WIRING FOR APPLIANCES

Transcription

1 RESIDENTIAL ELECTRICAL WIRING WIRING FOR APPLIANCES TEACHER S GUIDE SHOPWARE

2 INTRODUCTION This Teacher s Guide provides information to help you get the most out of Residential Electrical Wiring: Wiring for Appliances. The contents in this guide will allow you to prepare your students before using the program and present follow-up activities to reinforce the program s key learning points. This program is part of an eight-part video series entitled Residential Electrical Wiring. This series shows the student, step-by-step, how to safely and effectively connect, install, and repair residential electrical wiring. Common aspects of residential wiring are explored, including: Setting up the main panel Properly wiring appliances, fixtures, receptacles, and switches Ensuring safety through proper grounding and surge protection devices. In addition to procedures involved with new construction and wiring, examples of what an electrician might find when performing renovation work are also incorporated. Safe work practices and techniques are emphasized throughout the programs, and the importance of following the current National Electrical Code and local regulations is stressed. Hardwiring doesn t have to be hard. Wiring for Appliances looks at some of the most frequently encountered appliances that get wired right into a house s electrical system: electric wall heaters, electric stoves, garbage disposals, dishwashers, thermostats, garage door openers, water heaters, and electric dryers. LEARNING OBJECTIVES After viewing the program, students will be able to: Determine the general-purpose circuits and receptacles needed in a dwelling. Calculate the minimum number of branch circuits for general outlets. Explain the importance of considering actual load values when determining branch circuits. Use the PIE formula to determine the correct conductors and overcurrent protection for large-appliance circuits. Define the American Wire Gauge (AWG) standard. Name and describe motor protection devices. EDUCATIONAL STANDARDS National Standards This program correlates with the National Competency Standards and Objectives from the National Center for Construction Education and Research. The content has been aligned with the following educational standards and benchmarks from this organization. Describe the risks associated with working around electricity and high voltage. Identify electrical hazards and how to avoid or minimize them in the workplace. 2 Copyright 2005 SHOPWARE

3 Define the units of measurement that are used to measure the properties of electricity. Explain how voltage, current, and resistance are related to each other. Using the power formula, calculate the amount of power used by a circuit. Describe how to determine electric service requirements for dwellings. Size wiring devices in accordance with NEC requirements. Determine the maximum load allowed on specific wiring devices. Describe rules for installing electric space heating and HVAC equipment. Size branch circuit overcurrent protection devices (circuit breakers and fuses) for non-continuous duty and continuous duty circuits. Use load calculations to determine branch circuit conductor sizes. Select and size overcurrent. Explain the role of the NEC in residential wiring. The competencies and objectives from the NCCER have been reprinted with permission. English Language Arts Standards The activities in this Teacher s Guide were created in compliance with the following National Standards for the English Language Arts from the National Council of Teachers of English. Students adjust their use of spoken, written, and visual language (e.g., conventions, style, vocabulary) to communicate effectively with a variety of audiences and for different purposes. Students use a variety of technological and information resources (e.g., libraries, databases, computer networks, video) to gather and synthesize information and to create and communicate knowledge. Standards for the English Language Arts, by the International Reading Association and the National Council of Teachers of English, Copyright 1996 by the International Reading Association and the National Council of Teachers of English. Reprinted with permission. Technology Standards The activities in this Teacher s Guide were created in compliance with the following National Education Technology Standards from the National Education Technology Standards Project. Students demonstrate a sound understanding of the nature and operation of technology systems. Students develop positive attitudes toward technology uses that support lifelong learning, collaboration, personal pursuits, and productivity. Students use a variety of media and formats to communicate information and ideas effectively to multiple audiences. Students employ technology in the development of strategies for solving problems in the real world. Students use technology tools to enhance learning, increase productivity, and promote creativity. The National Education Technology Standards reprinted with permission from the International Society of Technology Education. 3

4 PROGRAM OVERVIEW Hardwiring doesn t have to be hard. This video looks at some of the most frequently encountered appliances that get wired right into a house s electrical system: electric wall heaters, electric stoves, garbage disposals, dishwashers, thermostats, garage door openers, water heaters, and electric dryers. MAIN TOPICS Topic 1: Determining Branch Circuits and Outlets This program begins with a brief introduction to the importance of installing branch circuits safely and properly. Viewers realize how an electrician calculates the minimum number of general-purpose circuits and the number of outlets per branch circuit when planning a residential wiring installation. The importance of following the National Electrical Code is also stressed. Topic 2: Considering Load Values In this segment, viewers identify the importance of considering actual load values when determining branch circuits. They also learn how to decide what overcurrent device is appropriate, and what appliances are appropriate and safe to plug into a general-purpose receptacle. Topic 3: Special Circuits This final segment looks at some of the most frequently encountered appliances that are wired right into a house s electrical system, including electric wall heaters, electric stoves, garbage disposals, dishwashers, garage door openers, water heaters, and electric dryers. FAST FACTS Selecting the minimum number of general-purpose circuits is a beginning point in planning a wiring installation in a residence. Electricians must follow the standards established by the local electrical utility, local codes and ordinances, and the National Electrical Code. The National Electrical Code has established wiring standards to ensure that occupants have access to outlets at convenient locations. For receptacles, the basic standards require that no point measured horizontally along the floor line is more than 6 feet from a receptacle. At least one receptacle must be installed in any wall space that s 2 feet or more in width. In residential wiring, it s permissible to install lighting and receptacles on the same circuits. Actual load values should always be considered when determining branch circuits so that circuit overloading can be eliminated. A 15-ampere receptacle should never have anything rated more than 12 amperes plugged into it. A 20-ampere receptacle should never have anything rated more than 16 amperes plugged into it. Sometimes a special circuit is necessary for specific loads. Power divided by voltage equals amperage. This is referred to as the PIE formula. P equals wattage, I equals amperage, and E equals voltage. 4

5 Conductors are sized according to the American Wire Gauge, or AWG standard. As the wire size gets smaller, the gauge number gets larger. According to the NEC, if a branch circuit supplies lighting units, portable appliances, or both, then the total rating of utilization equipment fastened in place, other than luminaires, can t exceed 50% of the branch-circuit ampere rating. As a professional electrician, you should make sure that all your wiring exceeds minimum wiring requirements. VOCABULARY TERMS ampacity: Amperage capacity. amperage: Unit of measure denoting how much current a conductor is carrying. Represented by the letter I, for intensity of current flow. appliances: Any equipment made for a specific purpose that uses electricity to create light, heat, mechanical motion, etc. branch circuits: The conductors between the final overcurrent devices and the outlets or appliances. conductor: Anything that passes electricity from one point to another. Electrical wires and power lines are conductors. fixed appliance: An appliance, such as a dishwasher, that s fastened to a specific location. grounded: Connected to the earth or to something that conducts electricity to the earth, such as a water pipe. ground-fault: When something or someone provides an unintentional path between a source of electrical current and the ground. This can happen if you touch a faulty electrical appliance, and it can cause electrocution. Ground-faults can also cause fires. ground-fault circuit interrupter (GFCI): Detects a ground-fault and shuts off power to that circuit in a fraction of a second. interrupting rating: The highest current at rated voltage that a device is intended to interrupt, under standard test conditions. kilowatt: One thousand watts. load end: The end of a service conductor that feeds power through a branch circuit to whatever uses it. overcurrent: A current that is higher than the rated current for a conductor or a piece of equipment. overcurrent protection: Provided by circuit breakers or fuses that cause a circuit to automatically open up when the current gets higher than a preset value. voltage: A unit of measure denoting the force, or pressure, that moves current through a conductor. Represented by the letter E, for electro-motive force. wattage: A unit of measure denoting amount of usable power. Represented by the letter P, for power. 5

6 PRE-PROGRAM DISCUSSION QUESTIONS 1. How is electricity generated? 2. How does electrical power change between the main service panel and the receptacle? 3. What are the hazards of working with electricity? 4. What is the NEC? Why is it important? 5. What do you think are the pros and cons of working as an electrician? POST-PROGRAM DISCUSSION QUESTIONS 1. What local requirements or codes in your area regulate the wiring of appliances? 2. What challenges might you face when installing new receptacles in an older home? 3. What factors might prompt an electrician to do work that exceeds or is above code? 4. Why is it important to follow the current NEC code? 5. What other OSHA regulations might apply to your job as an electrician? GROUP ACTIVITIES On-the-Job Journal In this activity, students visit a new residential construction site to observe the way branch circuits are configured at the site. They ask an on-site electrician to show them the various hardwired appliances and explain any factors affecting the wiring needs of the residence. When students return to the classroom, ask them to write a one or two-page journal entry about their field trip. Students should discuss hard-wired appliances and note any special comments the electrician made during their visit. They should also include their thoughts about what they learned during their field trip and any questions they may have about hardwired appliances. Tools of the Trade As a group, students prepare a list of the tools they would need in order to work as a residential electrician. Students may consult the video, the Internet, and any other sources that is available. They should divide the list into hand tools and electric tools, and find or illustrate pictures of each tool. Students should then prepare a poster for each group of tools, labeling each tool with its name and its use, and share their posters with the class. INDIVIDUAL STUDENT PROJECTS Power to Your Home In this activity, students write two to four paragraphs on how power is consumed in their home and how they think this usage can be modified. Students should keep the following questions in mind: Which appliances are used most often? Do students think certain appliances are used more often than they should be? 6

7 How can students cut down on the amount of power they use at home? What are the benefits of cutting down on power usage at home? What is the NEC? In this activity, students use the Internet or their local library to obtain a current edition of the National Electrical Code. They write a one page paper that explains what the NEC is and why it is important, summarize the types of information that can be found in the NEC handbook, and explain why it is updated annually. INTERNET ACTIVITIES Job Search In this activity, students choose an electrical career that interests them and then go to at least three job sites on the Internet (such as Monster.com, Hotjobs.com, and a local or statewide job site) and search for jobs in that field. Then, students compile the listings they find in a word processing document and answer the following questions for each listing: What kind of education do you need for this job? What kind of experience is required? Do the listings provide a salary range? What is it? What tasks would you be responsible for doing in this job? Where is the job located? Occupational Outlook In this activity, students visit the U.S. Department of Labor s Bureau of Labor Statistics website ( to explore the Occupational Outlook Handbook. They search the database to find out more about the job outlook for electricians over the next decade including salary ranges, work conditions, and future industry trends. When students have completed their research, ask them to create a poster that summarizes the job outlook according the information they found in the Occupational Outlook Handbook. What are the Electricity Needs of Your Area? In this activity, students use Google ( or a similar search engine to research the average energy needs versus the average energy usage of their area. When they have completed their research, they should answer the following questions: Does the average energy requirements of their area equal the average energy usage, or does their area use more or less energy than it actually needs? If their area is using more energy than it needs, what do students think that energy is being used on? If their area is using more energy than it needs, what can residents of that area do to conserve energy? Students should present their answers in two-three written paragraphs 7

8 ASSESSMENT QUESTIONS Q: measures the force, or pressure, that moves current through a conductor. a. Wattage b. Current c. Voltage d. Charge A: c Feedback: Voltage equals power divided by current. Q: The has established wiring standards to ensure that occupants have access to outlets at convenient locations. a. National Electrical Code (NEC) b. Occupational Safety and Health Administration (OSHA) c. National Fire Protection Association (NFPA) d. American Wire Gauge (AWG) A: a Feedback: The National Electrical Code is a document produced by a consensus process that is open to proposals for changes and public comments. Technical committees review each proposal and vote on accepting or denying changing code standards. Q: Describe the formula for calculating the minimum number of branch circuits for generalpurpose outlets in a residence. A: Find the square footage of the dwelling and multiply that number by the National Electrical Code volt-ampere requirement. Then, divide by the branch circuit voltage-amperage value. Feedback: There is another set of standards for determining the number outlets in a dwelling both receptacle outlets and lighting outlets. Q: If your branch circuit calculations say you need 4.19 branch circuits in the dwelling, you would round to the nearest number, four. (True or False) A: False Feedback: You must round up to the nearest whole number, which would be five in this case. Q: True or False. In residential wiring, it s permissible to install lighting and receptacles on the same circuits. (True or False) A: True Feedback: The National Electrical Code requires that the load be divided equally between the branch circuits. Q: The rating of any particular piece of cord-and-plug-connected equipment can t exceed of the branch-circuit ampere rating. a. 40% b. 60% c. 80% d. 90% A: c Feedback: For example, a 15-ampere receptacle should never have anything rated more than 12 amperes plugged into it. 8

9 Q: Which of the following appliances is not likely to need its own branch circuit? a. Electric dryer b. Garage Door Opener c. Air Conditioner d. Computer A: b Feedback: For a typical residential overhead garage door operator, the current draw is usually so small that it could be connected to the garage lighting branch circuit. Q: What do the letters PIE stand for in the PIE formulas? A: P equals wattage, I equals amperage, and E equals voltage. Feedback: A PIE formula can be used to determine the overcurrent protective device permitted for an appliance. Q: As wire sizes get smaller, the gauge numbers. a. get smaller b. get larger c. stay the same d. double A: b Feedback: Conductors are sized according to the American Wire Gauge, or AWG standard. Q: The standard cord-set for an electric range is. a. 100 ampere b. 60 ampere c. 40 ampere d. 50 ampere A: d Feedback: The National Electrical Code permits a 50-ampere receptacle in order to standardize connections for electric ranges. ADDITIONAL RESOURCES WEB SITES National Electrical Code International Brotherhood Of Electrical Workers National Electrical Safety Foundation 9

10 National Electrical Contractors Association BOOKS Wiring a House (For Pros by Pros) Revised and Updated edition by Rex Cauldwell The Taunton Press, August 2002, Paperback 256pp ISBN: Residential Wiring by Harry Sorge Delmar Learning, December 26, 2002, Paperback 432pp ISBN: OTHER PRODUCTS Electrical Safety, VHS/DVD, Meridian Education Corporation Those who work with electricity encounter many hazards, including electric shock and electrical fires. This video details safety procedures for these hazards as well as protection of electrical instruments and solid-state devices. An excellent overview for those who work with electricity and as a general safety video for everyone. A Meridian Production. (21 min.) Order #: Electrical Principles, VHS/DVD, Meridian Education Corporation This live-action video introduces the basics of electricity. Computer animation adds interest and excitement as the video comes to life in its coverage of atoms, conductors, insulators, free electrons, voltage, current, resistance, magnetism, attraction-repulsion, electromagnets, a simple circuit, and other electrical principles. Ideal for courses in electricity, physics, science, automotive, and technology. A Meridian Production. (19 min.) Order #: 25282, Electrical Repairs, VHS/DVD, Meridian Education Corporation This video looks at common automotive electrical problems. It covers how to use a DVOM to check continuity, voltage, resistance, and amperage; inspect, test, and replace fusible links, circuit breakers, and fuses; and work on batteries and alternators. Don t get a shock develop a well-grounded knowledge of electricity. Correlates to the standards for the Collision Repair and Refinish Technician Training Certification Program, from the National Institute for Automotive Service Excellence and the National Automotive Technicians Education Foundation. A Shopware Production. (20 min., includes teacher s guide) Order #: 32783,

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