Installation Instructions for Allen-Bradley 1756-RM2 ControlLogix Redundancy Modules

Comprehensive installation guide for Allen-Bradley 1756-RM2, 1756-RM2K, and 1756-RM2XT ControlLogix Redundancy Modules. Includes hardware setup, fiber-optic connection procedures, safety precautions, and technical specifications.

Quick answers from the manual

Quick answer

The 1756-RM2 modules provide redundancy for ControlLogix systems. Installation requires matching modules in the same slot of each chassis, connected via a 1756-RMCx fiber-optic cable. p. 6, 7

Key actions

Install the redundancy module p. 6
Connect fiber-optic cable p. 7

First start

Install chassis, power supply, communication modules, and controller before installing the redundancy module. p. 6

Problems and fixes

System not synchronizing

Ensure components in the first and second chassis match exactly.

p. 6

Technical specifications

Parameter	Value	Meaning	Pages
Wavelength	1310 nm	Operating wavelength	p. 8
Max Cable Length	10 km	Maximum fiber-optic cable length	p. 8

Where to find it in the PDF

Module Overviews p. 5
Hardware Installation p. 6
Fiber-optic Connection p. 7

Table of contents

Manual images

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Page 5

Page 12

Quick Guide from the Manual

This document provides installation instructions for the ControlLogix Redundancy Modules (1756-RM2, 1756-RM2K, 1756-RM2XT). These modules are designed to work in pairs to supervise operating states and synchronize control data between chassis. Important: Ensure all power is off before installing or removing modules. Modules must be identical in firmware and hardware revisions and must occupy the same slot in their respective chassis.

Safety and Environment

ESD Protection: The equipment is sensitive to electrostatic discharge. Use a grounded wrist strap and static-safe workstation.
Hazardous Locations: Specific requirements apply for Class I, Division 2 and Zone 2 environments. Ensure the enclosure is IP54 rated or better.
UV Radiation: This equipment is not resistant to sunlight or UV radiation.
Port Protection: Keep port plugs installed in unused ports to maintain corrosive atmosphere ratings.

Hardware Installation

Install the chassis and power supply.
Install communication modules.
Install the controller.
Install the redundancy module: Align the circuit board with the top and bottom guides in the chassis and slide it in until flush.

Connecting Redundancy Modules

Use a 1756-RMCx fiber-optic communication cable (sold separately) to connect the modules.

Remove the black protective channel cover on the first module.
Remove protective caps from cable ends.
Plug the cable connector into the CH1 or CH2 port on the first module.
Plug the other end into the corresponding channel on the secondary module.
Note: It is recommended to match channel to channel (CH1 to CH1, CH2 to CH2) for troubleshooting simplicity.

Technical Specifications

Connector Type: LC-type (fiber-optic)
Cable Type: 8.5/125 μm single-mode fiber-optic cable
Max Length: 10 km
Transmission Speed: 1000 Mbps
Wavelength: 1310 nm
Operating Temperature: 0 to 60 °C (1756-RM2/RM2K); -25 to +70 °C (1756-RM2XT)

Manufacturer information

Allen-Bradley

Brand profile

Manufacturer website https://www.rockwellautomation.com Support https://www.rockwellautomation.com/en-us/support.html Manufacturer manuals https://www.rockwellautomation.com/en-us/support/literature-library.html

Practical help

Common problems

Redundancy system not synchronizing

Ensure modules are in the same slot in their respective chassis and that firmware/hardware revisions are identical.

Fiber link failure

Check for sharp bends in the cable and ensure it is not damaged. Verify the cable is not routed where it can be cut or abraded.

Corrosion issues in hazardous locations

Ensure port plugs are installed in all unused ports at all times.

Before use

Verify all required components are present.
Order 1756-RMCx fiber-optic cable if not available.
Ensure firmware revisions match for both modules.
Confirm chassis slot alignment.
Ensure system power is off before installation.

Images and diagrams

Front view shows status indicators and CH1/CH2 ports.
Side view illustrates the backplane connector alignment.

Model compatibility

1756-RM2 and 1756-RM2XT modules can only be used with other 1756-RM2 or 1756-RM2XT modules.
XT modules must be used with an XT chassis.

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Manual page author

Emily Carter

User documentation editor

Prepares concise manual descriptions and highlights the most useful setup, operation, and maintenance information for readers.