National Electrical Code ExplanationsBased on the 2017 NEC
National Electrical Code Tips: Article 830, Network-Powered Broadband Communications Systems Part 2
- Make sure you bond any metallic entrance cable to the grounding electrode conductor [830.49] or an existing ground rod. Don't misread this Section as saying that you should drive a separate ground rod for this system and call it a day. You can drive a separate ground rod if you want, but you must also bond it to the other ground rods. You'll find this requirement in 250.94, but also realize that the earth isn't a bonding jumper. Ground rods must be bonded to each other to eliminate dangerous differences of potential.
- Part III of Article 830 provides the requirements for primary electrical protection [830.90].
- Generally, you must provide primary electrical protection on all ungrounded /uninterrupted network-powered broadband conductors run aerially and not confined within a block [830.90(A)]. The exception is where electrical protection is provided on the derived circiuit(s). Carefully read Informational Notes 1 and 2, plus Informational Note 3 (this last was added with the 2017 revision).
- So what the heck is this "primary electrical protection?" It's a specific kind of device called a primary protector. Primary protectors can be fuseless or fused; limits on the use of fuseless and requirements on where fused ones must be used are in 830.90(A)(1) and 830.90(A)(2), respectively.
- You must install a primary protector on each network-powered cable external to and on the network side of the network interface unit (NIU) [ 830.90(B)(1)]. The NIU must also have this function integral to it 830.90(A)(2). And you must place these protectors on the output side of the NIu 830.90(A)(3).
- You can't install a primary protector in a Hazardous Location 830.90(C).
- Where the network-powered cable enters a building, ground the shield per 830.100 as close as practicable to the point of entrance [830.93(A)].
- The requirements for grounding methods are in Part IV. Nothing here should be especially surprising. The requirements include such things as keeping the bonding conductor or grounding electrode conductor as short as is practicable.
- As noted earlier, you must bond your grounding electrode to those of other systems [830.100(B) and 830.100(D)].
- Special grounding and bonding requirements exist for mobile homes. These are provided in 830.106. The particulars depend upon whether the building disconnect is within 30 ft of the exterior wall of the mobile home it serves.
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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.
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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.