the light.

Light on surfaces on which it falls. Thus the illumination makes the surface look more

or less bright with a certain colour and is this brightness and colour which the eye sees

and interprets as something useful, or pleasant or otherwise. Where there is no natural

light, use of artificial light is made. Artificial lighting produced electrically, on account

of its cleanliness ease of control, reliability, steady output, as well as its low cost. Is

playing an increasingly important part in modern every day life. Light may be

produced by passing electric currents through filaments as in the Incandescent lamps,

through arcs between carbon or metal rods, or through suitable gases as in neon and

other gas tubes. In some forms of lamps the light is due to fluorescence excited by

radiation arising from the passage of electricity through mercury vapour.

2.1.2 Basic Definitions

- Light

It is defined as the radiant energy from a hot body, which produces the visual sensation

upon the human eye.

- Luminous Flux ( ):

It is defined as the total quantity of light energy emitted per second from a luminous

body. It is represented by symbol F and is measured in lumens.

-Illumination ( E )

The number of lumens, falling on the surface per unit area. It is denoted by symbol E

and is measured in lumens per square meter or lux.

E

=

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-Luminous Intensity ( I)

The luminous flux from a source, In a specified direction inside a small solid angle.

And measured in lumen per steradian or candela (cd)

I

=

- Luminance ( L )

It is the intensity per apparent unit area of the surface of the actual light source. And

measured in candela per square meter (cdm-2)

IL

A=

-Reflectance (Error! Objects cannot be created from editing field codes.):

The ratio of reflected flux to incident flux (either luminous or radiant)

Luminous Efficacy ( )

It is defined as the ratio of the luminous flux to the power input, And measured in

lumen per watt ( -1lumen W ).

-Utilization factor (U.F.)

The ratio of the lumens actually received by a particular surface to the total lumens

emitted by a luminous source. This factor is varies widely according to the following

factors:

a-The type of lighting system whether it is direct or indirect.

b-The shape and relative dimension of the room.

c-The wall surface and its colour fit reflectance of light.

-Maintenance factor (M.F.)

During the deterioration of lamp accumulation of dust on the globes and reflectors, the

efficiency of reflection of light from walls due to the insufficient clearing. The

illumination under normal conditions usually less than that when every thing is

perfectly clear the relative between the two cases is the maintenance factor.

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The following comparison illustrates this point:

Table 2-1 Main characteristics of incandescent lamp

Lamp type

Light

Output

(Lumens)

Efficacy

(lumens/watt)

100W GLS 1350 13.5

100W Double Life 1200 12.0

100W Plus life 1050 10.5

- Incandescent Lamp Advantages

(1) Simple to use - direct connection into socket.

(2) Lowest initial lamp cost.

(3) Immediate starting and re-starting - no warm-up or cool down required.

(4) Excellent optical control - concentrated light source is easiest to direct or focus.

(5) Easiest to dim - simple variable resistor circuitry may be all that is required.

(6) Wide design flexibility - variety of styles, outputs, and colours fill nearly every

need.

(7) Output not affected by operation over a wide range of ambient temperature.

(8) Available in wattage ratings from 10 to 100W.

- Incandescent Lamp Disadvantages

(1) Sensitive to shock and vibration .

(2) High overall operating cost - low efficacy and short life.

(3) Sensitive to voltage variations

(4) Sensitive to thermal shock - high bulb surface temperature requires that the lamp

be protected from moisture. Exceptions are hard glass bulbs and low wattage lamps

(less than l0W). Lowest efficacy - all other lamp types surpass incandescent

performance by a large margin.

(ii) Halogen Lamps

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A halogen lamp is a special kind of incandescent lamp. The light output is more

consistent than a standard incandescent lamp and the life is longer. Size is smaller

because it is important for the halogen cycle to have a high bulb wall temperature,

which requires quartz or hard glass to be used. Better beam control is possible because

of the small source size. Basic Halogen Lamp Types The common types of halogen

lamps are:

(1) Linear (sometimes called double-ended)

(2) Single-ended

(3) Capsule (single-ended but no outer bulb)

(4) PAR (capsule contained in PAR shape bulb) Used for gardens or stage lighting.

Also known as spot or reflector lamps Lens

(5) Low Voltage Reflector (Precise lamps)

(A) Features Of The Halogen Lamps

(1) Luminous Efficacy :

Luminous efficancy increases with higher tungsten temperature. Using Xenon (larger

atoms) the temperature can be raised to increase the luminous efficacy by 5%-10%

and colour temperature by about 100 degrees Kelvin. Xenon can only be used in low

voltage lamps because the lower ionizing energy of Xenon would lead to an electrical

discharge with higher voltages.

(iii) Fluorescent Lamps

The fluorescent lamp is commonly used. It has hundreds of sizes, wattage, colours,

voltages and specific application designs the typical fluorescent lamp is a hot cathode

type, consisting of a sealed glass tube containing a mixture of inert gas and mercury

vapour. The cathode causes a mercury arc to form inside the tube. This arc produces

ultraviolet (UV) light, which is not visible to the naked eye. The UV light strikes the

phosphors coating that is inside of the tube which will fluoresce producing visible

light. By changing the type of phosphors, the lamp colour, output can be controlled.

The fluorescent lamp requires a ballast in its circuit. Its purpose it limits the current in

the circuit, without the ballast the lamp would draw excessive current, and the fuse or

circuit breaker would open. The lamp also

consists of a starter, which acts as switch.

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Figure 2-2 Fluorescent lamps

(A) The life of fluorescent lamps

Fluorescent lamps have outstandingly long life. This life however is affected by the

number of times the lamp is turned on and off, since switching tends to wear out the

cathode. An average fluorescent lamp burned continuously will last about 30000hours;

with 3 burning hours per start, it will last about 12000hours.Most users replace lamps

when they reach about 75% of burn out life because the light output has dropped at that

point to about two third.

(B) Power Factor of Fluorescent LampOrdinary incandescent lamps have a power factor of 100%. A fluorescent lamp

connected to a circuit has a power factor of somewhere between 50% and 65% to

improve power factor.

(C) Advantages and Disadvantages of Fluorescent Lamps

Table 2-2 Advantages and Disadvantages of Fluorescent Lamps

Advantages Disadvantages

Low surface brightness Requires a ballast and sometimes a starter

Low heat output Sensitive to ambient temperature

Low bulb wall temperature Ballast may produce audible hum if

not operated by an electronic ballast

Variety of colours Lamp flicker may irritate some

occupants if not operated by an electronic

ballast

Long life (easier maintenance) Colour rendering not as good asincandescent, but can be very close

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Reduced shadowing

Efficiency is much higher

(D) Compact Fluorescent

Compact fluorescent lamps resulted from research into energy saving lighting. The

goal was to develop smaller, more efficient light sources with greater lumen output

per watt. One solution was to re-design the fluorescent lamp and its cap. Two basic

designs have emerged:

(1) Biaxial

(2) Square plane

The internal construction and function of all variants is very similar to linear (straight)

fluorescent lamps.

(iv) Discharge Lamps

Gas discharge lamps are used in virtually all areas of modern lighting

As for fluorescent lamps the electrical energy is transformed into radiated energy by

the discharge through a gas/metal vapour, The spectral distribution is dependant on the

chemical and the pressure/temperature of the discharge

(A) Types of Discharge Lamps

(1) Low Pressure Sodium

(2) High Pressure Sodium

(3) High Pressure Mercury

(4) Metal Halide

Figure 2-3 OSRAM clear Mercury vapour lamp HQA 80 Watt.

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Figure 2-4 OSRAM colour corrected Mercury vapour lamp HQL 80

The choice of colours, size and rating is greater for Metal Halide than any other lamp

type Some Metal Halide lamps use a third electrode for starting, but other, especially

the smaller display lamps, require a high voltage ignition pulse The halides act in a

similar manner to the tungsten halogen cycle. As the temperature increases there is

disassociation of the halide compound releasing the metal into the arc. The halides

prevent the quartz wall getting attacked by the alkali metals.

2.1.4 Designing of the lighting scheme

(i) Some factors should be considered(1) Illumination level:

This is the most vital factor because a sufficient illumination is the basic means by

where we are able to see our surroundings; it is the task of illumination to give objects

a distributed brightness.

Objects which are seen for longer duration of time require more illumination than

those for casual work. Similarly moving objects require more illumination than those

for stationary object.

(2) Colour of light:

The appearance of the body colour entirely depends upon the colour of the incident

light. In general the composition of the light should be such that the colour appears

natural i.e. its appearance by artificial light is not appreciably different from that by

day light.

(3) Shadows:

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In lighting installations, formation of long and hard shadow causes fatigue of eyes and

therefore is considered to be a short coming. Complete absence of shadows altogether

again does not necessarily mean an ideal condition of lighting installations.

(4) Mounting Height:

The mounting height will largely be governed by the type of building and type of

lighting scheme employed. In the case of direct lighting, in rooms of large floor area,

the luminaries should be mounted as close to the ceiling as possible. Lowering them

not only will make the illumination less uniform, but will also bring them more into the

field of vision, thus increasing the glare, without causing an appreciable increase in the

coefficient of utilization. In the usual case of small

rooms with high ceilings, there is something to be gained by lowering the luminaries.

(5) Spacing of luminaries:

Correct spacing is of great importance to provide uniform illumination. With

fluorescent luminaries it is good practice to aim at a value of unity for this ratio, and to

set an upper limit of () In this case of tungsten lamps combined with focusing

reflectors, it is good practice to aim at a horizontal spacing between rows

approximately equal to the height of the ceiling above the working plane, and in

no case should the horizontal spacing exceed 1 times this height.

(6) Colour of surroundings walls:The illumination in any room depends upon the light

reflected from the walls and ceiling. White walls and ceiling reflect more light as

compared to colored ones

2.1.5 method of calculations

For lighting distribution calculations, two methods are introduced:(1) VA method.

(2) Lux method.

(i) the VA method

The procedures:

(1) Determine the area of the room, (A) =width X length.

(2) Identify VA/m2 according to the room purpose.

(3) Total VA = (VA/m2) x area (A).

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(4) Identify the used luminary type.

(5) Calculate the output VA of one luminary.

(6) Number of luminaries = (total VA) / (VA of one luminary).

(7) Calculate the proposed number of luminaries.

(8) Calculate the new total VA.

(9) Distribute the number of luminaries on the area

Table 2-3 VA per square meter [NEC]

Type of occupancy Unit load

VA per square meter

BanksChurches

Clubs

Court rooms

Dwelling units

Hospitals

Industrial commercial buildings

Lodge rooms

Office buildings

Restaurants

SchoolsStores

Halls, corridors, stairways

Storage spaces

Bathroom

Cafeteria

Rest room

3911

22

22

33

22

22

17

39

22

3333

6

3

32.26

22

32.26

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(ii) by using lux method

The lumen method is used in calculating the average illuminance Eon the working

plane in an interior. This is defined as:

EA

=

where is the lighting flux [lumen], and A is the working plane area .A coefficient of

utilisation (UC) gives the fraction of lamp lumens that reach the workplane, directly

from sources and from inter-reflections. TheUC takes into account the efficiency of

the luminaire and the impact of the luminaire distribution and the room surfaces in its

derivation. Thus the number of lumens produced by the lamps, multiplied by thisUC ,

determines the number that reaches the workplane:

UcE=

Since the design objective usually is maintained illuminance, a light loss factorLLF

must be applied to allow for the estimated depreciation in lamp lumens over time, the

estimated losses from dirt collection on the luminaire surfaces (including lamps), and

other factors that affect luminaire lumen output over time. Theformula thus becomes

UC LLF E

A

=

Although design calculations are based on the LLF using both non-recoverable and

recoverable factors, it is sometimes necessary to calculate illuminance in a new

lighting installation. In such cases, repeat the calculation using the non-recoverable

losses, since the recoverable losses do not occur at 100 hours, the time at which lamps

are nominally at rated lumens[16].The lamp lumens in the formula are most

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conveniently taken as the total rated lamp lumens in the luminaires. If the desired

maintained illuminance is known, this equation can be solved for the

total number of luminaires needed:

E ANOL

LPL LL UC LLF

=

where NOL is the number of Luminaires, LL is the lamp lumen and LPL is the

number of lamps per luminaire.

(A) Limitations

The illuminance computed by the lumen method is an average value that is

representative only if the luminaires are spaced to obtain reasonably uniform

illuminance. The calculation of the coefficients of utilisation is based on empty

interiors having surfaces that exhibit perfectly diffuse reflectance. The average

illuminance determined by the lumen method is defined to be the total lumens reaching

the workplane divided by the area of the workplane. The average value

determined this way might vary considerably from that obtained by averaging discrete

values of illuminance at several points [16].

(B) Cavity Ratios

The radiative exchange between the top and the base of a rectangular space is a

function of the proportions of its length, width, and height. Cavity ratio values

approximate this effect by combining these proportions into a single quantity. In the

Zonal-cavity method, the effects of room proportions, luminaire suspension length, and

workplane height upon the coefficient of utilisation are respectively represented by the

room cavity ratio, ceiling cavity ratio, and floor cavity ratio. These ratios are

determined by dividing the room into three cavities, and substituting dimensions (in m

or ft) into the following formula[16, 17]:

5 ( )h l wCRl w+=

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where CR is the cavity ratio, h is the cavity height, l is the cavity length, and w is

the cavity width. The illuminance in rooms of irregular shape can be determined by

calculating the room cavity ratio using the following formula and solving the problem

in the usual

manner:

2.5h CCCR

CA

=

where CA is the cavity base area, and CC is the cavity circumference.

(C) Effective Cavity Reflectances

Table 2-10 provides a means of converting the combination of wall and ceiling or wall

and floor reflectances into a single effective ceiling cavity reflectance, CC ,and a

single effective floor cavity reflectance, FC . In lumen method calculations, the

ceiling, wall, and floor reflectances should be initial values. Note that for surface-

mounted and recessed luminaires, the ceiling cavity ratio equals zero and the actual

ceiling reflectance may be used for CC . Luminaires coefficient of utilization:

Absorption of light in a luminaire is taken into account in the computation of

coefficient of utilisation (UC) for that luminaire. Appendix A is a tabulation of

coefficients of utilisation calculated by the Zonal-cavity method for representative

luminaire types. These coefficients are for an effective floor cavity reflectance of 20%,

but any UC obtained from the table may be corrected for a different value of FC by

applying the appropriate multiplier from table Since the light loss factor includes the

effect of dirt deposited on wall surfaces, the selection of the proper column of wall

reflectances, W , should be based on the initial values expected. The wall reflectance

should also represent the weighted average of the reflectances of the painted areas,

fenestration or daylight controls,

chalkboards, shelves, and so forth in the area to be lighted. The weighting should be

based on the relative areas of each type of surface within the cavity being considered.

In using, it is often necessary to interpolate between room cavity ratios CR and

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effective ceiling cavity reflectances. This is most easily accomplished by interpolating

first between room CR to obtain CU for effective

ceiling cavity reflectances that straddle the actual CC

, and then interpolating between

these CU values.As a guide line the following utilisation factors can be adopted with

good accuracy for most applications [39]:

Table 2-4 Utilization factor table

Type of illumination Approximate Utilisation factor

Range average

Direct 0.45:0.6 0.53

Manly direct 0.4:0.55 0.48

Uniform 0.35:0.50 0.43

Mainly indirect 0.35:0.45 0.4

Indirect 0.2:0.35 0.28

Indirect (cornice) 0.10:0.20 0.15

2.2 Street lighting:

2.2.1 Introduction:

With the increase of high-speed traffic upon our roads, it has become essential ,in order

to reduce accidents, to provide adequate illumination on all streets ,roads, traffic

junctions, tunnels, bridges etc.

2.2.2 Arrangement of luminaries

The next table shows the most used type of arrangement according to height-to-width

Ratio:

Table 2-5 Arrangement of Luminaires

type of arrangement Ratio (height of luminaries / width of

carriage way)

Single sided 0.85(min. value) 1(recommended value)Staggered 0.5(min. value) 2/3(recommended value)

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opposite 1/3(min. value) ( recommended value)

Street lighting arrangements

2.2.3.1 Two way traffic roads

There are four basic types of street lighting arrangements, which can be

summarized in the following points.

Single sided

This type of arrangement, in which all luminaries are located on one side of the

road, is used only when the width of the road is equal to, or less than the mounting

height of the luminaries. This is shown in the next figure.

Figure 2-5 Single sided arrangement

Staggered or zigzag array

This type of arrangement in which the luminaries are located on both sides of the

road in a staggered or zigzag arrangement is used mainly when the width of the road is

between 1 to 1.5 times the mounting heights of the luminaries.

Figure 2-6 Staggered arrangement

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Opposite double side array

This type of arrangement, with the luminaries located on both sides of the road

opposite to one another, is used mainly when the width of the road is greater than 1.5

times the mounting height of the luminaries.

Figure 2-7 Opposite arrangement

Middle one side array

This type of arrangement, with the luminaries suspended along the axis of the road,

is normally used for narrow roads that have buildings on both sides.

Figure 2-8 Middle arrangement

Curves

Curves of large radius (in the order of 300 m) can be treated as straight roads and the

luminaries can be sited in accordance with one of the schemes outlined above.

The locations of luminaries on curves of smaller radius, however, should be such as

to ensure both adequate road-surface luminance and effective visual guidance. Where

the width of the road is 1.5 m less than the mounting height, the luminaries should be

placed above the outside of the curve in a single sided arrangement.

For wider roads an opposite arrangement should be used since the staggered

arrangement gives visual guidance, and should therefore be avoided.

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2.2.3 Choose of lamps for street lighting

(i) The selection of luminaries according to its lighting distribution

two way streets crowded streets and high way crosses and intersection.

(ii) Type of lamps which are used for street lighting

(A) Low pressure sodium lamp.

-law pressure sodium lamps are the best for:

More sharpness vision. High speed response. Less discomfort glare.

Obtain large brightness area at the same value.Note: the power used in high ways is usually:-150 W for 12 m width street.

-200 W for 15 m width streets.

(B) High pressure sodium lamps

High pressure sodium lamps are the best for the crowded ways because it can

transmitted the colours.

Note:

The power which is used in crowed ways is:

-150 W/12 m.-250 or 400 W/15 m.

2.2.6 Calculation of street lighting:

. .F M F U FE

W L

=

Where:

F: total luminous flux of the lamp.

UF: utilization factor ranges from (0.2:0.6).

MF: maintenance factor (0.8:0.9).

L: space between the poles in meter.

W: width of the road in meter.

E: Average illumination over the working plane. (10 lux for Submain streets and upto

30 lux for main streets).

Notes:

For primary initial design the street loading can be estimated accordingto the next table.

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Table 2-6 Primary initial designE(Lux) Rout loading with 8 m

road

Rout loading with 12 m

road

High pressure

mercury lamps

High pressure

sodium lamps

High pressure

mercury lamps

High pressure

sodium lamps

26

19

13

6

4

(15:28)KW/K

m

(12:14)KW/K

m

(8:16)KW/Km

(6:10)KW/Km

4 KW/Km

(11:18)KW/K

m

(9:14)KW/Km

(6:10)KW/Km

(24:38)KW/K

m

(18:29)KW/K

m

(12:20)KW/K

m

(9:14)KW/Km

(13:20)KW/K

m

(11:16)KW/K

m

(9:12)KW/Km

2.2.4 llumination level for street for lighting and mounting height of

lamps

Table 2-7 Lux according to type of road , way

Type of road , way lux level

high way , main road and main streets 20 30 lux

Secondary road 15 20 luxResidential area street ,industrial area street 10 15 lux

Table 2-8 Table of luminous flux of luminaries according to Mounting height of

luminaries

luminous flux of luminaries Mounting hight of luminaires

3000 to 10000 6 to 7 meter

10000 to 20000 7 to 9 meter

More than 20000 more than 9 meter

Example for street lighting

For 300 meter road of width 12 meter , compute the luminaries spacing (L) for average

illumination of E = 30 LUX using 250 watt h.p. sodium lamp of 25000 lumen (take uf

= 0.33 , Mf = 0.9 , pole height 6 meter)

Solution:

25000 0.9 0.3321

12 30

F MF UFL

W E

= = =

meter

So that, number of luminaires =300

21=15 luminaires

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Note: the best tilt angle ( ) for maximum light utilization ranging from 10:15 degree

2.2.5 Methods of streets lighting design

(i) The factors which effect on the street lighting design

Passi

ng safety.

Safet

y of people.

The

region which pass through the street. Type

of street.

Numb

ers of crimes , rubbers and security requirement.

(ii) The steps which must be known design street lighting

Street

profile.

The

average lighting of street surface.

The

degree of permanent glare.

The

rate of visible direction which must be find.

The

degree of required the lighting regulation.

2.3 Comparison between good and bad design of outdoor lighting

Below are bad and good examples of outdoor lighting. Lighting with high glare will

have a bright ball of light around the fixture where as lighting that is well shielded, low

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glare, and with minimal spillage will appear with a smaller or ball of light. First we

will look at some bad lighting examples, then some good.

2.3.1 Bad Lighting design Examples

Figure 2-9 Bad street lighting design

6 Mile by Laurel Park Mall. Notice the large halos around the lamps. These are bright

400 watt HPS fixtures that have very high glare giving a harsh appearance, plus

causing unnecessary stress and distraction to the eye . This problem could be

significantly reduced by using shielded fixtures and/or reduced wattage.

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Figure 2-10 Bad canopy lighting design

Mobil gas station on NW corner of Merriman and I-96. Notice the bright balls of light

under the canopy, indicating high glare.

2.3.2 Good Lighting design Examples

Figure 2-11 Good street lighting design

Livonia City Hall's parking lot on Farmington and 5 Mile. The area uses non-excessive

flat glass shoe box fixtures rendering good visibility with low glare. Notice how halos

are smaller compared to previous pictures and the parking lot is well lit. (Camera

shows HPS brighter that the blue white Metal Halide fixtures in earlier photos).

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Figure 2-12 Good canopy lighting design

Sunoco on SW corner of 6 Mile and Farmington. Although the fixtures are not

shielded, they are recessed under the overall canopy, and because they are not overly

bright, the station is well lit and does not have obtrusive glare. Because the fixtures are

not glaring or at excessive levels, attention is not drawn away from the area or activity

because of lighting.

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Chapter 4 Branch Circuit Design

CHAPTER 3 BRANCH CIRCUIT DESIGN

3.1 Introduction

-A branch circuit is any segment of a wiring system extending beyond the final

automatic over current protective device that is approved for use as branch circuit

protection & designated by the NEC as the branch circuit protective device.

-Branch circuits generally originate in panel boards, but individual branch circuits

to motors commonly originate at individual fused switches or C.B. tapped from

bus ways.

-In an electrical system, the branch circuits are the circuits of lowest capacity and

current rating. They are the circuits to which load devices (light, motors, etc.)

are connected.

-A branch circuit consists of two wires, which carry current at a particular voltage

from protective device to utilization device. Although the branch circuit

represents the last step in the transfer of power from the service or source of

energy to the utilization devices. It is the starting point for modern design

procedures.

-Each & every branch circuit , whether for a power or lighting load in a

commercial, industrial, or residential building , should be sized for its load, with

spare capacity added where possible load growth is indicated .

-The rating of the circuit fuse or C.B. must not be less than 125% of the

continuous current load.

3.2 General

A branch circuit consists of two wires, which carry current at a particular voltage

from protected device to utilization device. Although the branch circuit represents

the last step in the transfer of power from service or source of energy to the

utilization devices, it is the starting point from modern design procedures.

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3.2.1 The definition of branch circuit

The circuit conductors between the final over current device protecting the circuit

And the outlet (load).

Figure 3-13 Branch circuit layout

3.2.2 General purposes of branch circuit:

Branch circuit that is supplies two or more outlets for lighting and other

equipment.

3.2.3 Individual branch circuit:

Branch circuit that is supplies only one utilization equipment.

3.2.4 Multi wire branch circuit :

It is consists of two or more ungrounded conductors that have voltage betweenthem and grounded conductor have equal volt between it and each ungrounded

conductor in the circuit and it is connected to neutral and the grounding of the

system

3.2.5 Rating of branch circuit:

The rate of branch circuit can be indicated according to the maximum current of

the circuit. and also the over current protective device will be rated according to

the maximum current of branch circuit.

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The wiring conductor must be withstand the current pass through it The rate of

branch circuit based to the rate of over current protective device.

For example:

Branch circuit wire with 10 AWG copper has an allowable ampacity of at least 30

ampere, however if branch circuit over current protective device is 20 ampere

circuit breaker of fuse the rating of branch circuit is 20 ampere on the size or

rating of over current protective device. The branch circuit greater than 50

ampere used to supply the non lighting loads for the industrial purposes we can

use the several single receptacles to make easy to relocation for production or

maintenance purposes such as electric welders machine.

3.2.6 The electrical requirements for place have equipment or

devices:

Receptacles, switches, lampholders, dimmers, pilot lamp and home automatic

control the receptacles can be supplied from different nominal voltages which one

half of the receptacles supply by line to neutral voltage and another half supply by

line to line voltage and this type of receptacle called split wired receptacle The

branch circuit which supply the receptacle must have an over current protective

device such as two pole circuit breakers or single pole circuit breakers which

handle Tie.

Figure 3-14 Combination receptacle

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Figure 3-15 Combination receptacle and switch

3.2.7 Ungrounded conductors:

If multiwire branch circuit supplied from different nominal voltages the under

grounded conductors in multiwire branch circuit shall be identified by separated

colour coding, marking tape ,tagging and shall be permanently posted at each

branch circuit panelboard.

Figure 3-16 Multiconductor armoured cable

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Figure 3-17 Branch circuit panelboard

3.3 Lighting branch circuit:

3.3.1 The electrical applications of different voltages:

(i) The voltages does not exceeds of 120 volt ot is used as the followings:

- luminaries(lighting fixtures).

- cord and plug connected loads 1440 VA.

the voltage of 120 volt between conductors is used to supply the followings:

-the terminals of lampholders which rated by this limit of voltage the auxiliary

equipments of electric discharge lamps such as ballasts and starting devices.

-cord and plug connected or permanently connected utilization equipment.

(ii) the voltage of 277 volt to ground used to supplies the following:

-electric discharge luminaries.

-the incandescent luminaries which supplied be voltage of 120 volt output from

Step-down autotransformer.

-lampholders which rated by this value of voltage.

-auxiliary equipments of electric discharge lamps.

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-Cord and plug connected or permanently connected of utilization equipments

The voltage of 600 volt between conductors which used to supply the electric

discharge lamps where the height of must not less than 6.7 meter for high ways

roads and bridges and less than 5.5 meter for tunnels.

Figure 3-18 Street-tunnel lighting

3.3.2 Continuous and non-continuous loads:

The rate of over current protective device must be not less than the rate of non-

continuous loads plus 125% of continuous loads.

For example:

if the continuous load is equal to 16 ampere we can select the over current

protective device according to 125%x16=20 ampere.

And the branch circuit rating can be indicated as 20 ampere.

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Figure 3-19 Continuous load branch circuit

Another example:

Determine the minimum size over current protective device and the minimum

conductor size for the following circuit:

-25 ampere of continuous load.

-60 degree over current device terminal rating.

-type THWN conductors.

-four current carrying copper conductors in a raceway.

Solution:

-the size of over current protective device =125%x25=31.5 ampere

-we can take 35 ampere as an rating

-computed load

the conductor ampacity=percent adjustment factor

-the percent adjustment factor is indicated from table at 60 degree

so that:

-the conductor ampacity=31.5

0.8=39.06 ampere

from the above we can select the conductor size which permitted to pass through

it 40 ampere at 60 degree.

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3.3.3 The ground fault circuit interrupter protection for

personnel:

When fault circuit contact with ground the high current pass through the circuit

and this value of current must be reduced by any protection methods.

3.3.4 Storage or equipment:

For attics, underfloor spaces, utility rooms, and basements at least one lighting

outlet containing or controlled by a wall switch shall be installed where these

spaces are used for storage or contain equipment requiring servicing. At least one

point of control shall be at the usual point of entry to these spaces.The lighting

outlet shall be provided at or near the equipment requiring servicing.

3.3.5 Other than dwelling units:

For attics and underfloor spaces containing equipment requiring servicing, such

as heating, air-conditioning, and refrigeration equipment, at least one lighting

outlet containing a switch or controlled by a wall switch shall be installed in such

spaces at least one point of controlled shall be at the usual point of entry to these

spaces the lighting outlet shall be provided at or near the equipment requirement

servicing.

3.3.6 Lighting outlets required:

-dwelling units:

in dwelling units, lighting outlets shall be installed in accordance with:

-habitable rooms:

at least one wall switch controlled lighting outlet shall be installed in every

habitable room and bathroom.-additional locations:

additional lighting outlets shall be installed in accordance with :

(1) at least one wall switch controlled lighting outlet shall be installed in

hallways , stairways ,attached garages, and detached garages with electric power.

(2)for dwelling unit ,attached garages ,and detached garages with electric

power ,at least one wall switch controlled lighting outlet shall le installed to

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provide illumination on the exterior side of outdoor entrances or exits with grade

level access ,a vehicle door in a garage shall not be considered as an outdoor

entrance or exit.

(3) Where one or more lighting outlets are installed for interior stairways , there

shall be a wall switch at each floor level , and landing level that includes an

entryway , to control the lighting outlets where the stairway between floor levels

has six risers or more.

3.3.7 15-and 20- ampere branch-circuit:

A 15-and 20- ampere branch-circuit shall be permitted to supply lighting units or

other utilization equipment or a combination of both, and shall comply with:

-cord and plug connected equipment not fastened in place:

the rating of any one cord and plug connected utilization equipment not fastened

in place shall not exceed 80 percent of the branch-circuit ampere rating

3.3.8 30-ampere branch circuits:

A 30-ampere branch shall be permitted to supply fixed lighting unites with heavy-

duty lampholders in other than a dwelling unit(s) or utilization equipment on any

occupancy.

A rating of any one cord-and plug-connected utilization equipment shall not

exceed 80 percent of the branch-circuit ampere rating.

3.3.9 Required outlets

-cord pendants:

a cord connector that is supplied by a permanently connected cord pendant shall

be considered a receptacle outlet

-cord connections:

a receptacle outlet shall be installed wherever flexible cords with attachment

plugs are used . Where flexible cords are permitted to be permanently connected,

receptacles shall be permitted to be omitted for such cords.

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-Appliance outlets:

appliance receptacle outlets installed in a dwelling unit for specific appliance

,such as laundry equipment , shall be installed within 1.8 m of the intended

location of the appliance.

3.3.10 Dwelling unit receptacle outlets:

This section provides requirements for 125 volt ,15 and 20 ampere receptacle

outlets ,receptacle outlets required by this section shall be in addition to any

receptacle that is part of a luminaries (lighting fixture) or appliance , located

within cabinets or cupboards.

3.3.11 40 and 50 Ampere branch circuit:

A 40-50 ampere branch circuit shall be permitted to supply cooking appliances

That are fastened in place in any occupancy. in other than dwelling unites, such

circuits shall be permitted to supply fixed lighting unites with heavy-duty lamp

holders, infrared heating units, or other utilization equipment.

3.3.12 Branch circuits larger than 50 amperes:

Branch circuits larger than 50 amperes shall supply only nonlghting out load

3.4 Receptacles

3.4.1 Single Receptacle on an Individual Branch Circuit:

A single receptacle installed on an individual branch circuit shall have an ampere

rating not less than that of the branch circuit.

3.4.2 Total Cord-and-Plug-Connected Load:

Where connected to a branch circuits supplying two or more receptacles or

outlets, Receptacle shall not supply a total cord and-plug-connected load in

excess of the Maximum.

Table 3-7 Maximum Cord-and-Plug-Connected Load to Receptacle

Circuit rating in (A) Receptacle rating in

(A)

Maximum load in (A)

15 or 20 15 12

20 20 16

30 30 24

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3.4.3 Receptacle Ratings

Where connected to a branch circuit supplying two or more receptacles or outlets,

receptacle ratings shall conform to the values listed in Table210.21(B)(3), or

where larger than 50 amperes, the receptacle rating shall not be less than the

branch-circuit rating.

Table 3-8 Receptacle Ratings for Various Size Circuits

Circuit rating in (A) Receptacle rating in (A)

15 Not over 15

20 15 or 20

30 30

40 40 or 50

50 50

A single receptacle installed on an individual branch circuit must have an ampere

rating not less than that of the branch circuit. For example, a single receptacle on

a 20-ampere individual branch circuit must be rated at 20 amperes; however, two

or more15-ampere receptacles or duplex receptacles are permitted on a 20-ampere

general purpose branch circuit. This requirement does not apply to specific types

of cord-and plug-connected arc welders.

3.4.4 Branch-Circuit Requirements Summary

Table 3-9 Summary of Branch-Circuit Requirements

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Note that the conductor size is converted to square mm in the project

design to match the Egyptian market.

3.4.5 Dwelling Unit Receptacle Outlets

This section provides requirements for 125-volt, 15- and 20-ampere receptacle

outlets .Receptacle outlets required by this section shall be in addition to anyreceptacle that is part of a luminaries (lighting fixture) or appliance, located

within cabinets or cupboards, or located more than 1.7 m (5 1/ 2 ft) above the

floor.

Figure 3-20 Dwelling unit receptacle outlets

Circuit rating 15 20 30 40

Conductor (min size)

circuit wires

14 12 10 8

Taps 14 14 14 12

Over current protection 15 20 30 40

Outlet devices

Lamp holders Any type Any type Heavy duty Heavy duty

Receptacle rating 15 max. A 15-20 A 30 A 40 or 50 A

Maximum load 15 20 30 40

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3.4.6 Spacing

Receptacles shall be installed so that no point measured horizontally along the

floor line in any wall space is more than 1.8 m (6 ft) from a receptacle outlet.

3.4.7 Wall Space

As used in this section, a wall space shall include the following:

-Any space 600 mm (2 ft) or more in width (including space measured around

corners) and unbroken along the floor line by doorways, fireplaces, and similar

openings.

-The space occupied by fixed panels in exterior walls, excluding sliding panels.-

The space afforded by fixed room dividers such as freestanding bar-type counters

or railings.

Figure 3-21 Wall space

3.4.8 Floor Receptacles

Receptacle outlets in floors shall not be counted as part of the required number of

receptacle outlets unless located within 450 mm (18 in.) of the wall.

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3.4.9 Bathrooms

In dwelling units, at least one receptacle outlet shall be installed in bathrooms

within 900 mm (3 ft) of the outside edge of each basin. The receptacle outletshall

be located on a wall or partition that is adjacent to the basin or basin countertop.

Figure 3-22 General load branch circuit

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3.4.10 Hallways

In dwelling units, hallways of 3.0 m (10 ft) or more in length shall have atleast

one receptacle outlet. As used in this subsection, the hall length shall be

considered the length along the centerline of the hall without passing through a

doorway.

3.4.11 Heating, Air-Conditioning, and Refrigeration Equipment

Outlet

A 125-volt, single-phase, 15- or 20-ampere-rated receptacle outlet shall be

installed at an accessible location for the servicing of heating, air-conditioning,

and refrigeration equipment. The receptacle shall be located on the same level

and within 7.5 m (25 ft) of the heating, air-conditioning, and refrigeration

equipment. The receptacle outlet shall not be connected to the load side of the

equipment disconnecting means.

3.4.12 Receptacle Outlets

Except as covered in 220.14(J) and (K), receptacle outlets shall be calculated at

not less than 180 volt-amperes for each single or for each multiple receptacle on

one yoke. A single piece of equipment consisting of a multiple receptacle

comprised of four or more receptacles shall be calculated at not less than 90 volt-

amperes per receptacle. This provision shall not be applicable to the receptacle

outlets specified in 210.11(C)(1) and (C)(2).As illustrated in Exhibit 220.3, the

load of 180 volt-amperes is applied to single And multiple receptacles mounted

on a single yoke or strap, and a load of 360 volt-amperes is applied to each

receptacle that consists of four receptacles. These are considered receptacle

outlets, in accordance with 220.14(I). The receptacle outlets are not the lighting

outlets installed for general illumination or the small-appliance branch circuits, as

indicated in 220.14(J). The receptacle load for outlets for general illumination in

one- and two-family and multifamily dwellings and in guestrooms of hotels and

motels is included in the general lighting load value assigned by Table 220.12.

The load requirement for the small-appliance branch circuits is 1500 volt-amperes

per circuit, as described in 220.52(A). Note in Exhibit 220.3 that the last outlet of

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the top circuit consists of two Duplex receptacles on separate straps. That outlet is

calculated at 360 volt-amperes because each duplex receptacle is on one yoke.

The multiple receptacle supplied from the bottom circuit in the exhibit, which

comprises four receptacles, is calculated at 90 volt-amperes per receptacle (4 90

VA = 360 VA). For example, single-strap and multiple receptacle

devices are calculated as follows: Device Computed Load

Duplex receptacle 180 VA

Triplex receptacle 180 VA

Double duplex receptacle 360 VA (180 2)

Quad or four-plex-type receptacle 360 VA (90 4)

Figure 3-23 Receptacle outlets

In Exhibit 220.4, the maximum number of outlets permitted on 15- and 20-

Ampere branch circuits is 10 and 13 outlets, respectively. This restriction does

not apply to outlets connected to general lighting or small-appliance branch

circuits in dwelling units.

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.

Figure 3-24 Receptacle branch circuit

Exhibit 220.4 Maximum number of outlets permitted on 15- and 20-amper branch

circuits. For circuits supplying loads consisting of motor-operated utilization

equipment that is fastened in place and has a motor larger than 1/ 8hp in

combination with other loads, the total calculated load shall be based on 125

percent of the largest motor load plus the sum of the other loads.

3.4.13 Small Appliance Circuit Load

In each dwelling unit, the load shall be calculated at1500 volt-amperes for each 2-

wire small-appliance branch circuit required by

Where the load is subdivided through two or more feeders, the calculated load for

each shall include not less than 1500 volt-amperes for each 2-wire small

appliance branch circuit. These loads shall be permitted to be included with the

general lighting load and subjected to the demand factors provided in Table

220.42.

3.4.14 Appliance Load Dwelling Unit(s)

It shall be permissible to apply a demand factor of 75 percent to the nameplate

rating load of four or more appliances fastened in place, other than electric

ranges, clothes dryers, space-heating equipment, or air-conditioning equipment,

that are served by the same feeder or service in a one-family, two-family, or

multifamily dwelling. For appliances fastened in place (other than ranges, clothes

dryers, and space-heating and air-conditioning equipment), feeder capacity must

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be provided for the sum of these loads; for a total load of four or more such

appliances, a demand factor of 75 percent may be applied. See Table 430.248 for

the full-load current, in amperes, for single phase ac motors, in accordance with

220.50.

General Loads:

The general calculated load shall be not less than 1

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