The Model PAD-3 from Siemens Building Technologies, Inc. is a notification and auxiliary power
expander that provides up to 6 amps of 24 volt DC for powering notification appliances and auxiliary
devices. The PAD-3 provides its own AC power connection, battery charging circuit, and battery
connections. Used with a fire alarm control unit, this enables you to connect and distribute power to many
more devices than your control unit may normally allow.
1.1 GENERAL DESIGN FEATURES
The PAD-3 has two optically isolated inputs that provide the connection from the fire alarm control unit
notification appliance circuit to the PAD-3. The inputs also provide a connection for returning a trouble
condition to the control unit notification appliance circuit.
The fire alarm control unit supervises its notification appliance circuit used for communicating with the
PAD-3 the same way it supervises ordinary NACs. The inputs on the PAD-3 monitor the polarity of the
voltage coming from the fire alarm control unit's NACs to determine when to operate the notification
appliance circuit outputs. The PAD-3 emulates the trouble behavior of a NAC by opening the EOL
supervision current for trouble conditions. Note that the PAD-3 will sense the polarity of the fire alarm
control unit's NACs to drive the outputs whether or not the supervision connection is intact.
The following situations will open the EOL supervision at the inputs indicating a trouble condition:
No or Low AC power.
No and Low battery condition.
Ground fault to the output wiring.
Auxiliary Power Supply output over-current condition.
NAC output open, shorted or over-current condition on outputs associated with its input.
If input 1 controls all four outputs, a fault on any output will cause input 1 to indicate trouble. The fault
does not affect input 2.
If input 1 controls outputs 1 and 2, and input 2 controls outputs 3 and 4, a fault condition on output 3 or 4
will cause input 2 to indicate trouble. The fault does not affect input 1.
Once the PAD-3's inputs and outputs are activated, the fire alarm control unit will not be able to sense
trouble conditions through its notification appliance circuit connected to the PAD-3 input circuits. Use the
PAD-3 trouble relay when it is necessary to monitor trouble conditions and active alarm conditions at the
Notification Appliance Circuit Outputs
The PAD-3 has four dedicated, power-limited, NAC outputs that can be configured as two Style Z (Class
A) or four Style Y (Class B) circuits.
The PAD-3 provides three configuration options that will drive outputs as slaves that will follow the input
or if the inputs are on constant as ANSI temporal code or Sync strobe/horn operation.
Each of the four outputs is rated at 3 amps, though a total of 6 amps maximum can be drawn from the
PAD-3 outputs. The yellow Output LEDs (DS1-DS4) will indicate an open, shorted or over-current
condition on its associated NAC Output.