Power Supply Calculations Calculating the System Current Draws72 NFS-640 Installation Manual P/N 51332:B1 12/01/2003A.2.1 Calculating the Maximum Secondary Power FireAlarm Current DrawUse the table below to determine the maximum current requirements of secondary power sourceduring fire alarm conditions. The result obtained is the amount of current that the batteries must beable to supply to the fire alarm system. Use the result in Table 14 to determine the size of thebatteries needed for the fire alarm system.Results taken from the table below assume that, while in a fire alarm condition, batteries must feedthe main power supply (and any additional supplies such as the APS-6R and AA-30) with themaximum rated power each supply can provide.Note: The Secondary Fire Alarm Load cannot exceed the following:• 9 A with PS-12120 batteries.• 12 A with PS-12250 batteries.• 20 A with PS-12550 batteries.Contact rating (maximum current) for battery-switching relay in the control panelTable 13 Maximum Secondary Power Fire Alarm Current DrawDevice QuantityCurrent(in amps)Total Current/TypeAlarm Current, from Table 12, col 2 =APS-6R11. Actual load current may be used in place of maximum rated supply current. Tocalculate actual load current, sum the current draws for each appliance connected toAPS-6R supplies.[ ] X 6 =AA-3022. Exclude Amplifiers that are employed for backup.[ ] X 3 =AA-1202 [ ] X 7.3 =Sum Column for Secondary Fire Alarm Load =
