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By Mike Holt
The National Electrical Code
Learning to use the NEC is somewhat like learning to play the game of chess; it's a great game if you enjoy mental warfare. You must first learn the names of the game pieces, how the pieces are placed on the board, and how each piece moves.
In the electrical world, this is equivalent to completing a comprehensive course on basic electrical theory, such as:
Once you understand the fundamentals of the game of chess, you're ready to start playing the game. Unfortunately, at this point, all you can do is make crude moves, because you really do not understand how all this information works together. To play chess well, you will need to learn how to use your knowledge by working on subtle strategies before you can work your way up to the more intriguing and complicated moves.
Again, back to the electrical word, this is equivalent to completing a course on the basics of electrical theory. You have the foundation upon which to build, but now you need to take it to the next level, which you can do by reading this textbook and answering the Unit Questions.
CAUTION: Electrical work isn't a game, and it must be taken very seriously. Learning the basics of electricity, important terms and concepts, as well as the basic layout of the NEC gives you just enough knowledge to be dangerous. There are thousands of specific and unique applications of electrical installations, and the Code doesn't cover every one of them. To safely apply the NEC, you must understand the purpose of a rule and how it affects the safety aspects of the installation.
NEC Terms and Concepts: The NEC contains many technical terms, so it's crucial that Code users understand their meanings and their applications. If you do not understand a term used in a Code rule, it will be impossible to properly apply the NEC requirement. Be sure you understand that Article 100 defines the terms that apply to two or more Articles. For example, the term "Dwelling Unit" applies to many Articles. If you do not know what a Dwelling Unit is, how can you possibly apply the NEC requirements for it?
In addition, many Articles have terms that are unique for that specific Article. This means that the definitions of those terms are only applicable within that given Article. For example, Article 250 Grounding and Bonding has the definitions of a few terms that are only to be used within Article 250.
CAUTION: Electricians, engineers, and other trade-related professionals use slang terms or technical jargon that aren't shared by all. This makes it very difficult to communicate because not everybody understands the intent or application of those slang terms. So, where possible, be sure you always use the proper word, and do not use a word if you do not understand its definition and application. For example, lots of electricians use the term "pigtail" when describing the short conductor for the connection of a receptacle, switch, luminaire, or equipment. Although they may understand it, not everyone does. Figure
Small Words, Grammar, and Punctuation: It's not only the technical words that require close attention, because even the simplest of words can make a big difference to the intent of a rule. The word "or" can imply alternate choices for equipment wiring methods, while "and" can mean an additional requirement. Let's not forget about grammar and punctuation. The location of a comma "," can dramatically change the requirement of a rule.
NEC Style and Layout
The National Electrical Code is organized into nine components.
1. Table of Contents. The Table of Contents displays the layout of the Chapters, Articles, and Parts as well as the page numbers. It's an excellent resource and should be referred to periodically to observe the inter-relationship of the various Code components. When attempting to locate the rules for a particular situation, knowledgeable Code users often go first to the Table of Contents to find most quickly the specific Section that applies.
2. Chapters. There are nine Chapters, each of which is divided into Articles. The Chapters fall into one of four groupings: General Requirements (Chapters 1 - 4), Specific Requirements (Chapters 5-7), Communications Systems (Chapter 8), and Tables (Chapter 9).
3. Articles. The NEC contains approximately 140 Articles, each of which covers a specific subject. For example:
4. Parts. Larger Articles are subdivided into Parts. For example, Article 110 has been divided into three parts:
CAUTION: Because the Parts of a Code Article aren't included in the Section numbers, we have a tendency to forget what "Part" the Code rule is relating to. For example, Table 110.34(A) contains the working space clearances for electrical equipment. If we aren't careful, we might think this table applies to all electrical installations, but Table 110.34(A) is located in Part III, which contains the requirements for Over 600 Volts, Nominal installations. The rules for working clearances for electrical equipment for systems rated 600V or less are contained in Table 110.26(A)(1), which is located in Part II. 600V, Nominal, or Less.
5. Sections and Tables.
Section 210.8(A)(1) is located in Chapter 2, Article 210, Section 8, Subsection (A), Sub-subsection (1).
Note: Many in the industry incorrectly use the term "Article" when referring to a Code Section. For example, they say "Article 210.8," when they should say "Section 210.8."
From this point on in the textbook, Section references will be referenced without using the word "Section." For example, "Section 250.118" will just be referred to as "250.118."
Tables: Many Code requirements are contained within Tables, which are lists of Code requirements placed in a systematic arrangement. The titles of the Tables are extremely important; they must be carefully read in order to understand the contents, applications, limitations, etc., of each Table in the Code. Many times notes are provided in a table; be sure to read them as well, since they are also part of the requirement. For example, Note 1 for Table 300.5 explains how to measure the cover when burying cables and raceways, and Note 5 explains what to do if solid rock is encountered.
6. Exceptions. Exceptions are Code requirements that provide an alternative method to a specific requirement. There are two types of exceptions - mandatory and permissive. When a rule has several exceptions, those exceptions with mandatory requirements are listed before the permissive exceptions.
7. Fine Print Note (FPN). A Fine Print Note contains explanatory material intended to clarify a rule or give assistance, but it isn't a Code requirement.
8. Index. The Index contained in the NEC is excellent and is helpful to locate a specific rule.
9. Annexes. Annexes aren't a part of the NEC requirements, and are included in the NEC for informational purposes only.
Changes to the NEC since the previous edition are identified in the margins by a vertical line (|). However, rules that have been relocated aren't identified as a change and no identifier is shown at the location from which the Code rule was removed.
Customizing Your Code Book
Highlighting: As you read through this textbook and answer the questions in the workbook, be sure you highlight those requirements in the Code that are most important to you. Use yellow for general interest and blue for important requirements you want to find quickly. Be sure to highlight (in the same color) terms in the Index and Table of Contents as you use them.
Because of the size of the 2005 NEC, I recommend you highlight in green the Parts of Articles that are important for your applications, particularly:
Underlining: Underline or circle key words and phrases in the NEC with a red pen (not a lead pencil) and use a 6-in. ruler to keep lines straight and neat. This is a very handy way to make important requirements stand out. A small 6-in. ruler also comes in handy for locating specific information in the many Code tables.
Tabbing the NEC: Placing tabs on important Code Articles, Sections and Tables will make it very easy to access important Code requirements. However, too many tabs will defeat the purpose. You can order a custom set of Code tabs, designed by Mike Holt, online at www.MikeHolt.com, or by phone at 1.888.NEC.Code (1.888.632.2633).
Mike Holt's Comment: Please let me know if you find any errors. Next week well start discussing the 2005 NEC changes, so be sure you have a 2005 NEC Code book, which you can order online at www.mikeholt.com.
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