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RakerAppliance Repair Professionals, Inc.

Electricity Made Simple

Manual 5

Copyright © 2003 Harry D. Raker

WARNING

SAFETY PRECAUTIONS

Safety is very important when working on any appliance.

Disconnect power before servicing any appliance.Always keep the work area and your shoes dry.

All appliances have sharp edges and should be handled carefully.

Before working on any gas appliance extinguish all open flames andbefore attempting any gas associated repair, cut off the gas feed.

Always sniff for gas leaks and soap bubble test any parts that may havebeen disturbed by repair work.

To minimize any potential buildup of gas in case there is a leak, alwayshave the room open to the outside.

Table of ContentsManual 5

Electricity Made Simple

Introduction ..................................................................................... . 1Current Flow ........................................................................... 2Ohm’s Law .................................................................................... 3Loads .......................................................................................... 4Power Sources .................................................................................. 5Current Loops ............................................................................... 5Making Current Tests ..................................................................... 7Making Voltage Tests ................................................................... 9Understanding Common, Ground and House Wiring ........................ 11Series and Parallel Circuits ......................................................... 18Electrical Switches .......................................................................... 21Using Your Multimeter ................................................................... 23Solenoids ..................................................................................... 24Relays and Contactors ...................................................................... 25Electric Motors ............................................................................. 26High Impedance Motors ..................................................................... 26Shaded Pole Motors ........................................................................... 27Split Phase Motors ........................................................................... 28Motor Starting Switches ..................................................................... 29Ammeters and Amprobes ................................................................. 30Circuit Patterns ............................................................................... 32Circuit Diagnosis ...................................................................... 34Safety Techniques ............................................................................ 35Accidents ............................................................................................. 37Accident Prone Tasks ................................................................... 37Working on a Live Appliance ................................................................38Circuit Symbols ................................................................................. 40Sample Circuits ............................................................................. 41Examination ...................................................................................... 45Examination Answers ............................................................................... 47

Manual 5, Electricity Made Simple


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ELECTRICITYMADE SIMPLE:Introduction

his lesson is going to teach youthe practical electrical knowledgethat you need in order to properlyservice all electrical appliances.

Most books on electricity deal with theflow of electrons, deep theory, and agreat amount of detail on Ohm's Law.

Theoretical knowledge is not necessaryto properly diagnose and repair electricalappliances. Uncle Harry going to teachyou electricity in a way that will causemy old teachers in ElectricalEngineering Department at The JohnsHopkins University to roll over in theirgraves.

For our purposes the theory doesn'tmatter. The things that do matter are thefollowing:

1. The concepts must be easy to understand.

2. They must be easy to remember.

3. They must provide a fast reliable method of diagnosis.

Uncle Harry’s Story Time

Stephen Hawking chairs the TheoreticalPhysics Department at OxfordUniversity. He is reputed to be one ofthe most intelligent people alive today.

Incidentally, he is so physically disabledthat he can only speak through a voicesynthesizer and is totally confined to awheelchair. A few years ago he wrote abook, “On Space and Time”, for laymanlike you and me. It is a great bookintended to help people understand theconcepts of “Black Holes” and the “BigBang” theory.

His editor advised him that for eachequation that he presented in his book,sales would drop by one half. Heincluded only one, in the last chapter,E=mc2. It is very doubtful that UncleHarry is smarter than Hawking’s, butyou will find no formulas in this book.

Unfortunately electricity can be a bitdry, but Uncle Harry will do his best toliven it up. First, why do we spend awhole lesson on electricity? A very highpercentage of appliances can be repairedwith little or no knowledge of electricity.Probably 90%! But that is not nearlygood enough for Uncle Harry.

You can’t afford to be caught on 10% ofyour jobs. It is critical to be able todiagnose and repair every job. If youget stuck, one job can completely foulup a day, or even a week. One job in 10comes along pretty often. Uncle Harrywants you to be ready for it.

Many mechanics manage to get by withonly the smallest amount of electricalknowledge. Recently, I was amazed tosee a sign up list a local parts supplyhouse. It was for a free course in basicelectricity, and most of the veteranmechanics I knew had signed up.

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Obviously, even after years ofexperience, they still felt uncomfortablewith electrical problems.

Incidentally, yours truly, Uncle Harry,was teaching summer school inelectricity in 1961. You are in goodhands.

The problem seems to be that mostmechanics don’t understand the basicconcepts and get confused with thesimplest problems.

Being capable of electrical diagnosisreally separates the men from the boys.When I had a number of mechanics onthe road, I could usually get them out oftrouble over the phone. Except for onearea; if they were stuck on an electricalproblem, I too, was in trouble.

Usually, I had to go to the house todiagnose the problems. All too often,they were unable to perform the tests Isuggested. They could not supply mewith accurate facts that I needed to helpthem.

Not being able to perform properelectrical diagnosis leads to guessingand a lot of errors and callbacks. Youwill avoid that situation and learncorrectly from the beginning.

There are a number of basic conceptsthat must be mastered in order tounderstand how electricity works inappliances.

They are the following:

1. Current Flow 2. The Language of Switches 3. Using your Multimeter 4. Circuit Diagnosis In this lesson we will cover theseconcepts, along with a great deal ofpractical information.

Current flow

lectricity is often compared to waterflow in the pipe. I have never reallyliked the analogy. To some extent

it’s true, however, electrons don't fall outof the end of the wire onto the floor andpile up like water does out of the end ofan open hose. If electrons did that, we'dhave a big pile of them underneath allthe receptacles in our house, wouldn'twe?

There are other problems with the wateranalogy. Electricity follows it’s own setof very specific laws. Those laws arevery different from the flow of water andwill be covered in this lesson.

For our purposes, electricity only flowsthrough a good conductor, mostlycopper wires. Air is a very poorconductor, and that is why electronsdon’t pile up on the rug. It take a veryhigh voltage to create a current flowthrough a poor conductor. Lightning forinstance has a high enough voltage,millions of volts, in fact. Lightning willjump right out of an outlet and burn apath across a rug.

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A “good ole boy” told me a story of hisfarming childhood. A storm wasbrewing and he decided to come in fromthe field. While walking down the road,he found a big black snake also gettingout of the rain. He picked it up andwrapped it around his arm. As the rainbegan he rushed into the family’s largechicken coop, black snake still wrappedhappily around his arm.

One of the farm hands had just finishedloading up two large baskets of eggs andwas getting ready to leave. At thatmoment, lightning hit the coop and camedown the hanging light fixture. Itjumped to the floor and seared a pathbetween the two men.

The snake immediately uncurled anddropped to the floor. Seeing the snakeand the lightning, the worker instantlydropped the baskets of eggs and headedwest, as fast as his legs would go.

It takes about 10,000 volts to jump aninch of dry air. Standard householdvoltages is a maximum of 240 volts.This is too small to jump at all.

Only in TV’s and microwaves do wefind high voltages. In microwaves, thehigh voltage section is clearly markedfor danger. The high voltage in themicrowave is between 10,000 and

15,000 volts. BE CAREFUL, IT CANJUMP!

Ohm’s Law

n order for electricity or “current toflow”, it must complete a loop orcircuit. Lightning is special, it flows

from the clouds to the ground. Inappliance work, we only concernourselves with normal circuits or loopsthat are controlled by copper wire.

Copper has a very “low resistance” tothe flow of electricity. Copper carriesvery large amounts of electricity or“current” with ease. For instance, if youtook a piece of copper wire and stuckone end into each side of a normal 110VAC socket, current would flow. Infact, a lot of current would flow. Itwould probably kick the breaker, andmaybe, blow up the receptacle, and you.

The amount of the current flow isdetermined by the resistance in the loopor circuit.

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Short Circuit

If the resistance in the loop is low, thecurrent is high. If the resistance is highthe current is low.

This inverse relationship is known asOhm’s Law. Pretty simple really,wouldn’t you say. The typical analogy,often used, is a pinch in a water pipe. Arestriction acts the same as a resistancein an electric circuit.

In the experiment above, when you blewup the receptacle, there was noresistance and a “short circuit” occurred.In order for a controlled amount ofcurrent to flow we need to introduce thecorrect amount of resistance. On mosthousehold circuits we need to keep thecurrent at less than 20 amperes.Otherwise we will pop the circuitbreaker.

Loads

he component or resistance thatdetermines the amount of current iscalled a load. Loads include

devices that actually do work. Examplesof loads are:

1. Motors (fan motors, drive motors, compressors, timer motors)

2. Heating elements (bake elements, dryer elements, defrost heaters)

3. Copper Coils (water valve solenoids, dump valve solenoids)

4. Light Bulbs

Switches, timers, controls, andthermostats are not loads.

They are merely breaks in the circuit.They only serve to connect anddisconnect the loads.

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Power Sources

or our purposes, the power source isthe utility and the power in either110 or 220 VAC (volts alternating

current). There is no need for us tostudy direct current and compare it toalternating current. It is too complicatedand will accomplish little. All of thelogic in this lesson works equally wellon direct and alternating current. Today,direct current is only found in portable

devices, toys, and cars. Most of theworld operates on AC.

For the moment, we assume that wehave a stable power supply provided bythe local utility. House power problemsand breaker panel circuitry will comelater.

Current Loops

Look carefully at a simple circuit.

The current flow in any one

loop is uniform throughout

that loop.

For instance, in the above circuit weconnected a light bulb with a line cord toa 110 VAC outlet. The two metersmeasure the same current flow in eitherwire. The light bulb does not use upthe electricity as it passes through.

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Measuring Current



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Whatever enters a load mustalso exit that load.

The tungsten filament within the lightbulb is the only resistance in the circuit.The resistance drops the current flow

down to a fraction of an ampere, about0.5 amps, enough to light the bulb.

Each load device must be provided withits own loop. In symbolic terms, allappliances or even a house are wired inthe following way.

The loops may be numerous and lookcomplicated but the logic doesn’t change

Now you may be wondering why all thistalk about loops. The reason is simple.Loops are circuits.

Diagnosis of electrical circuits involves“breaks or failures” in circuits.

Once you understand a circuit , it is nothard to find breaks.

Look at a more complicated circuit:

Circuit Loops



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Making Current Tests

n the second example there are twocircuits, one to the bulb and one to thecompressor.

Simple symbols are used for the lineplug, switches, the bulb, and thecompressor. Wires A and D are the linecord wires. The current in both of themis always the same.

Current A = Current D

When the light and the compressor areboth on, the current in circuit A will be:

Current A = Current B + Current E

Likewise

Current D = Current E + Current C

In practical terms, the currents might be:

Both A & D = 5.2 amps

Both B & C = 5.0 amps

E = 0.2 amps

The logic is simple. No currentdisappears. It merely divides into thevarious circuits and neatly adds back upat the second line cord wire. Circuitscan get very complicated with manyloops carrying currents simultaneously.During diagnosis, only one circuit ischecked at a time.

Simple Manual Defrost Refrigerator Circuit

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For instance, while checking a frost-freerefrigerator defrost heater, thecompressor circuit is of no concern.Even in the previous, simple example, aproblem in the door switch, completelyeliminates the cold control andcompressor circuit from consideration.

Technicians often get confused becausethey are not sticking to one circuit at atime. They get lost, by unknowingly,testing other parts of the circuit.

Unfortunately, it is usually impractical,and often not very informative, to makecurrent tests. Most of the time the basicproblem is “lack of current flow”.

Common examples are:

1. A dead bake or broil element

2. A cold dryer heating element

3. An inoperative defrost heater

4. A dead dryer

5. No water to a dishwasher

Testing for current flow with anammeter wouldn’t tell you very much.

You already know there is no currentflow!

Uncle Harry’s Trick of the Trade # 80

Uncle Harry owns a nice Amprobeammeter, but it gets used less than twicea year in 1000 service calls. Learn touse a voltmeter properly for the surestdiagnosis.



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Making Voltage Tests

oltage tests are a lot harder tounderstand than current tests.However, if properly performed,

they provide essential information.

Go back to the simple refrigerator circuitand turn on the light and the compressor.This is the equivalent of standing infront of the frig with the door open,deciding on dinner.

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Making Voltage Tests



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Using test leads that terminate in smallalligator clips, imagine connecting themas shown. The star indicates the“common side of the line” a concept wewill cover momentarily.

Test point “A” will read the line voltage,if the power supply and line cord areintact. If the reading is zero, the solutionis simple.

You will be surprised at how simplemuch of electrical diagnosis really is.


Until you really are into this business, itis hard for you to imagine howincapable many people are of using thesimplest logic to repair their ownappliances. My secretary fixes a greatnumber of appliances right over thephone.

She doesn’t even tell me about most ofthem anymore. She simply asks logicalquestions. For instance:

1. If an appliance is dead she asks , “Isit plugged in?” “Have you checked thecircuit breaker?”

2. If a refrigerator is thawing out anddead she asks, “Is the light on when youopen the door?” “Was it on before youstarting having the problem?”

3. If a disposer is dead she asks, “Haveyou checked the reset buttonunderneath?”

4. On a cold gas stove, “Does it have apilot light? Have you checked it?”

5. No water coming into a washer,“Have you checked the water cutoffs?”

Yes, it all really happens!

Overall, it is not good for business tocharge “service charges” for stupidinformation. It is best to eliminate allthe obvious things before going on acall. In doing so, a better relationship isestablished and more referrals result.

Next, connect the meter between “B”and the common. It should measure 110VAC. There are now two possibilities.These possibilities lead us to a series ofvery important electrical laws. Theselaws must be memorized.

1. Law #1. If line voltage ismeasured across a load, the loadshould be operating. If it is notoperating the load is bad or the internalload wiring is broken.

2. If no voltage is present at the loadthere is a break somewhere else in thecircuit.

Connect the meter between Test Point“A” and “B”

There are again two possibilities.

1. If line voltage appearsacross a closed switch theswitch is faulty. It is notclosed, it is open.

2. If no voltage appears the switch maybe closed and operating properly.



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No voltage will ever appearacross a closed switch.

Law #2. An open circuit willmeasure full voltage.

Law #3. A short circuit willmeasure zero voltage.

Unfortunately, there are other reasonsfor no voltage. No voltage is only a clueand requires further testing.

By testing and using these three simplelaws, you can analyze any circuit, nomatter how complex.

As you can see, it is important tounderstand the difference between loadsand switches. The laws apply to eachone in different ways.

We will leave the heavy theory for awhile and come back later.

Understanding “Common,”“Ground,” and Home Wiring

or your own safety and overallunderstanding we are now going tostudy house wiring. Improperly

installed house wiring, and problemswith ground systems are common andimportant to understand. Applianceservice calls are frequently the result ofhouse wiring problems.

Fortunately for us, over the years,electrical engineers have developedstandard ways of wiring homes andappliances. We will review thedevelopment of these conventions.

Back in history, early in this century,homes were first wired with electricity.Originally, only two wires were broughtinto the house and the voltage betweenthem was 110 VAC.

Actually Thomas Edison, in New Jerseyabout 1900, believed direct current wasthe best method and built a large utilitydistributing it. But that’s real historyand we don’t need to go back that far.

Following is a sketch of the early type ofhouse wiring.

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Early Electrical House Wiring