National Electrical Code Explanations
Based on the 2020 NEC
National Electrical Code Tips: Article 800, Communications Circuits, Part 1
- Article 800 is the first Article in Chapter 8. The Chapter title is "Communications Systems" and the Article title is "Communications Circuits."
- Article 800 follows the convention in the NEC of being the foundation article for either the whole Chapter or for the first series of Articles (not all 00 Articles follow this convention).
- Logically, it would seem that some of the Articles in Chapter 7 belong in Chapter 8. For example, Article 770 provides the requirements for optical fibers and raceways. These don't seem to fall under the Chapter 7 rubric of "Special Conditions." Have you ever seen an optical fiber circuit not used for communications? Perhaps not, but they are, in fact, used for other purposes such as for control circuits in high electrical noise environments. So when you're looking through Chapters 7 and 8, keep in mind that Article 800 will apply if the circuit is used for communcations but if the application isn't in Chapter 8 look for it in Chapter 7.
- As of the 2104 edition, Article 800 no longer uses the vague and misunderstood term "grounding conductor" but uses "bonding conductor" or "grounding electrode conductor" as appropriate. That correction has remained in subsequent revisions. See the Article 100 definition of bonding (creating a metallic path) and grounding (connecting to the dirt).
- Some people are confused over what is meant by "abandoned cable." It's a cable that isn't terminated to equipment or is not identified for future use with a tag [800.2]. This definition has changed over time, and it does not seem as accurate as the old definition from a few Code revisions back. By that older definition, an abandoned cable isn't terminated at either end and is not identified for future use with a tag. By this latest definition, a cable can be connected at each end but would be considered abandoned simply because it is not identified for future use with a tag. Even if it's in present use. And how can a cable be abandoned if it's still connected to anything? If it's connected at one end but not the other, wouldn't that simply mean it's disconnected rather than abandoned?
Cables are abandoned because they aren't needed, and are left in place because removing them poses too many problems. However, such cables may be used in the future as a need arises. Instead of pulling a new cable, use an abandoned one. Toward this end, it's a good practice to mark each abandonded cable with a tag and to keep a catalog of such cables. Now, this practice seems to put you into conflict with the requirements of 800.25; we will discuss that after the next two items in our list here.
- There's also confusion over what is meant by "exposed to accidental contact." This doesn't mean contact with people, but with other circuits [800.2]. So don't assume there's no problem just because the circuit isn't where people are likely to touch it (e.g., in raceway, boxes, and termination cabinets). The idea of "accidental contact" is based on what happens if there's a failure of supports or insulation.
- We find in Article 800 a repetition of 110.12, that circuits and equipment shall be installed in a neat and workmanlike manner [800.24]. This is repeated in many other places in the NEC. Basically, the requirement applies to all installations. Some additional verbiage in 800.24 is also rewarmed from other places in the NEC. Keep in mind that Chapter 8 installations must conform to the requirements of Chapters 1 through 4 (mostly Chapter 1) unless amended by the relevant Chapter 8 Articles.
- In item 5, we recommended tagging and cataloging abandoned cables, and we noted this seems to conflict with 800.25. What does 800.25 require? That the accessible portion of abandoned cables be removed. How do we reconcile this? By really understanding the definition of abandoned. You may, for example,"abandon" four cables because you installed a new system that needs 18 cables instead of 22. In reality, you're just not using those cables at the moment. Rather than classify them as abandoned, classify them as unused or spare and tag them for "undetermined future use" rather than "abandoned." This will allow you to conform with the 800.2 definition of "abandoned" and the 800.25 requirement to remove the accessible portion. In other words, don't be too hasty to abandon any cables.
- The Code minimum is that when you install communications cables, your methods don't substantially increase the possible spread of fire or combustion [800.26]. For example, don't punch a big hole in the ventilation duct through which you're routing the cable. That's good as far as it goes, but where practical go beyond the Code minimum. For example, discuss with your customer why it makes sense to firestop every hole made rather than just those in fire-resistant-rated walls and other places where it's required. That means more money for you, and ity makes a safer installation for your customer.
- Other codes apply in cases where you do penetrate a fire-resistant wall and similar barriers [Informational Mote under 800.26]. Don't see what you can get by with, as in, "The NEC doesn't require it" but review all applicable codes (e.g., International Building Code) to know what you must do and also what would make good sense to do from an engineering standpoint even if not strictly required. Understand that those codes provide the minimum. Always discuss with the building owner/manager good design practices that will enhance safety, improve maintainability, imrpove appearance, etc. Have this discussion before submitting a quote, estimate, or bid. The goal should never be to have a cheap installation, but to have a good installation at a reasonable price.
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.
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