Using Remote I/O in the Main Control Enclosure

Feb. 15, 2022
Learn the differences among remote I/O, distributed I/O, and local I/O; why using remote I/O in the main control enclosure makes sense, even though it may seem counterintuitive; and how wireless remote I/O can be beneficial depending on the application.

Read the full transcript below 

David Greenfield: Welcome to the Automation World Gets Your Questions Answered podcast, where we connect with industry experts to get the answers you need about industrial automation technologies. And you can find even more answers by subscribing to automation world at Subscribe

I'm David Greenfield, Director of Content for Automation World and the question we'll be answering in this episode is how to use remote IO in the main electrical enclosure. So joining me today to answer this question is Brian Liddell of events eon in industrial automation system integrator. So thanks for joining me today, Brian.

Bryan Little: Thanks for having me.

David Greenfield: So given that an IO module is an input output device that processes inputs from a field device, such as a sensor or actuator to send to a controller, and then sends output commands back from the controller to the device, let's start by explaining the differences among remote IO distributed IO and local IO.

Bryan Little: Yeah, absolutely. Um, you know, local IO usually assumes that the IO modules are in the same rack or chassis as the controller, right. So they're, they're right next to it, doing they're doing their job. Distributed IO, you know, can be in a separate or different location than the main controller. But distributed IO usually has some kind of computing power at that remote location. So it's doing its own processing of information, and maybe turning on and off the outputs, regardless of the main processor. And then basic remote IO is, again, that remote location, but it doesn't have any local computing power.

David Greenfield: Okay, thanks for clarifying the differences among those three. So with the definition of remote IO, essentially indicating that the IO modules aren't located in the main electrical enclosure, let's get to the reader question behind this podcast question, which is, how do you use remote IO in the main electrical enclosure? And what would be the benefit of doing this? I mean, it seems like doing that goes against the whole point of remote IO.

Bryan Little: Oh, yeah, I would say that that statement probably applied to, you know, a few years ago or whatever. But um, you know, there's actually a lot of good benefits of doing it. Now. Three of them being number one, safety. Number two, you can save a lot of wiring inside of larger enclosures. And also standardization. I'll go back to the safety. Obviously, there's big pushes now for arc flash, inside of panels. So what you can do is, you know, separate different different doors inside your panel where you might have your high voltage side, and your low voltage side, and you can put remote IO in that high voltage side, and then, you know, that can assist with troubleshooting, without having to open those doors. The other one is there's a lot of safety controllers now that use remote IO. So again, if you need to put some kind of safety into a door, and that higher voltage side you can and from a standardization, you know, if you use all remote IO, a plant, or a company can standardize on their spare parts, they can, you know, trip down their training on the same parts, and then also Drawing Standards just by using the same part in different locations. 

David Greenfield: Thanks for explaining that, Brian. So Brian, I understand that the upfront costs for remote IO can be more expensive than local IO. Is that understanding still correct? And if so what are the key advantages to remote IO that make this higher initial costs worth it?

Bryan Little: Yeah, I actually don't feel that to be true anymore. As far as the cost, you really can get the same performance from a more compact IO module anymore. That may be less expensive than main PLC IO cards. I think really the upfront costs, maybe come down to the network infrastructure, you might need to do remote IO. But again, the industry is all you know, trending towards everything being on some kind of network so that infrastructure is probably already in place. Right. So if you already have ethernet for your PLC and your HMI throwing on an Ethernet Remote i o isn't much of an addition. And really, I would go back to the, you know, the, as far as the key advantages, I would go back to that, that safety factor. But I would also add future expansion, you know, as a good benefit of doing the upfront design that way, you know, main PLC chassis usually only has a maximum number of slots, but you can always add remote IO. So having that in place adds for expansion in the future.

David Greenfield: So I guess, you know, using remote IO in the main electrical cabinet wouldn't impact these benefits that you're missing in any way? Or is there potentially some impact with that?

Bryan Little: I don't, I don't think it impacts it at all. Actually, I think it sets you up for the future, actually.

David Greenfield: Okay. Alright, so it seems like the way to go. So whether it's local or remote IO, you know, we've essentially been discussing wired IO modules here. But what about wireless remote IO? You know, as with anything wireless and industrial control, you know, there seems to be as many detractors as supporters. So what's your opinion of wireless remote IO? And would there be any point in using it if you were installing the remote IO in the main electrical cabinet?

Bryan Little: I think that really depends on your application, it is independent of what other remote IO you already have. There's a lot of things going on with data collection now. So if you already had a panel in place, and you needed to do some data collection, whether it be vibration or temperature inside your panel, you can easily add some wireless remote IO to collect that data. And you wouldn't have to build a whole new infrastructure.

David Greenfield: So Brian, this has been a pretty straightforward topic for this podcast that we've covered. So given that, do you have any further advice as a system integrator for manufacturers who are you know, making choices about the types of IO they use as part of their network networking strategy?

Bryan Little: Yeah, I would say it really comes down to the standardization and and the safety that I mentioned earlier. You know, maintaining the same spare parts for our customers and is a very important thing we try to lean towards. But I would also say you know, setting yourself up to have remote IO is actually a very good choice. Like I said, it's future expansion and the ease of use.

David Greenfield: Okay, well thank you for joining me for this podcast Brian. And thanks of course to all of our listeners. And please keep watching this space for more installments of Automation World Gets Your Questions Answered. And remember that you can find us online at And subscribe to our print magazine at to stay on top of the latest industrial automation technology insights, trends, and news.