Power Supply Calculations Panel Programming
70 XPIQ PN 51013:C 7/01/03
SECTION 4 Power Supply Calculations
This section contains instructions and tables for calculating power supply currents in alarm and
standby conditions. Power supply and battery calculations require a four-step process which
consists of the following steps:
1. Calculating the total amount of AC branch circuit current required to operate the system
2. Calculating the power supply load current for non-fire and fire alarm conditions and
calculating the secondary (battery) load
3. Calculating the size (Ampere hour) of batteries required to support the system if an AC
power loss occurs
4. Selecting the proper size batteries for the system
AC Branch Circuit Calculation
The XPIQ transponder requires connection to a separate, dedicated AC branch circuit (120 VAC or
240 VAC), which must be labeled FIRE ALARM. This branch circuit must connect to the line
side of the main power feed of the protected premises. No other nonfire 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 fire alarm control panel. Overcurrent
protection for this circuit must comply with Article 760 of the National Electrical Codes as well as
local codes. Use 14 AWG wire with 600 volt insulation for this branch circuit.
The total amount of current, in AC amperes, that must be supplied to the system is as follows:
• XPIQ-PS 120 VAC branch circuit requirements: 3.0A
• XPIQ-PSE 240 VAC branch circuit requirements: 1.5A
Calculating the System Current Draw
The XPIQ transponder must be capable of powering all internal and external devices continuously
during the nonfire alarm condition. To calculate the nonfire alarm load on the system power supply
when primary power is applied, use Calculation Column 1 in Table 4.2. The control panel must
support a larger load current during a fire alarm condition. To calculate the fire alarm load on the
power supply, use Calculation Column 2 in Table 4.2. The secondary power source (batteries) must
be able to power the system during a primary power loss. To calculate the nonfire alarm load on the
secondary power source, use Calculation Column 3 in Table 4.2.
When calculating current draw and the battery size, note the following:
• ‘Primary’ refers to the main power source for the XPIQ transponder
• ‘Secondary’ refers to the XPIQ transponder’s backup batteries
• All currents are given in amperes. Table 4.1 shows how to convert milliamperes and
microamperes to full amperes
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 4.1 Converting to Full Amperes
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