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EKAS 2.8.1.1

Basic Electrical Principles

UEE31307 Certificate III in Refrigeration and Air Conditioning Stage 2A Units: UEENEEPOO1B, UEENEEPOO2B Chris Hungerford Monday, April 27, 2020

2..8.1.1A

Hazards & Unsafe work practices

• Electric Shock • Arcing • Smoke

10.

11.

Unauthorized electrical work.

Inadequate work practices.

Live work.

Disregarding earthing circuits.

Untested test equipment.

Lack of tool maintenance.

Laziness & fatigue.

Workplace fool.

Untested work before commencing work.

Untested work connected to a supply.

Disregard to Australian Standards.

2..8.1.1A

Safety practices in the use of common tools and plant Employees who are exposed to the hazards of falling, flying, abrasive and splashing objects, or exposed to harmful dusts, fumes, mists, vapors, or gases must be provided with personal protection equipment (PPE) necessary to protect them from the hazard. All hazards involved in the use of tools and plant can be prevented by following five basic safety rules: 1.

Keep all tools and equipment in good condition with regular maintenance. 2.

Use the right tool for the job. Examine each tool and plant for damage before use. Operate according to the manufacturer's instructions. Provide and use the proper protective equipment.

Low voltage rescue Accident

2..8.1.1.B

Rescuer’s safety Yes Isolate Supply Free victim Yes No Rescue kit, Gloves & crook Correct PPE No Unsafe area No Fire Clear area Yes Use fire blanket Use drag method Assess victim’s condition Resuscitate, treat burns & injuries Await medical assistance

Send for help as soon as the situation allows

Burns

WARNING • Do not apply lotions, ointment or fat to burn.

• Do not touch the injured area or burst any blisters.

• Do not remove any thing sticking to the burn.

• Keep a check for shock.

2..8.1.1.B

Management • Remove casualty from danger, DRABC.

• Cool the burnt area, hold under cold running water for 10 min.

• Remove any constrictions, unless sticking to the burn.

• Cover burn.

• Calm casualty • Call 000 for an ambulance.

Bleeding

WARNING • Wear gloves to guard against infection.

• If casulalty becomes unconscious - DRABC.

• Do not apply a tourniquet.

Management • Apply pressure to the wound.

• Raise and support injured part.

• Bandage wound.

• Check circulation below wound.

• Treat for shock.

• Call 000 for an ambulance.

2..8.1.1.B

Signs & symptons • weak, rapid pulse • cold, clammy skin • rapid breathing • faintness/dizziness • nausea • pale face, fingernails, lips

Shock

Management • Lie casualty down, protect them from cold ground.

• Calm the casualty.

• Follow DRABC.

• Manage any injuries.

• Ensure comfort, if thirsty, moisten lips.

• Monitor breathing and pulse.

• Place in recovery position.

• Call 000 for an ambulance.

2..8.1.1.B

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A

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B

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C

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D

DRABCD

danger response airway breathing circulation defibrillator

Danger

• • •

to you to others to the casualty Make sure you don’t become a second casualty 2..8.1.1.B

2..8.1.1.B

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Response

is the casualty conscious?

• gently shake the casualty and ask “Can you hear me?”, “What is your name?” • if the casualty is

conscious

, check for and manage bleeding and other injuries.

• if the casualty is

unconscious

, they should be turned on the side

2..8.1.1.B

Airway

Australian Resuscitation Council http://www.resus.org.au/ Guideline 4.

Clear airway: If foreign material is present in mouth, roll casualty on side and clear mouth with their fingers.

Tilt head backward. Place one hand on the forehead and use the other hand to lift the chin.

2..8.1.1.B

Breathing

Look for the chest rising and falling Listen for the sound of breathing

Breathing

Yes

- place casualty in side position

No –

seal nose and give 2 breaths into mouth.

2..8.1.1.B

Circulation

feel the pulse at the neck (carotid pulse)

- commence CPR (cardiopulmonary resuscitation), 2 breaths & 30 compressions at a rate of approximately 100/ minute. 5 cycles in 2 minutes Compress 1/3 depth of chest.

Rescuers should minimize interruptions of chest CPR to check for signs of life.

2..8.1.1.B

Defibrillator

• Minimise interruptions to chest compressions • Give a single Defibrillator shock for ventricular fibrillation.

• If arrest is witnesses by a health care professional and a manual defibrillator is available, 3 shock may be given.

• After each defibrillation attempt give 2 minutes of CPR.

2..8.1.1.C

The FIRE triangle

Three components are required for a fire to exist: fuel, heat, and oxygen Removing any one of these components the fire will not exist.

To reduce the chance of fire in the workplace all three need to be kept separate.

Oxygen Fuel Heat

2..8.1.1.C

PCB’s Polychlorinated biphenyl

PCB,s congeners are odourless, tasteless, clear to pale-yellow, viscous liquids. They are formed by electrophilic chlorination of biphenyl with chlorine gas. They have high dielectric constants, very high thermal conductivity, high flash points (from 170 to 380 °C) and are chemically fairly inert, being extremely resistant to oxidation, reduction, addition, elimination, and electrophilic substitution.

PCBs readily penetrate skin, PVC (polyvinyl chloride), and latex (natural rubber).

PCBs are very stable compounds and do not degrade readily. Their destruction by chemical, thermal, and biochemical processes is extremely difficult, and presents the risk of generating extremely toxic dibenzodioxins and dibenzofurans through partial oxidation. PCBs were used as coolants and insulating fluids ('transformer oil') for transformers and capacitors especially in components of early fluorescent light fittings, electrical transformers, plasticizers in paints and cements, stabilizing additives in flexible PVC coatings of electrical wiring and electronic components, pesticide extenders, cutting oils, reactive flame retardants, lubricating oils, hydraulic fluids, sealants, adhesives, wood floor finishes, water-proofing compounds, casting agents, vacuum pump fluids, fixatives in microscopy, surgical implants, and in carbonless copy ("NCR") paper.

Studies of workers indicate that PCBs were associated with specific kinds of cancer in humans, such as cancer of the liver and biliary tract. Polychlorinated biphenyls (PCBs) have been shown to mimic the action of oestrogen in breast cancer cells and can enhance breast carcinogenesis. PCB waste must be treated by a licensed/approved operator. Solid and liquid scheduled waste must not go to landfill. Quantities above 10kg must be notified to Department of Environment and Heritage.

2..8.1.1.C

2.8.1.1 D

Simple Electric Circuit

• The basic electric circuit consists of the following three components.

1. a source 2. a complete path 3. a load to do work

2.8.1.1 D

The Source

• a source of electrical pressure :-

battery to provide electrical energy for the system

• other types of sources: generators, alternators, solar cells, piezo crystals.

The Source

2.8.1.1 D

The source is known as an EMF device.

Electron Motive Force

.

It places the electron in motion by creating a pressure difference, therefore the unit of an EMF is volts

2.8.1.1 D

Types of sources

Electro-magnetic - alternators, generators.

Photo-electric ----- solar cells.

Thermo-electric --- thermocouples Piezo-electric ----- gas lighters, microphones Chemical ---------- cells and batteries Static ---------------- lightning.

Component identification Resistive components:-

all devices that have a principle function of producing heat.

Inductive components:-

any device that has a coil and principle operation uses magnetism.

2.8.1.1 D

Capacitive components:-

device that stores an electro-static any charge.

Resistance is a lot like friction; they both act to oppose motion and generate heat.

2.8.1.1 D

Resistance

Resistance is the opposition to the flow of electrons.

All materials exhibit a value of resistance to the flow of electrons. A good conductor has a small resistance, while an insulator has very high resistance.

Component function

Impedance

AC resistance

2.8.1.1 D Urns Heaters

Resistance

Irons

Reactance

Toasters

Inductance

Motors Transformers Relays

Capacitance

Capacitors

Open Circuit

An open circuit prevents current flow. A switch, fuse, or circuit breaker when operated will produce an open circuit.

2.8.1.1 E

An open switch

Open switch lamp is off.

Closed Circuit A closed circuit allows current to flow. A switch can control both open and closed circuits.

2.8.1.1 E

Closed switch

Closed switch lamp is on

2.8.1.1 E

Short Circuit

This type of circuit is to be avoided whenever possible. The lamp is bypasses by a conductor connected directly across the supply and reducing the circuit resistance. High current flow

Little current flow through the lamp, however excessive current flows in the short.

The pressure of the circuit (volts) will also drop.

Little current Short circuit

2.8.1.1 E

Ohms Law

The current flowing in a circuit is proportional to the voltage and inversely proportional to the resistance of the circuit.

V = Voltage I = Current R = Resistance

V I R

2.8.1.1 E

Proportional to

Proportional to , values that are directly opposite to each other in a formula is proportional to each other.

Hexagon is proportional to the square.

= Star is proportional to the circle.

2.8.1.1 E

Inversely proportional to

Inversely proportional to, values that are diagonal to each other are inversely proportional to each other.

This technique applies to all formularies.

The star is inversely proportional to the square.

= The hexagon is inversely proportional to the circle.

2.8.1.1 E

Triangle & thumb

To transpose the formula, draw the triangle as shown.

Voltage = ? Move thumb over voltage and the remainder equals the voltage.

I V R

2.8.1.1 E

Triangle & thumb

Voltage = current X resistance Determine the resistance.

I V R

2.8.1.1 E

Triangle & thumb

Thumb over the resistance.

Resistance = the remainder.

Resistance = voltage/current

I V R

2.8.1.1 E

Transposing formula

Current = voltage / resistance Resistance = voltage / current Voltage = current X resistance

I = V R R = V I V=I R

2.8.1.1 F

Applying Ohms Law

Determine the current flow.

I=?

I V R 10v 5

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I = V = 10 = 2A R 5

2.8.1.1 F

Applying Ohms Law

Determine the Resistance.

I=5A I V R 100v R=?

R = V = 100 = 20

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I 5

2.8.1.1 F

Applying Ohms Law

Determine the Voltage.

I=12A I V R V=?

20

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V=I R = 12 x 20 = 240v

2.8.1.1 F

Problem Solving

Voltage Current Resistance

I

50v 5A 240v 1A 16

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12

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V R

Calculate the missing value using ohms law.

2.8.1.1 F

Summary

Ohms law is the relationship between voltage, current, and resistance.

50v 5A 240v 12v 15A 1A 10

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16

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12

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2.8.1.1 F

Problems

Determine the resistance of a 240v heating element that has a current of 20amps.

A 240v light bulb, has a measured resistance of 960  , determine the circuit current.

A 240v element of 48  has been replaced by a 240v element with a resistance of 16  . If the circuit is protected by an 8A circuit breaker, determine the effects on the circuit.

AS/NZS-3000:2007, Wiring Rules

3.7 ELECTRICAL CONNECTIONS 3.7.1 General Connections between conductors and between conductors and other electrical equipment shall provide electrical continuity and adequate mechanical strength.

2..8.1.1.G

Solderless lugs

Ross - Courtney lug. Stanco lug

2..8.1.1.G

Crimps

Terminating - crimp lugs.

Joining cables of the same size - crimp links.

When crimping it is important that the correct crimp type lug for the cable and the correct tool for that lug is used.

AS/NSZ 3000 cl 3.7.2.3.2

2..8.1.1.G

Terminal connections

AS/NZS 3000 cl 3.7.2.4

Blue point connectors (BP) Line taps.

Articles terminals.

Terminal strips.

Bolted & clamp connectors,

AS/NZS-3000:2007 Wiring Rules 3.7.2.7 Soldered connections Where a soldered connection is used the design shall take account of creep, mechanical stress and temperature rise under fault conditions.

2..8.1.1.G

Stripping of Insulation.

• Avoid using a knife on smaller cables.

• Tear the insulation off, don’t cut.

• Do not indent any conductor material.

• Be sure not to remove excessive insulation.

• Remake any damaged insulation.

• The only connection for an extension lead is via an approved plugtop and socket.

2..8.1.1.G

AS/NZS-3000:2007 Wiring Rules 3.7.2.2 Preparation for connection The insulation on a conductor shall not be removed any further than is necessary to make the connection. For connections between insulated conductors the connection shall be insulated to provide a degree of insulation not inferior to that of the conductors. Any damaged insulation shall be reinstated.

Terminations and connections • Connections must not be soft soldered before compression terminations.

• Must be seated correctly.

• Free of dirt and oxides.

• Use a suitable lug or connector.

• Insulated to the equivalent of the original insulation.

• Earth connection must be painted if exposed to weather

2..8.1.1.G

AS/NZS-3000:2007 Wiring Rules 3.7.2.6 Mechanical stress All cables and conductors shall be installed so that there is no undue mechanical stress on any connection.

AS/NZS-3000:2007 Wiring Rules

3.7.2.3.1 Loosening of connections

Connections shall be made so that no loosening is likely because of vibration, alteration of materials or temperature variations to which the connections are likely to be subjected in normal service.

2..8.1.1.G

Further reading: Workbook Risk management Questions: Workbook, Topic 3, Q1 – Q90