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NFS2-640/E Installation Manual —
P/N 52741:P2 7/10/14
Power Supply Calculations
Calculating the Battery Requirements
A.3 Calculating the Battery Requirements
A.3.1 Calculating the Battery Capacity
Use this table to determine the battery capacity needed for the system:
Current (amps)
X
Time (hours)
=
AH
Secondary Non-Fire Alarm Current
(from column 3 in Table A.2)
(see Note 8)
________________
X
Required Secondary Non-Fire Alarm
Standby Time (24 or 60 hours)
________________
=
_________AH
APS-6R
Standby Load Current
________________
X
Required Secondary Non-Fire Alarm
Standby Time (24 or 60 hours)
________________
=
_________AH
Secondary Fire Alarm Load
(from Table A.3)
(see Note 8)
________________
X
Required Fire Alarm Standby Time:
(for 5 minutes, enter 0.084; for 15
minutes, enter 0.25)
________________
=
_________AH
Sum Column for Total Secondary Amp Hours calculated
=
_________AH
Multiply by the derating factor x 1.2 (see Note 7)
=
_________AH
Battery Size – Total Secondary Amp Hours Required
=
_________AH
1.
NFPA 72 Local, Proprietary, and Central Station systems require 24 hours of standby power followed by
5 minutes in alarm.
2.
NFPA 72 Auxiliary and Remote Station Systems require 24 hours of standby power followed by 5 minutes
in alarm.
3.
Batteries installed in a system powered by an automatic starting engine generator need to provide at
least 4 hours of standby power.
4.
Factory Mutual requires 90 hours of standby for deluge-preaction systems.
5.
Emergency voice/alarm communications systems require 2 hours of operation in the alarm condition.
Due to the sporadic nature of voice operation, however, NFPA 72 permits 15 minutes of operation at a
maximum connected load to equal 2 hours of normal use.
6.
If the total exceeds 26 AH, the system requires a separate NFS-LBB, BB-100 or BB-200 battery
enclosure for two larger capacity batteries.
7.
The following battery derating factors must be used for Canadian installations using NFS2-640/E
charger:
• For a 26 AH battery, use derating factor of 1.5
• For a 55 AH battery, use derating factor of 1.8
• For a 100 AH battery, use derating factor of 2.5
• For a 200 AH battery, use derating factor of 2.5
8.
For 26 AH batteries: maximum standby current cannot exceed 0.65A; maximum alarm current cannot
exceed 6.75A.
Table A.4 Secondary Power Standby and Fire Alarm Load
