HPFF12 NAC Expander — P/N 53576:B 11/24/2010 49
Calculating the System Current Draw Power Supply Requirements
6.3 Calculating the System Current Draw
6.3.1 Overview
The power supply must be able to power all internal and external devices continuously during the
non-alarm condition. To calculate the non-alarm condition load on the power supply when primary
power is applied, use the Calculation Column 1 in Table 6.4. The power supply must support a
larger load current during an alarm condition. To calculate the fire alarm load on the power supply,
use the Calculation Column 2 in Table 6.4. The secondary power source (batteries) must be able to
power the system during primary power loss. To calculate the non-alarm condition load on the
power supply when primary power is applied, use the Calculation Column 3 in Table 6.4.
When calculating current draw and the battery size, note the following:
• Primary refers to the main AC power source for the power supply.
• Secondary refers to the Power supply's backup batteries.
• All currents are given in amperes (A). Table 6.2 shows how to convert milliamperes and
microamperes to full amperes.
The following table shows the maximum number of Notification Appliances that can be connected
to the NAC outputs per manufacturer. These maximum numbers are equivalent to the full 12 Amps
capability of the power supply. The maximum number of devices will have to be reduced if an
Auxiliary load is present, see Table 6.4.
To convert... Multiply Example
Milliamperes (mA) to amperes (A) mA x 0.001 3 mA x 0.001 = 0.003 A
Microamperes (µA) to amperes (A) µA x 0.000001 300 µA x 0.000001 = 0.0003 A
Table 6.2 Converting to Full Amperes
Device Manufacturer Maximum Number of Devices
Cooper Wheelock 200 total
50 for 3.0 Amp loaded NAC
System Sensor SpectrAlert
Advanced
184 total
46 for 3.0 Amp loaded NAC
SpectrAlert 200 total
50 for 3.0 Amp loaded NAC
Amseco 136 total
34 for 3.0 Amp loaded NAC
Faraday 132 total
33 for 3.0 Amp loaded NAC
Gentex 144 total
36 for 3.0 Amp loaded NAC
Table 6.3 Maximum Number of Notification Appliances per Extender
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