For how many hours should the secondary supply be capable of operating central station or proprietary fire alarm systems under max normal load?

For how many hours should the secondary supply be capable of operating central station or proprietary fire alarm systems under max normal load?

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

Answer: (B)

Backup power for fire alarm systems is there to keep the system operating when the building loses power. The standby (secondary) power supply must be able to run the system for a full day under its normal operating load, meaning the system is functioning as designed with its standard power draw and signaling duties, not during a heavy alarm surge. This 24-hour requirement ensures the central station or proprietary system can continue monitoring, reporting, and signaling through typical outages without needing immediate external power. It balances reliability with practical battery sizes and cost. Longer durations would demand much larger, more expensive battery banks for little added real-world benefit in most cases, while shorter durations risk losing monitoring capability during an outage. So, the duration specified for the secondary supply under normal load is 24 hours.

Backup power for fire alarm systems is there to keep the system operating when the building loses power. The standby (secondary) power supply must be able to run the system for a full day under its normal operating load, meaning the system is functioning as designed with its standard power draw and signaling duties, not during a heavy alarm surge.

This 24-hour requirement ensures the central station or proprietary system can continue monitoring, reporting, and signaling through typical outages without needing immediate external power. It balances reliability with practical battery sizes and cost. Longer durations would demand much larger, more expensive battery banks for little added real-world benefit in most cases, while shorter durations risk losing monitoring capability during an outage.

So, the duration specified for the secondary supply under normal load is 24 hours.