National Electrical Code ExplanationsBased on the 2014 NEC
National Electrical Code Tips: Article 800, Communications Circuits, Part 2
- The requirements for communication system wires and cables outside and entering buildings are in Article 800, Part II. They are, as you would expect, different for aerial versus undergound.
- If the wires and/or cables are on poles and in-span, four rules apply. 1, locate them below the electric light and/or power conductors, if practicable. 2, don't attach them to a cross-arm that carries light and/or power wires. 3, provide climbing space per 225.14(D). 4, observe the clearance requirements of 800.44(A)(4).
- If the wires and/or cables are above roofs, the vertial clearance must be at least 8 ft from all points of roofs above which they pass [800.44(B)]. Three exceptions exist.
- The requirements for communication system wires and cables that are underground and entering buildings depend and are with electric light and power conductors and depend upon whether they are installed using the block distribution method or not [800.47].
- If not using the block distribution method, the conductors must be in a section separated by brick, concrete, or tile partitions or by means of a suitable barrier [800.47(A)].
- If using the block distribution method (see 800.47(B) for what this is), then you don't need insulating supports for the conductors or bushings where the conductors enter the building. A few other requirements are waived, as well.
- You can use unlisted outside plant commuication cables, but they can be installed only in spaces other than risers andenvironmental air pathways (ducts, plenums, etc.). 800.48
- If you use metallic conduit for communications entrance wire or cable, it must be bonded to the grounding system [800.49].
- Some circuits require primary protectors. These must comply with the requirements of 800.50. For example, raceways or bushings shall slope upward from the outside; where this isn't possible, install a drip loop.
- Where possible separate communications wires and cables from lightning conductors by at least 6 ft. [800.53]. The idea of "possible" includes routing them way out of the way instead of taking the shortest route right past the down conductors. Remember, the lightning conductors basically cannot be relocated and must have the gentlest bends possible with the straightest possible path from the roof to the ground. Communications cables give you a lot more leeway here, take it if you need to.
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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.