NEC Code Layout

Understanding the NEC structure is important to use, understand and apply its rules easily. However, The National Electrical Code is organized into 5 main components as follows:
    National Electrical Code 2011 Handbook (National Fire Protection Association//National Electrical Code Handbook)
  1. Introduction 
  2. Table of Contents 
  3. Chapters 
  4. Appendices 
  5. Index 

A short description of each component follows:

1- Introduction: 

The introduction sets forth the purpose, scope, enforcement and rules or information that are general in nature as in article 90.

2-Table of Contents. 

The Table of Contents located in the front of the Code book displays the layout of the Chapters, Articles, and Parts as well as their location in the Code book.

3. Chapters: see fig.1 

There are nine chapters in the NEC. Each chapter is a group of articles, parts, sections, and tables. The nine chapters fall into four categories:

Chapters 1 through 4: 

These Chapters cover definitions and rules for installations (voltages, connections, markings, etc), circuits and circuit protection, methods and materials for wiring (wiring devices, conductors, cables, etc), and general-purpose equipment (cords, receptacles, switches, heaters, etc).

Chapters 5 through 7: 
These Chapters deal with special occupancies (high risk to multiple persons), special equipment (signs, machinery, etc) and special conditions (emergency systems, alarms, etc).

Chapter 8: 
This Chapter is specific to additional requirements for communications systems (telephone, radio/TV, etc)

Chapter 9: 
This Chapter is composed of ten tables regarding conductor, cable and conduit properties

Chapter Structure: 
  1. Chapters divided to Articles 
  2. Articles divided to Parts 
  3. Parts divide to Code Rules 
  4. Code Rules include the following: 
  • Sections 
  • Lists 
  • Tables 
  • Exceptions 
  • Fine Print Notes 
  • Definitions 
  • Superscript Letter X 
  • Marginal Notations, Code changes (|) and deletions (bullet) 

NEC Code is coded as follows:

### is Article Number (First # is Chapter Number)

(.) Separator point

### is Code rule Number (sometimes called section number)

(Alphabet Caps Letter) is Subsection number

(#) is sub-subsection number

(Alphabet Small Letter) is point number

Example: 804.22(C)(3)(b)
8 means Chapter# 8 - 804 means Article # 804 - 22 means section or code rule #22 - C means subsection #C - 3 means sub-sub section #3 - b means point #b

sometimes , we used  # Roman-numerals which is Parts Number, sometimes mentioned in long chapters, sometimes ignored in other chapters

Example: see Parts Paragraph in below. 

The (9) NEC chapters divided to approximately 125 articles. An article such as:
  1. Article 110 - General Requirements 
  2. Article 250 - Grounding 
  3. Article 300 - Wiring Methods 
  4. Article 430 - Motors 
  5. Article 500 - Hazardous (classified) Locations 
  6. Article 680 - Swimming Pools 
  7. Article 725 - Control Wiring 
  8. Article 800 - Communication Wiring 


When an article is sufficiently large, the article is subdivided into parts numerically arranged. For example Article 250 contains nine parts, such as:

   I. General

   II. Circuit and System Grounding

   III. Grounding Electrode System

   IV. Enclosure, Raceway, and Service Cable Grounding

   V. Bonding

   VI. Equipment Grounding and Equipment Grounding Conductors

   VII. Methods of Equipment Grounding

   VIII. Direct-Current Systems

   IX. Instruments, Meters, and Relays

Code rules include the following:
1- Section - Each Code rule is called a Section and is identified with numbers, such as Section 225-26.

A Code Section may include subsections alphabetically arranged which in turn may be divided to sub-sub sections numerically arranged.

For example, the rule that requires all receptacles in a bathroom to be GFCI protected is contained in Section 210-8(a)(1). 
2-List :  The NEC Sections contain lists of items. If a list is part of a numeric subsection, such as Section 210-52(a)(2), then the items are listed as a., b., c., etc. However, if a list is part of a Section, then the items are identified as (1), (2), (3), (4), etc.

3-Tables : Many Code requirements are contained within Tables which are a systematic list of Code rules in an orderly arrangement. For example, Table 300-15 lists the burial depths of cables and raceways.

4-Exceptions :Exceptions provide an alternative to a specific rule. There are two types of exceptions: mandatory and permissive. When a rule has several exceptions, those exceptions with mandatory requirements are listed before those written in permissive language.

(a) Mandatory Exception :A mandatory exception uses the words "shall" or "shall not." The word "shall" in an exception means that if you are using the exception, you are required to do it in a particular way. The term "shall not" means that you cannot do something.

(b) Permissive Exception: A permissive exception uses such words as "shall be permitted", which means that it is accepted to do it in this way.

5-Fine Print Notes (FPN) : are explanatory material, not Code rules. Fine print notes attempt to clarify a rule or give assistance, but they are not a Code requirement. For example, FPN No. 4 of Section 210-19(a) states that the voltage drop for branch circuits should not exceed 3% of the circuit voltage. This is not a Code requirement but only a suggestion; there is no NEC requirement for conductor voltage drop.
National Electrical Code 2011 (National Fire Protection Association National Electrical Code)
6-Definitionsare listed in Article 100 and throughout the NEC. In general, the definitions listed in Article 100 apply to more than one Code Article, such as "branch circuit", which is used in many Articles.

Definitions at the beginning of a specific Article applies only to that Article. For example, the definition of a "Swimming Pool" is contained in Section 680-4 because this term applies only to the requirements of Article 680 - Swimming Pools.

Definitions located in a Part of an Article apply only to that Part of the Article. For example, the definition of "motor control circuit" applies only to Article 430, Part F.

Definitions located in a Code Section apply only to that Code Section. For example, the definition of "Festoon Lighting" located in Section 225-6(b) applies only to the requirements contained in Section 225-6.

7- Superscript Letter x: This superscript letter is used only in Chapter 5. The superscript letter X means the material was extracted from other NFPA documents. Appendix A, at the back of the Code Book, identifies the NFPA document and the section(s) that the material was extracted from.

Changes and Deletions: are identified in the margins of the NEC in the following manner: Changes are marked with a vertical line (|) and deletions of a Code rule are identified by a bullet.

3. Appendices. 

These Appendices are related to referenced standards, calculations, examples, additional tables for proper implementation of various code articles (for example, how many wires fit in a conduit) and a model adoption ordinance, There are four appendices in the NEC:

Appendix A - Extract Information
Appendix B - Ampacity Engineering Supervision
Appendix C - Conduit and Tubing Fill Tables
Appendix D - Electrical Calculation Examples

4. Index. 

We all know the purpose of an index, but it's not that easy to use. You really need to know the correct term. Often it's much easier to use the Table of Contents.