Power Supply Calculations

Calculating the Battery Size

7.4 Calculating the Battery Size

Use Table 7.4 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 control panel under the loss of AC power. Complete Table 7.4 as follows:

1.Enter the totals from Table 7.3 on page 165, Calculation Columns 2 and 3 where shown

2.Enter the NFPA Standby and Alarm times (refer to ‘NFPA Requirements’ below)

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

Table 7.4 Total Secondary Power Requirements at 24 VDC

Secondary Standby Load

Required Standby Time

 

 

(total from Table 7.3 Calculation

(24 or 60 hours)

 

 

Column 3)

 

 

 

 

 

[

]

X[

]

=

AH

 

 

 

 

Primary Alarm Load

Required Alarm Time

 

 

(total from Table 7.3 Calculation

(for 5 min., enter 0.084,

 

 

Column 2)

 

for 10 min., enter 0.168)

 

 

[

]

X[

]

=

AH

 

 

 

 

 

Sum of Standby and Alarm Ampere Hours

 

=

AH

 

 

 

 

 

Multiply by the Derating Factor

 

 

X 1.2

 

 

 

 

 

Battery Size, Total Ampere Hours Required

 

=

AH

 

 

 

 

 

 

7.4.1 NFPA Battery Requirements

•NFPA 72 Local and Proprietary Fire Alarm Systems require 24 hours of standby power followed by 5 minutes in alarm

•NFPA 72 Central, Auxiliary and Remote Station Fire Alarm Systems require 60 hours of standby followed by 5 minutes in alarm. Batteries installed in a system powered by a generator need to provide at least 4 hours of standby power

7.4.2 Selecting and Locating Batteries

Select batteries that meet or exceed the total ampere hours calculated in Table 7.4 . The control panel can charge batteries in the 7 AH to 18 AH range. The control panel cabinet is capable of housing batteries up to 18 AH. Batteries larger than 18 AH require a UL listed external battery charger and cabinet such as the BB-26, F or other UL listed external battery cabinet.

166

MS-9200UDLS PN 52750:A 11/04/05