HPF24S Series Power Supplies — P/N 52751:E1 4/14/2011 41
Calculating the Battery Size Power Supply Requirements
6.4 Calculating the Battery Size
Use Table 6.4 to calculate the total Standby and Alarm load in ampere hours (AH). This total load
determines the battery size (in AH) required to support the power supply under the loss of AC
power. Complete Table 6.4 as follows:
1. Enter the totals from Table 6.3 on page 40, Calculation Columns 2 and 3 where shown.
2. Enter the NFPA Standby and Alarm times. Refer to Section 6.4.1, “NFPA Battery
Requirements”.
3. Calculate the ampere hours for Standby and Alarm, then sum the Standby and Alarm ampere
hours.
4. Multiply the sum by the derating factor of 1.2 to calculate the proper battery size (in AH).
5. Write the ampere hour requirements on the Protected Premises label located inside the cabinet
door.
6.4.1 NFPA Battery Requirements
NFPA 72 Local and Proprietary Fire Alarm Systems require 24 hours of standby power followed by
5 minutes in alarm.
6.4.2 Selecting and Locating Batteries
Select batteries that meet or exceed the total ampere hours calculated in Table 6.4. The power sup-
ply can charge batteries in the 7 AH to 18 AH range. The power supply cabinet is capable of hous-
ing batteries up to 7 AH. Batteries larger than 7 AH require the BB-17F or other UL listed external
battery cabinet.
Secondary Standby Load
(total from Table 6.3 Calculation
Column 3)
[ ]
Required Standby Time
(24 or 60 hours)
X [ ]
=AH
Primary Alarm Load
(total from Table 6.3 Calculation
Column 2)
[ ]
Required Alarm Time
(for 5 min., enter 0.084,
for 10 min., enter 0.168)
X [
=AH
Sum of Standby and Alarm Ampere Hours = AH
for nonULC applications, multiply by the Derating Factor
1
1 Multiply by only one of the Derating Factors, depending on whether the power
supply is being used for a ULC (Canadian) application or nonULC application.
X 1.2
for ULC applications, multiply by the Derating Factor
1
X 2.5
Battery Size, Total Ampere Hours Required = AH
Table 6.4 Total Secondary Power Requirements at 24 VDC
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