BASICS OF ELECTRICAL DOMESTIC
INSTALLATION
CLASS: Y1 ELT & ETT B/D
INSTRUCTOR: ENG. KARANGWA AUGUSTIN
TEL : 0787173363
ELT WORKSHOP
OBJECTIVES OF THE
COURSE
At the end of the course you should be able to:
1.
Select and use appropriate tools , materials and equipment
2.
Practice safe working habits
3.
Install various wiring system from a given diagram
4.
Install various wiring system in accordance with relevant wiring
regulations.
5.
Test and inspect a completed installation
CONTENTS:
I. Working effectively and
safely with electricity
II. Supply system, protection
and earthing
III.Basic electrical circuits
I.
WORKING EFFECTIVELY AND
SAFELY WITH ELECTRICITY
• 1.0. ACCIDENTS
What is an accident?
• This is an unplanned and unpleasant event that happens
unexpectedly which causes death, injury or damage.
• How do accidents occur?
Most accidents occur as a result of human error and statistics
prove that 98% of all accidents are avoidable.
CONT’
Causes for accidents:
• Unawareness of danger: not knowing, not expecting.
• Disregard for safety: not treating as important
• Negligence: the failure to give something enough care.
• Lack of understanding of proper safety procedures.
• Untidy condition of workplace.
• Inadequate light and ventilation.
• Improper use of tools.
• Unsafe conditions.
CONT’
Responsibilities
Safety doesn’t just happen automatically. It has to be organised
and achieved like a work process of which it forms part.
The law states that both the employer and employees have
a responsibility on safety.
Employers’ responsibilities:
• Providing equipment
• Providing safe working environment
• Giving instructions to employees on work
CONT’
Employees responsibilities:
• Proper use of tools, materials and equipments provided.
• Substance of a good working environment
• Procedures and manner of doing work.
• General attitude to safety
1.1. SAFETY SIGNS
The four basic categories of signs are:
• 1. Prohibition signs:
- shape: Circular
- Colour: - Red border
- Black symbol on white background
• Meaning: shows what must not be done.
Example: No Smoking
CONT’
2. Mandatory sign:
- shape: Circular
-Colour: White symbol on Blue background
• Meaning: shows what must be done.
• Example:
Wear hand protection
CONT’
3. Warning sign:
- shape :-Triangular
- Colour:Yellow background with black border and symbol
• Meaning: warns of hazard danger
• Example: caution risk of electrical shock
CONT’
4.Information sign:
- shape: Square
- Colour: White symbol on green background
• Meaning: Access to information on safety
• Example: First aid point
1.2 . FIRE AND FIRE
EXTINGUISHERS
1.2.1 FIRE
Fire arises from the burning of combustible materials. A fire in an
unwanted place can cause damage. Therefore every effort must be
made to prevent unwanted fire.
Factors that must be present in combination for a fire to start and to
continue burning are:
• Fuel
• Heat
• Oxygen
TYPES OF FIRE
• Class A fire from wood, paper, cloths
• Class B fire from flammable liquids
• Class C fire from gases
• Class D fire from metals
1.2.2. CAUSE OF FIRE IN
ELECTRICAL INSTALLATION
• Loose connections
• Wrongly rated fuses
• Overloaded circuits
• Damaged insulation
1.3. FIRE EXTINGUISHERS
Various things can be used to put out fire are:
1.
Water
2.
Sand or dry soil
3.
Foam Extinguishers
4.
Carbon Dioxide extinguishers
5.
Dry powder extinguishers
6.
Fire Blankets
ELECTRICAL SHOCK
• Received when current passes through
the body
• Severity of the shock depends on:
• Path of current through the body
• Amount of current flowing through the body
• Length of time the body is in the circuit
DANGERS OF ELECTRICAL
SHOCK
• Currents greater than 75 mA can cause ventricular fibrillation
(rapid, ineffective heartbeat)
• It will cause death in a few minutes unless a defibrillator is used
• 75 mA is not much current – a small power drill uses 30 times as much
HOW IS AN ELECTRICAL SHOCK
RECEIVED?
• When two wires have a different potential
(voltages),
current will flow if they are connected together.
• If you come into contact with an energized (live)
black wire, and you are also in contact with the
neutral wire or ground, current will pass through
your body and
YOU WILL RECEIVE A SHOCK.
ELECTRICAL BURNS
• Occurs when you touch electrical wiring or
equipment that is improperly used or maintained
• Typically occurs on the hands
• Very serious injury that needs immediate attention
WORKING EFFECTIVELY AND SAFELY
•
3 major points
1
Safe working environment.
2
Safe working methods.
3
Safe electrical installation.
SAFE WORKING ENVIRONMENT
• Note: The many laws and regulations
controlling the work environment have one
common purpose:
To make
the work environment
SAFE
for everyone!!
Safe working environment
What is wrong in this workshop?
SAFE WORKING METHODS
What is wrong in this workshop?
SAFE ELECTRICAL INSTALLATION
What is wrong in this picture?
SAFE ELECTRICAL INSTALLATION
Well organized and arranged
CLASSIFICATION OF
CONDUCTORS
Wires and cables can be classified by the type of covering they have.
1.Bare conductors
These are conductors that have no covering. The most common use of
bare conductors is in overhead electrical transmission and
distribution lines.
2. Insulated conductors
These are conductors that have a coating of insulation over the metals
3. Stranded conductors
They consist of many strands of fine wires
CABLE SELECTION GUIDE
• Choosing the correct size cable for a new
electrical installation is crucial.
• The selection of an incorrectly rated cable
could cause the cable to overheat, which may
result in a fire.
• The table guide below is accurate enough for
general domestic installations.
Situation:
cable to be
used for:
Recommended
cable size :
Recommended
Fuse / MCB
rating :
General Lighting
1.0mm/1.5mm
Twin+Earth
General Power
ring circuit
2.5mm Twin Earth
30 / 32 amp
(x2)
General Power
radial circuit
2.5mm Twin Earth 15 / 16 amp
5 / 6 amp
Cookers up to 40
6.0mm Twin Earth 30 / 40 amp
amps MAX load
Showers up to
9Kw
6.0mm Twin Earth 40 amp
4. INSULATORS
The desirable characteristics of insulation are:
• High dielectric strength
• High insulation resistance
• Temperature resistance
• Flexibility
• Mechanical strength
6. CABLE
• A cable consists of two or more conductors inside a single
covering. The conductors in a cable may either be bare or
insulated. Cables are available in different types. There are
single core cable, twin core cable, three, four core and
multi-core cables.
6.1. CABLE CONSTRUCTION
6.2 CROSS-SECTIONAL VIEW
OF A CABLE
• Single Core cable
• Twin core and earth (general internal power cables) cables
• Three-core and earth (normally used for the connections
between two way switches) cables
CONT’
PROTECTION DEVICES
Why do we use protective devices?
•
Overload
• An overload current is where too much current is drawn down
an electrical circuit.
•
For example
• Too many appliances are plugged in but there is no fault in the
circuit.
•
Cause
• A properly designed circuit will interrupt an overload before
any damage is done to the circuit.
CIRCUIT BREAKERS
• Short Circuits
This is where a fault of
negligible impedance
(resistance) occurs between
live conductors.
• In other words
A direct connection between
a phase, neutral or
protective earth is there
• Effect
The value of current, which
will flow, will depend on
where the fault occurs.
FUSES
• Types of Fuses:
•1
VDE 0635 DZ type fuse:
• This is a cartridge type fuse
available in four body sizes D1,
D11, D111 and DIV
• Current ratings from 2 Amps up
to 100 Amps.
• Breaking capacity up to 60kA.
FUSES
• Types of Fuses:
• 2 VDE 0636 NEOZED or DO type
fuse:
• This is also a cartridge type fuse
available
in three body sizes D01, D02 and
D03
• Current ratings from 2 up to
100Amps.
• Breaking capacity up to 50kA.
FUSES
• Types of Fuses:
• 3 BS 1361 fuse:
• This is a cartridge fuse available in ratings
from 5 to 60 Amps.
• They are most commonly used in domestic
installations.
• They have a breaking capacity of 16.5kA
which is adequate for most domestic
installation.
FUSES
• Types of Fuses:
•4
VDE 0636 NH type fuse:
• Breaking capacity of 120kA.
• They are not designed for
replacement by unqualified
personnel
• They are available in ratings up
to 1250 Amps.
ELECTRICAL TERMINOLOGY
•
Current – the movement of electrical charge
•
Resistance – opposition to current flow
•
Voltage – a measure of electrical force
•
Conductors – substances, such as metals,
that have little resistance to electricity
•
Insulators – substances, such as wood, rubber, glass
and Bakelite, that have high resistance to electricity
•
Grounding – a conductive connection to the earth
which acts as a protective measure
DISTRIBUTION BOARDS
.
MAIN ELECTRICAL TOOLS USED
The basic tools required by anyone in the
electro technical industry are:
•General Pliers
•Side cutters
•Knife
•Screwdrivers
OTHER ELECTRICAL TOOLS AND EQUIPMENT
ELECTRICAL MEASUREMENTS
AND MEASURING INSTRUMENTS
MULTIMETER:
• The three most commonly measured electrical quantities
are current,Voltage and resistance. Current is measured by
an ammeter, voltage by a voltmeter and resistance by an
ohmmeter.
• A single instrument used for measuring all the above three
quantities is known as a MULTIMETER. It is a portable
multi range instrument
CONT’
CONT’
• When measuring current (figure a) you switch the selector switch to 10 Amps .Full
scale deflection is 10 Amps. If the pointer reads 4 then that is 4 Amps.
• When measuring voltage (figure b) the selector switch is switched to voltage in the
values i.e 10; 50; 250 or 1000 which all give full scale deflection at each respective
range.
• When you select it at 250 and the pointer reads a 100, is indicates a 100 volts. It is
necessary to always start with the highest scale.
• When measuring resistance (figure c) the selector switch is switched to Ohms range
i.e X1; X10; X100; X1K or X10K. If the switches set at X10 and the pointer reads 50,
this value is multiplied by 10 to give 500 Ohms.
PROCEDURES FOR USING
MEASURING INSTRUMENTS
• An ammeter is use to for measure current and the meter is
connected in series to the circuit as shown below
CONT’
• In order to measure resistance one uses an Ohmmeter
which and the meter is connected in parallel to the circuit,
as shown below
CONT’
• Voltage can be measured by using a Voltmeter, and the
meter should be connected in parallel to the circuit
SUPPLY VOLTAGE SYSTEM
• Supply voltage is a voltage from a generating plant which is
transmitted by transmission line wires and then transformed to
different levels.
• TYPES OF SUPPLY
There are two types of supply
1.
SINGLE PHASE SUPPLY
This in the simplest form is from a single phase generator, i.e a generator
with only one winding.
The voltage from this generator is 230V in Rwanda between Line and
Neutral or Earth and this voltage is known a phase voltage
2.THREE PHASE SUPPLY
• If in an AC generator not only one , but three coils are
fitted at displacement angles of 1200 to one another, then
we get an AC in each of the three coil, The coils of a 3phase generator are named as follows
Coils
Start
Finish
1
2
3
U
V
W
X
Y
Z
WIRING COLORS
STANDARD CIRCUITS
1.
COMPONENTS OF AN ELECTRICAL CIRCUIT
• The main components of an electrical circuit comprise the following:
• A source of supply, AC or DC depending on the type of circuit
• A fuse, which is a weak link in the circuit that will break if too much
current is one that is above the rating of the current.
• A cable comprising phase and neutral or supply and return conductors.
• A switch to enable the circuit to be switched ON or OFF. (A main switch
serves as a main disconnection for the flow of electricity to a building, unit
or house, whereas, a local switch is located in every final circuit.)
• A current- using device or devices in general called a load or loads.
CONT’
2. SERIES AND PARALLEL
CIRCUITS
2.1 SERIES CIRCUITS
• A series circuit is a circuit where by the loads (or consumers) are connected in way that the
leaving point of the 1st load is the entering point of the next load, as shown in the figure below.
• The conductors, control and protection devices, loads, and power source are connected with
only one path for current flow
CONT’
• Observations
• The same amount of current will flow through each component in the
circuit.
• The voltage across each component will be different depending upon
the value of resistance for each one of them.
• If the path is broken, no current flows and no part of the circuit work.
• Consumers or loads of different value or capacity will not work
properly, as the driving force (emf) across each component may not
be adequate.
2.2 PARALLEL CIRCUITS
• A parallel circuit is a circuit where by the loads (or
consumers ) are connected in way that the entering points
of all consumers (loads) are connected together and leaving
points are also connected together as shown in the figure
below
OPEN AND SHORT CIRCUITS
• Two important extreme conditions can occur in a
circuit.
• These are: i) Open circuit
ii) Short circuit
➢An open circuit causes a high resistance in the circuit
because either a wire is broken or a switch is open, as
shown in the figure below. Therefore, no current can
flow.
CONT’
➢ A short circuit occurs when the circuit is not completed
through the load, but through a side very small resistance
path as shown in the figure below. This will cause a high
current in the circuit up to the side path.
GRAPHICAL SYMBOLS USED FOR ELECTRICAL
INSTALLATIONS IN
BUILDINGS
WALL SOCKET OUTLET
DRAWING TIPS
DIAGRAMS
• ..
SINGLE POLE ONE WAY SWITCH
SINGLE POLE ONE WAY SWITCH
SINGLE POLE ONE WAY SWITCH
SINGLE POLE ONE WAY SWITCH
SERIES SWITCH
TWO WAY SWITCH
DETACHED OR CIRCUIT DIAGRAM
ASSEMBLED REPRESENTATION
INSTALLATION REPRESENTATION
INSTALLATION EXERCISE
INTERMEDIATE SWITCH
DETACHED-REPRESENTATION OR
CIRCUIT DIAGRAM
ASSEMBLED-REPRESENTATION OR
WIRING DIAGRAM
PLAN INSTALLATION DIAGRAM
WIRING INSTALLATION
THANK YOU!!!!!!!!!