Johnson Controls IOM3731 Installation Manual page 7

Table 3: Cable length guidelines for recommended wire sizes for low-voltage (<30 V) Inputs and Outputs
Guideline Wire size/Gauge and type
1.0 mm (18 AWG) stranded copper
0.8 mm (20 AWG) stranded copper
B
0.6 mm (22 AWG) stranded copper
0.5mm (24 AWG) stranded copper
See Maximum cable length versus
C load current
Use stranded copper wire
Maximum cable length versus load current
Use the following image to estimate the maximum cable
length relative to the wire size and the load current (in
mA) when wiring inputs and outputs.
Note: The following applies to low-voltage (<30 V)
inputs and outputs only.
Figure 8: Maximum wire length for low-voltage (<30
V) Inputs and Outputs by current and wire size
SA/FC bus and supply power wiring
guidelines
Table 4 provides information about the functions, ratings,
and requirements for the controller communication bus
and supply power terminals; and guidelines for wire sizes,
cable types, and cable lengths when wiring the controller
communication buses and supply power.
In addition to the guidelines in Table 4, observe these
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.
Maximum cable length
and type
229 m (750 ft) twisted wire
137 m (450 ft) twisted wire
91 m (300 ft) twisted wire
61 m (200 ft) twisted wire
See
versus load current
to select wire size/gauge.
determine cable length. Use
twisted wire cable.
Assumptions
100 mV maximum voltage drop
Depending on cable and the connected input or
output device, you may have to define an offset
in the setup software for the input or output
point.
Maximum cable length
to
N/A
IOM3731 Input/Output Module Installation Guide 7