74 XLS140 Installation Manual Form Number 95-7673-3 P/N 51927:C 12/06/2005
Power Supply Calculations Calculating the System Current Draws
A.2.1 Calculating the Maximum Secondary Power Fire Alarm
Current Draw
Use Table A.3 below to determine the maximum current requirements of secondary power source
during fire alarm conditions. The result obtained is the amount of current that the batteries must be
able to supply to the fire alarm system. Use the result in Table A.4 to determine the size of the
batteries needed for the fire alarm system.
Results taken from Table A.3 below assume that, while in a fire alarm condition, batteries must
feed the main power supply (and any additional supplies such as the APS-6R and AA-30) with the
maximum rated power each supply can provide.
Device Quantity
Current
(in amps)
Total Current/Type
Alarm Current, from Table A.2, col 2 =
APS-6R
*
* Actual load current may be used in place of maximum rated supply
current. To calculate actual load current, sum the current draws for each
appliance connected to APS-6R supplies.
[] X 6 =
AA-30
†
† Exclude Amplifiers that are employed for backup.
[] X 3 =
AA-120
2
[ ] X 7.3 =
Sum Column for Secondary Fire Alarm Load =
Table A.3 Maximum Secondary Power Fire Alarm Current Draw
NOTE: The Secondary Fire Alarm Load cannot exceed the following:
• 9 A with BAT-12120 batteries (12 V, 12 AH).
• 12 A with BAT-12250 batteries (12 V, 26 AH).
• 20 A with BAT-12550 batteries (12 V, 55 AH).
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