AFP-400 Installation
PN
50253
:
A2 03/12/96
2-35
Calculating the System Current Draw
Throughout these current calculation tables, Primary refers to the FACP
primary source of AC power. Secondary refers to the FACP backup
batteries (or any other 24 VDC uninterruptable, regulated power supply
listed for Fire Protective Signaling and connected in place of the batteries).
The Primary Power Source Non-Alarm Current and Alarm Current columns
of Table 2-2 are current calculations. These calculations confirm that the
MPS-400 can supply enough current to support the system during Primary
Non-Fire Alarm and Fire Alarm conditions.
Column 1
(Primary, Non-Fire Alarm Current in amps
)
Sum column 1 of
Table 2-2 to get the current drawn from the MPS-400 during a non-alarm
condition, with AC power applied. This current draw cannot exceed
3 amps.
Column 2
(
Primary, Fire Alarm Current in amps) Calculation column 2 of
Table 2-2 lets the system designer determine the current load that the
MPS-400 must support during a fire alarm. The total current drawn from
the MPS-400 during a fire alarm cannot exceed 6 amps.
Typically, a system should contain capacity to activate all output circuits
and relays, and support fire alarms on no less than 10% of initiating device
circuits, subject to the requirements of the Local Authority Having Jurisdic-
tion (LAHJ).
If using four-wire detectors
In Table 2-2, the primary fire alarm current
to be entered for four-wire smoke detectors equals the manufacturer's
rated fire alarm current minus the manufacturer's rated non-fire alarm
current.
If using notification appliances
The MPS-400 provides a regulated
supply for Notification Appliance Circuits, allowing the use of any
24 VDC notification appliances UL listed for Fire Alarm Systems.
Column 3
[Secondary (Battery) Non-Alarm Current] The last column of
Table 2-2 lets the system designer calculate the secondary non-fire alarm
current. This is the current drawn from the secondary source in a non-fire
alarm condition during AC power loss. This figure is required to complete
the standby battery calculations. After summing all current draws, insert
the total figure in Table 2-3.
No more than 6 amps of
current can be drawn from
the MPS-400 during an alarm
condition.
How to Use Table 2-2
1
2
3
Calculation Columns
for Table 2-2
Continued on the next page...
