Understanding the NEC


Before you can use the NEC, you must remember that is intended for use by experienced persons, such as electrical contractors, inspectors, electrical engineers, and qualified electricians. The NEC is not intended to be used as an instructive or teaching manual.

Learning to use the NEC is like learning to play the game of chess. If you have never played chess, you will need to learn the terms used to identify the game pieces, the theory of how each piece moves and how the pieces are set up on the board. Once you have this basic understanding of the game, you may start to play the game; but all you can do is make crude moves because you don't completely understand how the pieces work together.

To play the game well, you need to study the rules, understand the subtle and complicated strategies, and then practice, practice and more practice.

Learning the terms, theory, and layout of the NEC gives you just enough knowledge to be dangerous. The hard part is understanding how all the parts work together. Perhaps the most difficult part is the subtle meanings in the Code rules themselves.

The rules in the NEC are not as simple as we would want them to be. There are thousands of different applications of electrical installations and there cannot be a specific Code rule for every application. You must learn the purpose of the NEC and then use common sense when you applying the rule. Please don't get so caught up with the rule, that you forget to use common sense.

This book is designed to help you with electrical terms, theories, and how to understand the NEC rules. A companion workbook that contains over 1,000 questions is available to give you the practice you need on how to use the NEC.



There are many technical words and phrases used in the NEC. It is crucial that you understand the meanings of words like ground, grounded, grounding, and neutral. If you do not clearly understand the terms used in the Code, you will not understand the rule itself.

It isn't always the technical words that require close attention. In the NEC, even the simplest words can make a big difference. The word or can mean: alternate choices for equipment, wiring methods, or other requirements. Sometimes, the word or can mean any item in a group. The word and can mean; an additional requirement or any item in a group. Be aware of how simple words are used.

Electricians, engineers, and other trade-related professionals have created their own terms and phrases. This is what we call slang. One of the problems with a slang terms is that they mean different things to different people and they are not used in the NEC. Example, the words sub-feeder and bond wire. The proper names associated with most slang terms have been identified. This book should help you understand the proper terms so that you no longer need to use the slang terms.

In this book the first time a glossary term is used it will be printed in boldface type. Words that are defined in Article 100 of the NEC and which are particularly important to understand will be italicized in each unit. As you read each unit, please review both the glossary terms located in the back of this book and the important NEC definitions, located in Unit 2 - Article 100.

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