National Electrical Code ExplanationsBased on the 2014 NEC
National Electrical Code Tips: Article 728, Fire-Resistive Cable Systems
At about 3/4 of a page, this is one of the shortest NEC Articles. It's also new with the 2014 NEC.
- From the title, you would think this Article belongs in Chapter 3. After all, isn't a cable system a wiring method? What's going on is Chapter 7 covers special conditions and apparently being in a fire is considered kind of special. And this isn't really about cables, it's about entire systems (the cables are part).
- That system is, in turn, part of an electrical cirucit protective system.
- These systems are designed to keep critical circuits working for a specified time under fire conditions [728.2].
- What makes them critical? They serve loads such as the fire pump room, for example.
- We said this Article is about systems. In fact, the fire-resistive cables, fire-resistive conductors, and components of each system must be tested and listed as a system [728.4].
- Components of one system are not interchangeable with components of another system [728.4].
- Install these per 728.5(A) through (H). The theme that recurs with nearly every one of these is that you use listed components, install per the listing, and follow the manufacturer's instructions.
- Would it make any sense to use fire-rated cables for the current-carrying conductors, but not for the equipment grounding conductor (EGC)? Nope. That's why you must use the same fire-rated cable described in the system or use alternative EGCs listed with the system. If using an alternative, make sure it's marked with the system number [728.60].
- The cables and conductors must have the marking required in 310.120 (it's a fairly detailed set of instructions) and be surface marked with the suffix "FRR" plus the circuit integrity hours, and with the system identifier [728.120].
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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