How do I calculate battery size for a Fire-Lite MS-9200UDLS fire alarm panel

Updated Source: 52750 Rev MSource: 52750 Rev M
Quick answer

For the Fire-Lite MS-9200UDLS, list every device's standby and alarm current in Table 7.3, multiply the battery-powered standby load by 24 hours and the alarm load by the alarm time (0.084 for 5 minutes), add the two ampere-hour figures, then multiply by the 1.2 derating factor. The result is the battery size in AH. The panel charges and houses batteries from 7 AH to 18 AH; bigger sets need an external charger and cabinet.

Steps

From: MS-9200UDLS Series manual, pp. 162-163

  1. List every powered device
    In Table 7.3 with its quantity. Start with the main circuit board, which draws 0.275 A in alarm and 0.145 A in standby on battery, then add annunciators, relay and LED modules, the 4XTMF, 4-wire detector heads and power supervision relays.
  2. Add the SLC devices
    Each addressable detector and module has its own standby current in the table, for example 0.00030 A for most detector heads and 0.00040 A for an MMF-300 monitor module.
  3. Add the NAC load
    Enter the alarm current of the horns and strobes on NAC #1 to NAC #4. These draw only in alarm, so they go in the fire alarm load column, not standby.
  4. Total the columns
    Calculation Column 2 is the battery-powered fire alarm load and Column 3 is the battery-powered standby load. Copy both totals to Table 7.4.
  5. Multiply by the required times
    Standby load times 24 hours. Alarm load times 0.084 for 5 minutes of alarm, or 0.168 for 10 minutes. NFPA 72 Local, Proprietary, Central, Auxiliary and Remote systems require 24 hours of standby followed by 5 minutes in alarm.
  6. Add and derate
    Add the standby and alarm ampere-hours, then multiply the sum by the derating factor of 1.2. That is the battery size in AH.
  7. Pick and label the batteries
    Use sealed lead acid batteries that meet or exceed the calculated AH, and write the requirement on the Protected Premises label inside the cabinet door.

Specs & limits

From: MS-9200UDLS Series manual, pp. 17, 162-163

Standby time24 hours
Alarm time multiplier0.084 for 5 minutes, 0.168 for 10 minutes
Derating factor1.2
Charger and cabinet range7 AH to 18 AH in the panel cabinet
Total panel load3.0 amps with one transformer, 6.0 amps with the optional XRM-24B(E)
Per NAC2.5 amps max per circuit

Common mistakes

From: MS-9200UDLS Series manual, pp. 162-163

  • Putting NAC current in the standby column. Horns and strobes only draw in alarm, so their current belongs in the alarm column.
  • Forgetting the 1.2 derating factor. Without it the battery is undersized as it ages.
  • Planning batteries larger than 18 AH in the panel cabinet. Larger batteries need a UL listed external battery charger and cabinet such as the BB-26 or BB-55F.

Applies to

MS-9200UDLS · Series manual P/N 52750:M

Also asked as: “how to size fire panel batteries”

Sources

  1. MS-9200UDLS Series Manual, p. 162 (52750 Rev M)
  2. MS-9200UDLS Series Manual, p. 163 (52750 Rev M)
  3. MS-9200UDLS Series Manual, p. 17 (52750 Rev M)
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