National Electrical Code ExplanationsBased on the 2014 NEC
National Electrical Code Tips: Article 760, Fire Alarm Systems, Part 4
All of the following tips apply to Power Limited Fire Alarm (PLFA) circuits.
- The supply side has requirements in 760.127. The load side has requirements in 760.130.
- Conductors and equipment on the supply side of the power source must be installed per the appropriate requirements of Article 760 Part II and Chapters 1 through 4 [760.127]. In other words, it's a normal circuit except for some minor adjustments in Part II (and it still resembles a normal circuit, unlike its NPLFA counterpart).
- Transformers or other devices supplied from power supply conductors must be protected by overcurrent devices rated 20A or less [760.127]. An exception applies (see Exception note in 760.127].
- You can't use aluminum conductors on the load side [760.130(A)].
- You must install load side conductors per 760.46, but three exceptions exist (see 760.130(A) and the Informational note below the three listed exceptions).
- Any sort of ad hoc enclosure is strictly prohibited. You must make splices and/or terminations in listed fittings, boxes, enclosures, fire alarm devices, or utilization equipment [760.130(B)(1). Note that modifying an enclosure (e.g., drilling a hole in it rather than using a knockout) violates its listing and consequently renders its use a violation.
If cables pass through a wall or floor, you must enclose them in metal raceways or rigid nonmetallic conduit [760.130(B)(2)] (unless building construction such as detailed in 760.130(B)(1) provides adequate protection or there's an equivalent solid guard).
If the cables are installed in hoistways, you must enclose them in rigid metal conduit, intermediate metal conduit, or electrical metallic tubing [760.130(B)(3)]. Each of these has its own Article in Chapter 3.
- New with the 2014 NEC is a long section [760.135] that details the requirements for installing PLFA cables in buildings. Mostly, it details which type of cables you can use in which type of application. So find your application (e.g., risers) and see which types of cables are permitted.
- A portable fire alarm system provided to protect a stage or set (when not in use) can use the wiring methods provided in 530.12 [760.135(J) ].
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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