48 HPFF12 NAC Expander — P/N 53576:B 11/24/2010
Section 6: Power Supply Requirements
6.1 Overview
This section contains instructions and tables for calculating power supply currents in standby and
alarm conditions. This is a four step process, consisting of the following:
1. Calculating the total amount of AC branch circuit current required to operate the system
2. Calculating the power supply load current for non-alarm and alarm conditions and calculating
the secondary (battery) load
3. Calculating the size of the batteries required to support the system if an AC loss occurs
4. Selecting the proper batteries for your system.
This section also contains related calculations for NAC circuits; see Section 6.5, “NAC Circuit
Loop Wiring Requirements”.
6.2 Calculating the AC Branch Circuit Current
The power supply requires connection to a separate, dedicated AC branch circuit, which must be
labeled FIRE ALARM. This branch circuit must be connected to the line side of the main power
feed of the protected premises. No other non-fire alarm equipment may be powered from the fire
alarm branch circuit. The branch circuit wire must run continuously, without any disconnect
devices, from the power source to the power supply. Overcurrent protection for this circuit must
comply with Article 760 of the National Electrical codes as well as local codes. Use 14 AWG (2.08
mm²) wire with 600 volt insulation for this branch circuit.
Use Table 6.1 to determine the total amount of current, in AC amperes, that must be supplied to the
system.
Device Type
Number
of Devices
Current
Draw
(AC Amps)
Total Current
per Device
HPFF12/HPFF12CM
or
HPFF12E/HPFF12CME #
X
5.0
or
2.80
=
( ) ( ) X ( ) =
( ) ( ) X ( ) =
Sum Column for AC Branch Current Required =
Table 6.1 120/240 VAC Branch Circuit Requirements
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