Cable And Wire Length Guidelines; Maximum Cable Length Versus Load Current - Johnson Controls ATC1510 Installation Manual

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.
Table 3: Cable length guidelines
1
Guideline
A
B
C
1 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.

Maximum cable length versus load current

Use the following figure to estimate the maximum cable length relative to the wire size and the load current (in
mA) when wiring inputs and outputs.
Note: Figure 5 applies to low-voltage (<30 V)
inputs and outputs only.
Figure 5: Maximum wire length for low-voltage (<30 V) Inputs and Outputs by current and wire size
Wire size/Gauge and type
2
(18 AWG) stranded copper 457 m (1,500 ft) twisted wire
1.0 mm
2
0.75 mm (20 AWG) stranded copper
297 m (975 ft) twisted wire
2
0.5 mm (22 AWG) stranded copper
183 m (600 ft) twisted wire
2
0.25 mm (24 AWG) stranded copper
107 m (350 ft) twisted wire
2
(18 AWG) stranded copper 229 m (750 ft) twisted wire
1.0 mm
2
0.75 mm (20 AWG) stranded copper
297 m (975 ft) twisted wire
2
0.5 mm (22 AWG) stranded copper
183 m (600 ft) twisted wire
2
0.25 mm (24 AWG) stranded copper
107 m (350 ft) twisted wire
See Figure 5 to select wire size/
gauge.
Use stranded copper wire.
Maximum cable length and
type
297 m (975 ft) twisted wire
183 m (600 ft) twisted wire
107 m (350 ft) twisted wire
137 m (450 ft) twisted wire
91 m (300 ft) twisted wire
61 m (200 ft) twisted wire
See Figure 5 to determine cable
length.
Use twisted wire cable.
ATC1510 Advanced Terminal Unit Controller Installation Guide
Assumptions
100 mV maximum voltage drop
Depending on the cable length
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 the cable length
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
7