Fire Alarm, Security, and Life Safety System Wiring
Fire alarm versus security
Fire alarm wiring is governed by Article 760 and NFPA 72; security and access control usually fall under Article 725 Class 2/3. Fire alarm cable must be listed and marked FPL, FPLR, or FPLP; plenum spaces require FPLP. Non-power-limited fire alarm conductors follow Chapter 3 methods, while power-limited fire alarm has its own separation and cable rules.
- Keep fire alarm conductors separated from power by at least 2 in. or a barrier; 760.130 addresses PLFA and NPLFA separation.
- Class B notification appliance circuits are supervised and generally require an end-of-line resistor; T-taps defeat supervision.
- Secondary power: commercial fire alarm systems commonly require 24 hours of standby plus 5 minutes of alarm; voice systems require 15 minutes of alarm.
- Maintain firestopping and, where required, circuit integrity cable for survivability.
Worked example
An installer tees a horn/strobe off a Class B NAC to save cable. The panel can no longer supervise the branch, so an open at the tee is invisible until a fire. The correct design runs the pair continuously through each appliance and terminates at the end-of-line resistor at the last device.
Traps
Using FPLR in a plenum; sharing a raceway with power; omitting firestopping; forgetting battery calculations; mixing Class A and Class B supervision.