# User guide

74 Distributed Audio Panel Manual — P/N 52265:B1 6/8/2010

Power Supply Calculations Calculating the Battery Size

6.4 Calculating the Battery Size

Use Table 6.3 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 ACC-25/50DA under the loss of AC

power. Complete Table 6.3 as follows:

1. Enter the totals from Table 6.2 on page 73 Calculation Columns 1 and 2 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 get 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 requires 24 hours of standby plus 15 minutes activation for audio systems. The total ampere

hours required cannot exceed 18 AH with an internal charger. An external charger can be used to

increase the total ampere hours (internal charger must be disabled).

6.4.2 Selecting and Locating Batteries

Select batteries that meet or exceed the total ampere hours calculated in Table 6.3. The audio panel

can charge batteries in the 7 AH to 18 AH range. The ACC-25/50DA Series can house up to 18 AH

batteries.

Secondary Standby Load

(total from Table 6.2 Calculation

Column 1)

[ ]

Required Standby Time

(24 or 60 hours)

[ ] = AH

Secondary Alarm Load

(total from Table 6.2 Calculation

Column 2)

[ ]

Required Alarm Time

(for 5 min., enter 0.084,

for 10 min., enter 0.168,

for 15 min., enter 0.250)

[ ]

= AH

Sum of Standby and Alarm Ampere Hours = AH

Multiply by the Derating Factor X 1.2

Battery Size, Total Ampere Hours Required = AH

Table 6.3 Total Secondary Power Requirements at 24 VDC