Section 10.4.1/Fire Alarm System Power Supply
NFPA 72 Section 10.4 covers primary and secondary power supply requirements for fire alarm systems including battery backup sizing.
Fire alarm systems must have a primary power supply from a dedicated branch circuit with no other loads. The circuit must be mechanically protected (in conduit or armored cable) and must be supplied from ahead of the main disconnect or from a source that is not controlled by a disconnect accessible to unauthorized persons. A secondary (battery) power supply must be capable of operating the system in normal supervisory mode for 24 hours and then operating all notification appliances for 5 minutes (or 15 minutes for voice evacuation systems).
Why this section exists
Fire alarm systems must operate during power outages and building emergencies when the normal power supply may be interrupted. The dedicated circuit requirement prevents a tripped breaker on a shared circuit from disabling the fire alarm. The 24-hour plus 5-minute battery requirement ensures the system operates through extended power outages and still has capacity to sound the alarm if a fire occurs during the outage.
What plan reviewers look for
Plan reviewers check the electrical panel schedule for a dedicated circuit to the fire alarm control panel (FACP). They verify that the circuit is labeled and that no other loads share it. They check the fire alarm riser diagram for the secondary power supply (batteries) and look for a battery calculation demonstrating the 24-hour plus 5-minute capacity. They also verify that the primary circuit is mechanically protected per NEC 760.
Common violations
Related NFPA 72 requirements
Section 10.5 covers fire alarm system monitoring requirements. NEC Section 760.41 covers the supply circuit power source requirements. Section 10.6 covers the fire alarm system wiring methods. NEC Article 700 covers emergency system power supply requirements.