How To Use The NEC (National Electrical Codebook)
Written by Dustin Stelzer
Chapters, Articles, Sections, Parts, Subsections
Getting a copy of the National Electrical Code (NEC) can be a bit overwhelming when you’re first starting out. The jargon used is written similar to a court document, so the terms and phrases will be a difficult hurdle to overcome. Also, the layout of the book is not intended for ease of understanding, rather it’s a map that allows you to find destinations in several different ways. You’re never going to be expected to memorize the codebook, especially since it changes every 3 years. You will, however, be expected to know how to navigate the book rapidly to find information.
What the code is: A minimum agreed-upon standard ( by everyone in the industry) on how best to safely install materials and equipment with the intent to prevent injury/loss of life or property. It is a safety manual.
What the code is not: An instruction manual, a textbook, a visual guide, a how-to manual. It does NOT tell you how electricity works, or how to be a good electrician. That’s what I’m here for. So no worries, I got you.
To start out, the NEC is layed out in a specific way. Understanding the layout will help you get a birds-eye view of the entire “realm” that this map is covering. There are 9 Chapters to the book as well as a section of definitions in the front and some helpful informational Annexes in the back. That’s pretty much the meat and cheese of the book. To help you navigate the “map” there is a table of contents up front that shows you the relative areas and important sections of the map, as well as an index in the back with specific topics that you can use keywords to find “destinations.” If that’s all you remember from here on out, that will still help you tremendously when trying to learn to use the NEC.
Chapters
Layout of the 2017 National Electrical Code (NFPA 70)
Table Of Contents
Chapter 1 – General
Chapter 2 – Wiring and Protection
Chapter 3 – Wiring Methods and Materials
Chapter 4 – Equipment for General Use
Chapter 5 – Special Occupancies
Chapter 6 – Special Equipment
Chapter 7 – Special Conditions
Chapter 8 – Communications Systems
Chapter 9 – Tables
Annex A – Annex J
Index
These chapters all relate to each other in some way as well. There’s a reason for the organizational structure to the document. Chapters 1-4 deal with all wiring everywhere. This is the basic foundation for safely installing electrical materials and equipment and it applies to most occupancies (or buildings/structures). Chapters 5-8 are specific locations/equipment that change or overwrite something in Chapters 1-4 (technically they can overwrite anything elsewhere in the entire code, not just Chapters 1-4).
For example, if you’re installing equipment in a “Special Occupancy” (like a Motor Fuel Dispensing Facility – or gas station) you’d need to know the rules of Chapters 1-4 and how normal wiring methods apply, but you would then look to Chapter 5 (Article 514 for those of you that are curious) to see what rules override Chapters 1-4 for this specific occupancy. There are different rules regarding grounding and bonding in Article 514 that may override a rule in Article 250.
Articles
Articles are the different segments or topics within a chapter. In Chapter 2 you will have Articles like 200, 210, 225, 250 – Chapter 3 will be things like 310, 322, 340 etc…Articles can get pretty in depth, for instance you can have an article like T310.15(B)(15) – what does all of that mean?? Well it means that in Article 310 there are sections and subsections within that one Article. I know, it’s a lot…keep with me here.
Sections
Sections are always WITHIN an article. So for Article 310, we have SECTIONS 310.1, 310,15, 310.104 etc. These are all sections of the article 310. These sections deal ONLY with the Article 310, they don’t have anything to do with any other bit of code in the book. That’s an important key to remember.
Now from our example above with 310.15(B)(16) we’ve gathered that we are in Chapter 3, Article 310, Section 15, and in this example there are a few subsections in the section. I can see your eyes rolling. Stop it. Focus. We’re near the end of this fiasco, I promise. After a section (like 310.15) you may have a subsection (A), (B), (F) etc…, and within any of those subsections you may have multiple sets of rules. So Subsection (B) may have rule (1), (2), (3), and (4). That’s it! That’s as complex as the locations get when navigating the codebook. Now its just a matter of figuring out the main areas of our “map” so we know what city to look into when we’re trying to find codes that apply to our work environment.
Parts
The next division you may come across in several places in code, is the Part. Many large chapters of code have Parts. Parts are always in Roman Numerals (i.e. Article 250 Part IV) Due to the fact that there’s so much information being presented in a large chapter, they break all of the Articles into Parts to help better navigate specific groups of topics.
Tables
Notice our example above has a “T” in the front of it. T310.15(B)(16) – This “T” lets us know that we are talking about a Table in the article, rather than a paragraph of text. Paying attention to that little T at the beginning of a snippet of code is of great importance. Many of the values you need to follow when sizing conductors, overload protection, and overcurrent protection are in Tables, not in text.
Exceptions
Lastly we have Exceptions. Exceptions are little notes at the end of a snippet of code that tells you certain times or places where a code may be exempted because of a special circumstance or reason. One example is 310.15(A)(2) Ex. This is saying that if certain criteria are met in specific situations then you do not have to follow this specific code rule. The codebook is riddled with exceptions so be on the look-out for them.
Informational Notes
Informational notes are great little “helpers” that show us references to other areas of code that may help us understand better, what we’re reading and/or how it applies to other portions of the NEC that may apply to our situation. They’re only there as a little “arrows” as we’re walking down the path in our map that show us which way to go if we’d like to investigate a little deeper.
Ok, NOW we’re done. I promise.
Here’s a visual example of how all of this ties together.
Chapter 3
Article 300
Article 310
Section 310.15
Subsection 310.15(B)
Rule 310.15(B)(16)
Section 310.60
Subsection 310.60(A)(1)
Exception
Article 312
Section 312.7
Section 312.8
Subsection 312.8(A)
Subsection 312.8(B)
Rule 312.8(B)(1)
Rule 312.8(B)(2)
Chapter Breakdown
So what do the chapter titles mean? What is “general” or what are “special occupancies”? Let’s break it down a little further.
Chapter 1 – General
Chapter 1 is where you find the definitions (Article 100) for all of the crazy words you’ll find throughout the text. Well, not all of them, but a lot of them. There are terms within chapters that are defined in that chapter or article rather than in the beginning of the book. Chapter 1 also covers general requirements for electrical installations. (Article 110) Things like space around electrical equipment, voltages, wiring integrity, electrical connections and terminations, just general things about installing electrical materials and equipment.
Chapter 2 – Wiring and Protection
Chapter 2 deals primarily with minimum requirements for wiring most occupancies, as well as how to protect that wiring. It covers things like how to protect conductors in wet environments (GFCI protection – 210.13), what rooms need to have Arc-Fault protection in a home (AFCI – 210.12). It talks about conductors between buildings, overcurrent protection (breakers and fuses), number of outlets in a dwelling (home), requirements for services, grounding and bonding, and surge protectors. If you’re talking about running wire to something and trying to protect that wiring you’re most-likely going to be referencing Chapter 2.
Chapter 3 – Wiring Methods and Materials
Chapter 4 – Equipment for General Use
Chapter 5 – Special Occupancies
Chapter 6 – Special Equipment
Chapter 7 – Special Conditions
Chapter 8 – Communications Systems
Chapter 9 – Tables
Annex A – Annex J
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