You must understand that the National Electrical Code was designed and intended for use by experienced electrical contractors, inspectors, qualified electricians and electrical engineers. The NEC isnít intended as an instructional manual. Itís a set of complex rules, enforced by law, for the purpose of ďthe practical safeguarding of persons and property from hazards arising from the use of electricity.Ē To remain current, recommended changes to the NEC are evaluated yearly by a special panel, and every three years the Code is updated with a new edition.
History of the NEC
The National Electrical Code (Volume 70 of the National Fire Protection Agency) has been sponsored by the National Fire Protection Association (NFPA) since 1911, and is considered the best electrical code standard in use today. Itís not only used throughout most of the United States, but in many countries around the world.
The first electrical code was written by the National Association of Fire Engineers in 1897 and, since then, has been published, edited, and revised on a regular basis. One of the rules initially adopted to govern electrical installation actually prohibited intentional grounding of electrical systems. It was believed that intentional grounding increased fire danger. In later years, as grounding became better understood, authorities began to allow, then to require, grounding.
The National Fire Protection Association has many standards besides the NFPA-70 (our National Electrical Code) related to the electrical industry. These standards are in effect only where local legal jurisdictions have adopted them. See NEC Annex A (page 631) for more information about product standards.
Data for various NEC requirements is sometimes derived from research for other NFPA standards. Committees and panels responsible for the NEC often confer with technical experts responsible for those NFPA standards. NEC rules must correlate with other NFPA standards.
Effectively studying the NEC
Learning to read and understand the NEC is like learning a foreign language. You need to understand the basic structure of the language, study the words, and how those words are used in phrases, as well as the pronunciation. Having learned the basics, you try your hand at communicating, but at first, all you can manage are short phrases because you don't know how to put the words together in a complete sentence. For that, you need to study the rules and understand the subtle nuances of the language ó and then practice.
So, like learning a foreign language, understanding the terms, principles, and layout of the NEC takes hours of study. Seeing how all the segments work together, from one section to another, isnít easy. But perhaps the most difficult of all is grasping the subtle meanings in the Code rules themselves.
Simply said, the rules in the Code arenít spelled out as well as weíd like them to be. There are thousands of different applications of electrical installations, but no application has a Code rule specific to it alone. Letís begin our study of the Code by looking at words and phrases.
Understanding the Meanings of the NEC
Some words and phrases used in the NEC may be foreign to you. But itís imperative you understand the meanings of terms like grounding conductor, grounded conductor, and neutral conductor, for example. If you donít understand the terms being used, youíll never understand the Code itself.
Article 100 Definitions
Reading the definitions in Chapter 1, Article 100, is a great place to start learning about the Code and its wording. Once you have a grasp of how a word or phrase is used, youíll better understand it when you come across it in a Code reference. Keep in mind that the Codeís meaning isnít always in the technical words, but often in how those words are used. A variation in the simplest wording can change the entire meaning of an Article. A change of one word might mean alternate choices for equipment or wiring methods. Or, it could signify that additional measures must be taken to comply with the safety requirements. Donít overlook simple wording. It could be the key that unlocks the door to the intent of the rule.