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 was 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]. No, that reference is not a typo. We really do jump from 728.5 to 728.60. Then we jump from there to 728.120.
- 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].