fet first
electrical systems
and construction
Revised edition
NQF Level 2
Student’s Book
Jowaheer Consulting and Technologies
FET FIRST Electrical Systems and Construction
NQF Level 2 Student’s Book
© Jowaheer Consulting and Technologies, 2012
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Contents
Topic 1: Basic electrical circuits and systems................................................... 1
Module 1: Basic electrical installations and testing............................................................................ 2
Unit 1.1: Electrical circuit diagrams and related symbols.................................................... 3
Unit 1.2: Planning according to accepted standards.......................................................... 13
Unit 1.3: Work practices in an electrical environment........................................................ 14
Unit 1.4: Electrical installations according to relevant SABS regulations............................... 24
Unit 1.5: Testing a domestic electrical installation............................................................. 39
Summary......................................................................................................................... 55
Summative assessment..................................................................................................... 57
Topic 2: Low-voltage cables and wireways....................................................... 59
Module 2: Joining low-voltage cables............................................................................................... 60
Unit 2.1: Safety considerations when joining conductors.................................................... 61
Unit 2.2: Regulations relating to joining........................................................................... 64
Unit 2.3: Types of joints and joining methods................................................................... 66
Unit 2.4: Armoured cables and glands............................................................................. 74
Unit 2.5: Using a joining kit to join an unarmoured cable.................................................. 79
Summary......................................................................................................................... 81
Summative assessment..................................................................................................... 82
Module 3: The purpose and design of wireways................................................................................. 83
Unit 3.1: Wireways....................................................................................................... 83
Unit 3.2: Installing electrical wireways: conduits............................................................... 86
Unit 3.3: Installing wireways: trunking and trays............................................................... 95
Unit 3.4: Teamwork...................................................................................................... 101
Summary......................................................................................................................... 104
Summative assessment..................................................................................................... 104
Topic 3: Electrical machines........................................................................... 106
Module 4: Inspecting and cleaning an electrical machine.................................................................... 107
Unit 4.1: Statutory requirements when working on electrical machinery.............................. 108
Unit 4.2: Types of electrical machine and connection diagram............................................ 111
Unit 4.3: Permit to Work systems and lockout procedures.................................................. 131
Unit 4.4: Inspecting, cleaning and labelling electrical machines.......................................... 137
Summary......................................................................................................................... 152
Summative assessment..................................................................................................... 154
Topic 4: Fault-finding and testing.................................................................... 156
Module 5: Fault-finding and testing of electrical components............................................................... 157
Unit 5.1: Fault-finding and testing of electrical components................................................... 158
Summary......................................................................................................................... 170
Summative assessment..................................................................................................... 171
Contents
Topic 5: Protection and measuring instruments................................................. 172
Module 6: Installing and replacing metering units or measuring instruments......................................... 173
Unit 6.1: Introduction to electrical metering units or measuring instruments......................... 174
Unit 6.2: Planning the installation................................................................................... 185
Unit 6.3: Installing a metering unit or measuring instrument.............................................. 194
Summary......................................................................................................................... 206
Summative assessment..................................................................................................... 207
Module 7: Completing the installation and/or replacement of a metering unit or measuring instrument
on a panel...................................................................................................................... 209
Unit 7.1: Completing the installation and/or replacement of a metering unit or measuring
instrument on a panel...................................................................................... 210
Summary......................................................................................................................... 214
Summative assessment..................................................................................................... 216
Topic 6: Renewable energy............................................................................. 218
Module 8: Photovoltaic systems....................................................................................................... 219
Unit 8.1: Photovoltaic systems....................................................................................... 219
Summary......................................................................................................................... 229
Summative assessment..................................................................................................... 230
Module 9: Basic renewable energy circuit diagram............................................................................. 232
Unit 9.1: Worksite procedures........................................................................................ 232
Unit 9.2: Symbols and circuit diagrams........................................................................... 236
Summary......................................................................................................................... 241
Summative assessment..................................................................................................... 242
POE Guideline................................................................................................ 244
Glossary........................................................................................................ 249
Topic 1
Basic electrical
circuits and systems
Module 1
Basic electrical installations
and testing
Overview
Whether it is a construction site, minor household repairs or even
a simulated environment in a training workshop, working with
electricity is dangerous. Your own safety and that of your co-workers
is therefore of the utmost importance. Although electricity is a
modern convenience that many of us take for granted, there are
dangers associated with it.
In this module you are going to learn how to test, install or replace
basic electrical circuits and systems, including making domestic
wiring installations safe for use. Wiring and commissioning a
single-phase installation may seem like a simple task, but you will
need to know and apply all the statutory regulations and other
legal requirements relating to electrical installations. Ensuring that
electrical installations function and meet requirements, that work is
done to an acceptable standard, and that the worksite is left neat and
tidy on completion is also part of your task. Finally, you will need to
practise what you learn, as practice makes perfect.
When you have completed this module, you will be able to:
• Read and interpret electrical circuit diagrams and related symbols
correctly.
• Plan and prepare for an electrical installation job in accordance
with job requirements and workplace standards, and policies and
procedures.
• Perform an electrical installation according to relevant SABS
standards on domestic installations.
• Test the installation according to relevant SABS standards on
domestic installations.
• (Faults are simulated and the student does fault-finding and
reports on the outcome.)
• Make sure that electrical installations function properly and meet
job requirements.
• Replace and maintain electrical equipment in a domestic dwelling.
• Clean the worksite.
2
Topic 1 Basic electrical circuits and systems
Think about it
Electricity can kill. How can we make sure that electrical installations are safe for
use? The only way to do this is to make sure that an installation follows certain
rules and regulations. In South Africa, all electrical installations must, by law,
comply with the South African National Standards code for electrical installations,
also called SANS 10142-1: 2012 or the Code of Practice for the Wiring of
Premises. This code provides certain set standards for all electrical procedures.
These rules are not at all difficult to understand and apply. However, it is important
that you do not just memorise them, but that you think about what they are
prescribing and why. You will learn more about these standards in Unit 1.4.
Units in this module
Unit 1.1: Electrical circuit diagrams and related symbols
Unit 1.2: Planning according to accepted standards
Unit 1.3: Work practices in an electrical environment
Unit 1.4: Electrical installations according to relevant SABS regulations
Unit 1.5: Testing a domestic electrical installation.
Unit 1.1Electrical circuit diagrams
and related symbols
Introduction
Before starting any task, an electrician must study and understand various
electrical plans, drawings and circuit diagrams for an installation to form
a clear picture of what the actual completed electrical installation will look
like. Diagrams are valuable tools for field staff. Electricians use diagrams
to identify the connections of components and to work out accurately the
quantities of materials needed.
In this unit you are going to learn the important skill of being able to read
and interpret circuit diagrams and related symbols correctly.
Electrical wiring symbols
A drawing of components in a circuit makes it easier to understand how
the circuit components are connected. Wiring and circuit diagrams use
special symbols recognised by everyone who uses the drawings.
The electrical symbols on the drawings show how components such
as lights, switches, circuit-breakers and other electrical components are
connected. Electrical symbols not only show us where something is to
be installed, but they also help electricians to find out why a circuit does
not work correctly.
Words &
terms
alternating current (AC): an
electric current that reverses
direction at regular intervals
circuit breaker: a type of switch
with a pre-set current limit that
is used to protect a circuit from
electrical overload
direct current (DC): an electric
current flowing in one direction
only
fuse: a protection device that
destroys itself, or ‘blows’, and
breaks the circuit if the current
exceeds the rating of the fuse
Module 1 Basic electrical installations and testing
3
Table 1.1 shows the most common electrical wiring symbols. These
symbols are used to represent wiring, components and apparatus in circuit
diagrams. It is therefore important that you learn the various symbols and
what they mean.
?
??
Did you know?
If the circuit-breaker trips,
it can be reset by pushing
a button or flipping a
switch. However, the reason
for the overload must be
investigated because it may
indicate a fault in the circuit.
OR
X
Table 1.1 Electrical wiring symbols
Electrical diagrams
Electrical diagrams may represent anything from a simple single-line
drawing to a complex power control circuit. They are usually drawn using
different symbols for electrical devices. The three most common types of
diagram encountered in the field are:
• circuit diagrams
• wiring diagrams
• block diagrams.
Circuit diagrams
A circuit diagram uses symbols to represent all the circuit components
and shows how the components are connected in a circuit. It is drawn in a
4
Topic 1 Basic electrical circuits and systems
Words &
terms
circuit diagram: uses electrical
symbols to represent all circuit
components and shows how they
are connected
simple, clear way as shown in Fig. 1.1. The shape of the diagram
does not represent the physical layout of the circuit.
Wiring diagrams
A wiring diagram shows how the components are to be wired
and where the connections must be made. Unlike a circuit
diagram, the physical layout in a wiring diagram is taken into
consideration. The components and connections are shown as
pictures of what is found in the actual wiring and are often
drawn to look like what they represent. They are shown on the
drawing in the positions they will occupy as illustrated in Fig. 1.2.
The main purpose is to give information.
Fig. 1.1 A simple circuit diagram
Words &
terms
wiring diagram: shows how the
components are to be wired,
where the connections must be
made and takes the physical
layout into consideration
block diagram: sometimes
referred to as a ‘line diagram’;
uses either square or rectangular
blocks to represent plant or
equipment
Fig. 1.2 A wiring diagram
Block diagrams
A block diagram is sometimes referred to as a ‘line
diagram’. It uses either square or rectangular blocks to
represent plant or equipment. Lines are drawn to show
interconnections between blocks but do not represent
actual wiring. A block diagram is shown in Fig. 1.3.
Guidelines for drawing circuit
diagrams
Fig. 1.3 A block diagram
A circuit diagram should be drawn in such
a way that it allows the reader to identify its
purpose. When you draw circuit diagrams you
should:
• use the correct symbols.
• use a suitable symbol orientation.
• pay attention to the arrangement of symbols
on the diagram.
• pay attention to the routing of
interconnections.
• make sure your drawing is neat and tidy.
Input to output is always drawn from left to
right or from top to bottom. For example, if a
Fig. 1.4 The correct way of drawing input to output
transformer is used to step down voltage to a
circuit, the input is drawn on the left-hand side as shown in Fig. 1.4.
Module 1 Basic electrical installations and testing
5
Relays and switches in circuit diagrams are normally shown in their nonoperating mode, in other words when no current is flowing.
A line representing a conductor should not change direction at a point
where it crosses other lines. Lines from a symbol should continue for a
short distance before they change direction, cross another line or connect
to another symbol.
assessment activity 1.1
Work in groups of five
1. List the three most common types of diagram that you will come across in the field and briefly
describe each one with an example.
2. Your lecturer will supply you with an electrical drawing. Identify the symbols and abbreviations
on the drawing and exchange your answers with another group.
3. Sketch the symbols of the following:
a) A fuse
b) A single-pole switch
c) A lamp
d) A resistor
circuit diagrams of electrical subcircuits
subcircuits of luminaires
The accessories used to wire up lighting circuits include cables, screw
connectors, lamp-holders and switches. All circuits must include a
protection device such as a circuit-breaker and the switch must be placed
on the live side of the circuit. Never install a single-pole switch in the
neutral conductor of the circuit.
The following circuit diagrams show the correct way to wire subcircuits:
• One luminaire controlled from one switch (see Fig. 1.5)
• Two luminaires controlled from one switch (see Fig. 1.6)
• Two luminaires controlled from own switches (see Fig. 1.7)
• One luminaire controlled from two switches (see Fig. 1.8)
• Intermediate switching (see Fig. 1.9).
one luminaire controlled from one switch
Circuit breaker
Bulb
L
Switch
N
Fig. 1.5 One luminaire controlled from one switch
6
Topic 1 Basic electrical circuits and systems
note
Earthing in the luminaire
circuits has been removed for
clarity.
Words &
terms
luminaire: a complete lighting
fixture consisting of a lamp and
ballast together with the parts
designed to distribute the light,
position and protect the lamp,
and connect them to the power
supply
ballast: a device for star ting and
regulating fluorescent and highintensity discharge lamps
Two luminaires controlled from one switch
circuit breaker
L
switch
Bulbs
N
Fig. 1.6 Two luminaires controlled from one switch
Two luminaires controlled from own switches
circuit breaker
L
switch
Bulbs
N
Fig. 1.7 Two luminaires controlled from own switches
One luminaire controlled from two switches
It is sometimes necessary to control a light independently from two
switches. This may be necessary for staircases and long passages.
Fig. 1.8 shows the circuit diagram. Two-way switches are necessary for
this type of configuration. The live wire is connected to terminal A of
the first two-way switch. The movement of the switch makes contact
from the common terminal A to either terminal B or C. Another twoway switch is positioned further away from the first one. Two strapping
wires are run from B to B1 and C to C1. The diagram shows the circuit in
an open position. If either switch is moved the circuit is made and the
lamp therefore lights. When the lamp is on, moving either of the switches
breaks the circuit.
C1
C
L
A
B
Bulb
A1
B1
two-way switches
N
Fig. 1.8 One luminaire controlled from two switches
Module 1 Basic electrical installations and testing
7
intermediate switching
If more than two switch locations are necessary, such as in long passages
and multiple staircases, then intermediate switches must be used between
the two-way switches. The function of the intermediate switches is to crossconnect the wires between the two-way switches as shown in Fig. 1.9.
Bulb
circuit breaker
Fig. 1.9 One luminaire control from three different positions (intermediate switching)
in the workplace
It is common practice to use different colours when wiring light switches so that you can differentiate between the
incoming wire and the outgoing wire.
a low-voltage transformer circuit
Low-voltage lamps are becoming increasingly popular as display lighting.
These lamps are available as 6 V, 12 V or 24 V but 12 V is the most popular.
Fig. 1.10 shows a 12 V low-voltage lamp.
However, a step-down transformer must be used to operate low-voltage lamps.
For example, a 230/12 V, 50 VA transformer will give 12 V from a 230 V input
and can supply current for a 50 W lamp load. Fig. 1.11 shows the connection
diagram for a low-voltage halogen lamp with a step-down transformer.
Fig. 1.10 A 12 V low-voltage halogen
lamp
230 V / input
230 V / 12 V 50 VA transformer
12 V output
note
Low-voltage transformers are
also used in bell circuits.
Fig. 1.11 The connection diagram for a low-voltage halogen lamp with a step-down
transformer
a socket outlet circuit
A socket outlet must be controlled by means of a switch in each live
conductor. The socket outlet is connected in such a way that each socket
outlet is supplied from the previous one (see Fig. 1.12 for an example).
Different circuit-breakers control various sections based on the size of the
installation.
8
Topic 1 Basic electrical circuits and systems
Circuit breaker
Words &
terms
Socket outlet
Switch
Fig. 1.12 Two sockets supplied from one circuit-breaker
A geyser circuit
Fig. 1.13 shows a geyser circuit, including the isolator and ripple relay.
A double-pole switch must be installed within arm’s reach of the
geyser.
Ripple
relay
Double-pole
isolator
Thermostat
socket: a device with female
contacts that is installed with the
fixed wiring and that is intended
to receive a plug
isolator: a switch that isolates a
circuit by disconnecting both the
live and neutral lines
isolate: to make sure that a circuit
cannot become live while it is out
of service for maintenance
ripple relay: an electrical switch
that is remotely controlled by the
power supplier which introduces
a coded signal into the electrical
network
Element
L
N
Geyser
E
Fig. 1.13 A geyser circuit including isolator and ripple relay
A stove circuit
Fig. 1.14 shows a single-phase stove circuit with an isolator. Note that L1, L2
and L3 are joined or bridged together.
L1
L2
Bridged
together
L3
N
E
Back of
stove
?
??
Did you know?
Ripple relays are used to
switch the load off and on
from a distance (remotely).
For example, in many towns
ripple relays are installed
in households to allow the
supplier to switch the geyser
on and off at set times to cut
electricity usage, especially
during peak hours.
Fig. 1.14 A single-phase stove circuit including isolator
Module 1 Basic electrical installations and testing
9
in the workplace
The internal wiring of a stove is often subject to high temperatures so when rewiring stoves, use
heat-resistant wiring.
Wiring of a distribution board
Fig. 1.15 shows the wiring of a distribution board where all the subcircuits
are on the earth leakage unit. As can be seen in the diagram, different sizes
of circuit-breakers are used for protection.
Words &
terms
Fig. 1.15 The wiring of a distribution board
recommended conductor sizes for domestic
installations
Table 1.2 shows some of the recommended conductor sizes for domestic
installations.
electrical subcircuit
size of wire
Bell circuit
1 mm2
Light circuit
1,5 mm2
Socket outlet
2,5 mm2
Geyser
4 mm2
Stove
6/8 mm2
Distribution board wiring
10 mm2
Supply from meter to distribution board
16 mm2
Table 1.2 Recommended conductor sizes for domestic installations
10
Topic 1 Basic electrical circuits and systems
distribution board: an enclosure
that contains electrical
equipment for the distribution or
control of electrical power from
one or more incoming circuits to
one or more outgoing circuits
?
??
did you know?
The advantage of miniature
circuit-breakers (MCBs) is
that if they trip, they can be
reset. They also offer a more
precise tripping value.
A circuit-breaker has a line
side and a load side. The
incoming power line is
always connected to the line
side and the outgoing wires
to the load side.
Preparing the parts list
It is important for the electrician to prepare a parts list of materials that
will be required for a specific installation. These materials fall into two
main categories, namely numbered parts and measured parts.
Numbered parts
These are materials that can be counted, for example circuit-breakers,
socket outlets and lever switches. The most logical way to count these
items is to draw up a checklist with rows and columns as shown in
Table 1.3.
Customer name:
Customer address:
Name of chief electrician doing installation:
Contact numbers:
Item No
Description
Quantity
1
Single lever switches
8
3
2
Two way switches
2
3
3
...
...
4
....
...
5
...
...
Yes
No
Table 1.3 A checklist for numbered parts
Measured parts
These are materials that need to be charged per length required, for
example cable and PVC (polyvinyl chloride) trunking or tubing. These
materials must be measured accurately. It is common practice to add an
extra amount for termination of the cable at either end.
The electrician writes the list of materials (both the numbered and
measured parts) on a requisition, order or quotation form and hands it to
the customer or the store, depending on company policy. An example of a
materials requisition form is shown in Table 1.4.
Module 1 Basic electrical installations and testing
11
materials requisition form
date:
installation to be completed on:
customer name:
customer address:
name of chief electrician doing installation:
contact numbers:
account no:
erf no:
reference
description
Quantity
Distribution board
20-way flush mount
1
Earth leakage 63 A, 30 mA (CBI) with
overload
1
…
…
…
...
...
Table 1.4 A materials requisition form
assessment activity 1.2
Work on your own
1. Neatly draw the following subcircuit diagrams which must be labelled and include protection
devices:
a) Two luminaire circuits supplied from one circuit-breaker
b) A geyser circuit including the isolator and ripple relay
c) A single-phase stove including the isolator.
2. Are the following statements true or false? If a statement is false, correct it.
a) A switch is connected on the neutral side of the circuit.
b) A double-pole isolator disconnects both the live and neutral wires.
c) An isolator switch is installed near the geyser, usually within arm’s reach, for safety during
maintenance.
d) It is usual to use a 2,5 mm2 conductor for a stove connection.
e) Low-voltage transformers are also used in stove circuits.
3. Refer to Fig. 1.16 and identify the symbols labelled A, B, C and D.
4. What will happen if component C in Fig. 1.16 is removed and
replaced with a piece of 2,5 mm2 wire?
5. What will happen if component D in Fig. 1.16 is removed and
replaced with a piece of 4 mm2 wire.
Fig. 1.16 A circuit diagram
12
Topic 1 Basic electrical circuits and systems
Unit 1.2 Planning according to
accepted standards
Introduction
Proper and effective planning is vital in any electrical work. Planning
is the organisational process of creating and maintaining a plan. It is
concerned with:
• what is to be done
• where is it to be done
• how it is to be done.
Note
A plan should be a realistic
view of the expectations.
The term is also used to describe the formal procedures used in such a
job, for example creating documents or diagrams, or holding meetings to
discuss important issues that need to be addressed, the objectives or goals
to be met, and the strategy to be followed.
Before you start a project, it is important to plan properly the procedure
you will follow, prepare the work area, and select and obtain the right
tools for the job. In this unit you are going to learn how to plan a job
according to accepted standards.
Why do we need to plan?
It is important to prepare a plan, keeping in mind the fundamental
requirements of the project (Fig. 1.17). The five main reasons for planning
are to:
• provide direction
• minimise waste
• set the standards to facilitate control
• identify and commit resources to achieve goals
• decide which tasks must be done to achieve these goals.
A plan plays an important role to help you avoid mistakes. Preparing a
satisfactory plan of the project is therefore essential. The planning process
lets us understand more clearly what we want to achieve, and how and
when we can do it.
Factors relating to the completion of a task in
accordance with acceptable standards
Fig. 1.17 Planning involves the
setting of goals
Think about it
Preparing a comprehensive
plan will not guarantee
success, but not having
a proper plan will almost
certainly mean total failure.
What are your views?
When planning, it is necessary to consider certain factors to make sure that
the task is completed in accordance with acceptable standards. When you
are assigned a task, take the following factors into consideration:
• by what date must the task be completed?
• obtain as much information as possible about the task to be done.
• obtain the necessary plans, documents and diagrams.
• when must the task start?
• how many workers will be available?
• what tools and equipment will be needed?
Module 1 Basic electrical installations and testing
13
•
•
•
•
what materials must be ordered?
what documentation is needed according to the job instructions?
inform all the relevant parties affected.
submit appropriate requests to the supply authority, for example an
application for an electricity connection?
• what will happen in the case of unforeseen circumstances, such as a taxi
strike or if materials are not available?
think about it
A well-prepared and designed plan shows that the person knows what he or she is
doing and that they have thought through the process before starting the job. This
is in contrast to someone who does not ‘waste’ any time planning and preparing,
but instead jumps right in and strips everything in the hope of finding the fault
by a stroke of good luck. Which type of person do you think will inspire the most
confidence in the client?
assessment activity 1.3
Work in pairs
1. List five main reasons for planning.
2. List at least ten factors for making sure that a task is completed within acceptable standards.
3. Create a checklist for the completion of a task in accordance with acceptable standards.
unit 1.3 Work practices in an
electrical environment
introduction
It is important to have a good understanding of sound work practices and
adhering to them. Working safely in an electrical environment is important
for your own well-being and for the well-being of others around you.
Electricity can kill and injure people.
To overcome these threats, planned and proactive work practices are vital.
This unit introduces you to essential work practices and will also help
you to appreciate some of the potential electrical hazards that exist in the
workplace.
14
Topic 1 Basic electrical circuits and systems
Words &
terms
electrical hazard: a dangerous
condition in which an accidental
or unintentional contact or
equipment failure can result in
shock, arc flash burn or thermal
burn
in the workplace
If you find any hazards during your inspection of the work area, make a note of them in writing and tell your supervisor.
If it is something small, such as some tools lying around, then you can correct the situation yourself. However, the
supervisor must still be informed so that action can be taken to prevent it from happening again. If it is a faulty tool or
wire connection, then the proper procedure must be followed. Work must not start before the supervisor has taken the
correct action and the danger has been removed.
In the workshop, if you regularly inspect your workbench, keep it clean and inspect your tools every time before you use
them, then you will be compliant with the rules and regulations.
Hazards
Electrocution remains the leading cause of electrical injury. Understanding
and recognising the hazards of electricity is the key to preventing injury.
Electricians must be trained to identify and avoid the hazards involved in
working with electricity.
What is a hazard?
The Occupational Health and Safety Act No. 85 of 1993 defines a hazard
as a source of danger such as the risk of being electrocuted, or exposure to
excessive heat and noise. No one wants to be injured or become sick as a
result of risky or hazardous working conditions. Although some hazards
are fairly obvious and easy to identify, others are not, and you should
therefore take all necessary safety precautions to identify hazards in the
workplace and be aware of hazardous areas (Fig. 1.18).
Fig. 1.18 A sign indicating a
hazardous area
Hazard management
For any system to work properly people must be trained so that they
know what to do, when to do it, how to do it and why. Obviously no one
wants to be injured or become sick as a result of their working conditions.
If everybody is aware of possible hazards and knows how these can affect
them, as well as what equipment is available to protect them from injury,
hazards can be effectively avoided.
Workplace inspections should focus on identifying hazardous conditions,
unsafe work practices and violations of standards. These inspections are
also used to follow up on accident reports.
As a good work practice, time should be set aside for general health and
safety procedures which could include the following:
• report all hazards, and know how and to whom they should be
reported.
• where possible, make all potential hazards safe.
• report all incidents immediately.
• follow all health and safety instructions regarding making equipment
safe, and also use all required personal protective equipment.
• maintain all personal protective equipment and replace if defective.
Module 1 Basic electrical installations and testing
15
Hazards can arise from:
• the work environment
• the use of machinery and substances
• poor work design
• inappropriate systems and procedures.
?
??
Example of a hazard assessment
You need to conduct a review of your employer’s operations from a safety
and health perspective. During the walk-through, assess various health
and safety issues, including but not only, the following:
• the building, floors and stairs for physical hazards
• the functionality and placement of fire exits (see Fig. 1.19), fire
protection equipment and first aid signs (see Fig. 1.20)
• the space layout in aisles and between machines
• electrical and mechanical hazards
• the control of worker exposure to occupational hazards, including toxic
and corrosive substances, and especially air contaminants
• the availability and functioning of all necessary personal protective
equipment and whether employees know how to use and care for the
equipment
• workers’ exposure to noise, vibration, lighting or other environmental
factors
• the use of adequate safety signage (see Fig. 1.21)
• work practices, including general housekeeping
• the use and maintenance of hand and portable power tools.
Fig. 1.19 Fire exit
Fig. 1.20 First aid sign
Did you know?
Hazards are classified into
five broad areas, namely
physical, mechanical and/
or electrical, chemical,
biological and psychological.
Think about it
You can help prevent
workplace injuries and
illnesses by looking at
your workplace operations,
establishing proper job
procedures, and ensuring
that all employees are trained
properly. Management must
demonstrate its commitment
to safety and health, and
correct any uncontrolled
hazards that have been
identified. If management
fails to do this, it will lose
credibility and employees
may hesitate to report
dangerous conditions. What
is your viewpoint?
Fig. 1.21 Safety signs
The dangers of electricity
Electricity has become such a basic part of our society that it is often taken
for granted. Yet electricity remains a dangerous hazard for people (Fig.
1.22). Because the human body can conduct electricity, people can be
shocked, burned or killed as a result of electrocution.
Types of injury associated with electricity
There are four main types of electrical injury:
• electrocution
• electric shock
• burns
• falls.
16
Topic 1 Basic electrical circuits and systems
Fig. 1.22 Danger sign
Causes of electrical accidents
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??
Some common causes of electrical accidents are the following:
• inattention and carelessness
• inadequate power-line clearance
• poor housekeeping
• taking chances
• overloading of electrical circuits
• careless use of mobile scaffolding
• failure to adhere to sound work practices (see Fig. 1.23)
• bypassing or ignoring safety procedures
• lack of knowledge
• fatigue
• faulty or unguarded machinery (see Fig. 1.24)
?
??
Effect on body
1
First sensation noticeable
2,5
Palms start to tingle
7,5
A fatal electric shock is
referred to as electrocution.
Did you know?
Current (mA)
5
↑
Safe zone
Cramping starts
Hands stiffen; still possible to let go
10–15
Cramps increase; difficult to let go
25–30
Severe cramping in chest area; limit of safe current
30–50
Did you know?
50–60
Danger
zone
60–75
↓
Blood pressure increases; irregular heartbeat
Difficulty breathing; loss of consciousness (fainting)
Heart failure and death
Fig. 1.23 Not adhering to sound work practices Fig. 1.24 Unguarded machinery
Module 1 Basic electrical installations and testing
17
Electrical safeguards
There are several safeguards typically used to reduce the possibility of
electrical accidents, for example the use of:
• circuit-breakers
• direct earthing
• isolating transformers
• double-insulated appliances
• earth leakage circuit-breakers.
?
??
Did you know?
The international symbol for
double insulation is a square
within a square. See Fig.
1.25 for an example.
Safety precautions when working with or near electricity
• Do not use power tools with defective cords (see Fig. 1.26).
• Use only cords or equipment rated for the level of amperage or wattage
that you are using.
• Always use wooden ladders or other non-conductive materials when
working with or near electricity or power lines.
• Remember that the risk of electric shock is greater in areas which are
wet or damp.
• Know where the distribution board is in case of an emergency.
• Label all circuit-breakers so that it is easy to identify which circuits they
protect.
• Make sure that the lockout isolator is in the OFF position with a tag on
it to inform others (see Fig. 1.27).
• Do not use outlets or cords that have exposed wiring.
• Do not block access to circuit-breakers.
• Do not touch a person or electrical apparatus if there is an electrical
accident. Always disconnect the current first and then attend to the
accident.
Fig. 1.25 The symbol for
double insulation
An appliance labelled with
this symbol has additional
insulation between any
exposed metal parts. The
usual insulation of the
current-carrying parts is
therefore also insulated,
hence the term ‘double
insulation’.
Words &
terms
insulation: a material that does
not conduct electricity and which
is used to isolate current-carr ying
wires or components from other
metal parts
lockout: the placement of a
lockout device, for example a
padlock, to isolate certain circuits
or devices from the power source
Fig. 1.26 Defective power cords Fig. 1.27 A lockout and tagout devices
Think about it
Locking out equipment is the only sure way to prevent serious or fatal injuries that
could result from the unexpected start-up of machines. A tagout device, on the
other hand, is a prominent warning sign, such as an easily visible tag, securely
attached to an energy-isolating device. When you find a tagged power box, make
no attempt to restore the power until the repairs have been made and the tag has
been removed by the person who placed it there. What would you do if you could
not find the person who put the lock and tag on the device?
18
Topic 1 Basic electrical circuits and systems
Manual handling
Many accidents occur due to manual handling of loads. Sprains and
strains, particularly of the back, are quite common. In many cases, these
injuries result in a temporary absence from work, but they can sometimes
be serious enough to lead to permanent disablement. When you lift loads,
use the correct lifting procedures to prevent back injuries. Fig. 1.28 shows
how you can do this.
7
3
Words &
terms
Manual handling: the
transpor ting or supporting of
loads by hand or by bodily force,
including lifting, putting down,
pushing, pulling and carr ying a
load
Fig. 1.28 Lifting techniques
Safe work practices must be used for manual operations. Staff should be well
trained and supervisors must make sure that correct procedures are followed
and the necessary personal protective equipment is worn at all times.
Some safe practices to follow when lifting loads are the following:
• do not lift a load manually if at all possible. Rather use mechanical (see
Fig. 1.29) or electrical means.
• use trolleys.
• plan properly so that any obstacles can be eliminated.
• lift and lower gently.
• use gloves to avoid injury to hands.
• use a safety sign to remind workers to lift correctly (see Fig. 1.30).
Fig. 1.29 Using a mechanical aid to move a load
Fig. 1.30 ‘Lift correctly’ signs
Module 1 Basic electrical installations and testing
19
assessment activity 1.4
Work on your own
1. What do you understand by the word ‘hazard’?
2. What causes hazards?
3. List at least five common causes of electrical accidents.
4. List at least ten safety precautions to follow when working with or near electricity.
5. List some safe practices to follow when lifting loads.
Housekeeping
An uncluttered workplace is fundamental to any company’s safety
programme. In addition to cleanliness, housekeeping must include other
factors such as orderliness and proper arrangement of materials.
When we think of housekeeping it is useful to think of the common
phrase, ‘A place for everything and everything in its place’. This means
that tools and equipment are not left lying around and that they are
properly stored in the correct place. A clean, well-ordered working area
and good housekeeping improve a company’s image and reflect a wellrun business. An orderly workplace will impress anyone who enters it.
Remember, first impressions last!
It is important to know the benefits of good housekeeping. Let's review
why we need good housekeeping and some common signs of poor
housekeeping.
Why good housekeeping?
Sloppy working conditions lead to a lack of pride in your work and
also create hazards that can lead eventually to injury or accidents. Poor
housekeeping thus creates hazards for all employees.
common signs of poor housekeeping
There are many signs of poor housekeeping. The following are some
examples:
• excessive materials or waste in the work area
• overcrowded passageways and aisles
• tools and materials left on machines or walkways
• dusty, dirty floors and wet work surfaces
• overflowing waste containers
• untidy or dangerous storage of materials, for example materials packed
in corners or on overcrowded shelves
• cluttered and poorly arranged work areas
• items stored overhead in such a way that they could easily fall
• objects stored on ladders or stairs
• storage of items that are obsolete (no longer needed).
20
Topic 1 Basic electrical circuits and systems
For a housekeeping programme to be effective, everyone must play their
part. Do not expect maintenance personnel, a labourer or a co-worker to
clean up your area. However, management should provide brooms, mops
and cleaning materials.
Think about it
Housekeeping is more than just sweeping the floor and wiping dust off machines
and equipment. Cleanliness is only one part of housekeeping. The most critical and
most overlooked part of housekeeping is order. A work area is in order when there
are no unnecessary objects in the area and when all necessary items are in their
proper places. A daily conscious effort by everyone working in the area is necessary
to maintain order. What do you think?
Testing tools and equipment
In general, tools and equipment that are poorly maintained,
inappropriately used or not fit for purpose can cause injuries. With
electrical work, there is also the added risk of electric shock.
The tools and equipment used by electricians often have special design
characteristics. For example, many are insulated as a safety measure.
However, it is important that you inspect and maintain the tools and
equipment regularly. Dangers arise from faulty tools and equipment, for
example the insulating material may hide a mechanical defect that could
cause an open circuit in the lead of a testing device.
Users should be competent in the use of tools and equipment.
This means:
• being able to use the device safely and in the manner for which it was
intended
• being able to determine, by inspection, that the device is safe for use, in
other words, the device is not damaged and is fit for purpose
• understanding the limitations of the equipment, for example when
testing to prove an AC circuit is de-energised whether the testing device
indicates the presence of hazardous levels of direct current (DC)
• being aware of the electrical safety implications for other people near
you when the device is being used
• knowing what, the interest of electrical safety, when you get an
incorrect result.
When selecting tools and equipment, keep the following guidelines in
mind:
• the device must be fit for purpose.
• you must test your equipment and test instruments at least every six
months and recalibrate once a year to check they are in proper working
order.
• repairs and maintenance should meet appropriate standards and the
manufacturer’s specifications.
Module 1 Basic electrical installations and testing
21
• inspect the device and perform functional checks immediately
before and after use to confirm that the device is operating correctly
(see Fig. 1.31).
• the work practices employed during use should be in line with
documented procedures. These documented procedures should
include the manufacturer’s instructions and recommendations.
• the function, range and class of accuracy of the device should be
appropriate to both the job at hand and the general working conditions.
• the combination of leads and instruments used should be capable of
withstanding the impulse voltages and fault current levels that may be
experienced at the particular location.
Fig. 1.31 Checking for voltage before
working
in the workplace
If you notice a problem during inspection that makes the tool unsafe for use or discover that some part of the tool does
not work, then it is important that you do not use it, but remove it and mark it for repairs. The marking procedure differs
from workshop to workshop. Some companies use labels attached with strings, while others use stickers that you can
stick onto the tool. Find out from the supervisor which procedure is followed at your place of work. What is important is
that you must identify the problem as far as possible and note it on the label you put on the tool. After you have identified
the fault and written it on the tool, return the tool to the store. Make sure the attendant signs off on it so that it is not
longer issued in your name!
Warning signs and notices
Appropriate warning signs and notices should
be openly displayed in the workplace (see Fig.
1.32). It is important to learn the different types
of sign and what they mean. Some examples
are:
• these signs must be fixed securely where
they can be seen clearly (and not obscured
in any way) at all entrances to hazardous
areas and in all workplaces.
• if the warning or instruction applies during
the hours of darkness, the signs must be
placed or illuminated in such a way that
they can be easily read.
• warnings of hazards must be displayed
near machinery that could cause injury to
operators if improperly used, for example
abrasive wheels. A reminder notice should
also be displayed, for example ‘Goggles
must be worn’.
• signs and notices should conform to
recognised national standards.
22
Topic 1 Basic electrical circuits and systems
Fig. 1.32 Different safety signs
tools
Tools for the electrical environment must be insulated. For example,
Fig. 1.33 shows insulated screwdrivers. The following criteria can be used
when selecting tools:
• use the correct tool for the job.
• use the tool properly and within its limitations.
• always store tools safely after use.
• always buy good-quality tools and keep them in good condition.
it's more than following work practices
To be truly safe, keep to work practices during a project or task and make safe
work habits second nature. Look out for everyone. Take responsibility for noticing,
reporting and correcting hazards.
stay alert
Many electrical injuries could be prevented if people were alert to hazards. Stay
aware by keeping focused on your job and do not let emotions such as anger and
frustration get in the way.
Fig. 1.33 An insulated screwdriver
set
avoid unsafe shortcuts
It may take longer to keep your area clean and dry, or inspect cords for wear, but
it is worth a few minutes to prevent shock or fire. Shields, barriers, insulation and
earth leakage devices protect you so do not modify them just to get a job done
faster.
use personal protection equipment
Personal protective equipment is your line of defence against shock and electrical
burns. Keep boots, gloves and other gear in good condition at all times.
learn to say ‘no’
If the task assigned to you will be a threat to safety, say ‘no’.
Warning notices and barriers
Check that warning notices and barriers are fitted and installed correctly.
clean up
Make sure that when you have completed the project or task, you remove
equipment and material from the workplace and store it safely as laid down in
company policy. Clean up the work area, throw away rubbish and return any
unused material to the main stores.
assessment activity 1.5
Work in groups of five
1. There are many signs of poor housekeeping in the workplace. Do a check in your workshop and
suggest ways to overcome the problems.
2. What guidelines should you follow when selecting tools and equipment?
3. What method will you use to test for isolation?
Module 1 Basic electrical installations and testing
23
unit 1.4 electrical installations
according to relevant saBs
regulations
introduction
Electrical installations in South Africa must conform to the South African
National Standards Code SANS 10142-1 : 2012, also called the Code of
Practice for the Wiring of Premises or simply the Wiring Code. This code
is published by Standards South Africa, a division of the South African
Bureau of Standards (SABS).
The code sets out specific requirements for the wiring of premises. Most
of these rules and regulations involve common-sense ideas, such as
using only high-quality materials that will not fail under normal use
and conditions. In this unit you will explore some of the relevant SABS
regulations for domestic installations.
in the workplace
We strongly recommend that you have your own personal copy of the SANS
10142-1 : 2012 Wiring Code as you will often need to refer to the rules and
regulations in this document.
understanding sans 10142
The aim of SANS 10142-1 is to make sure that people, animals and
property are protected from hazards that can be caused by the operation
of an electrical installation under both normal and fault conditions.
The various types of protection required by an electrical installation are
listed in Table 1.5.
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??
did you know?
SANS 10142-1 is listed in
the Electrical Installation
Regulations of the
Occupational Health and
Safety Act No. 85 of 1993
(OHS Act) as a mandatory
(compulsory) safety
standard. This means that
the rules and regulations in
the code have the force of
law through the OHS Act.
Words &
terms
mandatory: containing a
command; not having an option
to do otherwise
frequency: the number of
complete waves that pass a
point in one second measured in
hertz (Hz); in electrical terms, it
refers to the number of complete
alternations per second of an
alternating current (AC); this is
50 cycles per second or 50 Hz in
South Africa
harmonics: frequencies of a
complex wave that are multiples
of say 50 Hz such as 100, 150
or 200 Hz
type of protection
explanation
Shock current
Current that passes through the body of a person or an animal that has a value likely to cause injury
depending on the frequency, harmonics and duration.
Overcurrent
Current that is greater than the rated current; depending on its magnitude (size) and duration, an
overcurrent may or may not be harmful.
Fault current
Current that results from an insulation failure or from the bridging of insulation.
Overvoltage
Voltage that is greater than the supply voltage.
Undervoltage
Voltage that is less than the supply voltage.
Excessive temperature
A temperature greater than:
70 °C in the case of metallic parts
90 °C in the case of non-metallic parts.
Electric arc
The heat and light energy that is released by the electrical breakdown of an electrical insulator such as
air and the subsequent electrical discharge through the insulator.
Table 1.5 Potential faults in an electrical installation
24
Topic 1 Basic electrical circuits and systems
If any of the problems listed in Table 1.5 arise, the protection devices
should automatically disconnect the power supply or limit currents and
voltage to a safe value. In the case of undervoltage, the protection device
should ensure that dangerous situations due to the loss and restoration of
power supply or voltage drops do not occur.
The designer of an electrical installation should be aware of:
• the nature of the power supply
• the nature of the demand
• the operating environment of each part of the installation.
Think about it
Electrical installations must be done in a consistent and uniform way. This is
why there are electrical codes such as SANS 10142 to make sure that everyone
recognises the correct and incorrect way of doing an electrical repair or installation.
If every building was wired according to a random standard, it would be difficult to
find and correct faults in a circuit.
Reading and interpreting regulations
When you read and interpret regulations, pay special attention to the
language that has been used. The same word may have different meanings
for different people and each one of us may interpret a regulation in a
different way. Pay particular attention to words such as shall and may:
• Shall: When this word is used, it means that you must do something in
a certain way. If you do not, then you are in violation of the code.
• May: When this word is used, it means that you have an option. You
can do something the way it is stated or you can do it another way. In
other words, the choice is yours.
SANS 10142-1 also includes certain provisions that are for information and
guidance only. These provisions do not use the word shall and they can be
found in the main text, in the notes and in informative annexures. Except
in tables, notes are always for information only.
There are therefore three types of rule:
• Mandatory rules: These use the words shall or shall not. These rules
must always be obeyed – if you do not do so, you will be in violation of
the code and will therefore be breaking the law.
• Permissive rules: These use words such as may, shall be permitted or
shall not be required. These rules give you permission to do or not to do
something, but you can decide whether to implement the rule or not.
• Informational rules: These rules do not prescribe any action; they are
for information and guidance only.
Words &
terms
rated current: the current that
an electrical device can carr y,
under specified conditions,
without resulting in overheating
or damage to the device; in the
case of conductors, the currentcarr ying capacity is considered to
be the rated current
?
??
Did you know?
Any distortions in the voltage
or current wave cause
harmonics. Harmonics
are harmful to electrical
distribution systems and
to sensitive electronics.
They cause transformers
to overheat, they overload
neutral conductors, have
a negative effect on relay
settings, metering, capacitors
and telephone lines, and
cause circuit-breakers to trip
for no obvious reason.
Think about it
To make sure you interpret
the rules and regulations
correctly, you must consider
each word individually. This
requires extra time and more
effort, but there is no other
way to arrive at the correct
interpretation.
Module 1 Basic electrical installations and testing
25