HCA Series Installation Manual
Page 13 of 58
V2.15
3.4 Calculating Current Draw and Battery Size
Use this section to determine the current draw and standby battery needs for your installation.
3.4.1 Maximum Battery Standby Load
The nominal battery capacity versus system standby current is shown in table 3.3.1 for typical battery sizes.
Make sure that the standby battery calculation of table 3.3.2 is less than the number of table 3.3.1 for the
battery chosen and the standby hours needed.
Table 3.3.1
Battery Size
Maximum standby load with 5 minutes
alarm, 24 hour standby
Maximum standby load with 5
minutes alarm, 60 hour standby
7AH
269mA
*
12AH
477mA
191mA
18AH
727mA
291mA
* 7AH size is not capable of 60 hour standby.
3.4.2 Calculating Maximum Current Draw & Battery Backup Requirements
Use table 3.3.2 to assist you in determining the worst case battery backup amp-hour requirements for the
particular installation.
1) The known standby and alarm current draws for the panel are already filled in for table 3.3.2. Note
that all EOL resistor currents for the zones and notification appliance circuits (NACs) are already
accounted for in the main panel current draw numbers and should not be included in the zone or
NAC current calculations.
2) Add in the total smoke detector standby current draw for each zone that is used and all standby
accessory loads on NACs configured as auxiliary power constant or auxiliary power resettable.
Note that auxiliary power door holder current is not included for battery standby because it is
powered down during battery backup. Put the appropriate current draw per device in the standby
and alarm current boxes and record the total number of devices per zone or circuit
in the “number
of devices” column.
3) Add in all notification appliance alarm current draws for each NAC configured as a notification
appliance circuit.
4) Add up the total standby and alarm current draw values and record the totals in the appropriate
boxes of table 3.3.2.
5) Multiply the standby and alarm currents with the standby and alarm hours to determine the total
amp-hours needed for both standby and alarm. Add up the standby and alarm amp-hour results
to get the total battery backup amp-hours required. Select a battery size that is at least 120% of
the total amp-hours required to achieve a 20% safety margin for the battery backup.
6) Make sure the total standby and alarm current you calculated (including the current for the panel
itself) does not exceed the 6.5 amps power supply rating. Also make sure you have not exceeded
the maximum current rating on any of the NACs.
