UNESCO-NIGERIA TECHNICAL &
VOCATIONAL EDUCATION
REVITALISATION PROJECT-PHASE II
NATIONAL DIPLOMA IN
ELECTRICAL ENGINEERING TECHNOLOGY
L
N
ELECTRICAL BUILDING
INSTALLATION
COURSE CODE: EEC 129
YEAR I- SEMESTER II
THEORY
Version 1: December 2008
1
Table of Contents
Week 1:
Electrical Safety--------------------------------------1
Week 2:
Electrical Safety----------------------------------------9
Week 3: Electrical and Electronics Symbols-----------------16
Week 4: Electrical and Electronics Symbols-----------------19
Week 5: Cables in Electrical installation---------------------22
Week 6: Cables in Electrical Installation---------------------24
Week7: Cables in Electrical Installation---------------------27
Week 8: Cables in Electrical Installation---------------------31
Week 9: Simple Lighting Circuits------------------------------33
Week 10: Cost Estimation in Planning-----------------------36
Week 11: Cost Estimation in Planning-----------------------39
Week 12: Electrical bill of Quantities-------------------------42
Week 13: Allocation Plan----------------------------------------45
Week 14: Allocation of Lighting and Power Points--------47
Week 15: Allocation of Lighting and Power point---------49
1. Electrical Safety
1.1
WEEK 1
Introduction
Electricity can kill. Whenever you work with power tools or on electrical circuits,
there is a risk of electrical hazards, especially electrical chocks. Working with
electricity can be dangerous. Engineers, electricians, and other professionals work
with electricity directly, including working on overhead lines, cable harnesses, and
circuit assemblies. Others, such as office workers and salespeople, work with
electricity indirectly and may also be exposed to electrical hazards.
Many workers are unaware of the potential electrical hazards present in their work
environment, which makes them more vulnerable to the danger of electrocution.
What are the Hazards?
 Contact with live parts causing shock and burns
 Faults which could cause fire
 Fire or explosion where electricity could be the source of ignition in a
flammable atmosphere
Electrical shock is caused by completing an electrical circuit by:
 Touching a live wire and an electrical ground
 Touching a live wire and another wire at a different voltage
The danger from electrical shock depends on:
 The amount1 of current through the body
 The duration of current through the body
 The path of current through the body
1
Amount of current is the number of free electrons passing, and is measured by (Ampere)
1
1. Electrical Safety
WEEK 1
Burns are the most common injury caused by electricity:
 Electrical burns
 Arc burns
 Thermal contact burns
Electric shock can cause muscle spasms, weakness, shallow breathing, rapid
pulse, severe burns, unconsciousness, or death.
In a shock incident, the path that
electric current takes through the body
gets very hot.
Burns occur all along that path,
including the places on the skin where
the current enters and leaves the body.
It’s not only giant power lines that
can kill or injure you if you contact
them. You can also be killed by a
shock from an appliance or power cord
in your home. Electrical Shock
2
1. Electrical Safety
Condition
WEEK 1
Readings
Effects
1 mA or less
Causes no sensation - not felt.
Safe Current
Values
Sensation of shock, not painful;
1 mA to 8 mA
Individual can let go at will since
muscular control is not lost.
Painful shock; individual can let go at
8 mA to 15 mA
will since muscular control is not lost.
Painful shock; control of adjacent
15 mA to 20 mA
muscles lost; victim can not let go.
Ventricular fibrillation - a heart
Unsafe Current
Values
Condition that can result in death - is
50 mA to 100 mA
possible.
Ventricular fibrillation occurs.
100 mA to 200 mA
Severe burns, severe muscular
Contractions - so severe that chest
200 mA and over
muscles clamp the heart and stop it for
the duration of the shock. (This
prevents ventricular fibrillation).
Table 1.1 Shows the dangerous of electricity according to the amount of current
Strange as it may seem, most fatal electrical shocks happen to people who
should know better. Here are some electro medical facts that should make you think
twice before taking chances.
It's not the voltage but the current that kills. People have been killed by 240
volts AC in the home and with as little as 24 volts DC. The real measure of a shock's
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1. Electrical Safety
WEEK 1
intensity lies in the amount of current (in milliamperes) forced through the body.
Any electrical device used on a house wiring circuit can, under certain conditions,
transmit a fatal amount of current.
Currents between 100 and 200 milliamperes (0.1 ampere and 0.2 ampere) are
fatal. Anything in the neighborhood of 10 milliamperes (0.01) is capable of
producing painful to severe shock.
As the current rises, the shock becomes more severe. Below 20 milliamperes,
breathing becomes labored; it ceases completely even at values below 75
milliamperes. As the current approaches 100 milliamperes ventricular fibrillation
occurs. This is an uncoordinated twitching of the walls of the heart's ventricles.
Since you don't know how much current went through the body, it is necessary to
perform artificial respiration to try to get the person breathing again; or if the heart is
not
beating,
cardio
pulmonary
resuscitation
(CPR)
is
necessary.
Prevention is the best medicine for electrical shock. Respect all voltages,
have a knowledge of the principles of electricity, and follow safe work procedures.
Do not take chances. All electricians should be encouraged to take a basic course in
CPR (cardiopulmonary resuscitation) so they can aid a coworker in emergency
situations.
Always make sure portable electric tools are in safe operating condition.
Make sure there is a third wire on the plug for grounding in case of shorts. The fault
current should flow through the third wire to ground instead of through the
operator's body to ground if electric power tools are grounded and if an insulation
breakdown occurs.
4
1. Electrical Safety
WEEK 1
1.1 First Aid
Shock is a common occupational hazard associated with working with
electricity. A person who has stopped breathing is not necessarily dead but is in
immediate danger. Life is dependent on oxygen, which is breathed into the lungs
and then carried by the blood to every body cell. Since body cells cannot store
oxygen and since the blood can hold only a limited amount (and only for a short
time), death will surely result from continued lack of breathing.
There are three stages of the safety model that are to be kept in consideration
1) Recognizing the Hazards
In order to avoid or control the hazards, you must recognize the hazards around you
2) Evaluating the Hazards
 Identify all possible hazards first
 Evaluate the risk of injury from each hazard
3) Controlling the Hazards
 Create a safe work environment
 Use safe work practices
In order to control the hazards around you in the workplace,
 You must know what could go wrong while performing the job
 You have the knowledge, tools and experience to do the work safely.
(You, coworkers and equipments should be safe)
5
1. Electrical Safety
WEEK 1
Figure 1-2
Use the safety model to recognize, evaluate and control workplace
And to control the hazards we should do the following:
a) Plan for the work to be done and plan for safety

Don't work alone, work with a
company who is trained and
who know what to do in an
emergency as well as you
should be aware of the hazards
around you in the workplace.

Figure 1-3
Know how to shut off and de-energize circuits to avoid any possible
electrical hazards
6
1. Electrical Safety
WEEK 1
 Make sure that the energy sources are looked out
 Remove jewelry and metal objects from your fingers, hands and neck
 Avoid falls from scaffolding or ladders
b) Avoid dangers like wet workplace
 Do not work wet
 Do not work in damp conditions
like working outdoors while it's
raining
c) Avoid overhead power lines when
performing tasks under overhead power lines
Figure 1-4
d)Use proper wiring and connectors
 Do not overload circuits like using a drill machine with a grinder and a
soldering iron in one extension cord
 Test your equipments and tools regularly
 Check switches and insulations of your tools
 Use correct connectors keeping into consideration the connectors
ratings, sizes and materials
e) Use the tools properly
 Inspect tools before using
 Protect your tools by storing them correctly and by using them
correctly
f)Wear correct safety protective equipment
 Wear proper clothing, overall, gloves, helmet, safety shoes, …etc
 Wear proper foot protection
 Wear safety eye glasses
 Follow directions
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1. Electrical Safety
WEEK 1
 Read the manufacturer's directions of cleaning and maintenance
carefully to know how the job should be done in the right way and with
the proper tools or equipments.
1.2 Using ladders
Ladders and scaffolding are used mainly in performing works at higher
positions than the reach of human body, like lights, street lights and overhead power
lines that are not too high.
To prevent dangers or injuries when climbing a ladder, do the following:
 Check the condition of the ladder
 Position the ladder at a safe angle to prevent
slipping
 Make sure that the floor is level
 Use special locks when necessary
 Be careful when placing the ladder on wet or
any slippery surfaces
 Follow the manufacturer's recommendations
for proper and safe use
Figure1-5 : Keeping the ladder
still is a must
8
1. Electrical Safety
WEEK 1
Figure1-6: Spot the wrong practice.
Figure 1-7: Carelessness may hurt you
1.3 Summary of chapter one:
Now since we incurred the safety in this chapter, you can relate this to your
major. In different tasks of maintenance operations in plants, laboratories, …, etc,
you should keep in mind:
 Do not perform what you do not know
 Be aware of what you are doing
 Use the proper inspected tools
 Wear the safety equipment
 Do not work alone (Why?)
 Do not work in bad moods
 Create a safe working environment
 Avoid, as much as you can, electrical hazards
 Follow the safe working procedures
 Do not take chances
 Check what you did after finishing to keep others safe

Clean the place you accomplished your task in
9
1. Electrical Safety
2.0
WEEK 2
Artificial Respiration
Victims of electrical shocks, drowning, gas poisoning or choking have
difficulty in breathing and may stop breathing altogether. Artificial respiration could
save their lives. Since most people die within 6 minutes after they stop breathing,
artificial respiration should begin as soon as possible after the breathing difficulty is
noticed.
2.1 Methods of Artificial Respiration
The are three methods of artificial respiration:
1. Mouth-to-mouth/ Mouth-to-nose
2. Chest pressure arm lift (Silvester)
3. Back pressure arm lift (Holger-Nielsen)
The most practical method is the mouth-to-mouth/nose method.
Step 1: Evaluation
a) Check for responsiveness of the victim.
b) Call for help.
c) Position the unconscious casualty so that he is lying on his back and on a firm
surface. If the casualty is lying on his
chest (prone position), cautiously roll
the casualty as a unit so that his body
does not twist (which may further
complicate a neck, back or spinal injury
as shown in figure 1).
Figure 1
2.2.1 Follow the following steps for rolling the victim:
1. Straighten the casualty's legs. Take the casualty's arm that is nearest to you
and move it so that it is straight and above his head. Repeat procedure for the
other arm.
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1. Electrical Safety
WEEK 2
2. Kneel beside the casualty with your knees near his shoulders (leave space to
roll his body). Place one hand behind his head and neck for support. With
your other hand, grasp the casualty under his far arm (See Figure above).
3. Roll the casualty toward you using a steady and even pull. His head and neck
should stay in line with his back.
4. Return the casualty's arms to his side. Straighten his legs. Reposition yourself
so that you are now kneeling at the level of the casualty's shoulders.
However, if a neck injury is suspected, and the jaw thrust be used, kneel at
the casualty's head, looking toward his feet.
Step 2: Opening The Airway-Unconscious and Not Breathing Casually
1. If there is any foreign matter visible in
the victim's mouth, wipe it quickly with
your fingers or cloth wrapped around
your fingers. Tilt the Head back so the
chin is pointing upwards. The victim
should be flat on his back. Pull or push
the jaw into a jutting out position for
removal of obstruction of the airway by
moving the base of tongue away from
back of throat (See figure 2).
2. Open your mouth wide and place it
tightly over the victim’s mouth. At the
same time pinch the victim’s nostrils shut
or close with your cheek. Or close the
with your cheek. Or close the victim’s
Figure 2
mouth and place your mouth over the nose blown into victim’s mouth or nose
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1. Electrical Safety
WEEK 2
(air may be long through the victim’s teeth even the are clenched the first
blown should be determine whether or not abstraction exists.
3. Remove your mouth, turn your head to side and listen for the return rush of
the air that indicate air exchange. Repeat the blowing effort. For the adult
blow vigorously at a rate of about 12 breaths per minute. For a child, take
relatively shallow breaths appropriate for the child's size, at a rate of about 20
per minute.
4. If the victim is not breathing out the air that you blew in, recheck the head
and jaw position. If you still do no get air exchange, quickly turn the victim
on his side and hit him sharply between the shoulder blades several times in
hope of dislodging foreign matter. Again sweep you finger through the
victim's mouth to remove foreign matter. If you do not wish to come in direct
contact with person, you may hold a cloth over the victim's mouth or nose
and breath through it. Cloth does not greatly affect the exchange of air.
5. After giving two breaths which cause the chest to rise, attempt to locate a
pulse on the casualty. Feel for a pulse on the side of the casualty's neck
closest to you by placing the first two fingers (index and middle fingers) of
your hand on the groove beside the
casualty's Adam's apple (carotid pulse).
(Your thumb should not be used for pulse
taking because you may confuse your pulse
beat with that of the casualty.) Maintain the
airway by keeping your other hand on the
Figure 1
casualty's forehead. Allow to 10 seconds to
determine if there is a pulse (See Figure).
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1. Electrical Safety
WEEK 2
a. If a pulse is found and the casualty is breathing --STOP; allow the
casualty to breathe on his own. If possible, keep him warm and
comfortable.
b. If a pulse is found and the casualty is not breathing, continue rescue
breathing.
c. If a pulse is not found, begin chest compression.
i.
Expose chest and find breast bone. Put the heal of one hand
on breast bone and other hand on top.
ii.
Compress the chest 15 times.
d. lf a pulse is not found, seek medically trained personnel for help.
For infants and small children:
If there is any foreign matter visible in the victim's mouth, wipe it quickly
with your fingers or cloth wrapped around your fingers.
i.
Place the child on his back and use the fingers of both hands to lift the lower
jaw from beneath and behind, so that it juts out.
ii.
Place your mouth over the child mouth and nose, making a relatively leak
proof seal and breathe into the child, using shallow puffs of air. The breathing
rate should be about 20/minute.
If you meet resistance in your blowing efforts, recheck the position of the
jaw. If the air passages are still blocked, the child should be suspended
momentarily by the ankles, or inverted over the arm and given two or three
sharp pats between the shoulder blades, in the hope of dislodging obstructing
matter.
Stopped breathing due to Suffocation:
After the person starts breathing give few doses of Camphor Q directly in
mouth which provides instant relief.
13
1. Electrical Safety
WEEK 2
1.2 Handling Hand Tools Safely
An estimated 8% of industrial accidents are caused by hand tolls. These accidents
are caused by using the wrong tool for the job, using the right tool incorrectly,
failing to wear personal protective equipment, or failing to follow safety guidelines.
Take a moment to review these safety tips for handling common hand tools.
Screwdrivers:

Always match the size and type of screwdriver blade to fit the screw.

Don’t hold the work piece against your body while using the screwdriver.

Don’t put your fingers near the blade of the screwdriver when tightening a
screw.

Don’t force a screwdriver by using a
hammer or pliers on it.

Don’t use a screwdriver as a hammer or as
a chisel.

Don’t use a screwdriver if your hands are
wet or oily.

Discard and replace your screwdriver if it
has a broken handle, bent blade, etc

Use an insulated screwdriver when
Figure 1
performing any electrical work.
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1. Electrical Safety
WEEK 2
Hammer:

Use the correct hammer for the type of
work to be done.

Have an unobstructed swing area when
using a hammer and watch for overhead
interference.

Don’t strike nails or other objects with the
‘’cheek’’ (side) of the hammer.

Don’t use a hammer as a wedge or a pry
bar, or for pulling large spikes.

Figure 1
Don’t use a hammer if your hands are oily
or greasy.
Pliers:

Don’t use pliers as a wrench or
hammer.

Don’t use pliers that are cracked,
broken, or ‘’sprung’’

Don’t attempt to force pliers by using a
hammer on them.

Figure 1
Use insulated pliers when doing
electrical work.

Keep pliers grips free of grease or oil, which could cause them to slip.
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1. Electrical Safety
WEEK 2
Cutter

Don’t use cutter as a wrench or hammer.

Don’t use cutter that are cracked, broken, or ‘’sprung’’

Use insulated cutter when doing electrical work.

Keep cutter grips free of grease or oil, which could cause
Figure 1
them to slip.
16
2. Electrical and Electronics Symbols
3.0
WEEK 3
Symbology
To read and interpret electrical Figure 1 Basic Transformer Symbols diagrams and schematics,
the reader must first be well versed in what the many symbols represent. This chapter discusses
the common symbols used to depict the many components in electrical systems. Once mastered,
this knowledge should enable the reader to successfully understand most electrical diagrams and
schematics.
The information that follows provides details on the basic symbols used to represent
components in electrical transmission, switching, control, and protection diagrams and
schematics.
Transformers
The basic symbols for the various types of transformers are shown in
Figure 1 (A). Figure 1 (B) shows how the basic symbol for the transformer is modified to
represent specific types and transformer applications. In addition to the transformer Figure 2
Transformer Polarity symbol itself, polarity marks are sometimes used to indicate current flow in
the circuit. This information can be used to determine the phase relationship (polarity) between
the input and output terminals of a transformer. The marks usually appear as dots on a
transformer symbol, as shown in Figure 2.
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2. Electrical and Electronics Symbols
WEEK 3
Figure 2.
On the primary side of the transformer the dot indicates current in; on the secondary side the dot
indicates current out. If at a given instant the current is flowing into the transformer at the dotted
end of the primary coil, it will be flowing out of the transformer at the dotted end of the
secondary coil. The current flow for a transformer using the dot symbology is illustrated in
Figure 2.
Switches
Figure 3 shows the most common types of switches and their symbols. The term "pole," as used
to describe the switches in Figure 3, refers to the number of points at which current can enter
a switch. Single pole and double pole switches are shown, but a switch may have as many poles
as it requires to perform its function. The term "throw" used in Figure 3 refers to the number
of circuits that each pole of a switch can complete or control.
Figure 3 Switches and Switch Symbols
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2. Electrical and Electronics Symbols
WEEK 3
Table 4 provides the common symbols that are used to denote automatic switches and explains
how the symbol indicates switch status or actuation.
Table 4 Switch and Switch Status Symbology
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2. Electrical and Electronics Symbols
WEEK 4
Fuses and Breakers
Figure 5 depicts basic fuse and circuit breaker symbols for single-phase applications. In addition
to the graphic symbol, most drawings will also provide the rating of the fuse next to the symbol.
The rating is usually in amps.
Figure 5 Fuse and Circuit Breaker Symbols
When fuses, breakers, or switches are used in three-phase systems, the three-phase symbol
combines the single-phase symbol in triplicate as shown in Figure 6. Also shown is the symbol
for a removable breaker, which is a standard breaker symbol placed between a set of chevrons.
The chevrons represent the point at which the breaker disconnects from the circuit when
removed.
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2. Electrical and Electronics Symbols
WEEK 4
Figure 6 Three-phase and Removable Breaker Symbols
Relays, Contacts, Connectors, Lines, Resistors,
and Miscellaneous Electrical Components
Figure 7 shows the common symbols for relays, contacts, connectors, lines, resistors, and other
miscellaneous electrical components.
Figure 7 Common Electrical Component Symbols
Large Components
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2. Electrical and Electronics Symbols
WEEK 4
The symbols in Figure 8 are used to identify the larger components that may be found in an
electrical diagram or schematic. The detail used for these symbols will vary when used in system
diagrams. Usually the amount of detail will reflect the relative importance of a component to
the particular diagram.
Figure 8 Large Common Electrical Components
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3. Cables in Electrical installation
WEEK5
4.1 Conductors
A" conductor " mean a material which allow the free passage of an electric
current along it, with very little resistance.
The conductor can be classified according its state as:
4.1.1 Gas Conductors
Used for electric-discharge lamps : neon, mercury vapour, sodium vapour,
helium; the latter is used in the "glow" type starter used in fluorescent starting
circuits.
4.1.2 Liquid Conductors
Used as electrolytes, like sulphuric acid ( lead-acid cells ), copper sulphate
acid ( in simple cells ). When salts are introduced to water,the liquid is used as a
resistor.
4.1.3 Solid Conductors
Copper and aluminium are the most common materials used as conductors
in electrical work.
a) Copper
Is available as :
 Wire.
 Bar.
 Rod.
 Tube.
 Strip.
 Plate.
It used for cables in domestic and industrial installations. Also in the basic
of
Many alloys found in electrical work.
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3. Cables in Electrical installation
WEEK5
b) Aluminium
Is available in many form, generally used in electrical applications.
The table (4-1) shows different types of conductors.
No.
Conductor
1
Copper
2
Aluminium
3
Nickel
4
Carbon
5
Silver
6
Gold
7
Brass
8
Tungsten
9
10
Applications
Properties
- Cable and wires.
- Busbars and contactors.
- Industrial applications.
- Power Cables .
- Industrial applications.
- Very good conductor.
- Easily-worked metal.
- Tough.
- Cheaper than copper.
- Low cost and weight.
- Ease for fabrication.
- Heating elements.
- Manufacture resistance.
- Motor bruches.
- Resistors.
- Some types of contants.
- Fine instrument wires.
- Plating contact surface.
- Plating contact surface.
-Terminals.
- Parts of electric fittings.
- Plug pins.
- Hard element.
- Resists corrosion.
- Hard.
- Low friction with other
metals.
- Best conductor.
- Expensive.
- Expensive.
- Does not corrode.
- Easily cast.
- Easily tinned for
soldering.
- Lamp filaments.
- Easily drawn.
- Switch gear compnents.
- cheap.
- Conduit and fittings.
- Resistance grids
- Special contacts.
- Liquid at normal temperature.
Mercury
- Discharge lamps.
- Vaporises readily.
Table (4-1) : Shows adifferent types of electrical conductors.
Zinc
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3. Cables in Electrical Installation
WEEK6
4. 2 Conductor characteristics
Conductors have three characteristics are:
1) Electrical.
2) Physical.
3) Chemical.
4.2.1 Electrical Characteristics
a) Resistivity
"Resistivity" is the resistance of a piece of the conductor with unit
length and unit cross- sectional area .
The resistivity is related by:
R =
Where
ρL
A
R: the value of the conductor resistance in ohm (Ω).
L: the length of the conductor in meters (m).
A: the cross-section area of the conductor, in square meters (m²)
ρ : resistivity (Ω.m ).
Example 4-1
Calculate the resistance of 1000 m of copper conductor, cross-sectional
area is 4 mm2 and the resistivity is 1.78 × 10-8 Ω.m ?
Solution:
ρ L
R =
R =
A
1.78 × 10-8 × 1000
4 × 10
R = 4.45 Ω
-6
L = 1000 m
ρ = 1.78 × 10-8 Ω.m
A = 4 mm2
= 4 × 10-6 m2
b) Conductivity
"Conductivity" is the degree of ease by which an electric current
passes through the material.
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3. Cables in Electrical Installation
WEEK6
The Conductivity is related by:
ρL
1A
ρ
: Conductivity (1/ Ω.m)
τR ==
Where
τ
ρ : resistivity (Ω.m ).
c) Temperature coefficient
Change of temperature can affect the resistance of a conductor.
If the temperature increase, the dimensions of the conductor increase, thus
increase their resistance.
The following formula gives the value of the resistance as a function of a
temperature
R2 = R1[ 1+ α (t2-t1)]
where
R1 : the resistance of the conductor at first temperature.
R2: the resistance of the conductor at second temperature.
α : temperature coefficient.
t1 : the first temperature.
t2 : the second temperature.
Example 4-2
The resitance of conductor is 20 Ω at temerature 30oC ,calculate the
resistance at 60 oC? assume α = 0.00396
Solution:
R2 = R1[ 1+ α (t2-t1) ]
R2 = 20 [ 1+ 0.00396 (60-30)]
R2 = 22.376 Ω
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3. Cables in Electrical Installation
WEEK6
4.2.2 Physical Characteristics
A conductor is physically characterized by different factors such as:
- Mass
- Volume.
- Density
- Tensil strength
- Flammability
- Elasticity
- Hardness.
- Fusion point.
- Toughness
4.2.3 Chemical Characteristics
The choice of a metal for being used as aconductor depends also on the
knowledge of its reaction with acids, bases and salts. Most of the metals are
attacked by acids, so we should be aware not mix or put acids on conductors.
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3. Cables in Electrical Installation
WEEK7
4.3 Insulators
"Insulator" is a material which does not allow the free passage of an
electric current.
Insulators are used to surround the conductor with a material that prevents
the direct touch of live conductor and to provide a protection from outer
damages.
Types of insulators
Table (4-2) shows different types of insulators.
Plastic materials
Organic materials Mineral materials Liquid materials
Bekalite
Formica
Cotton
Mica
Polyester
Rubber
Amiate
Mineral oil
Synthetic rubber
Paper
Glass
SF6
PVC.(poly-vinyl-
Wood
Porcelain
chloride)
Table (4-2): Different types of insulators.
4.4 Insulator characteristics
Insulator have two characteristics are:
1) Electrical.
2) Physical.
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3. Cables in Electrical Installation
WEEK7
4.4.1 Electrical characteristics
The electrical state of an insulator is characterized mainly by:
-
Dielectric strength.
-
Breakdown voltage or current.
4.4.2 Physical characteristics
- Variation in temperature.
- Humidity.
- Dust.
- Flammability
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3. Cables in Electrical Installation
WEEK7
4.5 Wires and cables
4.5.1 Introduction
Wire and cables are used to conduct electric power from the generated
point to the point where it is used. Copper is the material used as conductor in
practically all casesCables consists of conductors, insulators and sometimes
mechanical protectors.The conductor is generally in the form of either a singlecore or two-core or three-core or multicore.
4.5.2 Types of wires and cables
The range of types of cables used in electrical work is very wide : from
heavy lead-sheathed and armoured paper-insulated cables to the domestic
flexible cable. Some examples of different cables are shown in figure (4-1).
The practical electrician will meet two common types of cables used in his
work. This types shown in the following table (4-3).
Cables
Applications
a) Flexible cables ( flexible cord )
1- P.V.C insulated single core wire.
2- Tow core or (twin ) cable.
Domestic and industrial work.
( two single isulated-stranded wire ).
3- Three core ( twisted ).
b)Sheathed cables
1- P.V.C sheathed cables.
2- Tough rubber sheathed cables ( TRS ).
Domestic and industrial wiring.
3- Lead alloy P.V.C sheathed ( LAS ).
4- P.C.P ( polychloroprene sheathed cable ).
Table (4-3) : Wires and cables used in domestic installations.
30
3. Cables in Electrical Installation
WEEK7
The following groups of cables are to be found in electrical field:
1- Power cables.
2- Mining cables.
3- Overhead cables.
4- Communications cables.
5- Appliances-wiring cables.
6- Heating cables.
a) P.V.C insulated single core wire
7- Electric-sign cables.
8- Equipment wires.
c)
b) Circular flexible cable
Figure ( 4-1): Examples of different cable.
31
3. Cables in Electrical Installation
WEEK8
4-6 Cable Size
The cable size is classified according to current rating , where The rating
is defined as:
"cable rating" is the amount of current it can be allowed to carry continuously
without eteriorations.
The basic factor to be considerd when selecting the size of a cable is the
current of the circuit.
Many factors govern the rating of cable :
 Conductor cross-sectional area.
 Type of insulations.
 Ambient temperature.
 Type of protection.
 Grouping.
 Disposition.
 Type of sheath.
Also, the current rating of a final subcuirect depends upon the actual
connected load. The cable selected to supply this load must be able to withstand
at least the rating current absorbed by the load without undue heating. This rating
current is obtained by calculation depending on the nature of the circuit, the
power absorbed by the load and the supply voltage. The current is sometimes
called the design current, and used to select the size of cable.
For ambient temperature up to 30oC, the permissible current carrying capacity
and the corrdination of line protection fuses are given in table (4-4 ).
32
3. Cables in Electrical Installation
Nominal
Crosssectional
area of
copper
conductor
(mm2)
0.75
1
1.5
2.5
4
6
10
16
25
35
50
70
95
120
150
185
240
300
400
500
Group 1
One or more
Single-core
cable
in conduits
Carrying
capacity (A)
11
15
20
25
33
45
61
83
103
132
165
197
235
-
Group 2
Multicor
e
cables
Rated
fuse
current
(A)
6
10
16
20
25
35
50
63
80
100
125
160
200
-
WEEK8
Group 3
Singlecore
cable in
air
Carrying
capacity
(A)
12
15
18
26
34
44
61
82
108
135
168
207
250
292
335
382
453
504
-
Rated
fuse
current
(A)
6
10
10
20
25
35
50
63
80
100
125
160
200
250
250
315
400
400
-
Carrying
capacity
(A)
15
19
24
32
42
54
73
98
129
158
198
245
292
344
391
448
528
608
726
830
Rated
fuse
current
(A)
10
10
20
35
35
50
63
80
100
125
160
200
250
315
315
400
400
500
603
630
Table (4-4) : Conductors size and current carrying capacity
33
4. Simple Lighting Circuits
WEEK8
4.1 Introduction
A lighting circuit is a combination of cables, conduits,protection devices,
control devices and equipment allowing the user to benefit from electric power.
There are many methods in which these elements can be connected.
The main devices encounted in domestic installation, other than protection
devices ( circuit breakers, relays, contactors, etc……. ) are :
 Switches.
 Ceiling roses.
 Conduits and boxes.
 Wires and cables.
4.2 Switches
Switch is a mechanical device for making and breaking electric current, non
automayically, a circuit carrying a current not greatly in excess of the rated
normal current of the switch. A switch is used for controlling a circuit or part of
A circuit.
4.2.1 Types of Switches
 Single-pole switch
Usually called one way switch, controls the live pole of a supply, also these
switches provids ON and OFF control of a circuit from one position only. The
usual application to control the lighting circuits.
34
4. Simple Lighting Circuits
WEEK8
 Double-pole switch
Control two poles, use of double-pole switch means that a two-wire circuit
can be completely isolated from the supply.
Figure (4-5) shows single & double pole switches. The usual application is for
the main control of sub-circuit and for the local control of cookers, water-heater
and other fixed current-using apparatus.
Figure (4- 5 ) : single pole switch
The following types of switches are to be found in electrical field :
 Two-way switch.
 Intermediate switch.
 Two-gang switch.
 Push Button switch.
 Dimmer switch.
 Night-light switch.
 Pilot light switch.
 Card operated ceiling switch.
 Tumbler switch.
 Rocker switch.
35
4. Simple Lighting Circuits
4.2.2
WEEK8
Rating
Switch rating is the maximum current and voltage at which it should be
operate. In domestic installations, the rating of switches as follows :
4.2.3
Lighting circuits
5A or 6A
Water heater
15A or 20 A
AC circuit
25A or 45A
Regulations
Some of Bahrain regulations are :
 All switches must be fixed in P.V.C or a metal boxes.
 The minimum height of fixed a light switch is 1.37m above floor level.
 No switches can be situated in bathrooms.
 The minimum cross-sectional area of conductors used in lighting circuit is
1.5mm².
 An earthing terminal, connected to the protective conductor of the final
circuit, must be provided at each metal switch box.
36
COST ESTIMATION IN PLANNING
WEEK
10
5.6 Cost Estimation
5.6.1 Important of cost estimation planning.
Having considered the technical aspects of contracting, that is, how to technically
carry out a particular installation, we now have to consider the business side. It is
quite clear that without being able to estimate the cost of a particular job, or being in
a position to give prospective clients a price for carrying out work, a contractor may
never have the opportunity to use this knowledge.
We cannot afford to quote too low a price, as this would involve the business in a
loss, yet i f the price is too high against that of the competitors, the work will go
elsewhere, and this happens two or three times, the client may refrain from inviting
further tenders.
5.6.2 Measurements
Estimating involves taking into account how the fob is to be carried out. This will be
generally stated in the specification or brief, taking into consideration site
conditions, and the construction of the building, measuring the quantity of materials
required, if no bill of quantity is given and on the basis of this, costing the materials
and labour required to carry out the work involved, making due allowance in
measurements for the fact that runs are not always straight, for switchdrops, wastage,
etc. Estimating the cost of materials is relatively simple, as long as careful
measurements are made; the quantity is multiplied by the net trade cost price of the
material, and listed.
Estimating the labour involved and costing it, is far more difficult, and even
nowadays experienced estimators do not always agree on the number of labourhours required for identical'work. Yet every installation is in fact made up of a
large number of small jobs. the fixing of a fuse-board, lying of conduit, wiring of
conduit fittings, etc. No matter how large the installation, it can always be divided up
into smaller divisions, and finally split up into individual small jobs.
The time taken for each individual job in repetion work, in. let us say, a factory
production unit, can be fairly closely established by time-and-motion study as
working conditions are fairly constant. In the case of contracting however where site
and working conditions vary so very much from contract to contract, and where the
wiremen may be fixing conduit one day and fuse-boards the next, this is far more
difficult.
COST ESTIMATION IN PLANNING
WEEK
10
Nevertheless it is possible to establish an average time factor for certain operations,
and these are listed in tables. It is not claimed that these tables are exhaustive or
precise, but the labour-hours stated are an average time taken per pair of men for
laying, let us say, 100ft of conduit and fixing conduit accessories under various
conditions, and sufficient information is given in the tables to cover most of the
work encountered
in normal wiring of buildings and cabling.
When estimating the time allowed for each operation this must be consistent in the
same way as the price for materials, and must not change with the mood of estimator
from one estimate to another.
5.6.3. Estimating the materials for a house
For most installations in buildings, the best way to sub-divide the installation is to
adopt a system such as the following:
1. Main switchgear
2. Sub-feeders
3. Sub-distribution boards
4. Lighting installation
5. Lighting fittings
6. Socket-out let installation
7. Other power circuits (machines)
8. Special rooms
9. Boiler house installation
10.Telephone installation
11.Internal telephone and call systems
12.Fire-alann system
13.Emergency lighting
(a). Emergency lighting unit
(b). Lighting installation.
COST ESTIMATION IN PLANNING
WEEK
10
14. Earthing and testing
and so on, and to deal with each item separately. This makes estimating easier,
gives a better overall picture, and ensure that nothing is forgotten. In many cases it
is advantageous to start the estimate with the lighting installation, as this enables
the estimator to familiarize himself with the extent of the building and its
constructions before tackling the more
difficult parts.
Estimates should be made in an estimate book or special pricing sheets semi-bound
so that they can be removed when the estimate is completed and filed on a separate
estimate file. Price sheets should be laid out as
shown in Table. (5-1 of men. rather than priced immediately, as labour rates
change, whereas the time taken for given operations is fairly stable.
Week 11
Cost Estimation Continued
Step 1:
Draw the execution plan of the circuit.
Step 2:
Layout the route of the conduits and the location of the boxes on
the board.
Step 3:
Cut the conduit according to the sizes given on the layout diagram.
Step 4:
Make the required 90° bends as shown on the layout diagram. See Fig.
(1.3 a, b), for bending springs and methods of bending.
Step 5:
Secure the conduit ends to the boxes, use adopters where necessary.
Step 6:
Secure the conduits to the board by saddles.
19
Questions:
1. How are switches, lamps and socket-outlets located in an
installation?
2. Define in general terms a branch circuit and state the rules of the
determination of the branch circuit limit.
3. Show by drawings the difference between a main panel board and an
auxiliary board.
..
4. Show by means of drawings a single-phase distribution sequence in
an apartment.
5. Why cost estimation planning is important?
6. What are the factors involving estimating measurements?
7. Describe the procedure mostly used when estimating the materials
for a house.
8. How final cost for an installation is made up?
Fig.(5.9) Shows a 13A socket outlet ring-circuit layout in a typical house.
Fig.(5.9) A 13A socket outlet fing-circnit layout in a typical house,
Fig. (5.10) shows the distribution of socket outlets on a first floor plan of
four-bedroom house.
ELETRICAL BILL OF QUATITIES
WEEK
12
………………………………. ELECTRICAL CO LTD
Materials Manuf cv
Quaty
Unit price Mat cost
Labour
unit
Labour
hrs
remarks
Total
PRICE SHEET
Estimator………………
subject………. Date……
Table (5J) Price sheet
client………….
Est no/
sheet…………
ELETRICAL BILL OF QUATITIES
WEEK
12
5.6.4 Final Costing
From the price sheets the cost of materials and labour has been established, but
this price must now be modified to take into account all the other expenses, and
work that is involved in carrying out a satisfactory installation.
At the beginning of every year management must decide what turnover they are
looking for. This may be based on the previous year's turnover or indeed if a newly
established company, a minimum turnover must be aimed for, in order to cover
costs.
The number of engineers, estimators, and other employed at Head Office must bear
some relation to turnover, and these salaried staff, together with office rents and
other expenses, storage, ...etc. form a fixed expenditure on overheads, irrespective
of turnover which must be covered by the contract price.
Let us assume that the total turnover target is BD. 80000 and the fixed overheads
are BD. 5000 per annum. Then, as a percentage the overheads are 6.25 percent and
the overall contract price must be increased by this percentage to cover Ac
overheads.
Moreover, each contract requires:
- Site working tools.
- Transport, even when the materials are purchased locally, also, transport or
ELETRICAL BILL OF QUATITIES
WEEK
12
allowances for transport for labours.
- Insurance for workers and other insurance.
- Some other allowances when the working conditions are abnormal.
ALLOCATION PLAN
WEEK 13
INTRODUCTION
A technician should learn to read without errors in plans or schemes given to him by
an architect or a contractor for the realization of an electrical installation , He might
also need to establish by himself a plan or a scheme of an installation before
executing it or to modify an already done plan or scheme
Different type of plans and schemes exist, According to the importance and the
complexity of an electrical installation, plan may play different role. This chapter
will discuss the knowledge of many elements, which joined together, contribute in
making it easier for a technician to read and execute an electrical installation. And
after considering the technical aspects, we are going to discuss how to estimate the
cost of a particular job, or in other words how the job is to be carried out.
Examination and full understanding of allocation plan.
Allocation plan determines and shows the detail of an observed object according to
the direction from which we are looking at it. Accordingly ,six different location
plan exist, see fig. 5.1
ALLOCATION PLAN
WEEK 13
Fig 5.1 Location Plan
Top view: Looking at the object from above.
Front view: Looking at the right in front of us.
Side view: Right and left side view, looking at the object from the sides
Rear view: Looking at the object from behind.
Bottom view: Looking at the object from under
Multi-view drawings are also called orthographic drawings A floor plan is a single,
view orthographic drawing of the outline and partitions of a building as you see
them if the building were cut horizontally about 12m above the floor line as shown
in fig 5.2
Fig 5.2 Sectioned Building
There are many types of floor plans, ranging from very simple sketches to
completely dimensional and detailed floor plan working drawings.
Designers substitute symbols for materials and fixtures.It is obviously more
convenient and time saving to
ALLOCATION OF
POWER POINTS
LIGHTING
AND WEEK 14
Fig 5.3 shows the location plan of an apartment where the positions of the
door,windows and different sides of the apartment are indicated
Figure 5.3 Floor plan
Allocation of power points
After the basic floor plan is drawn,the designer should determine the exact position
of all appliances and lighting fixtures on the plan, as shown in fig 5.4
ALLOCATION OF
POWER POINTS
LIGHTING
AND WEEK 14
Fig 5.4 Allocation of power point
The exact position of the switches and outlets to accommodate these appliances and
fixtures should be determined Next, the electrical symbols representing the
switches, outlets, and electrical devices should be drawn on the floor plan. A dotted
line is then drawn from each switch to the connecting fixture.
Lighting
The main sources of light in a room should be controlled by a wall switch ,type of
switch plate cover should be selected.
Fig 5.5 location of wall switch
ALLOCATION OF LIGHTING AND POWER WEEK 15
POINT
Bedroom lights and lights for stairways and halls should be controlled with a twoway switch as shown in fig 5.6 andfig 5.7 The outside lights must also be controlled
with two way switch from the garage and from the exit of the house as shown in fig
5.8.While basement lights should be controlled by a two way switch and a pilot light
in the house at the head of the basement stairs.
Fig 5.6 lighting of Bedroom
ALLOCATION OF LIGHTING AND POWER WEEK 15
POINT
Fig 5.7 lighting of a stairway
ALLOCATION OF LIGHTING AND POWER WEEK 15
POINT
Fig 5.8 Outside lighting
ALLOCATION OF LIGHTING AND POWER WEEK 15
POINT
SOCKET OUTLETS
Thereare several types of electrical outlets. The convenient outlet is the plug in .It is
available in single, double, triple, or strip outlets .The socket outlet is a connection
point of a cicuit for one special piece of equipment.
The basic rules to follow when planning the outlets location on a floor plan are,
1 . No socket outlets shall be mounted in any bathroom except for shower outlet that
is of low voltage
2.No socket outlet shall be mounted within two meters of any tap sink, bisin in any
kitchen or any place.
3.All socket outlets shall be mounted 30 cm above the floor.
4.Each room shall have at least one easy to reach outlet for the vacuum cleaner or
other appliances, which are often used.