Cable and wire length guidelines
The following table defines cable length guidelines for the
various wire sizes that may be used for wiring low-voltage
(<30 V) input and outputs.
Note: The required wire sizes and lengths for high-
voltage (>30 V) Relay Outputs are determined by the
load connected to the relay, and local, national, or
regional electrical codes.
Table 4: Cable length guidelines for recommended wire sizes for low-voltage (<30 V) Inputs and Outputs
Wire size/Gauge and type
Maximum cable length and
type
Assumptions
1.0 mm (18 AWG) stranded copper 457 m (1,500 ft) twisted wire
0.8 mm (20 AWG) stranded copper 297 m (975 ft) twisted wire
0.6 mm (22 AWG) stranded copper 183 m (600 ft) twisted wire
A
0.5 mm (24 AWG) stranded copper 107 m (350 ft) twisted wire
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.
1.0 mm (18 AWG) stranded copper 229 m (750 ft) twisted wire
0.8 mm (20 AWG) stranded copper 137 m (450 ft) twisted wire
0.6 mm (22 AWG) stranded copper 91 m (300 ft) twisted wire
B
0.5 mm (24 AWG) stranded copper 61 m (200 ft) twisted wire
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.
C
See Figure 6 to select wire size/gauge. Use
stranded copper wire
See Figure 6 to determine cable
length. Use twisted wire cable.
N/A
Maximum cable length versus load
current
Use Figure 6 to estimate the maximum cable length
relative to the wire size and the load current (in mA) when
wiring inputs and outputs.
Note: Figure 6 applies to low-voltage (<30 V) inputs
and outputs only.
Figure 6: Maximum wire length for low-voltage (<30 V)
Inputs and Outputs by current and wire size
Communications bus and supply power
wiring guidelines
Communications Bus and supply power terminal
blocks, ratings, and requirements provides information
about the functions, ratings, and requirements for the
communication bus and supply power terminals. The
table also provides guidelines for wire sizes, cable types,
and cable lengths for when you wire the controller's
communication buses and supply power.
In addition, observe these guidelines when you wire 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 following documents depending on your
system (FX or BCPro): MS/TP Communications Bus for
the BCPro
™
System Technical Bulletin (LIT-12011908)
or FX-PC Series Controllers MS/TP Communications Bus
Technical Bulletin (LIT-12011670) for detailed information
regarding wire size and cable length requirements for
SA and FC buses.
FX-PCA4911 Advanced Application Controller Installation Guide 9
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