What you need to know about ControlLogix redundancy

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Over the years I've received many request for information about ControlLogix redundancy. During that time I've developed the following ten tips for new redundancy users:

  1. At a minimum you will need two processors, two communication modules, two redundancy modules, a redundancy module interconnect cable, two chassis, two power supplies, and at least one rack of whatever distributed I/O platform you plan to use (1756, 1794, etc.)
  2. The primary and secondary chassis detailed above should be identical. and should not contain any I/O modules.
  3. ControlLogix Redundancy The features and hardware supported is highly dependent on the version of RSLogix 5000 and redundancy firmware you choose.
  4. Not all versions of RSLogix 5000 support redundancy. Therefore, be sure to choose one which does support it BEFORE you begin writing your redundancy program.
  5. Not all processor firmware versions support redundancy. Versions which do end in “.5” or higher (i.e. firmware version 20.54 does support redundancy.)
  6. In some cases, redundancy and network module firmware will need to be flashed to a particular revision in order to be compatible with the version of redundancy you have chosen to implement.
  7. When sizing a processor for a redundancy system, the rule of thumb is you need double the processor memory for a redundant system versus a non-redundant system.
  8. When setting up the primary and secondary network modules, be sure to set both modules to the same network address (the redundancy module adds “1” to the secondary's network address automatically.)
  9. To enable redundancy in your RSLogix 5000 program, check the “Redundancy” checkbox in “Controller Properties.”

And my final and most important tip is to first read the below ControlLogix redundancy manual:


And then to read the release notes for the version of redundancy you plan on implementing (below is a link to the latest version, v20.5.)


I hope the above tips about using Rockwell's ControlLogix redundancy, and the links to the product manuals is helpful. If you have any comments, questions, or corrections please leave them with us by using the “leave a reply” form at the bottom of this page.


Shawn Tierney
Automation Blogger and Trainer

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