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)]. It's a good idea not to use them on the supply side, either; aluminum conductors have higher impedance than copper conductors and run hotter.
- 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. This section changed only slightly with the 2017 NEC and did not change at all with the 2020 NEC.
- 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) ].