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6.1 Overview
This section contains instructions and tables for calculating power supply currents in alarm and standby conditions. This is a four-step pro-
cess, 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 secondary non-fire and fire alarm conditions
3.
Calculating the size of batteries required to support the system if an AC power loss occurs
4.
Selecting the proper batteries for your system
6.2 Calculating the AC Branch Circuit
The power supply requires connection to a separate, dedicated AC branch circuit, which must be labeled FIRE ALARM. This branch cir-
cuit must connect 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 a minimum of 14 AWG (2.00 mm
Use Table 6.1 to determine the total amount of current, in AC amperes, that must be supplied to the system.
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 a fire alarm condition. The secondary power
source (batteries) must be able to power the system during a primary power loss.To calculate the non-fire alarm load on the power supply
when secondary power is applied, use Calculation Column 1 in Table 6.3 on page 39. The power supply must support a larger load current
during a fire alarm condition. To calculate the fire alarm load on the power supply as secondary power, use Calculation Column 2 in
Table 6.3 on page 39.
When calculating current draw and the battery size, note the following:
•
Primary refers to the main 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.
Milliamperes (mA) to amperes (A)
Microamperes (μA) to amperes (A)
38
Section 6: Power Supply Requirements
2
) wire with 600 volt insulation for this branch circuit.
Number of
Device Type
Devices
HPF-PS6(B)
or
HPF-PS10(B)
or
1
HPF-PS6E
or
HPF-PS10E
[
]
[
]
[
]
[
]
Sum Column for AC Branch Current Required
Table 6.1 120/240 VAC Branch Circuit Requirements
To convert...
Table 6.2 Converting to Full Amperes
Current Draw
(AC amps)
5.0
or
6.2
x
or
2.7
or
3.5
x
[
]
x
[
]
Multiply
mA x 0.001
3 mA x 0.001 = 0.003 A
μA x 0.000001
300 μA x 0.000001 = 0.0003 A
HPF-PS Series Instruction Manual — P/N LS10227-003HP-E:C 2/2/2022
Total Current
per Device
=
=
=
=
Example
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