National Electrical Code ExplanationsBased on the 2014 NEC
National Electrical Code Tips: Article 810, Radio and Television Equipment
- Article 810 seems to cover just about everything to do with radio and television equipment [810.1}. What specifically does it not cover? That would be equipment and antennas used for coupling carrier current to line conductors.
- Two new subsections were added with the 2014 NEC. 810.6 provides requirements for antenna lead-in surge protectors. These must be listed for the use and properly bonded or grounded. 810.7 provides requirements for grounding devices. These two new subsections really form a set.
- The requirement for secure supporting is repeated throughout the NEC, most notably for raceway. This is really part of good workmanship [110.12]. Notably for the systems covered by Article 210, outdoor antennas and lead-in conductors must be securely supported [810.12]. This does not mean anything else in the system doesn't also fit this requirement. If you install something electrical, it must be securely supported. Period.
- Receiving stations must meet several requirements, including size of wire-strung antenna [810.16], size of lead-in [810.17], and clearances [810.18]. These are in Part II, which takes up (by page count) about half of Article 810.
- The requirements for receiving stations are mostly about the mechanics of things and there's nothing new here. For example, the bonding and grounding electrode conductors must be protected where exposed to damage [810.21(D)]. That protection rule is perhaps the most common one in the NEC.
- The bonding conductor and/or grounding electrode conductor must be run in as straight a line as possible [810.21(E)]. This is the same rule we apply to lightning protection downconductors, and for the same reason (high frequency energy traveling on the skin of the conductor).
- Oddly enough, there are requirements for the antenna systems of citizens band transmitting and receiving stations even though by law radios operating on this band are limited to 4 watts. These requirements are in Part III.
- Part IV provides the requirements for interior installation at transmitting stations. There are three subsections. The first requires the transmitter to be enclosed in a metal frame or grill and separated from the operating space by a barrier or other means [810.71(A)]. All metallic parts must be bonded.
- The second requirement in Part IV requires bonding all external metal handles and controls accessible to personnel, ensuring they are effectively connected to the equipment grounding conductor if the transmitter is powered by the premises wiring system [810.71(B)]. If it's powered by some other means, bond and ground per 810.21.
- The third and final requirement in Part IV is that all access doors have interlocks [810.71(C)]. These must disconnect all voltages over 350V between conductors when any access door is opened.
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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