Under maximum normal load, the secondary supply should have capacity to operate a local, central station, or proprietary fire alarm system for how many hours?

• A. 12 hours
• B. 24 hours
• C. 36 hours
• D. 48 hours

Answer: (B)

The main idea is how long the secondary power (backup batteries) must keep a fire alarm system running when the main power is out. For local, central station, or proprietary fire alarm systems, the secondary supply is required to sustain operation for 24 hours at the system’s maximum normal load. This ensures the system remains fully supervised and able to signal and monitor for an entire day while awaiting power restoration or the arrival of a backup means (like a generator). A shorter duration (12 hours) wouldn’t cover a full outage, and longer durations (36 or 48 hours) would require much larger, more costly batteries without added benefit for typical outages.