AB ControlLogix Redundancy

Relatively new with AB products and was hoping to get some input on a question about redundancy.

I have a client that installed an AB ControlLogix system approximately 5 years ago. They have two chassis each with the same processor, I/O modules, and redundancy modules. Their intent at the time was to configure the chassis as a redundant system. For whatever reason, at the time they were told that they didn't have the necessary components; they mentioned something about requiring some ControlNet nodes? For this reason one chassis is currently setup as cold-standby. I would like to explore what is required to configure this as a true redundant system.

Below is a list of components in each chassis:

1756-A13 Chassis
1756-L61 Processor
1756-EN2T Enthernet/IP Module
1756-RM Redundancy Module
Various digital I/O modules (same type and quantity in each chassis)

From the reading that I have done and information I have found, it seems that they have the necessary components. Are there additional requirements that I should be looking into? Why would they have been told that they didn't have the necessary components to enable redundancy?

Thanks in advance for any assistance.

For one thing, there can't be I/O modules in the redundant chassis. Also you should get the manual on redundancy. It needs to be followed very closely.

You can't have I/O in controller chassis with redundancy.
All I/O needs to be in a separate chassis connected with Ethernet/IP

ControlNet I/O was requirement before version 19 and still can be used.
And there is no support for redundant I/O with 1756 platform.
This can be done with 1715 I/O only

I need to double check this but my experience is that redundant Logix chassis got no IO module and all IO are on remote chassis, for obvious reasons; since both PLC A and B needs to look out and see the same IO. Unless you are actually having redundant IO as well, which is possible. It is possible the integrator didn't know what they are doing and didn't design the IO properly.

You can start by going thorugh the Enhanced Redundancy Manual, 1756-um535_-en-p.pdf

Thanks guys. I've been reading the following manual:

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1756-um535_-en-p.pdf

Being that I'm relatively new to AB I appreciate the help. The manual isn't exactly explicit in terms of the requirements and restrictions.

I suspect whomever specified/installed the system wasn't well versed, hence running it as a cold-standby system.

The manual isn't exactly explicit in terms of the requirements and restrictions

Click to expand...

How about Chapter 2 of the same manual? It has all information including requirements and restrictions.

For example, specifically for you:
page 44 Important section

IMPORTANT You cannot install I/O modules in the redundant chassis pair.
You can only install I/O modules in remote locations accessed over the networks in this list.
You can connect to remote I/O modules over an EtherNet/IP network in an
enhanced redundancy system, revision 19.052 or later.

Click to expand...

So you will have to read the whole manual to make it right.

Something else to consider is not all versions/firmware support redundancy. I think 20 is the latest but it could 24. Could be way off on this to but I think if the minor revision .5x has something to do with it too

Looks like 20.056 is the latest enhanced redundancy firmware bundle available for download