For how long must a secondary power supply maintain capacitance when primary power is off, without alarm conditions?

The requirement for a secondary power supply in fire alarm systems, when the primary power is off and without any alarm conditions, is that it must maintain an adequate level of capacitance for a duration of 24 hours. This is crucial to ensure that the fire alarm system remains operational in the event of a power outage, allowing it to continue monitoring for alarms and keeping the system fully functional.

Maintaining secondary power for this period is grounded in safety standards that focus on the reliability and effectiveness of fire alarm systems. A well-designed secondary power supply ensures that even during an unexpected loss of primary power, the system can adequately respond to fire or smoke detection, thus providing ongoing protection for the occupants of the building.

While other durations may seem plausible, they do not meet the established criteria outlined in the fire protection standards, which emphasize a minimum of 24 hours of standby power. This duration ensures that the system can function effectively and provide a reasonable time for emergency services to respond, should the need arise.