Latest / The Refrigeration Mentor Podcast / Episode 340. Basics of CO2 Controls with Kevin Mullis (Part 1 of 4)

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Episode 340. Basics of CO2 Controls with Kevin Mullis (Part 1 of 4) · The Refrigeration Mentor Podcast

• 0:00
  Trevor: Well, welcome to this four part series. Super excited that you're here joining us. With my good friend Kevin. This is, this is gonna be awesome man. For the last couple of years, honestly, people are asking me on a weekly basis, we need some control training. We've done some already. We've done tons already.
• 0:01
  We were just having a conversation before we got in here, is about like. Let's go back to the fundamentals. And when I go back to the fundamentals, there's always something that we may have forgot or didn't really forgot how that actually worked, ? And so we're super excited about this.
• 0:02
  Kevin: It's always good to chat. As you say, we were just talking offline, weren't we? About about going through some of these things with, with technicians and I think controls is especially is one of those things that people are a little bit frightened of sometimes.
• 0:03
  It's not gonna work without electronic controls. And so it is important that we understand how to fault finds and electrics in general. I think Trevor speaking to people who are new into the industry, most of them they can learn brazen, not a problem. They can learn pressure testing, they can learn charging, refrigerant.
• 0:04
  Ultimately, there are gonna be more things we're controlling, but there's not gonna be an awful lot we haven't seen before. We may just not have seen the things put together like that. So yeah, it's, it's important that we get the basics right. And the thing is, no matter what we've done in the field, not a one of us is gonna have seen everything that we're gonna walk into, right?
• 0:05
  Okay. But there's so many other inputs that you can use and the digital, the difference between analog and digital inputs and the difference between analog outputs and digital outputs, you know, and so these are some of the things that we'll talk about today because I was, honestly, I was scared sometimes to ask those questions because where, where I was at, people were, you know, you asked this dumb question you get hollered at, ?
• 0:06
  Kevin: A lot of the time, people who wanna have a go, or technically when you ask a question about something are people who are insecure in their knowledge of it.
• 0:07
  Sometimes it will all be on one board. But as long as we know what they do and what we're looking for at them, we've got a good start and we can work the rest out. So let me share my screen on this one. There you go. And hopefully we will see my first screen there. Have we got that Trevor? Yeah. Looks great.
• 0:08
  So we've got just about everything that we're gonna see in controls covered on two slides. So in CO2, we've got more sensors and more valves generally than we'll have on a, a regular rack. It's just the way it is. You know, we've talked in other training sessions about why we need to control different pressures in different zones on CO2, I'm sure on your training you've talked about it a thousand times.
• 0:09
  We're gonna give them proportional control. We're gonna open them a little bit or a lot depending on what the system needs. We also use a lot of VFDs inverters. We're gonna use those for compressors. We're gonna use those for gas cooler fans. Nothing guys haven't seen before on racks, but we use them quite often, almost always on CO2 equipment.
• 0:10
  And we're gonna be in column four on page nine. Very handly, got the columns marked across the top so we even know what part of the page we're gonna be on for that wire. When we get down to all of these inputs and outputs, that's really important because that's gonna be across a lot of pages, right?
• 0:11
  It's, it's not gonna be a different voltage. It's gonna be the input's closed or the input's open. And we are gonna use that for faults. Usually or to say something's running. Yeah, it's something that's got a status. We could use it even if we had, let's say a three port valve and we wanted to know for certain that that valve had moved all the way open or all the way closed.
• 0:12
  Or you can tell it I'd like 24 volts, in which case it will send 24 volts around the circuit and you can use voltage. There are advantages to both. If you've got a long high resistance circuit, it might be better to use voltage. Because it's, if you have a high enough resistance in your circuit, that input isn't necessarily gonna see on Volt free that it's closed.
• 0:13
  Kevin: you need to, you need to use an auxiliary on a contactor or you need to use a relay contact for that. Even if you switch that to 24 volt mode. That really wants you to use the board 24 volts for it. It wants you to still use from S one to ground, but it will just send you 24 volts out. It doesn't want you to add 24 volts Danfoss.
• 0:14
  Kevin: Yeah. Or yeah, or we're we accidentally cross voltage into the circuit. We put the wire on the wrong auxiliary.
• 0:15
  You know, the, we, you look at some of the older controllers that are out there, they had two 40 status inputs and you, you know, you think now that is actually slightly crazy when you can do it with no vaults. So Yeah, vault free is very popular, but you have gotta be careful. The next bank on RDM is universal inputs and outputs on a lot of controllers.
• 0:16
  VFD. Yeah. So that's the sort of outputs we'll get. We'll also have on a CO2 rack, high pressure valve, medium pressure valve, if it's something like a dam Foss I-C-M-T-S valve. Yeah. Then that will want 10 volts or force 20 milliamps. To make it work. If it's a stepper valve, we'll have a dedicated output.
• 0:17
  You've gotta get those the right way around. Be careful on your wiring diagram for things like that. Things we're gonna have as inputs. Transducers is the obvious one where there are 101 transducers in the market. All slightly different ranges, slightly different max pressures, but they're really mainly in two categories that we would use.
• 0:18
  Trevor: sorry, go on. Yeah, I think you, that's important because now there's mo, like you just said, there's three different ones that you explained right there, Kevin.
• 0:19
  Really useful if you want to share the transducer. So let's say we move off racks for a minute. If you move to cases, you've got an island of 10 cases. You can fit one transducer on the island, you can power it up using one of the controllers and that five volt signal that tells you the pressure, you can just loop it between all the controllers, loop the five volts, loop the ground.
• 0:20
  Make sure you get 'em the right way around. With RDM, you've either gotta go by the drawing or you've gotta look in the setup and it will tell you in the setup whether it's configured as an input or an output, whether it's voltage or milliamps. So from this page, this first page, we dunno at the moment when we look further down the drawing, we'll know what it is 'cause it'll tell us on page 15, 19 23, whatever page it's, so your final group on this board is probe inputs and that's temperature probes, right?
• 0:21
  So you've got to make sure your probes are in good order and make sure they're wire to the right place and they're the right type of the probe. You know, you think there's a lot of transducers out there. There is a heck of a lot of different types of probes, right? And a lot of controllers are tied to one or two types of probe.
• 0:22
  The high pressure valve wasn't working. And one of the questions, when he came back the next week, it was like, you know what? We were using the Danfoss controller. They had a CPC sensor hooked up to the Drop Legg sensor, which PT one thousands, a Danfoss, which is a positive temperature coefficient one versus a negative temperature coefficient one, which is the ccpc one.
• 0:23
  And as you get colder in temperature, that resistance change might be in the range at when it's at a certain temperature, but when you get colder or a hundred, that total resistance changes. So this is so key and it's a, it's a basic thing.
• 0:24
  It's plausible, right. But it's not right. And you need to make sure it's the right type of probe. It's close enough, it could be right. It's not like sticking a PT 1000 in where a 5K should be and you'll know, 'cause it'll say like a hundred, you'll know it's wrong. Make sure you've got the right type of sensor in there.
• 0:25
  You can put the ground in that one and it'll be just fine. You can put it in P seven, P 65. That is not the case for all controllers. You with Carell, for example, the probes on a cabinet controller and NPX Pro, something like that are grouped. So probe one, two, and three are in a group probe four and five in a group.
• 0:26
  They may not. Little trick with RDM that I got told a little while ago, sometimes your temperature probes get affected by interference, right by noise. So what you can do is you can wire the ground to earth to your ground in the panel, and that will pull some of the noise out of your probe inputs because otherwise that ground will float.
• 0:27
  So he went to the communication wire, which was white to ground, and it got four volts, but he was like, Trevor, if I had my proper meter, 'cause I didn't have it with me, it's, you know, it's actually 3.2 or, ? So having that better meter makes a big importance. But then when he, if you plugged it back in, he only got one volt, you know, ground.
• 0:28
  Yeah, because you don't do it. You switch it off and switch it back on again. The fault goes away. You think? Yes. I'm on my way home. Will happen is the on-call guy, three hours later he is gonna get the same fault, come back and he is gonna be cursing you for not having done that before you left. So get a good meter, make sure don't scr where you're buying a meter.
• 0:29
  It doesn't matter if the company buys 'em for you or not. You are a professional. Those tools stay with you if you buy them. Yeah. And the better tools you have, you can troubleshoot a lot
• 0:30
  You walk up to a panel, the only way you've got to tell that that panel is li or dead is with a meter. You know, and I, I'm gonna say right now as well, do not ever trust your life to a volt stick because I see a lot of technicians trusting their lives to a pen with a light at the end. Please do not do that.
• 0:31
  They've marked up. That's a circuit breaker. Even if we didn't know that that was a circuit breaker by the, the symbol, we could be pretty sure when we see CB that that's gonna be circuit breaker. We're gonna use our intuition on that, even if we dunno the symbol. We know, even though that symbol right there doesn't look like a North American symbol for a relay contact, we, we can work out.
• 0:32
  Even in my trainings that I do the CO2 trainings, I get them to get the electrical wiring diagram for their store. And I'm like, go through the p and ID go through the electrical winery and then I ask them questions from the notes and they're like, well I didn't, I didn't read that. And I talk about a symbol just like this.
• 0:33
  The the other thing I wanted to point out on this, as you were saying before, the relays on a lot of controllers, now almost all controllers, I would say are volt free. Yeah. So unless you've got wires in that relay, in any of these relays, like number 12 there, you could meet to that in any position on or off, and there's gonna be no voltage.
• 0:34
  But you can put 24 ac, 24 dc 12 volts, 2 41 20, whatever you like through that relay. There will be a maximum, it's usually two 40 on a lot of our stuff because that's what everyone, everyone's maximum usually is. But you can go pretty much anywhere with the voltage on it. And you can use different voltages across the controller.
• 0:35
  You gotta understand on that page there, like we talked about earlier, that controller may not be getting 24 volts because that relay is open. So just Absolutely as we, as you start to go through and you start to look at these wiring diagrams, things happen for one thing happens to the next, you know, so understanding absolutely the, the flow because this 24 volts comes from one 20 or two 30 or whatever that higher voltage is through a transformer and then it's way down.
• 0:36
  You know, something in that relay is then stopping that circuit getting through. But yeah, it's, it's important to think, okay, I must have power here. I've tested this power here. Why is it not getting to my controller?
• 0:37
  Kevin: problem. Yeah, absolutely. And especially where you've got vol, three signals, even corrosion on the contacts can stop that signal. So you may even look in the side of the relay and the contacts look lovely, but if you put a meter across it, you might find there's like 50 ohms across the relay, and that might be enough to stop whatever you are using from detecting that.
• 0:38
  You can have a range of different kit on universal outputs and inputs, right? So we are doing all sorts on this page. We've got our transducers and we've got things like flow meters and pressures and what have you across the system right now. As I said, the inputs and outputs can do multiple things, but the draw the.
• 0:39
  We can't do that before to 20 milliamps. With a meter like that, we may see a voltage even if the circuit's broken because it's current that it's looking for. Yeah. The one thing I will say about both types of output. If you think, let's say we went to an output. Yeah. Let's say we were looking for a 10 volt output to one of these valves and we, the controller says we should be 50% open.
• 0:40
  If you're 12 volts or whatever, 14 volts reappears. The chances are you've got a short, somewhere on that circuit that's dragging the voltage down. Yeah, it's don't always assume. It's rarely in truth, very rarely is it actually the controller because they are protected against you blowing the outputs by shorting.
• 0:41
  So, yeah, a whole array of different things that we can have on analog inputs and outputs. As I say, it can be three-way valves like that. One is, it can be, that's called PIC valve, that's regulated water. We've got bypass valves. These are inputs. So this is what the system wants us to do. So it'll tell us zero to 10 volts how much it wants from us because this is actually a heat pump that this is connected to.
• 0:42
  Kevin: to test. If you've got a milliamp capable multimeter, you can wire it in series with the circuit and it will read it. Your your best bet to be honest, for four to 20 milliamps is to test it by substitution. Put a new transducer on it. If you've got a cable, wire it directly to the terminals or swap it with another one.
• 0:43
  Yeah. It may give you a silly reading 'cause it might be a different transducer if it gives you a reading. We know there was a fault on the other circuit. Yeah, that's, and to be honest, sometimes the easiest way to test it is the best way, you know, because it gives us the, the instant result, you know. But that's all we wanna know, isn't it?
• 0:44
  So the purple R on my first page was probes. This is all our temperature probes. We can see we've got a symbol for a probe there. We know that's telling us that that thing is a variable resistor.
• 0:45
  You can follow it to wherever it goes. Find the same cause. Find your temperature probe. That goes for pretty much all those probes. As we were saying. As we were saying earlier, some of these probes are absolutely critical to the operation of a CO2 system. Things like the gas cooler outlet temperature and the ambient temperature, for example, are gonna be critical and we know where they're gonna be, right?
• 0:46
  There are times, you know, stepping away from the drawings for a minute. There are times when you've got no drawings. Right. And the only way to find the circuit is to pull all the conduit caps off and trace the wire. Sometimes that is the only way. It's not the best way. It's sometimes it's the only way.
• 0:47
  I couldn't fix it. You know, you, you can follow a wire manually if you need to. You've gotta bear in mind if you do that, that is more like the time when you need to be powering down the panel because that wire could be loose. You might find broken wires in the conduit. Be safe if you're gonna trace wires in conduit.
• 0:48
  Inverter VFD. Hopefully you're all familiar with the terms. So that is our signal to tell the VFD how, how much you want. Do you want fast or slow? Yeah, and we can use our intuition a little bit and we can see it says AI one, AI one analog input. So we know we're on the right track there. We know what color wires we're looking for.
• 0:49
  We will sometimes have that fail safe, so if the controller dies, we'll have it wire to the normally closed contact so that the gas alarm will sound, or the ventilation fan will run regardless. There are times when it's better to have it fail safe. Obviously you do not want that compressor to start if the control is off.
• 0:50
  The final item on this page is the status input. So the other bit we looked at on the first panel was the status inputs. Very first thing we talked about and we can see it right there. So that compressor one tells you whether the inverter is happy or not. We can see on this circuit, there's a relay contact in there, IHR one.
• 0:51
  Trevor: So, and you let, just going back to that, yeah, you, this is the biggest thing that I see, especially with controls and CO2, if you go back to that page, there's a sequence of operation. And that's the biggest things where I see a lot of people, and even me, I'm training on a lot of different CO2 manufacturers equipment and I look at the wiring diagrams and to just say, this is the sequence is not always the case.
• 0:52
  Kevin: Absolutely, absolutely. And when we look at the zero zone drawing in a minute, we'll be able to see a little part of one of those circuits. Like you say with all the steps on it it's a little bit busy on that page, so I thought we'd do it on the, on the zero zone one. Now Trevor sent me very kindly a couple of days ago, this drawing.
• 0:53
  For MTLI know from being around the industry too long is a Bitsa compressor model number. Even if I didn't know that, that's, I can see down here that might be a Copeland actually. Sorry, Copeland, it's, yeah, very similar to a bit. So it's whichever one's put me in the line of a compressor. Sorry. You, you're quite right.
• 0:54
  That's why I'm here on this service call. What, what's gonna be stopping me is my contactor pulled in. I know this is a contactor. It's called C five. C is usually contactor and I can see it's got, these are gonna be a power terminals for your compressor and we've got three open contacts there. You can see they're open.
• 0:55
  I'm, I can follow. The line through everything. And as Trevor said, there's 1,000,001 components usually we know on this. We've got no wires coming into the page on here, so we know the only place we can be getting power is over here. So we've got ly, they've marked L one and neutral and they've told us this is the control module.
• 0:56
  Let's say I've got, I test the power out of this module and I've got nothing. Yeah. And I'm then gonna be like, why have I got nothing on this module? Because. That that can only mean I've got a fuse gone or a breaker gone. Right now I'm looking at this and I'm seeing the crank case heater, which I'm assuming is crank case heater 'cause it's CH and it's got a normally closed contact on the contactor.
• 0:57
  So I know the supply is coming all the way round here. I can then see there's loads of different things that have gotta work to enable C five to pull in. And again, I'm gonna use my intuition about some of what some of those are. This doesn't, from the drawing, give me an awful lot of information, but it says do.
• 0:58
  So. Unless the module's given us a fault, we might well be made in there. But then I've got OMC. Now I might know, or I might not know, that's probably an oil control module. Yeah. If we know tra soil Emerson control modules, that's probably an oil control module. But I'll know because I can track Y 1 0 6 and at some point I may find, let say I've got no power on 1 0 8, but I've got power on 1 0 6, in which case I need to be looking, have I got any oil in the compressor?
• 0:59
  You know, when you are reading it, read it in a logical order to see the components that are in it. But when you're testing it, test from where you lost it because you're gonna find the point quicker than if you start where you've definitely got it.
• 1:00
  Yeah. You don't, like I say, I, I would've, I've done a little bit of CPC and what have you, years ago I had a fair idea that's a relay, but there's nothing on the drawing to tell me what it is. But I can use my intuition. I know somewhere along the line, a controller is gonna be telling a compressor to go on or off.
• 1:01
  They would be like, they'd know this all the inside out, but then they would go to that clay one and they'd be like, I, I don't even know where to start. ? But yeah, yeah. Start from the beginning. Just like, or even the, the end where that compressor was like, Kevin, and then what does this, how does this really make sense?
• 1:02
  You're gonna have the, every manufacturer had, they can't, they can't build a store if they don't, unless it went bankrupt. And even at that point, you need a wiring diagram for someone to wire up the rack or do the piping. You can find 'em, give them a call and ask them, can you, can you supply it? The end users usually have it or someone at your thing.
• 1:03
  Trevor: Yeah, and I love it. I wanna thank you Kevin, so much, and we got another session tomorrow. Dive in in deeper on the programming. So if you're interested in learning, and this is on RDM, but the process is gonna be the same. All these control manufacturers, they have the same type of process. And what you want to do is understand that process.
• 1:04
  So hope to see you guys all there. If you know other people that would be interested to come into the session and learning, share, share the link with them. This is how we get better in the industry. You wanna get better with controls, get the wire and diagram, call the controls manufacturer. I don't know how many I, I haven't asked Kevin this, but I don't know how many, hundreds of maybe even thousands of times he calls a control manufacturer or a control person over the last 20 years, like he has friends now.
• 1:05
  Trevor: A hundred percent. I totally agree with that. If you're listening to this on the podcast later go and check the YouTube channel to look at the, the graphs that that Kevin's going through, because it really, really helps out the visual aspect. And I really challenge all of you to go out and get that wiring diagram and the control wiring of a system you're working on.