What is the consequence of incorrectly calculating battery capacity for a fire alarm system, and how does it impact system reliability?

The consequence of incorrectly calculating battery capacity for a fire alarm system is that the system may fail to operate as intended during a power outage, severely compromising its reliability. Fire alarm systems are required to have a secondary power source, typically batteries, to provide power in the event of a primary power failure. Incorrectly calculating the battery capacity means the batteries may not be able to power the system for the duration specified by applicable codes and standards, such as NFPA 72. This duration includes both a standby time, where the system is in normal operation awaiting an alarm, and an alarm time, where notification appliances are activated. If the calculated battery capacity is too low, the system might not be able to remain in standby mode long enough during a prolonged power outage, leading to a system failure before a fire even occurs. Furthermore, even if the system is in standby mode when a fire occurs, insufficient battery capacity will result in the system shutting down prematurely during the alarm, silencing notification appliances and potentially failing to transmit alarm signals to the fire department. For example, if a system requires 24 hours of standby power and 30 minutes of alarm power, but the batteries are only sized to provide 12 hours of standby and 15 minutes of alarm power, the system will fail to meet code requirements and could leave occupants unprotected in a real fire. This significantly reduces the overall reliability of the fire alarm system, making it unable to perform its life-safety function effectively when needed most.