National Electrical Code Top Ten Tips: Article 100, Definitions

Our remarks in are parentheses. Please note, we do quote from copyrighted material. While the NFPA does allow such quotes, it does so only for the purposes of education regarding the National Electrical Code. This article is not a substitute for the NEC.

These are the 10 NEC definitions we deem most important, based on the pervasiveness of confusion and the potential costs of same.

1. Ampacity. "The current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating." (Ampacity varies depending on many factors. You must use the appropriate NEC Tables to determine the correct ampacity.)
    
2. Bonding. "The permanent joining of metallic parts to form an electrically conductive path that ensures electrical continuity and the capacity to conduct safely any current likely to be imposed." (This is not the same as grounding, but bonding jumpers are essential components of the bonding system, which is an essential component of the grounding system. Please note that the NEC does not authorize the use of the earth as a bonding jumper—that’s because the resistance of the earth is more than 100,000 times greater than that of a bonding jumper.)
    
3. Continuous Load. "A load where the maximum current is expected to continue for 3 hours or more." (That is the maximum running current, exclusive of starting current.)
    
4. Feeder. "All circuit conductors between the service equipment, the source of a separately derived system, or other power supply source and the final branch-circuit overcurrent device." (If there is no branch circuit, a circuit originating at the service equipment is a feeder. This is a common approach for powering large motors.)
    
5. Ground. "A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth or to some conducting body that serves in place of the earth." (Please note, simply driving an electrode into the earth does not constitute grounding a circuit. The ground must be made with respect to the supply—service entrance or separately derived system—because electrons are always trying to get back to the source.
    
6. Grounded conductor. "A system or circuit conductor that is intentionally grounded." (This conductor isn’t meant to serve as the grounding path. It is simply a conductor that is grounded. The neutral is grounded on the service side of the service transformer.)
    
7. Grounding conductor. "A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes." (This is your supply "ground wire," not the neutral.)
8. Grounding equipment conductor. "The conductor used to connect the non-current-carrying metal parts of equipment, raceways, and other enclosures to the system grounding conductor, the grounding electrode conductor, or both, at the service equipment or at the source of a separately derived system." (Note the difference between this and the preceding items.)
    
9. Labeled. "Equipment or materials to which has been attached a label…acceptable to the authority having jurisdiction…." (It’s important to read the entire original definition, and distinguish this from "Listed."
    
10. Listed. Equipment, materials, or services included in a list…acceptable to the acceptable to the authority having jurisdiction…." (Listing is usually done by an organization like U.L. Most authorities will not recognize an item as Listed unless it is also Labeled. Here, too, reading the entire definition is a useful exercise.)

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How the NEC is arranged

1. The first four Chapters of the NEC apply to all installations.
2. Article 90 precedes Chapter One, and establishes the authority of the NEC.
3. Article 80 follows the body of the NEC; it exists as Annex H. It provides the requirements for administration.
4. Chapters 5, 6, and 7 are the "special" chapters, covering special: occupancies, equipment, and conditions (in that order).
5. Chapter 8 provides the requirements for communications systems.
6. Chapter 9 provides tables.
7. The appendices provide mostly reference information.
8. Appendix D contains examples that every NEC user should study.

Try your NEC moxy:

• Do you know the difference between bonding and grounding? Hint: Look in the NEC, Article 100.
• Does the NEC refer to grounding incorrectly in any of its articles? Yes! So be careful to apply the Article 100 definitions. Don't ground where you should bond.
• When doing motor load calculations, what Article covers hermetic motors? Answer: While Article 440 covers the application of hermetic motors, it does so only by amending Article 430 because hermetic motors are a special case of motors. For motor load calculations, refer to Article 430.
• Does the NEC provide a voltage drop requirement? Yes! It does so in a special case, which is Article 648 Sensitive Electronic Equipment. But for general application, it does not provide a requirement; it merely provides a recommendation in a couple of FPNs.
• Take our Code Quizzes.

Remember other applicable codes, rules, standards, and references:

• OSHA's electrical worker safety rules.
• IEEE standards.
• NETA standards.
• NFPA standards.
• International Codes (if applicable to the installation).
• State Codes (if the state has them).
• Local ordinances and permit requirements.
• Local fire codes.
• Manufacturer requirements or guidelines.
• Customer security requirements.
• Industry standards.
• Your company's own internal standards, practices, and procedures.
• Engineering drawing notes.

Here are a couple more NEC resources: Contractor Cafe Code Site | Joe Tedesco's National Electrical Code

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