TechTalk – ControlLogix – Adding IO On Powered PLC

Would I be able to successfully add IO card to a local rack while processor is in run mode? What about adding IO card to a remote rack (distributed I/O) while processor is in run mode? These are common questions asked by my clients when shutting down a ControlLogix PLC to add modules is out of question.

As far as ControlLogix family of product is concern, most of the module can be inserted and removed from the chassis while power is applied. In the world of Allen-Bradley, this is called Removal and Insertion Under Power (RIUP). This feature greatly improves the PLC availability as there is no disruption to the rest of the controlled process as upgrade or modifications are being done to the ControlLogix. However, RIUP is only available for ControlLogix with revision is 15 and above. If you have a revision of below 15, you will have to put your processor key switch in Remote Run, Remote Program, or Program mode (see picture below) before you can introduce IO cards to the processor while online.

Xybernetics Allen-Bradley ControlLogix - Adding IO On Powered PLC

When adding modules online on a ControlNet environment, the module refresh rate is performed in the unscheduled bandwidth portion of the Network Update Time, which is adequate for most applications, but that may not be true for application which demands high update rate and repeatability for high speed applications.

Modules listed below can be added to the rack while the processor is online.

  • 1756 I/O
  • PowerFlex Drives (PowerFlex Drives depend on their series and revision)
  • 1747 I/O
  • 5069 I/O
  • 56RF devices

However, not all IO modules has this capabilities, as listed below.

  • 1794 Flex I/O modules
  • 1734 POINT I/O modules
  • 1769 CompactLogix modules

The table (from Allen-Bradley Publication Logix-WP006) below give a high level of module RIUP support.

Xybernetics Allen-Bradley ControlLogix - Adding IO On Powered PLC