Allen-Bradley 1746-IO4 SLC 500 Combo I/O Module

1746-IO4 Allen-Bradley 2-Input 2-Relay Output Combo Module

The 1746-IO4 module offers a straightforward I/O solution for smaller control systems. This combination module belongs to the SLC 500 family and occupies one chassis slot. Specifically, it provides two 120VAC input channels and two Form A relay contact outputs. Therefore, it works well for applications with minimal I/O requirements. Additionally, its compact design saves both chassis slots and panel space for budget-conscious projects.

Input Specifications and Operating Range

The input section of the 1746-IO4 accepts AC voltage signals from simple field devices. It operates with a nominal voltage of 120VAC and accepts a range from 85 to 132VAC at 47 to 63Hz. Each input point dissipates 0.27 watts during normal operation. The input signal delay measures 35 milliseconds for the ON transition and 45 milliseconds for the OFF transition. Furthermore, the module includes LED indicators on the front panel that display the status of each input point. These indicators light up when the correct signal applies to the input terminal, simplifying troubleshooting.

Output Specifications and Relay Contact Ratings

The output section provides two Form A relay contacts for controlling external loads. These normally-open contacts support both AC and DC load types. Each output handles 1.5 amps at 120VAC and 1.2 amps at 24VDC. The total continuous current across both outputs reaches 4 amps maximum. Moreover, the relay outputs work with voltage ranges from 5 to 265VAC at 47 to 63Hz and from 5 to 125VDC. The module's total heat dissipation remains low due to its minimal channel count.

Backplane Current Draw and Power Requirements

This combination module draws 30mA from the 5VDC backplane and 25mA from the 24VDC backplane. These low current values make it suitable for systems with limited power supply capacity. The module's overall power consumption reflects its small I/O count. For proper operation, ensure your power supply can handle these requirements along with other modules in the chassis.

Mechanical and Environmental Specifications

The Allen-Bradley 1746-IO4 operates across a wide functional temperature range from -25°C to 60°C (-13°F to 140°F). This expanded low-temperature range distinguishes it from standard SLC 500 modules. It handles storage temperatures from -40°C to 85°C (-40°F to 185°F). The humidity tolerance ranges from 5% to 95% non-condensing for versatile deployment. Moreover, the module withstands operational vibration of 0.015 inches displacement at 5 to 57 Hertz. Its shock rating reaches 10G, which suits less demanding industrial environments.

Terminal Block and Wiring Features

The 1746-IO4 includes a terminal block with self-lifting lift plates for secure wiring. Each terminal accepts two 14 AWG (2mm) cables for convenient field connections. The self-lifting design prevents wire damage during tightening and ensures reliable connections over time. For safety, route input power to the module separately from the cable to the I/O device. This practice reduces electrical noise and improves signal integrity.

Installation Guidelines and Chassis Placement

Install this module in any available slot of the SLC 500 chassis except slot 1, which the processor occupies. The single-slot design simplifies integration into new and existing systems. You can mix it freely with other SLC 500 modules in local or expansion chassis. Always disconnect power before installing or removing the module, as it does not support RIUP. Regular maintenance and loop validation help ensure optimal operation over time.

Packaging and Shipping Information

• One 1746-IO4 digital I/O combination module

• One removable terminal block with self-lifting plates

• One installation instruction sheet

• Anti-static protective packaging

All orders ship via FedEx, UPS, or DHL with tracking numbers provided. Inspect all items upon delivery and report any transit damage immediately.

Frequently Asked Questions

1. What types of field devices can connect to the 1746-IO4 inputs?
The AC inputs accept signals from pushbuttons, selector switches, and proximity sensors operating at 85-132VAC. These inputs work with standard 120VAC control circuits.

2. Can the 1746-IO4 outputs switch DC loads directly?
Yes, the relay outputs handle DC loads up to 1.2 amps at 24VDC. This makes them suitable for small DC solenoids, indicator lights, and interposing relays.

3. How does the 1746-IO4 differ from the 1746-IO12?
The 1746-IO4 offers 2 inputs and 2 outputs, while the 1746-IO12 provides 6 inputs and 6 outputs. Choose the 1746-IO4 for smaller applications with minimal I/O requirements.

4. What is the purpose of the LED indicators on the module?
The front-panel LEDs show the status of each input point. When the correct signal applies to an input terminal, its corresponding LED lights up for quick visual verification.

5. Can I install the 1746-IO4 in a remote I/O chassis?
Yes, this module works in remote I/O chassis when connected through a compatible communication adapter. Its operation remains identical to local chassis installation.