National Electrical Code Articles and Information
National Electrical Code Top Ten Tips: Article 394 through Article 398 -- Wiring, Miscellaneous
Based on the 2008 NEC
by Mark Lamendola
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 Article 394 through NEC Article 398 items we deem
most important, based on the pervasiveness of confusion and the
potential costs of same.
- NEC Articles 394 through 398 contain the requirements for various
types of wiring, including concealed knob-and-tube wiring, messenger
supported wiring, and open wiring on insulators. Remember that, and your life will be much easier.
- Note that of these wiring types is a subcategory of wiring in general.
These are very specific wiring methods. The general wiring methods
also apply--but now you have additional requirements if you use any
of these three methods.
- Each Article in this series provides the uses permitted and the
uses not permitted.
- NEC Article 394 provides the requirements for concealed
knob-and-tube wiring. While this method is largely disappearing,
there's a huge installed base of this type of wiring. You can
install this kind of wiring only to extend or repair an existing
- Taps on concealed knob-and-tube wiring must be soldered.
- NEC Article 396 provides the requirements for messenger supported
wiring. You must use one of the cable types listed in Table
396.10(A) and follow the appropriate Article for that cable type.
- An exception to the rule just stated applies for industrial
- NEC Articles 398 provides the requirements for open wiring on
insulators. You won't find open "insulators" defined in
Article 100. So, what does this mean? Look no further than
398.2--this "open wiring on insulators" is a wiring
method. It is not an approach to wiring that involves generic
- If you use the open wiring on insulators method, you must use
bushings to pass the open conductors through framing members.
- The "open wiring on insulators" method has its own
support requirements, spelled out in 398.30.
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Learn more about:
How the NEC is arranged
- The first four Chapters of the NEC apply to all installations.
- Article 90 precedes Chapter One, and establishes the authority of the NEC.
- Article 80 follows the body of the NEC; it exists as Annex H. It provides the requirements for administration.
- Chapters 5, 6, and 7 are the "special" chapters, covering special: occupancies, equipment, and conditions (in that order).
- Chapter 8 provides the requirements for communications systems.
- Chapter 9 provides tables.
- The appendices provide mostly reference information.
- 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, which 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 applications, 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.