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Products: AO-8, AO-V-8, DI-16, DO-FA-12, DO-FC-8, RTD-DI-16, UI-16, UI-8/AO-4, UI-8/AO-V-4, UI-8/DO-FC-4

Functionalities: Hardware

Product version: 2.0, 2.1, 3.0, 3.1, 3.2, 3.3, 2022, 2023, 2024, 7.0

2/13/2024

Wire Sizes and Lengths for the Central IO Modules

This section provides recommendations on wire sizes and lengths for the Central IO modules.

For more information, see Central IO Modules .

The recommendations are for guidance only. Other wire sizes and lengths may be used, depending on wiring rules and when appropriate.

Table: Wire Sizes and Lengths for the Central IO Modules

Terminals	Minimum Cross-sectional Area	Maximum Cable Length
Digital inputs and universal inputs as digital ^a inputs	0.34 mm² (22 AWG)	200 m (650 ft)
Universal inputs as analog ^b inputs and RTD ^c inputs	0.34 mm² (22 AWG)	100 m (330 ft)
Universal inputs as temperature (thermistor) inputs, up to 75 °C (167 °F)	0.75 mm² (18 AWG)	75 m (250 ft)
Universal inputs as temperature (thermistor) inputs, up to 75 °C (167 °F)	1.5 mm² (15 AWG)	150 m (500 ft)
Universal inputs as temperature (thermistor) inputs, up to 150 °C (302 °F)	1.5 mm² (15 AWG)	75 m (250 ft)
Universal inputs, for transmitters powered from the same transformer as the PS-24V power supply	0.75 mm² (18 AWG)	20 m (65 ft)
Universal inputs, for transmitters powered from their own transformer (external or internal)	0.34 mm² (22 AWG)	200 m (650 ft)
Analog outputs as voltage or current outputs, for actuators powered from their own transformer (external or internal) or when the outputs have isolated converters	0.34 mm² (22 AWG)	200 m (650 ft)
Relay outputs	According to local wiring rules ^d	According to local wiring rules ^d
One Return (RET) terminal from each Central IO module connected to the signal ground rail	1.3 mm² (16 AWG)	As short as possible within the same panel, maximum 1.5 m (4.8 ft).

Digital or counter inputs.
Supervised, voltage, current, or resistive inputs.
2-wire or 3-wire RTD temperature or resistive inputs.
Confirm the voltage drop from the external load current and the wire resistance (the product of the wire size and length) to obtain the appropriate voltage arriving at the controlled field device (load), to reliably energize and maintain the control action.