CircuitConcepts(Residential)
Description
This Activity Planwill allow students to understandhowelectrical circuits work ina home.Students will alsogain knowledgeofservicepanel installationand understandingofhowtheCanadianElectricalCode(CEC) applies to residentialelectrical wiring.
Accordingtoresidential wiring requirements,tosafely wire ahome electricians mustunderstandtheconcepts ofbranchcircuitwiring.Manynew apprenticesspendtime wiring homes in ordertogainexperience.Thetime spentlearninghow to roughin a homewill help them to understandhowto wirea homeand learnaboutthe CEC requirementsfor residential wiring. Residentialhousewiring alsoteachesnew apprenticesabout:
•Electricalequipment
•Howto read electricaldrawings
•Understanding electrical symbols
•Usingpractical measurement and layout
•Distribution of electrical circuits
•ApplyingCEC rules toelectricalinstallations
Wiringa homeis asmall-scale electrical job,butit incorporatesmany oftheskillsneeded tomove on to morecomplex electrical jobs.Thebasicskillslearned duringresidential wiring arereally the foundationalskillsneededto advancein theelectrical trade.
LessonOutcomes
The student willbeableto:
•Understandhow electrical powerenters ahome and is distributed to branchcircuits
•Knowsomeof the CEC requirements for BC
•Learn aboutsafety issuesregarding electrical services
Assumptions
Thestudent:
•Has little or no knowledgeof residential wiring
•Has knowledge of abasic electrical circuit
•Understands electrical hazardsand safety
•Knows what roletheCanadian ElectricalCode playsin determining standards for electricalinstallations
Thisworkis licensedunder aCreativeCommonsAttribution-NonCommercial-ShareAlike4.0InternationalLicenseunlessotherwiseindicated.
Terminology
Branchcircuit:theportionofwiringfromthefinalcircuit breakertotheoutlet.
Drywall:gypsumwallboardusedtocovertheinteriorwallsofmosthomes.
Electricalbonding:thepermanentjoiningtogetherofmetalpartstoformanelectricallyconductivepaththathasthecapacitytoconductsafelyany faultcurrent likelytobeimposedonit.
Electricalequipment:equipmentsuchasreceptacles(outlets), lightfixtures,switches,conductors(wires),circuitbreakers, electricalpanels,conduit,etc.
Electricallayout:takinginformationfromablueprintorelectricaldrawingandtransferringittotheactuallocationsinaroomtodenote wheredeviceswillbeinstalled(e.g.,lights,switches,receptacles).
Electricalmeter:adevicethatmeasurestheamountofelectricalenergyconsumed byaresidence,business,orelectricallypowereddevice.
Grounding:theprocessofconnectingequipmenttoacommonground,or“earth.”Thisisdoneasasafetymechanisminorderto avoidthe unsafeenergizingofequipment.
Mainelectricalpanel:ametalelectricalserviceboxthatacceptsthemainpowertothehomeanddistributeselectricalcurrentandvoltage (power)tothevariouscircuitswithinthehome.
Thevariouscircuitsareprotectedfromover currentby theuseofcircuitbreakers orfuses.Theelectricalpanelisalsoknownasaservice panel, breaker panel, andfuse box(archaic).
Overload:anovercurrentthatexceedsthenormalfullloadcurrentofacircuit.Thistypeofovercurrentcharacteristicallydoesnotleavethenormalcurrent-carryingpathofthecircuit.Itflowsfromthesource,throughtheconductors,throughtheload,backthroughtheconductors,tothesourceagain.
Roughin:workperformedonabuilding’selectrical systembeforetheinteriorwallsareinsulatedandfinishedwithdrywall.
EstimatedTime
1–2 hours
RecommendedNumberofStudents
20, basedonBCTechnologyEducators’BestPractice Guide
Facilities
Computer lab,classroom, or shop
Tools
Pencils,pens
Materials
•Class copies of or enough for pairs:Electrical Code Simplified, House Wiring Guide.P.S.Knight.ISBNnumber 978-0-920312-48-3. Available at most homeimprovement stores.
•Projectorandscreen
•Computer with Internet access andsound
•Photocopiedhandouts oroverhead projector withtransparencies
Optional
Thiswould be a good opportunity for a field trip to a residential construction sitetoshowtheelectrical systembeingbuilt.This could alsoserve as an opportunity to show thecarpentry andplumbing trades performing their jobs.
Resources
UnderstandingWiring
Videoprovidinginformationontheelectricalpanel.
BasicsofYourHome'sElectricalSystem-TheHomeDepot
ElectricalCode Simplified, House Wiring Guide, BCBook1, published byP.S.Knight.Available at most home improvement stores.
Activity
1.Asaclass, watch the“UnderstandingWiring”video(see theResourcessection). This videois from the United States,but itgivesagoodoverview of an electricalpanelandconceptsof branchcircuitwiring. Italsocovers someimportant safety issuesrelatedto housewiring.
2.Watch the“PanelUpgrade” video toshow studentshow powercomes into an electricalservicefrom the powerauthority.It will alsoshow and explain to studentshowa panelisupgradedfrom asmallerserviceto alarger service. Theelectricalportionofthis 23:44videoisthefirst16:05.
3.Discuss these videosas aclass andhelp studentsunderstandthat electrical wiringinhomes is done very similarly acrossNorthAmerica, althoughdifferentareas have differentcoderequirementsfor electrical work. The teacher should preview these videosandgenerate somediscussion topics and questions to check forstudent understanding.
4.Have studentspairupor work individually onthe questions onthe nextpage,basedon
Electrical Code Simplified, House Wiring Guide, BC Book 1.
EvaluationGuidelines
Thestudent:
•Participates indiscussions about the videos
•Displays knowledgeand understandingofbranch circuitsthroughdiscussion andquestioning
•Demonstrates understanding of some of the safety issuesaroundelectricalservices andbranchcircuitwiring
•Displays knowledgeand understandingofthe mainservice ofthehome throughdiscussion andquestioning
•Answers questions on coderequirementscorrectly
ExtensionActivity
If thereareenough copies of Electrical Code Simplified,studentsinsmall groups coulddraw upa fewquestions from specific chaptersinthebook,thentradequestionswithanothergrouptofindtheanswers from thebook.This activity willhelpstudents become morefamiliarwith coderules aswellashowtofindtheminthesimplified code book.
ElectricalCodeQuestions
All questionsaregeneratedofpages52–53ofElectrical Code Simplified, House Wiring Guide.Theimages on pages52–53leadto a pageinthe book thathastheanswer.Providethe coderuleaswell asthe answertothe questions. Wire sizes and ampacities are:
•#14wire—15amps
•#12 wire—20 amps
•#10wire—30amps
•#8wire—45amps
•Allwire is NMD90copperAnswer keyon thenext page.
1.What isthe maximum amperage and wire size thatmay beused for awashing machineinalaundry room? What typeofreceptacleis it?
2.What isthemaximum size of circuitbreaker to beused for an electricwaterheater?
3.How manyconductorsand what size ofwire should beused to supplyan electricdryer?What size ofcircuit breakershould be used?
4.InBritishColumbia is itmandatory foroutdoor plug outlets to becontrolledby aswitchinsidethe house?
5.What isthe minimumwire size and ampacityusedto supplyafridge? How manyconductors should beused? Whatother load may besupplied byafridgecircuit?
6.Isitallowable to installan outletboxbehinda baseboardheater?
7.How manyconductorsand what size ofwire should beused to supplyan electric rangeoutlet?What shouldthe plugreceptacleratingbe?Isit acceptable to fasten arangereceptacle outletbox onone side only?
8.What types ofreceptacles arerequired ina bedroom? What is theirpurpose?
Answers
1.Rules 26–710(e)(i), 26–720(b):20 amp #12 copper,20 amp T slotreceptacle2. 26–750 (4):20amps
3. 26–744(2)(3): 3wire #10copper,30 amp
4.26–717(a):No,but recommendedby CSA
5.26–720 (a):#14wire15amps,twoconductors, clock outlet6. 12–506, 12–3002(6):Yes,butnotpreferred
7. 8–300,26–744,26–746: 3 wire#8copper, 45 ampreceptaclerating,12–3012(3):No,supportedon two or more sides
8. 26–722 (f) & (g):AFCI type, arcfaultcircuitinterrupters,to trip quicklytoavoidfirehazards