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National Electrical Code Articles and Information

Based on the 2014 NEC

by Mark Lamendola

National Electrical Code Tips: Article 690 -- Solar Photovoltaic Systems, Part 11

Only about 15% to 20% of the work of installing a Solar Photovoltaic (PV) System is electrical. But that electrical portion can easily result in disaster if not done correctly. Thus, Article 690 provides requirements for that portion.

Something many people don't realize is that as the battery systems of PV systems get larger, they begin to resemble the battery systems in data centers. People in the battery industry are very aware of this, as are the relevant NEC CMP (Code Making Panel) members and their counterparts on the IEEE battery committee. Consequently, the battery requirements for PV systems draw from a rich depth of experience, practical knowledge, and empirical data.

We continue here with the battery requirements coverage that began in Part 10.

  1. If the battery installation has more than 24 2V cells connected in series (48V nominal), you must provide a disconnecting means accessible only to qualified persons. This must disconnect the grounded circuit conductors to permit maintenance [690.71(E)]. If, by some really strange set of conditions, these batteries are not subject to field maintenance, then you don't need to provide this disconnect.
     
  2. Pertaining to point 1 above, you must also have a disconnect for the ungrounded circuit conductors [690.71(F)]. It can't be the same disconnect as the one above.
     
  3. A battery system that consists of more than 24 2V cells (operates above 48V) can operate with ungrounded conductors  [690.71(G)] . But only if four conditions are met. Those are spelled out in  [690.71(G)].
     
  4. New with the 2014 NEC is [690.71(H)]. This provides five requirements you must meet if the energy storage device input and output terminals are more than 5 ft from connected equipment. This is a very likely scenario.
     
  5. The five requirements of [690.71(H)] also apply if the circuits from input or output terminals pass through a wall or a partition.
  1. Charge control is another major issue with batteries. Getting it right is tricky, and it gets trickier as the battery grows in size. For example, a four-tier battery rack in a data center presents thermal complexity that simply does not exist in a single-tier rack. The NEC provides an exemption for providing charge control if you meet certain conditions [690.72(A).]
     
  2. If the PV has a diversion charge controller as its sole means of regulating the charging rate, it must also be equipped with a means to prevent overcharging [690.72(B).]
     
  3. The NEC provides specific requirements to meet if your regulator is of the buck/boost type [690.72(C).]
     
  4. You can use flexible cables (as identified in Article 400) in sizes 2/0 and larger within the battery enclosure to connect from the battery terminals to a nearby junction box [690.74]. In that box, they must connect to an approved wiring method.
     
  5. Flexible cables can be only those listed for hard service. If you use flexible cables that are fine-stranded (and most of them are fine-stranded), you can terminate them only with terminals, lugs, devices, or connectors per Article 110 requirements [690.74].

This concludes our coverage of Article 690 requirements for batteries. The NEC presents those requirements in Part VIII.

The next and final Part of Article 690 addresses specific requirements for systems over 1000V. Since those requirements are minimal and plainly expressed, we won't cover them. Thus, this Part 11 in this series also concludes our coverage of Article 690/

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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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