Johnson Controls IOM2721 Installation Manual page 8

Communications bus and supply power terminal blocks, ratings, and requirements
Table 4: Communications bus and supply power terminal blocks, functions, ratings, requirements, and cables
Terminal block/Port
Terminal labels Function, electrical ratings/Requirements
label
+
-
COM
FC BUS
or
SHLD
SA BUS
or
SA PWR
HOT
24~
COM
Note: See to determine wire size and cable lengths
for cables.
Note: The SA Bus and FC Bus wiring
recommendations in this table are for MS/TP bus
at 38,400 baud. For more information, refer to
the MS/TP Communications Bus Technical Bulletin
(LIT-12011034).
8 IOM2721 Input/Output Module Installation Guide
FC or SA Bus Communications
Signal Reference (Common) for FC or SA Bus
communications
SHLD on FC Bus: Isolated terminal (optional
shield drain connection)
SA PWR on SA Bus: 15 VDC power lead
connection.
Note: The SA PWR terminal on an IOM
expansion module does not supply 15
VDC. The SA bus supervisor supplies 15
VDC to devices on the SA bus requiring
power.
24 VAC Power Supply - Hot
Supplies 20–30 VAC (Nominal 24 VAC)
24 VAC Power Supply - Common
required cable type
FC Bus: 0.6 mm (22 AWG) stranded, 3-wire
twisted, shielded cable required.
SA Bus: 0.6 mm (22 AWG) stranded, 4-wire
(2 twisted-pairs), shielded cable required.
Note: On the SA Bus, the + and - wire
are one twisted pair, and the COM
and SA PWR are the second twisted
pair of wires.
0.8 mm to 1.0 mm
(18 AWG) 2-wire