Appendix C
Calculations
This section describes current-loading and the process for determining the standby-battery rating and
the NAC wiring length.
Current loading calculations do not include the combined detector currents of the Sigma A-CP Fire Control
Panel. These combined currents are negligible in comparison to currents of the fire control panel, ancillary
devices and NACs and are therefore excluded from the current loading calculation.
Determining the Amp-Hour Rating
Installers must identify the load current for each device connected to the fire control panel. The sum of
this current must be below the operating limits of the fire control panel and within the load capacity
of the standby-batteries.
To determine the load rating of the fire control circuit:
1
Record the standby and alarm currents of the Sigma A-CP Fire Control Panel.
2
Record the standby and alarm currents of Ancillary Devices.
3
Record the alarm currents of NAC Devices.
4
Total the standby and alarm currents of the Sigma A-CP Fire Control Panel,
Ancillary Devices and NAC devices.
5
Calculate the Total Standby Amp Hours.
6
Calculate the Total Alarm Amp Hours.
7
Determine Total Amp-Hours by adding the Total Standby Amp Hours to the Total Alarm Amp Hours.
8
Determine the minimum Amp Hour rating for the battery by multiplying the Total Amp-Hours to the
Derating Factor (1.20).
9
Verify that the rating determined from the Load Capacity Worksheet does not exceed the 7 AH or 12 AH
capacity of the Standby-Batteries specified for operating the Sigma A-CP Fire Control Panel.
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