Cable And Wire Length Guidelines; Maximum Cable Length Versus Load Current - Johnson Controls IOM3721 Installation Instructions Manual

Cable and Wire Length
Guidelines
Table 3: Cable Length Guidelines for Recommended Wire Sizes for Low-Voltage (<30V) Inputs and Outputs
Guideline Wire Size/Gauge and Type
A 2
1.5 mm (18 AWG) stranded copper
0.8 mm (20 AWG) stranded copper
0.6 mm (22 AWG) stranded copper
N/A (24 AWG) stranded copper
B 2
1.5 mm (18 AWG) stranded copper
0.8 mm (20 AWG) stranded copper
0.6 mm (22 AWG) stranded copper
N/A (24 AWG) stranded copper
C See Figure 8
Use stranded copper wire
Maximum Cable Length versus
Load Current
Use Figure 8 to estimate the maximum cable length
relative to the wire size and the load current (in mA) when
wiring inputs and outputs.
Figure 8: Maximum Wire Length for Low-Voltage (<30V) Inputs and Outputs by Current and Wire Size
IOM3721 Input/Output Module Installation Instructions
to select wire size/gauge.
Table 3 defines cable length guidelines for the various
wire sizes that may be used for wiring low-voltage (<30V)
input and outputs.
Maximum Cable
Length and Type
457 m (1,500 ft) twisted
wire
297 m (975 ft) twisted wire
183 m (600 ft) twisted wire
107 m (350 ft) twisted wire
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 Figure 8 to determine
cable length. Use twisted
wire cable.
Note: Figure 8
outputs only.
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.
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.
N/A
applies to low-voltage (<30V) inputs and
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