PLC software update issue

I am certain this is a fairly easy thing to fix but I am still having problems. We are using two AB PLCs on a Fire and Gas detection system. One set as primary of course and the other set as the backup. My question is this:

Is it possible to sever the redundancy so that I can keep one PLC online while I update the software on the other? The Rockwell Controlnet is plugged into a PC where we can push up the update but so far it takes both PLC's offline during the update.

They are not down for long but once this site goes into production there are some concerns about having no F&G system online if this is needed.

Suggestions?

Thanks!

Can you do an online edit? The process will continue to run during this event.
Is this a redundant setup. With such a setup, both processors get updated simultaneously.

Welcome
Please specify the details, what firmware you have now, and hardware p/nos. and rev levels, as that will get you more specific answers from the a/b redundancy gurus.
Paul

You definitely need to post more details about the controller platform (is it ControlLogix ?) and firmware revision (v13, v15, v16, and v19 have Redundancy options) and most importantly exactly what you mean by "update the software".

Do you mean "upgrade the firmware" or "load a completely new application program" ?

You can perform a firmware upgrade on some Redundancy systems "on the fly" by disabling redundancy features in the 1757-SRM/1756-RM modules and following a specific sequence of firmware load steps described in the Release Notes or in the RA Knowledgebase.

You could even disable redundancy features and load a completely new application program into the "secondary" controller. But there is no way (that I know about) to then switch to the new controller without having some interruption in control, because when two controllers contain different programs they can't run as a Redundancy pair.

Once a Redundancy system is online, you need to perform all your edits during runtime unless you can schedule an outage. That's just how things work.

I've been working on a v19 Enhanced Redundancy system for the past three weeks and we do a lot of Import/Export of whole Routines. It has required some good co-ordination among the three engineers working on the system but has worked perfectly.

I generally forget that I'm working on a Redundant system except when my screen goes gray during a switchover event (it's like being locked out of Edits) because somebody's testing the power distribution. We haven't touched the ControlNet configuration or the Redundancy configuration for weeks.