[00:00:03] Speaker A: Hello and welcome to the Consulting Specifying Engineer podcast. I'm your host Amara Roskas, and I've connected with Steve Flynn from stantech. We're going to be discussing building controls in both new construction and retrofits. But to get more specific, today I'm talking with Steve Flynn, senior associate in studio lead automation from stantec, based in Chicago. Steve leads a team of automation engineers at stantec, producing detailed design drawings and specifications for some of the largest hyperscale data center clients in the industry.
These projects include new builds, retrofits and leased facilities.
Steve possesses expertise in many different PLC platforms. Thanks for joining me today, Steve.
[00:00:55] Speaker B: Yeah, thanks Mara.
[00:00:58] Speaker A: Good. Well, building automation and controls, it's not something we talk about a lot, so I'm happy that we're speaking today.
Let's start with the basics. What are the main differences between direct digital controls or DDC and programmable logic controllers or plc?
What's the difference between these systems and why are these differences important?
[00:01:25] Speaker B: One of the key distinctions between direct digital controllers and programmable logic controllers is going to be sort of a commercial versus industrial use.
DDC controllers have sort of historically been known for the commercial uses in building automation.
All the standards are really geared towards buildings and the PLCs are going to be more for these industrial applications. And where we're kind of seeing this come into play is going to be in more of these mission critical data center type applications where it's sort of a mix between commercial and industrial loops. And that's kind of the reason we have these conversations on why these are important.
So sort of the main key areas I can touch on today is going to be the controller types, the network architecture for how these controllers communicate, some nuances with the programming, some of the hardware differences, and then an assessment of cost and maintenance, because those are going to be one of some of the really important things as you're actually going to build a facility with either one of these controllers.
So hopping into some different controller types.
So in the DDC platform you're sort of seeing three different controller types. You have your top level building controller, which is doing a lot of your system level control set points and routing information between these controllers and your user interface or your SCADA system.
And then you have your advanced application controllers which are going to have a variety of inputs and output counts and what they control. Usually this is going to be at a piece of equipment like a chiller or an air handling unit.
And then you have your lowest level controller, which is your application specific controller. And this is Going to be something that's more factory programmed, that is very much standardized. And an example could be a variable air volume box, for example.
On the PLC side of things, you don't really have this distinction between these different types. You may have different form factors or sizes for the PLCs and different inputs and output counts. They may have different hardware inside for different processors. But for the most part a PLC is a plc. It's not going to have these sort of distinctions between what they're, what they're used for.
You may be able to use one PLC as your building controller and the same PLC as your smallest application for a VAV box. So you don't really have that same distinction.
For the network architecture differences, your DDC controllers are going to use bacnet as its typical protocol.
This is your typical building automation control network protocol in the industry. It's very standardized like you would see in this commercial use.
So your building controllers will communicate to your network via bacnet, typically using IP based controls. So your Internet protocol addresses your application.
Your advanced application controls can be either or. You're seeing a lot of this in the industry now of a lot of IP based controls, you know, directly connected to your network versus a serial network.
But you can communicate serially to all your building controllers with the advanced application controllers and your application specific controllers.
On the PLC side, this is more using modbus, some more industrial based protocol.
Most of the time you're probably using the IP based modbus or modbus TCP ip. In this instance they do also use Ethernet IP as a protocol. So and you're just seeing some different ways that these controllers will talk to your network.
So if you have a preference in the industry, that's, you know what may gear you towards one or the other.
For, for programming, there are some nuances between the 2.
For DDC you may see some differences in how you program these per manufacturer with different strategies and styles. And you really have to kind of learn each manufacturer individually and understand exactly how you're going to program it. On the PLC side you have that to an extent as well. But ladder logic will tend to be pretty typical across more industrial industry. You get into function block and structure text programming ways as well, but it's going to be a little bit more the same across different vendors.
On the hardware side you're going to have a lot of similarities between DDC and plc. You're going to have analog inputs, digital inputs, digital outputs, analog outputs, serial communication. It's going to be pretty, pretty typical between the two but there are going to be some nuances with the capacities and how much you can really connect to that system.
On the processor side, this is where you really see a big difference as well as how fast these programs run.
So DDC systems are typically measured in seconds, sometimes even could be minutes. They're it's not meant to be particularly fast since it is a more commercial use.
But on the PLC side you're typically measuring your time in milliseconds. So these actions are happening very quickly. The system is checking its inputs to see what the state of the system is, it's running through its program to execute it and then changing outputs based on that execution of the program, which will again, it'll be so fast that you don't even see it happen in milliseconds. So this is really where that, that difference kind of comes into play where how important is it to be a fast acting application?
In industrial use cases, a lot of times you do need to be able to react very, very fast.
But in a more H Vac based application you don't always need to have to react within milliseconds because if you're changing temperature, temperatures maybe not always going to be changing that quickly.
So then getting into cost and maintenance, the cost of a PLC system is going to be drastically higher than a DDC commercial based product.
In terms of the whole system cost, you're probably looking at about a two times cost difference between using a PLC system versus a ddc.
So this is really why there's some cons also to the PLC side. It may be faster, but it's going to be more expensive for maintenance.
For the DDC systems you're getting a more simple programming application. So something that's maybe a little more user friendly, a little less complex to program, but you may have to maintain more program files.
So you may have to have a program file for your building controller and your application specific controllers and all your advanced application controllers. You have different files, you have to maintain, they may be the same and be able to use across different controllers. But ultimately there's going to be an individual program per controller.
On the PLC side of things, you don't really have to have a program per system like that. You could have a single controller program that communicates to downstream remote inputs and output racks. So you can kind of get away with having less to maintain on the program side, which I'm sure a lot of operators appreciate.
But it is going to be a little bit more complex to program that you have on the DDC side.
The other part of that is going to be where you can put these controllers. DDC is a little bit more meant for the commercial use, like I mentioned earlier. So you may not be able to use them in as rigid of conditions, so they may have a shorter lifespan depending on where you put them. Versus the PLC side is really meant for those robust, harsh environments and really meant to last in that kind of kind of space.
[00:09:41] Speaker A: All right. Well, Steve, you mentioned one thing. Ip, that's Internet protocol, right?
[00:09:46] Speaker B: Correct. Yes. So that's going to be, you know, the same kind of IP address that you'd have for your computer or those types of things that you'd see. It's just our way of telling the network what your device is and how to communicate to it.
[00:10:02] Speaker A: Okay, I just wanted to make sure I had that clear. Thank you.
[00:10:05] Speaker B: Yes.
[00:10:06] Speaker A: All right. Well, that was a lot of information.
But I want to jump into one of the things that you specialize in and that is the data center industry.
What are some of those data center industry trends and what are, what's pushing a client to use PLCs versus DDCs? I mean, are there specifications that define this?
[00:10:28] Speaker B: Yeah, so this is where there's always a kind of a gray area here. There's no, there's no right answer.
You know, some clients may specify certain things in their, you know, client specific specifications that they.
I'll give you an example.
They may ask for a smooth transition between redundant controllers and critical applications.
So for something like a chilled water system, that might be very, very critical, and some clients may consider it less critical than others. So in a system where a client says, hey, my chilled water system is my most critical piece, I need this to be highly available, they may say, hey, I want to have redundant controllers controlling the system and a seamless transition if one were to fail.
And this is where the difference between how DDC and PLC controllers communicate may make it more difficult for a DDC system to meet a client specification.
I've seen this come up with different vendors asking, well, how do I do this?
So to talk about a little bit more, the PLCs have the ability to connect and communicate to each other and sort of seamlessly tell when one has failed and swap over to another one versus ddc, you can achieve something somewhat similar, but it's not as seamless. So a lot of the DDC vendors can't meet that part of a specification.
The other part of this, and I mentioned earlier, is going to be that cost. So getting outside of the specification portion of depends on what's important to the client. So they may say, hey, I'm trying to save money as we move forward.
There's definitely a trend for wanting to spend less if we don't need to.
So that's really when you're going to say, well, how do I make the DDC controllers work in the system that I want?
And you can make it work. It's not that the one is better than the other.
They have different pros and cons.
[00:12:34] Speaker A: So to look at it a little bit broader, you would say the PLCs are smarter, more expensive, kind of like the Harvard of controllers.
[00:12:45] Speaker B: Exactly.
That's a good way to put it.
[00:12:48] Speaker A: Got it, got it. Okay, so how are vendors then responding to these industry trends to keep up with the functionality and to keep up with all the technology as it keeps changing.
[00:13:00] Speaker B: So that key, the key piece about trying to make systems more available, when I say available, I mean making sure that they are not ever seeing downtime. And that's where I'm seeing a lot of the DDC vendors start trying to find a way to bridge that gap, to add additional functionality to be able to create this more redundant controller swap. And I think you'll start seeing some more of these DDC vendors adding more of this functionality to their systems to be able to meet the specifications that maybe only a PLC could have met previously.
And the other part, on the other side of things I think you may see if PLC vendors wanted to get into this space, is finding ways to provide a lower cost product to sort of bridge that cost gap as well.
[00:13:48] Speaker A: All right, good. Thank you for that very, very broad overview.
And one last question for you. I am a travel junkie and I love to ask this question.
What's your favorite vacation? I mean, do you connect to this with traveling to see clients ever?
[00:14:06] Speaker B: Oh, I wish, I wish I got to go to some of the amazing places I've been able to travel for work that would, that would have made all the world to me.
Not a lot of international travel for me from work, but I definitely love to travel internationally for, for fun.
A couple of my favorite vacations that I've gone on, I've gone on some African safaris that were just breathtaking. Seeing, seeing those animals sort of in their natural habitat and it's just amazing.
Africa is just one of my favorite places to go.
South Africa in particular was, was one of the places that I enjoyed the most.
You get a really great mix of big cities and safaris and there's wine country out there and it's just it's a really, truly amazing country.
Me and my wife have an upcoming trip to Norway to try to see the northern lights.
Never, never, never seen it. But going to really try this year and later this month in March.
[00:15:11] Speaker A: Awesome. Well, I'm definitely jealous.
All right. Well, that was Steve Flynn from Stantec talking about building controls and some data center industry trends. Thanks, Steve. It was an absolute pleasure to chat with you.
[00:15:27] Speaker B: Yeah, thanks. Thanks for having me today. Really, really had a great time. This was very enjoyable.
[00:15:33] Speaker A: Great. Well, for more information on building automation systems, data centers, building controls, or similar topics, visit Consulting specifying
[email protected]. thanks for listening and catch you next time. Bye. Bye.
