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National Electrical Code Articles and Information

National Electrical Code Tips: Article 215 -- Feeder Circuits

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.

One thing that jumps right out to people studying the NEC is that Article 215 is  very short. This is surprising to people who've just studied Article 210, Branch Circuits, and are moving on to the next logical step.

You might be thinking feeders are just a heavy version of branch circuits, so Article 215 should just be Article 210 on steroids. But, don't think that way because "it aint so."

Article 210 covers many permutations of branch circuits, and devotes extensive text to dwelling area branch circuits. Dwelling areas donít have feeder circuits.

Hereís an object lesson in the value of Article 100. Go there now and review the definitions of branch circuit and feeder circuit. Once youíve done that, you will understand why Article 215 is so much shorter than Article 210.

  1. Article 215 covers feeders, but not feeders for electrolytic cells [215.1]. Those are covered in 668.3.
     
  2. To size the feeder correctly, you must first determine the total load [215.2(A)(1). To do that, follow the calculation requirements of Article 220.
     
  3. The grounded conductor (which is usually, but not always, the neutral) must be sized at least as large as required by 250.122 [215.2(A)(2)].
     
  4. The feeder ampacity has to be at least that of the service conductors, if the feeder conductors carry the total load of the service conductors with an ampacity of 55A or less [215.2(A)(3)].
     
  5. Feeder conductors to individual dwelling units don't need to be larger than the service conductors [215.2(A)(4)].
     
  6. If supplying only transformers, the ampacity of feeder conductors over 600V must be at least the sum of the nameplate ratings of the transformers [215.2(B)(2)].
     
  7. If supplying transformers and utilization equipment, the ampacity of feeder conductors over 600V must be at least the sum of the nameplate ratings of the transformers and 125% of the utilization equipment that will operate simultaneously [215.2(B)(3)]. That is, you can allow for load diversity and mutually exclusive loads. For example, you count the heater load or the air conditioning load, whichever is larger.
     
  8. If the feeder supplies branch circuits in which equipment grounding conductors are required (and usually, they are), then the feeder must also include (or provide) an equipment grounding conductor [215.6].
     
  9. Feeders that supply 15A and 20A receptacle branch circuits can be protected by a ground-fault circuit interrupter instead of complying with 210.8 and 590.6(A) [215.9].
     
  10. Don't derive feeders from autotransformers unless the system supplied by the feeder has a grounded conductor that's electrically connected to a grounded conductor of the system supplying the autotransformer [215.11].

 

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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, 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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