Preface
This edition covers the 2005 National Electrical Code. The text and questions and answers have been completely revised where appropriate to reflect the 2005 Code rule changes. New comprehensive examinations have been added to the chapters, and a new final examination has been added. However, the successful style and format of the previous editions have been retained.
This book is in response to an increasing demand in the industrial and academic communities for a detailed guide to the National Electrical Code and the principles of electrical design based on the Code. In particular, the information presented should serve the aspiring and practicing Master Electrician and the electrical technology student. Each area of interest to the modern-day electrician is discussed in detail, with an ample number of example problems and their solutions. This Guide differs from other publications that treat the National Electrical Code in that the emphasis here is on the types of questions and problems that typically appear on Master Electrician’s Examinations given throughout the country. Because these examinations reflect the knowledge expected of a Master Electrician in practice, their content has guided the authors in selecting material for this Guide.
The Master Electrician should be competent in three major areas, the first two of which are based on the National Electrical Code. The first two areas are (a) the design of electrical wiring systems and (b) the construction and installation of electrical systems. The Guide covers these subjects in Part I and Part II, respectively. The third major area, presented in Part III, is basic electrical theory and practice. This material is, for the most part, outside the scope of the Code, although the Master Electrician is expected to be familiar with the principles presented in Part III.
This Guide can serve as a self-study text, or it can form the basis for a one- or two-semester course covering the rules of the National Electrical Code and related material. The Guide presents all rules and problem-solving techniques necessary to pass a Master Electrician’s examination. The problems also treat practical situations arising in the design and construction of electrical installations. The only other reference text required is the National Electrical Code itself.
Part I of the Guide presents the rules and wiring design calculations required to determine the ratings of electrical services, feeders, and branch circuits for typical electrical installations. Beginning with a general discussion of these circuits, the chapters in Part I present increasingly complex situations. The final two chapters in Part I, Chapters 4 and 5, present detailed calculations for the design of electrical systems in dwellings and in industrial or commercial occupancies, respectively. A quiz is given after each unit to summarize the knowledge in that unit and provide practice for the reader. A lengthy examination after each chapter covers the material presented in the chapter. Wherever a rule from the National Electrical Code affects a calculation, reference is made to the particular rule in the margin of the text.
Part II of this Guide covers the major sections of the National Electrical Code and provides summaries of important rules, which govern the construction and installation of electrical equipment. A large number of tables, problems, and quizzes organize the material logically to aid understanding.
Part III of the Guide begins with a treatment of basic direct-current circuits. Subsequent sections present a review of the properties of conductors, basic alternating-current circuits, and equipment in AC circuits. The discussion and examples cover material useful for the solution of design problems presented in other parts of the Guide.
The final portion of the Guide, Part IV, contains examinations covering the material presented in the first three parts. The final examinations are representative of examinations for the Master Electrician’s license given by various city and state examination boards.
The Appendixes contain information of general interest, such as a detailed list of useful electrical formulas. Most important, the Appendixes contain the solutions to all quizzes, tests, and final examinations given in the Guide. The solutions to problems have been worked out in complete detail, showing the method used and the appropriate references to the National Electrical Code.
Notes to the Student
Preparation for a Master Electrician’s License is a long and difficult procedure involving practical experience and a thorough knowledge of the material presented in this Guide. A fundamental knowledge of elementary algebra and simple direct-current and alternating-current circuit theory is most helpful in fully understanding the approaches to problem solving taken in the Guide. If this material is not familiar to you, a self-study program or a course at a local community college covering these basic subjects would be helpful.
For students with the proper background knowledge, the Guide can be studied with the National Electrical Code to prepare for required city or state electrician’s examinations. You should master each principle before going on, although your study program may begin with Part I, Part II, or Part III of the Guide, depending on your previous knowledge or preference.
When you feel prepared, take the final examinations presented in Part IV of the Guide according to the directions and time limits specified for each test. You can score the examinations by referring to the solutions given in the Appendixes. Although a score of 70% is passing, a score of 80% or more on each examination indicates that you are well prepared for the real thing.
Notes to the Instructor
This Guide is unique because it presents the more difficult subject of electrical wiring design calculations in Part I and the general Code rules and basic electrical theory in Part II and Part III, respectively. This was done because many students who take courses covering the National Electrical Code are familiar with the general organization of the Code and its rules. It is necessary for those students to concentrate on problem solving rather than Code rules and basic theory that can be briefly presented and understood by the student. In addition, typical Master Electrician’s examinations separate the questions concerned with wiring design from those dealing with installation and general electrical practice. To avoid confusing students, the instructor can divide this course similarly and begin with the most important subject, that of electrical design. The other Code rules and the basic theory support this activity. If the students are not well prepared, the instructor might decide to begin with Part III, basic electrical theory, proceed to Part II, and finally present the design calculations of Part I. These three parts are not dependent on each other; each contains quizzes and tests based on only the material presented in that part. The examinations in Part IV, of course, cover the entire range of topics presented in the Guide.
As an adjunct to the material in the Guide, it would be appropriate for the instructor to present rules that are covered by local ordinances. Such material could be added to the examinations given in the Guide.
Notes to the Practicing Electrician or Designer
This Guide has been prepared to explain in detail the use of the National Electrical Code, particularly as it applies to design of electrical wiring systems. With this intent, the Guide does not attempt to present design techniques that necessarily result in the most efficient or economical electrical system. For instance, no provisions are made for future expansion in the examples given in the Guide. The author assumes that experienced electricians or designers will use their own approaches to problem solving while using the Guide as a reference. In the same way, the selection of equipment such as circuit breakers and service equipment in the examples presented in the Guide is based on the minimum Code requirements. The rating of such equipment may not be adequate or convenient for a practical installation. The judgment of the designer must be relied on to determine the design that best fits a particular installation.
The problems presented in Part I of the Guide deal with standard alternating-current circuits used as services, feeders, or branch circuits. Other special electrical systems such as two-phase alternating-current and direct-current installations are not discussed. The unique rules for these circuits concerning grounding, size of neutral, and so on will be found in the Code and should be used in addition to or in place of the rules presented in the Guide.
Finally, the design requirements for circuits supplying equipment such as x-ray machines are not covered in detail in the Guide. Reference is made when necessary to the appropriate section of the Code that covers such equipment.
I appreciate the various comments received on the previous edition. In particular, a number of students in my National Electrical Code classes have made helpful suggestions that served to improve the presentation of the material. Readers can forward comments concerning this edition to the publisher, or contact me at mailto:[email protected].
Acknowledgments
I would like to acknowledge the many colleagues, code panel members, and students who have contributed to the development of this Guide. Particular thanks go to Jeanne Leslie for her help with production and mailings as well as her encouragement over the years. My wife, Karen, deserves credit for her patience and encouragement during the many hours needed to complete this book.
About the Author
Thomas L. Harman is an electrical engineer with a Ph.D. in electrical engineering from Rice University. He has held Master Electrician’s Licenses in many cities and states around the United States and has been a Master Electrician since 1973 in Houston, Texas. He has also had considerable practical experience in industrial, commercial, and residential electrical design and installation. The experience includes industrial construction in hazardous locations. Dr. Harman has been called as an expert witness in numerous cases involving electrical accidents and faulty electrical designs.
He has been a member of the National Electrical Code Panel Number 2 since 1978. The panel deals primarily with branch-circuit, feeder, and service calculations. This is one of the panels that contributes to the National Electrical Code published by the National Fire Protection Association. Guide to the National Electrical Code is now in its ninth edition. In private classes, Dr. Harman has used this textbook to train many electricians to prepare for their Master’s examination.
Dr. Thomas Harman’s article “A Personal View of the NEC Code Making Panel 2” was published in the Journal of the International Association of Electrical Inspectors, July/August 2003. The article is available on Dr. Harman’s Web site at http://sce.cl.uh.edu/harman/PubPapers/NECcodeMakingPanel2.pdf