
VISTA-128FBP/VISTA-250FBP Installation and Setup Guide
3-28
Determining the Control’s Power Supply Load
In the event of an AC power loss the VISTA-128FBP/VISTA-250FBP and the PS24 Power Supply Module must be
supported by backup, rechargeable batteries. When the system is used without the PS24, a 12VDC, 12AH to 34.4AH
battery must be connected the control panel. When the system is used with a PS24, two 12VDC, 7AH to 17.2AH
batteries must be connected to the PS24.
The PS24 configures these batteries to provide 24V backup power to its outputs and 12V backup power to the control
panel.
The battery’s capacity must be sized to provide 24 hours (central station fire) followed by 5 minutes (fire only) or 15
minutes (fire and burglary) alarm time. Use only sealed lead-acid batteries with a minimum charging current handling
capacity of 1.8A.
Use the worksheets that follow to calculate the total current for Auxiliary Power 1, Auxiliary Power 2, Bell 1, Bell 2,
Polling Loop and the total current load of the control panel. In each worksheet, multiply each device’s standby and/or
alarm current by the number of units used.
Then, if you are using the PS24, fill out the Total PS24 Module Load Worksheet, found in the PS24’s instructions, to
determine the required capacity of the backup batteries that must be connected to the PS24. Select two batteries from
the Battery Selection Table in the PS24’s instructions that have a capacity greater than or equal to the calculated
capacity.
If you are NOT using the PS24, fill out the Battery Capacity Calculation Worksheet, following the other worksheets
below, to determine the required capacity for the backup battery. Select a battery from the Battery Selection Table
(found later in this section) that have a capacity greater than or equal to the calculated capacity.
1. In Worksheet 1, enter devices used on the polling
loop. Calculate total current draw on the polling
loop.
Worksheet 1: Total Polling Loop Current Draw
Polling Loop Device Current # of Units Total
Polling Loop Subtotal
(terminals 28 & 29 – 128mA) ✳
✳The total current cannot exceed 128mA. If total load exceeds
128mA, then a 4297 Loop Extender Module can be used. This
module is powered from the panel’s auxiliary power, and
provides a separate polling loop output, which can support an
additional 128mA load. Note that the total number of points
connected to the panel cannot exceed 119.
2. In Worksheet 2, enter devices used on Auxiliary
Power 1. Calculate standby and alarm currents,
then add to get Auxiliary Power 1 current subtotal.
Worksheet 2: Auxiliary Power 1 Current Load
Total Current
Device
Model #
Device Current X
# of Units
Standby Alarm
Auxiliary Power 1 Subtotal
(terminals 10 & 11)
1A max.
1.7A max.
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