Codes and Standards: NFPA 72, NEC Article 760, and Building/Fire Codes
Who says what
NFPA 72 is the installation and performance standard: fundamentals, circuits and pathways, initiating devices, notification appliances, inspection/testing/maintenance, and documentation. The building and fire codes (780 CMR, which references the IBC, and 527 CMR 1.00, built on NFPA 1) decide when a system is required and what performance features an occupancy must have. NEC Article 760 governs the wiring. Learn the division of labor, because questions frequently test it.
NEC Article 760 essentials
Article 760, not Article 725, applies to fire alarm systems. Power-limited fire alarm cables are marked FPL, FPLR, and FPLP; non-power-limited cables are marked NPLF, NPLFR, and NPLFP. Ratings nest: a higher-rated cable may substitute for a lower one (FPLP may be installed where FPLR is required), but never the reverse. Power-limited and non-power-limited fire alarm conductors must be separated by at least 2 in. or a barrier, and the branch circuit feeding the control unit must be dedicated to the fire alarm system.
Traps
Substituting CL3 or other Class 2/3 cable in a fire alarm circuit is a fail: it is not listed to Article 760. Installing FPLR in a return-air plenum is another fail. Confusing Article 725 with Article 760 is the single most common wiring question.
Worked example
A specification calls for FPLR in a corridor that is a return-air plenum. FPLR is not permitted in a plenum, so the correct substitution is FPLP, which is rated for plenum use and is also acceptable wherever FPLR is required.