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Method of Battery Calculation for Fire Alarm System as per NFPA 72

Question asked by md.sadidrahman on Mar 12, 2020

Hello all, I am looking for a clear method to complete battery calculation for a Fire Alarm System. As per NFPA 72 [2013], "The secondary power supply shall have sufficient capacity to operate the system under quiescent load (system
operating in a nonalarm condition) for a minimum of 24 hours and, at the end of that period, shall be capable of operating all alarm notification appliances used for evacuation or to direct aid to the location of an emergency for 5 minutes". It indicates 

I (total) = I (standby) + I (alarm). 

in this case I(alarm) = what ? current consumption of  a) Only notification device??  or b) All Alarm and Notification device??


I am receiving both method from different source.