Fire Alarm and Signaling Systems: NEC Article 760 and NFPA 72 Fundamentals
What this domain tests
Fire alarm work combines NEC Article 760 with NFPA 72 performance rules. The exam tests power-limited versus non-power-limited fire alarm circuits, cable markings, separation, initiating device circuits (IDC), notification appliance circuits (NAC), and basic NFPA 72 supervision concepts.
Core rules
- Article 760 covers fire alarm conductors and equipment. Power-limited fire alarm (PLFA) circuits use listed PLFA cable and power sources; non-power-limited fire alarm (NPLFA) circuits follow Chapter 3 methods.
- Cable markings: FPL general, FPLR riser, FPLP plenum. Match the cable to the environment.
- Fire alarm circuits must be separated from power and other circuits as required by 760.139 unless permitted otherwise.
- NFPA 72 requires supervision of IDCs and NACs. Class B tolerates a single open but loses devices beyond it; Class A returns to the panel and survives a single open.
- Notification appliances must meet voltage drop and audibility and visibility requirements.
Worked example
A 2-wire Class B IDC uses an end-of-line resistor. An open occurs mid-circuit. The panel shows a trouble, and devices beyond the break are no longer supervised. A Class A IDC would return the circuit to the panel and continue to supervise both directions after one open. The fix is not just replacing the resistor; the break must be located and repaired.
Traps
- Substituting CL2 cable for FPL where fire alarm cable is required.
- Running fire alarm cable in the same raceway as power without separation.
- Forgetting battery standby and voltage-drop calculations.
- Treating a trouble as an alarm or silencing without investigating.