Technical data

Chapter 4: Installation
SP40S Multi-Function Facility Communication System Manual, Revision L
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4.8.3 Calculating Backup Battery Requirements
A Worksheet for assisting in calculating battery backup is available in Chapter 11.
Due to the current drain on the battery, the maximum battery size for the SP40S Multi-Function Facility
Communication System is 33 Amp-Hours (Ah). The enclosure can accommodate up to 12 Ah. Batteries greater
than 12 Amp-Hours (Ah) are required to be installed in a UL listed battery box.
It is necessary to calculate the current draw for battery backup requirement. The current requirement depends on
the system configuration and the appliances connected to the Speaker output circuits. Battery Backup current has
two separate calculations that are added together: Standby Current and Alarm Current.
4.8.3.A Standby Current
The Standby Current consumes the largest part of the storage battery capacity. The Standby Current of the
SP40S Multi-Function Facility Communication System is 0.130 Amps. Multiply this value by the number of
standby hours required. Normally this is 24 hours. This represents the total Standby current in Amp-Hours for
the panel.
4.8.3.B Alarm Current
The maximum Alarm Current for the SP40S Multi-Function Facility Communication System is 4.70 Amps (1.6
Amps for audio, 2.0 Amps for strobe, and 0.5 Amps for auxiliary power).
1. Calculate the strobe output current by adding the current draw of all strobes. Current draw is in Amps.
2. Calculate speaker output current by totaling all the speaker wattage settings. Multiply the sum by 0.040.
The result is the current draw in Amps.
3. Add the strobe current, the speaker current, and auxiliary current together. The result is the total Alarm
Current in Amps.
Alarm circuits are required to operate for 15 minutes on battery power. Multiply Step 3 by 0.25 hrs. The result is
the total Alarm Capacity Required in Amp-Hours.
4.8.3.C Battery Calculations
Good engineering practices recommend the total Amp-hours required for backup should not exceed 90%
of the Backup Battery capacity. The SP40S Multi-Function Facility Communication System has been UL
approved for a maximum of 33 Ah batteries. The enclosure can accommodate up to 12 Ah. Batteries
greater than 12 Amp-Hours (Ah) are required to be installed in a UL listed battery box.
1. Add the total Standby Capacity Required to the total Alarm Capacity Required.
2. Multiply Step 1 by 1.25. This is the minimum Backup Battery requirement for this panel.
3. Record results on worksheet.