46 Flex 402 & Flex 404 Instruction Manual — P/N 52194:D4 3/27/2015
Power Supply Calculations Calculating the Battery Size
1. Enter the totals from Table 5.3 on page 45, Calculation Columns 2 and 3 where shown.
2. Enter the NFPA Standby and Alarm times (refer to ‘NFPA Requirements’ below).
3. Calculate the ampere hours for Standby and Alarm, then sum the Standby and Alarm ampere
hours.
4. Multiply the sum by the derating factor of 1.2 to calculate the proper battery size (in AH).
5. Write the ampere hour requirements on the Protected Premises label located inside the cabinet
door.
5.4.1 NFPA Battery Requirements
• NFPA 72 Local, Central and Proprietary Fire Alarm Systems require 24 hours of standby
power followed by 5 minutes in alarm
• NFPA 72 Auxiliary and Remote Station require 60 hours of standby followed by 5 minutes in
alarm. Batteries installed in a system powered by a generator need to provide at least 4 hours
of standby power
5.4.2 Selecting and Locating Batteries
Select batteries that meet or exceed the total ampere hours calculated in Table 5.4 . The control
panel can charge batteries in the 7 AH to 18 AH range. The control panel cabinet is capable of
housing batteries up to 7 AH. Batteries larger than 7 AH require the BB-17F or other UL listed
external battery cabinet.
Secondary Standby Load
(total from Table 5.3 Calculation
Column 3)
[ ]
Required Standby Time
(24 or 60 hours)
X[ ] = AH
Primary Alarm Load
(total from Table 5.3 Calculation
Column 2)
[ ]
Required Alarm Time
(for 5 min., enter 0.084,
for 10 min., enter 0.168)
X[ ] = AH
Sum of Standby and Alarm Ampere Hours = AH
Multiply by the Derating Factor X 1.2
Battery Size, Total Ampere Hours Required = AH
Table 5.4 Total Secondary Power Requirements at 24 VDC
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