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National Electrical Code Articles and Information

National Electrical Code Top Ten Tips: Article 406 -- Receptacles, Cord Connectors, and Attachment Plugs

by Mark Lamendola

Based on the 2017 NEC

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 406 items we deem most important, based on the pervasiveness of confusion and the potential costs of same.

  1. Donít dismiss receptacles as not deserving your attention. There's a reason why the NEC has finally devoted an entire Article to them. Even the trade magazines, such as EC&M, are writing about receptacles.
  2. If you use a receptacle with aluminum wiring, make sure it's marked CO/ALR. Otherwise, don't use it [406.3(C)].
  3. If you install a 3-wire (grounded) receptacle, you must ensure you have a ground wire running to that receptacle. If you have a two-wire system, then use GFCIs rather than regular receptacles [406.4].
  4. Use a receptacle designed and rated for the voltage of the circuit in which you are installing it. Ditto for attachment plugs. Receptacle and plug configurations exist for a reason--they are supposed to "idiot proof" plugging something in to the correct voltage and wiring scheme (e.g. 4-wire vs. 3-wire).
  5. If your receptacle mounting box is set back from the finished surface, mount the receptacle such that the mounting yoke or strap of the receptacle is held rigidly to the finished surface [406.5(A)].
  6. If your receptacle mounting box is flush to the finished surface, mount the receptacle such that the mounting yoke or strap of the receptacle is held rigidly against the box or box cover [406.5(B)].
  7. Make sure that your receptacle faces are flush with (or project slightly from) plastic faceplates (or other insulating face plates). If you use a metal faceplate, your receptacle must project at least 0.4mm from the faceplate [406.5(D)].
  8. Don't install receptacles face-up in countertops [406.5(E)].
  9. If you install a 120V or 250V receptacle of 15A or 20A in a wet location, the enclosure for that receptacle must be weatherproof. This doesn't mean only when the cord isn't plugged in--the enclosure must protect the receptacle from water even if that receptacle is in use [406.9(B)].
  10. You can't install a receptacle within or directly over a bathtub or shower stall. It doesn't matter if that receptacle is a GFCI--don't put it in there! [4069.(C)]


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, 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.


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