terminal block and so they share only one communication
protocol. See Communications Bus and supply terminal
blocks, functions, ratings, requirements, and cables for
more information. The FC Bus port pin assignment is
shown in Figure 4 and Table 2.
Figure 4: Pin number assignments for FC Bus port or
SA Bus port
Table 2: Pin number assignments for FC Bus port or SA
Bus port (RJ12 modular jack)
Callout Signal
1 FC Bus or SA Bus (+)
2 FC Bus or SA Bus (-)
3 Bus and Power Common
4 Power (15 VDC)
5 Bus and Power Common
6 Power (15 VDC)
Connecting to the FC Bus terminal
About this task: To connect devices to the FC Bus,
complete the following steps:
1. Connect the 3-wire bus cable to the removable blue
4-pin terminal block labeled FC BUS as shown in
Figure 5.
Figure 5: FC Bus terminal block and wiring connections
2. Set the FC EOL switch to the proper position. See
the note in Setting the EOL switch.
3. Go to Connecting the power source.
Connecting to the SA Bus port
The SA Bus port is an RJ12, 6-position modular jack that
provides a connection for the MAP, or other SA Bus
devices with RJ12 plugs.
The Sensor port is connected internally to the SA Bus
terminal block. See Communications Bus and supply
terminal blocks, functions, ratings, requirements,
and cables for more information. The SA Bus port pin
assignment is shown in Figure 4 and Table 2.
Connecting to the SA Bus terminal
1. Connect the 4-wire bus cable to the removable
orange 4-pin terminal block Sensor/Actuator (SA)
Bus, labeled SA BUS.
Note: Only connect terminal devices to either
the SA Bus port or to the SA Bus 4-pin terminal
block, not both.
Figure 6: SA Bus terminal block wiring
2. Go to Connecting the power source.
Connecting the power source
1. Connect power to the SNC using a 24 VAC power
transformer, connect the 24 VAC supply power
wires from the transformer to the gray 2-pin
terminal block labeled 24 V~ on the SNC (Figure 7
and Table 3 ). The connections are HOT and COM
(common).
Note: Power supply wire colors may be
different on transformers not manufactured
by Johnson Controls. Follow the transformer
manufacturer’s instructions and the project
installation drawings.
F4-SNC Installation Guide6
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