Figure 7: Maximum wire length for low-voltage
(<30 V) Inputs by current and wire Size
Communications bus and supply power
wiring guidelines
Table 4 provides information about the functions,
ratings, and requirements for the expansion
module's communication bus and supply power
terminals; it additionally provides guidelines for wire
sizes, cable types, and cable lengths when wiring
the expansion module communication buses and
supply power.
In addition to the guidelines in Table 4, observe the
following guidelines when wiring an SA or FC bus
and the 24 VAC supply power:
• Run
all
low-voltage wiring and cables separate
from high-voltage wiring.
• All SA and FC bus cables, regardless of wire
size, should be twisted, insulated, stranded
copper wire.
• Shielded cable is strongly recommended for all
SA and FC bus cables.
• Refer to the
MS/TP Communications Bus
Technical Bulletin (LIT-12011034)
for detailed
information regarding wire size and cable
length requirements for the SA and FC buses.
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
label
Terminal labels Function, electrical ratings/Requirements
Recommended cable type
+
-
FC or SA Bus Communications
COM
Signal Reference (Common) for FC or SA Bus
communications
FC Bus
or
SA Bus
SHLD
or
SA PWR
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.
FC Bus: 0.6 mm (22 AWG) stranded, 3-wire
twisted, shielded cable recommended.
SA Bus: 0.6 mm (22 AWG) stranded, 4-
wire (2 twisted-pairs), shielded cable
recommended.
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.
SA/FC BUS
(Port)
RJ-12 6-Position Modular Connector provides:
FC or SA Bus Communications
FC or SA Bus Signal Reference and 15 VDC
Common
Commissioning Converter or ZFR /ZFR Pro
Wireless Router
(Maximum total current draw for SA Bus is 100
mA.)
Wireless Commissioning Converter
retractable cable or 24 AWG 3-pair CAT 3
Cable <30.5 m (100 ft)
HOT
24 VAC Power Supply - Hot
Supplies 20–30 VAC (Nominal 24 VAC)
24~
COM
24 VAC Power Supply - Common
0.8 mm to 1.0 mm
(18 AWG) 2-wire
IOM3723 Input/Output Module Installation Guide
8