1791-24A8 | Allen-Bradley Block I/O Module - Petro Auto Tech

Product Overview

The 1791-24A8 is a Block I/O module from Allen-Bradley, part of the 1791 Block I/O product line. It combines a power supply, PLC interface, I/O connections, and signal processing circuitry in a compact, self-contained assembly. This module is designed for Remote I/O architecture, making it a reliable choice for distributed control systems.

Technical Specifications Analysis

The 1791-24A8 features Twenty-Four (24) 120VAC input channels organized into 3 groups of 8. The input on-state voltage range is 79-132VAC, with an on-state current of 12.3mA at 132V max. The off-state voltage is 35V max, and off-state current is 2.3mA min. For outputs, it provides Eight (8) 120VAC outputs in 1 group of 8, with an output voltage range of 20-123VAC. The module requires an external power supply of 85-132VAC at 150 mA. Maximum power dissipation is 18.76 Watts, and thermal dissipation is 63.97 BTU/Hr. The module supports vertical or horizontal mounting and weighs 1.88 lbs (0.85 kg).

Application Scenarios & Usage Methods

This module excels in remote I/O applications where distributed control is needed. For example, in a manufacturing plant, you can place the 1791-24A8 near a conveyor system to monitor 24 sensors and control 8 actuators, reducing wiring costs. In a water treatment facility, it can handle discrete I/O for valve and pump control. To use it, connect the module to a PLC-2, PLC-3, PLC-5, or SLC 500 controller via the built-in Remote I/O interface. Use Belden 9463 cable for communication. Configure the scanner for baud rates of 57.6K, 115.2K, or 230.4K, with cable distances up to 10,000 feet at 57.6K.

Installation Guide & Packing List

Mount the module vertically or horizontally on a DIN rail or panel. Ensure the external power supply meets 85-132VAC at 150 mA. Connect the Remote I/O cable to the module and the scanner. For daisy-chain topology, install a terminating resistor (82 Ohm or 150 Ohm) on the last node. The package typically includes the 1791-24A8 Block I/O module and documentation. Additional cables and resistors may be ordered separately.

Purchasing Advice

When buying a 1791-24A8, verify it matches your system voltage (120VAC) and I/O count (24 inputs, 8 outputs). Check compatibility with your controller (PLC-2, PLC-3, PLC-5, or SLC 500). Petro Auto Tech offers genuine Allen-Bradley modules with reliable support. Order from Petro Auto Tech for fast delivery and expert assistance.

Repair & Maintenance Tips

Regularly inspect the module for dust or debris and clean with a dry cloth. Check all cable connections for tightness. Store the module in a dry, static-free environment when not in use. Monitor the power dissipation (max 18.76 Watts) to prevent overheating. Replace the module if input or output channels fail testing.

Frequently Asked Questions (FAQs)

Q: What is the input voltage range for the 1791-24A8?
A: The input on-state voltage range is 79-132VAC.

Q: How many outputs does this module have?
A: It has Eight (8) 120VAC outputs in 1 group of 8.

Q: What cable is recommended for Remote I/O connection?
A: Use Belden 9463 cable, a three-wire cable with Blue, Clear, and Shield wires.

Q: Can this module be mounted horizontally?
A: Yes, the module supports both vertical and horizontal mounting.

Q: What is the maximum power dissipation?
A: The maximum power dissipation is 18.76 Watts.