Latest / The Refrigeration Mentor Podcast / Episode 243. Step-By-Step Walkthrough of a CO2 Service Call with Patrick Gregory

Transcript

Episode 243. Step-By-Step Walkthrough of a CO2 Service Call with Patrick Gregory · The Refrigeration Mentor Podcast

• 0:00
  Speaker: Today we're going to be diving into it more of a technical talk, which I'm super excited about because this is, this is very important for technicians out there.
• 0:01
  Trevor: So I have Patrick Gregory with me this guy is an expert at supermarket refrigeration.
• 0:02
  Speaker: You've been doing this for six, seven, eight years now, super industry now getting into CO2 for the last couple of years. So the technology has grown. There's a. Math, fast amount of advancement, even in HFO systems or HFC systems, it's more digital, variable speeds, electronic case controllers, electronic valves via these, you know, all these things are happening at a very fast rate and the technical side, we need to get better technically because the old, you know, and this has been years and years, the old Contactor and relay systems are a thing of the past.
• 0:03
  You know what I mean? They're out there. There's lots of them out there, but all these newer stores in the last 10 years, there's so much control, so much stuff. And so this is what I want to dive in today. And hopefully we'll, uh, be able to share some good knowledge with, , with all the people listening.
• 0:04
  For sure. So when you go out and take a, a service call and it's a store you never dealt with before, and let's talk about a CO2 service call. You haven't been at the store, you don't know the manufacturer, but your dispatch says, Hey, it's a CO2 call. What's your first steps when you get to this store?
• 0:05
  Okay. Thanks.
• 0:06
  Speaker 2: So I've actually been in that situation a lot. Last year, um, I went to a different part of our company a few states away and their customers are completely different. And, um, you know, that particular customer has a lot of cascading CO2 stores that, um, I just walked in having no idea what was going on.
• 0:07
  Essentially, what's actually going on, but luckily I can rely on your previous experiences and knowledge, you know, piece things together. So, um, in regards to whether it's transcritical or cascading CO2, there's just some few common things across the board that you can look for, um, and it starts with, um, just using your eyes and your, your hands, baby, feeling stuff, looking at stuff, just keeping things as simple as you can.
• 0:08
  And then get more, um, more into it as you go and just try not to get ahead of yourself. So, um, um, it pretty much just starts trying to start simple and working way up from there.
• 0:09
  Speaker: Let's say, okay, let's start with the differences. Let's talk about what is a cascading CO2 system first. Well, the
• 0:10
  Speaker 2: past, the cascading CO2 systems that we see use a conventional refrigerant, um, 448, 404, 407 to, um, cool the CO2 that is, um, um, circulating throughout the store on the store level.
• 0:11
  So there's never any, conventional refrigerants on the store level, it's confined to, um, basically a chiller, a rack upstairs, and it uses that cold CO2 to circulate through the store to, um, cool your, cool your product.
• 0:12
  Speaker: And so some people call this liquid overfeed, CO2 secondary pump system, CO2 secondary system.
• 0:13
  So lots of different people are going to use different terms. Just make sure when someone's talking to you, understand out there what they're exactly talking about. Because I had lots of people come to my CO2 program and they're like, Trevor, I worked on tons of CO2. But they were all secondary system or cascading systems via not transcritical.
• 0:14
  And these are totally two different animals, you know, when we get out to the field, because they're different components, there's a different way they work. But let's start with the, uh, the cascade or the secondary pump system, CO2 system. So you went out to these new customers and you had these, this new system, your first thing was going around.
• 0:15
  Listening, looking, understanding the system before you'd even take any tools out. What is the kind of the next step that you would go from there?
• 0:16
  Speaker 2: So then I'm going to go to their PLC, their rack controller, and see if there are any, you know, alarms staring me in the face and pointing in the right direction.
• 0:17
  Do I have a low vessel pressure? Do I have a, um, an issue with the, um, the upper cascade, the conventional rack? Um, and then try to kind of separate the two, the CO2 side versus the conventional side, that way you're not going down a rattle hole unnecessarily. Okay. So, um, usually I like to look at the conventional rack first and make sure that, you know, those pressures that we all know and love or where they should be and we're all more familiar with, you know, that refrigerant level, those pressures and, you know, that kind of stuff, make sure that's operating as it should be before I necessarily look over to the CO2 side of things.
• 0:18
  Speaker: Yeah. And I totally agree with that because these systems, there are systems that you've been working on now. It's just like a regular rack, regular condensing unit. Even if you want to think like that multiple compressor condensing unit, it's just a regular, the system, but the big difference is instead of having evaporators there, you have that plate heat exchanger or, you know, some sort of exchanger there.
• 0:19
  And usually it's a plate heat exchanger where you have. On that, uh, the secondary side, you have electronic valve or a TXV into the plate. And on the other side, like you said, is that CO2 system, or CO2 refrigerant on there that now it's being circulated through, , with a circulating pump.
• 0:20
  So you check that and then if you, you find that everything is going okay in there, you check your, uh, approach on there. So what do you do checking your approach is, you know, we're actually checking how that chiller is running. Seeing how that, the temperature of that, um, the, the plate chiller is cooling, making sure it's cooling that CO2.
• 0:21
  So you get that thermal siphon effect, and we'll get into that in a little bit. , what's your next step?
• 0:22
  Speaker 2: So then, , I start to diagnose where my actual issue is. Um, read the work order. If it's, um, a one particular case issue or, um, multiple cases you see, multiple circuit issue. , it kind of points you in a better direction rather than thinking, Oh, no, it's catastrophic pump failure.
• 0:23
  There's no CO2 circulating when you're only there for one singular case. I tend to be that might have a blocked, um, filter dryer that we still have in those systems before your, your solenoid valve inside of the case. Um, so that's, that's usually why I look as well as to try to further pinpoint what my issue is.
• 0:24
  Is it a bigger issue or is it pertaining to one particular circuit or issue or something like that?
• 0:25
  Speaker: And something I want to point out too, that I forgot before, when we talk about a secondary CO2 pump system, we're usually having, uh, circulating pumps, circulating the CO2 around the stores, where when we talk about a cascade system, usually on that secondary side, you have compressors, so you're pumping, it's like a DX system, so that's how I differentiate, I'm From cascade and secondary system.
• 0:26
  Speaker 2: So
• 0:27
  Speaker: I guess from here on out, we'll refer to it as liquid overfeed system. Liquid overfeed. See, perfect. Cause the first time I heard liquid overfeed, I was like, what do you guys mean by that? Cause I was always taught secondary CO2 system, you know what I mean? Or secondary CO2 fluid system versus liquid overfeed, but that's exactly what it is.
• 0:28
  Right. So, so you go on, you, you make sure that you, you, you check your, your order and it says, okay, it's a certain case. You check the primary side, that 4, 4, 8. 404, whatever it is on that. It could even be a natural refrigerant. You verified that. That is good. Now, what's your next steps?
• 0:29
  Speaker 2: After I confirm that the primary or the primary side is running fine, um, that's what I'll go.
• 0:30
  If it's a particular case issue, let's say it's, um, a 51 that's running warm. Um, I'll decide if it's a low temp application or readme application. And then just look at the case and see what kind of components I have inside the case. Do I have a, you know, a filter dryer before my solenoid? Do, is my solenoid energized?
• 0:31
  Is my evaporator flooded? Is it, um, is the solenoid bleeding, bleeding by? Is the case iced up? And then different things, different Cs when you would go to different, um, options. Is our, is our solenoid stuck closed, stuck open? My fan's running? Is the case put together properly?
• 0:32
  Speaker: And one thing is that, um.
• 0:33
  If you haven't worked in these systems before these solenoids, they're different solenoids. They're just not your standard refrigeration solenoid. You'd have it before a TX valve. They're actually CO2, uh, solenoids for them. Cause there's a special capacity for them. Can't just throw any solenoid in there that, okay, it's a five, eight line.
• 0:34
  Just throw a five, eight solenoid in there because it's like, you have to definitely get the right one. Uh, and I've seen these where I've worked on some of these systems where the liquid and the suction line were crossed. Have you ever come across that?
• 0:35
  Speaker 2: Yes, with the liquid overfeed, it's like you're looking at the same size pipes, and when they're insulated, when you're looking for isolation, you're like, well, which one do I gotta close first here? So yeah, so that is a slight difference, is, you know, generally the pipes could be the same size.
• 0:36
  Speaker: Yeah. And so super important when you're doing that is to understand the flow of the refrigerant. And this is where I would always go back to the PNID if it's on there or tracing out the pipe, like you, you mentioned before, like you got to trace this pipe out to make sure which one is your, uh, you're in and you're out.
• 0:37
  Yes, so let's talk about the solenoids because this is something that's different most most systems you go to you have a TX valve You know what? I mean feeding you get a circuit and you get that TX that is cooling the DX coil But now when we talk about these coils, they're different. They're not the they're not the same.
• 0:38
  They're not DX coils Now these are they're fluid coils because you have co2 going into them. You're using solenoid valves Let's talk a little bit about some of the differences between Um, using a standard DX, , system with, one of their evaporator coils versus a solenoid evaporator or case, , that you would see.
• 0:39
  What are some of the differences that you notice?
• 0:40
  Speaker 2: So, um, generally with the DX system, you may have a liquid solenoid, but you're going to have a meter device after it, because that's how conventional refrigeration works in that regard, is, um, you need the liquid refrigerant to be metered to go into your evaporator, whereas in the liquid overfeed CO2 system, it's just, um, On off open closed solenoid to allow the cold liquid to go inside the cold fluid to go through the evaporator to, um, to cool.
• 0:41
  And that solenoid will cycle based on if you're looking for a medium temperature application or a low temp application.
• 0:42
  Speaker: And this is all controlled by, uh, Case controller or back at the main controller because it wants to maintain that proper temperature. One of the big differences is too, if you worked on glycol system, secondary glycol system, it's all sensible heat.
• 0:43
  With that. So the in and out there's you do your Delta between your in and out. So you can check what the temperature is, but it's all sensible where with CO2, what's really cool about it, the heat transfer properties. Now you get sensibly plus latent heat because it's boiling off as it goes through that boil.
• 0:44
  Speaker 2: Yeah. Which is, which, when I first, um, kind of learned about the differences between like a glycol, um, system versus the liquid overfeed is, is that difference, like you said, it's not just, it's not just as black and white as. You know, sensibly,
• 0:45
  Speaker: and it's, it's good to understand that because there's different ways to troubleshoot because as it starts to leave, like the, the glycol one that, that, you know, that's going to be full liquid, you know, a fully a glycol going back where with the CO2, there could be a mixture of liquid and gas going back to that massive right vessel, right?
• 0:46
  I, I know one of the biggest things with these systems is where a lot of guys get tricked up is the pumps, you know, like, and you said it earlier, you know, people think it's a pump and as a major catastrophe, we don't deal with a lot of, , pump curves, fluid, you know, fluid in a system we're just used to, you know, pressure drop and pressure increase and regulating valves.
• 0:47
  Let's talk a little bit about, , About that. Because I think that's important. I'm, I'm assuming too, when you started out, I don't know if your background is in VFDs and in motors, but mine wasn't, you know what I mean? Right. First time I seen pumps on there, I'm like, what is, what is going on here? Why do we even have these?
• 0:48
  Speaker 2: Yeah, um, most of the times you'll see a VFD on those circulated pumps to, so we can, you know, to, um, change like the flow of, so that way we have full capacity, half capacity and stuff like that. There may not be necessarily a reason to run those pumps, you know, 100 percent all the time based on our load.
• 0:49
  Speaker: And, and one thing is you could have a case issue and, you know, you're down there and you're looking at the sold oil and you're looking at the case. But it may not be the solenoid or the case itself or the fans. It might be actually chiller pack, that pump skid, maybe people call you, they call it pump skids.
• 0:50
  You know what I mean? Pump skid, yeah. Yeah, so there could be something going on with the flow there potentially, but this is where it's so important getting back to that PLC, like you said, taking a look at the, the graphs, what's going on there, because this gives you a full picture of what's going on in the whole system.
• 0:51
  Speaker 2: Yeah,
• 0:52
  Speaker: for sure. What are your thoughts on the different PSCs? Which ones actually have you seen? Have you seen them on with an E2, Micro Thermal, Danfoss? Which ones have you
• 0:53
  Speaker 2: been working on? We primarily see E2 and Danfoss. Okay. Or Emerson and Danfoss, the different, the different series of Danfoss series of Emerson.
• 0:54
  Okay. Site Supervisor, E2, E3, the 880 series, 255, all reliable, I like to call it. Yeah. And, and basically that's pretty much the most that we see around here.
• 0:55
  Speaker: Yeah. No, and, and that's totally fair. Have, do you notice there's a lot of controls issues versus more mechanical issues on these systems? So when you go in, it's like, Oh my God, it's all control issues.
• 0:56
  Or is it more mechanical issues? Like the sole noise, the plug, honeycombs.
• 0:57
  Speaker 2: I guess it's pretty close to 50 50. Hopefully the controllers are kind of locked out, so guys can't go in there and necessarily make changes. They don't know what they're changing. Um, sometimes you might have a open, a free range controller where guys will make a change, you know, at two o'clock in the morning till, you know this happens.
• 0:58
  And then don't necessarily, you know, they consider. They can disconnect, you know, what could happen. So, um, hopefully there's not a whole lot of, um, EMS issues, but, um, it's usually mechanical for us really. Yeah,
• 0:59
  Speaker: yeah, no, no, I agree with that. So let's get back to the case. I kind of jumped ahead getting into the drives and, uh, and the circulating part, but down in the case, if you run into, uh, A solenoid issue.
• 1:00
  What are some of your main checks right off the bat? Just say you don't feel like it's opening or if it's closing, what do you use? Do you use your amp clamp? Do you have a solenoid tester? What are you, what are you testing with?
• 1:01
  Speaker 2: I always lose the solenoid tester. So I just use my amp clamp, um, just put on amps, put the jaws over the solenoid coil and see if I'm seeing some sort of amp jaw that signify that it's energized.
• 1:02
  And then whether I see that or not, it goes into my next steps is, is it, am I getting voltage here? Where is the valve stuck closed? Is it getting power, not opening and stuff like that.
• 1:03
  Speaker: And I think that that's very important. Just grab that amp clamp, put it on there. If you got amps, great. You know, it's, it's open.
• 1:04
  If not, then like, uh, Patrick said, get into the voltage, get your meter up, get into the wiring diagram. I think this is so key in these systems is looking at the wiring. How is this actually wired up? Is it wired up even correctly? Has, you know, I think after you get the piping, you check the flow in and out, like you already talked about checking the solenoid, what's your next
• 1:05
  Speaker 2: step?
• 1:06
  Um, if I'm verifying flow through the solenoid valve that I'm getting, getting power to it and draw signify that it's, it's working. Um, sometimes you can, you can watch it, um, cycle if it happens to be cycling on temperature or whatever reason it's cycling, you can see that, hear it, see it. And, um, verify if that's what it's supposed to be doing.
• 1:07
  And like I said, we see a lot of filter drives before that, that, that seem to block up pretty often. So, um, um, that you can do a, a temp drop across. Sometimes you can even, you can see it. You can see, like, if it's blocked well enough, just like you can in conventional refrigeration. If, if, if that filter drive is blocked well enough, you're gonna, you're, you're gonna see just by looking at it, you're gonna see a frost, a frost buildup or a metering, a metering going through it.
• 1:08
  Speaker: Yeah, no, exactly. You should not see frost at the outlet of that. Liquid line, a telltale sign there. So, but like you said, I like that is the, you take your temperature probe and check across it. If you have a five degree temperature drop across it, that's, that's plugging out. So let's talk about the steps.
• 1:09
  If someone asked to now. They got to change that filter dryer. What's your process in changing the filter dryer?
• 1:10
  Speaker 2: So what I do is I, um, find the inlet. You know, we talked about the pipes are the same size. So just use your hands, use your eyes. Trace your inlet from a solenoid dryer back to your nearest isolation points.
• 1:11
  And let that pump down to your return pressure. As low as you're going to go. And then move, and then isolate it. And then if you can, move the refrigerant elsewhere. And then, um, a lot of times the valves that we see are actually rebuildable. We can get a rebuild kit if the, if the valve is an issue, you can rebuild it, or we might have to replace it and stuff like that.
• 1:12
  Um, then the filler dryer, um, you just, um, find a corresponding replacement. Once you're isolated, um, safely, make sure there's no, um, fluid CO2 in there building up, and then you can just cut it out and braze in a replacement like you normally would.
• 1:13
  Speaker: Yeah. Uh, one of the, the thing is to make sure is that, like you said earlier, is When you isolate the, the inlet, you just wait, wait till it pumps out.
• 1:14
  You look at your, your gauges. If you close it off and then the pressure increases a ton again, then you start to know that, uh, there's still liquid in there. And then what's your best, what's your solution on pumping it out? You said, well, if there's still some in there, I pump it out. What do you do? Do you use a recovery unit?
• 1:15
  How, how's, what's your process of getting the last bit of CO2 out?
• 1:16
  Speaker 2: A lot of times, um, the stores that we have have a little bit of overfeed. It's not a whole lot of accessibility for, um, you know, gauging up and stuff like that. And I'm using a recovery machine. So, um, if we can get it down to return pressure, then at that point, Uh, maybe we can turn on the pump skid, another pump, see if we can get that return pressure a little lower to even get us even more refrigerant out.
• 1:17
  Similar to it, like I said, a conventional system, um, you close the liquid and you pump the rack down to suction pressure to get as much of that refrigerant out of that wrapper as possible, then isolate it. So there's a lot of things that'll go hand in hand with what we already do that some guys may not necessarily, you know, realize that you can do.
• 1:18
  Yeah.
• 1:19
  Speaker: And that's the big thing. And then when you're, like you said, when you're putting that filter dryer back in, the same process. Yeah. Wrap it, you know, make sure you don't burn, burn toward it. So you burn the filter dryer inside and you put it in just like you would do in a regular system. What's your next step to get that case up and running.
• 1:20
  So now you put that in, , pull an evacuation. If. If you can, like, how are you going to pull the evacuation? Where's your fittings? Do you have any fittings to pull an evacuation on the, those systems that you're talking about? Because I think that's important for guys to know.
• 1:21
  Speaker 2: Yes. Um, usually we have a, um, at least one access on the evaporator that you can gauge up to, um, to, uh, pull a vacuum.
• 1:22
  Um, if not, for some reason, I hope you put one in once you isolated it and got the system open. If you see there's no, um, access. And even if the access is actually on the wrong side of your ball valves, whatever reason But one on the, uh, case, the case side of the evaporator, just for, you know, future serviceability.
• 1:23
  Speaker: That's a huge tip right there. Because just because there's not one in there, doesn't mean you cannot add something. Right. And it's always better to burn one in than using those, you know, those. Three way valves or three way, uh, access fitting flare fittings. Don't use those things, burn those in.
• 1:24
  So you have less chances of leaks and, uh, and then you're the refrigeration mechanic. You can make that decision. You have them in your truck. You should have some stuff in your truck, add that in, and then it's going to make it easier for the next. Technician out there, because this is the same thing on compressors.
• 1:25
  A lot of guys, well, I talked to them about doing a blow by test. You know what I mean? From the suction to the crank. Well, there's no fitting on the compressor. Put a fitting on the compressor, the fitting yourself. You are the, the, the specialist, right? So, so the, so I love, I love that. Put the fitting on, pull a proper evacuation, get it down.
• 1:26
  And then what's your next step after you do that? You get the filter dry in, you got down below 250 microns. , What's your next step?
• 1:27
  Speaker 2: And then at that point, I'm going to open the, uh, the return of this, the evaporator. And then, um, well, I'll crack it, meter it, not allow all the pressure down there at once to make sure that I'm, I'm leak free and there's no other issues there.
• 1:28
  Then once I'm, I'm positive there's no leaks or other issues there, I will, um, open return all the way, open supply all the way. Um, make sure my fans are on, make sure all that good stuff is going on and I'm doing some other operation and make sure that that, um, perceived, , repair, it was the grip repair and verify that.
• 1:29
  Speaker: And I like that too. It's you crack it and you, everything in CO2, any valves you open, it doesn't matter if it's subcritical transcritical, you're always opening and closing valves slowly. Do not like HSC, you, you know, I remember just ripping them, even then you should be doing them. Yeah. Then we do them.
• 1:30
  But. You've got to take your time with CO2 because, you know, you could cause issues like potentially dry ice in a system, you know, you don't, you don't do it slowly. You could cause a hydraulic shock to the piping because you've got some, some system you have so much pressure, you know what I mean? So it's all just do it slowly, just do it slowly.
• 1:31
  So you get, Patrick gets a little bit of like, um, Pressure inside it verifies probably with soap or something that those, those filter dryer burns or, or the installs the braze in as well as access fitting. If he has there, he would check those with it's good. Now he slowly opens it to get it back online.
• 1:32
  So now you got your, your return opened up and then the next step I'm assuming is open up your supply.
• 1:33
  Speaker 2: Yeah. And I guess one thing I want to add before that is, um, once you, if you make any repair brace or something like that, um, everyone makes mistakes. Um, you can always miss the bottom of that brace joint.
• 1:34
  I'd rather see that, um, mistake with a mirror before you put pressure in the system and have to repeat that process all over again. So like, just actually double check your work and don't just assume that you're perfect because you know, we aren't sometimes. So, um, so, so get a mirror out, um, visually inspect it.
• 1:35
  Oh, it's a simple. Simple task. It takes five seconds, but I'd rather do it then than hear the hissing sound. So, and I've done that before,
• 1:36
  Speaker: you know, I've done it where I've got it and all of a sudden there's leaking and it's like another 30 minutes sometimes, you know what I mean? Yeah, you got to go back up.
• 1:37
  You got to do the whole process over again instead of just you know, getting out that little bit of gas is in there, your, your test gas for a leak. I totally love that because I think that's a great, great way to do it. So now, so that's the process of, you know, if you get a plug filter dryer, uh, it would go hand in hand, the same thing, if you have an issue with the solenoid valve, you know, that, that you're metering device for that.
• 1:38
  CO2, , overfeed system, same thing, same process so what would be a, another call that you would get our calls that you have gotten at these stores?
• 1:39
  Speaker 2: Um, A lot of times it's either, um, a case particular issue like we were talking about, and sometimes you might have an issue with, um, the primary side, the conventional rack, with the, um, the EEVs that are, um, that go to your heat exchanger for your CO2, um, they may get stuck wide open and you're floating out your, your, your primary rack, um, and that presents a whole other set of issues, and, um, so whether it be, um, EEV configuration, a failed sensor, transducer, something like that, Even that you just, you can kind of see that you see the flood back.
• 1:40
  You look over to heat exchanger and you see, you see all this flood back coming from there. And it's, um, that's just like kind of simplifying things to stuff. What we already know, like, where do you know, EVs, heat exchangers and stuff like that. So that's, um, some of the other issues that I've seen.
• 1:41
  Speaker: What are some of the controllers you've seen for those EVs?
• 1:42
  Are you seeing the sport on ones? Are you seeing, yes. I see the spoiling, uh, Calvin controllers, the Calvin controller. So that, that's a good point. I've seen lots of those out there as well, is you got to understand how to. Uh, work on those controls. They're not difficult. Like, No,
• 1:43
  Speaker 2: and the manuals are readily, there's like a 60 page manual on that Kelvin that breaks down every single parameter value, everything that, um, you can, you know, like, like we, we should all know how to do is go through a table of contents and be able to, you know, get to what we're looking for.
• 1:44
  And I don't think you necessarily need to know everything on top of your head in this industry because of so much information is readily available at your fingertips. So, um, like in that regard for any control, RDM, Danfoss, E2, Kelvin, stuff like that, you can probably find resources to help you wade through it.
• 1:45
  Speaker: Yeah. And once this is part of our job, like doing some research to get this system up and running, you know, so if it takes you 30 minutes to go through that manual for short, the end user, the contract want you to do that. So when you leave there, it's done right. And you don't have to go back and there's another, not another callback.
• 1:46
  What I see a lot of the times they look at it, like even me, I remember when I first started out a 60 page manual, Oh man, this is going to take forever and stress about it more and take 15 minutes of stressing about having to read this manual than just getting in and having that 15 minutes going through the manual and going through, even if you go to the troubleshooting section.
• 1:47
  Like a lot of these manuals, you, like you say, go to the index, where's troubleshooting and start there. Because if there's an error on the controller, you go right there and it's going to tell you exactly where to start. It doesn't mean that's the problem all the time, but that's where to start, you know what I mean?
• 1:48
  Oh, P1 is not working or whatever it is, you know, is that pressure, is that temperature? And then you go take a look at it. And a very simple controller, think of a TX valve. That's what they're doing. There's only electronic now, you know, and there's a few more things to check. What are some of your tips on checking an EEV if you're running into issues with an EEV?
• 1:49
  Speaker 2: Um, I think what you have to decide is if you're looking at an EEV or a stepper valve, and if it's like a modulating, you usually can hear it. You can hear it clicking. Opening and closing. Yes, and then make sure you actually know what you're looking at for sure. That way, if you have questions, you know, you know, the questions to ask, if you need to ask somebody and you got the answers, if they ask you questions.
• 1:50
  So, um, um, stuff like that is making sure you got tight connections, um, either way on the EV at your board that controls it or at your pulse valve, uh, make sure you got tight connections electrically and just stick to those kind of fundamentals there.
• 1:51
  Speaker: If it's a stepper valve, you've got to go into the manual.
• 1:52
  If it's Uh, Emerson, or if it's a Danfoss or if it's Borland or Corral, it doesn't matter. The, the manufacturer, you got to go in and check what their specs are for those valves as well. So some of them, you're going to have to own it out and you're going to see, okay, well, 75 Ohm, it's, it's a hundred Ohms, whatever it's 12 Ohms.
• 1:53
  It doesn't matter. Whatever it is, you got to go match it up and make sure it's right. And then go to like, to the body of it. So make sure that motor is not short. A lot of times you can just put your hand on it and you can feel it. It's moving. Yes. Okay.
• 1:54
  Speaker 2: Yeah, so you can, you can feel it, um, in here and stuff like that.
• 1:55
  And, um, like you said, um, Those various pulse valves, almost all those manufacturers have, you know, their own readings and resistance across the windings and stuff like that. There's step rates and make sure that, uh, perhaps the step rate is configured correctly in your Kelvin controller and stuff like that.
• 1:56
  Um, so like those things can change, you know, someone's in there doing something and they, they move the dial and all of a sudden the, uh, your, it's no longer configured correctly. So stuff happens and there's gotta be aware of that.
• 1:57
  Speaker: Yeah, and it's just understanding it like going always go back to that manual and go through it step by step, you know, you don't have to understand that the very first time you're looking at every parameter, but if you're working on these all the time, you should understand over time.
• 1:58
  What each parameter does. And that's where I learned it took me a long time to learn controls, but I really learned it when I was working with the people from Dixel, like the experts from there, and when we were going through a controller manual, and this was not during, not on a call, you know, but just step by step, every parameter I was going through with them.
• 1:59
  And then anyone I did know, I would circle, you know what I mean? So step by step, okay. I understand this is the fan one. If you do, this is fans on fans off, whatever it is, and then go through everyone to defrost. And everyone I did know I would circle. And then that's the one when I'm calling up technical support or I'm calling up the experts.
• 2:00
  I don't understand what this parameter means. It doesn't make sense. Cause sometimes we get manuals and it doesn't make sense. You know what I mean? The description doesn't make sense. Yeah. Um, and so those ones that don't make sense to you always follow up with tech support because a lot of people at, and I see this time and time again at the manufacturers, there's people there who want to help.
• 2:01
  You know, you might get a bad day when you call someone and they're not helpful and it's terrible, but there are other people that want to help. So call back and get the person who really understands the controller and then ask them those questions and because they want to help. And then the ones that you don't know.
• 2:02
  And then after you start learning them, you'll see when you read a Dan Foss manual or an RDM manual or the next one, they're all, they're all doing the same thing. It's just a different parameter name or list number, but they're all kind of doing the same thing. Right, so, so you check, you're running into an issue with the chiller, um, which is the primary system you see in flood back.
• 2:03
  What are some of the things that, that you would check? You said you'd check the temperature probe, you'd check the pressure probe, you'll go into their parameters. If you check all that stuff and that was looking good, is there any
• 2:04
  Speaker 2: other things that you would look for? Um, you always want to make sure your pressure transducers, um, and your sensors are reading spot on, and then make sure that, um, those are correct, and make sure they're configured correctly, like I was saying, make sure it's, you're configured correctly with the EEV.
• 2:05
  If it's an EUV and then make sure that, um, if it says it's at 100%, does it, is it, or is it, is it lost? Is it confused? Or is it stuck? And stuff like
• 2:06
  Speaker: that. Because this is, this, depending on the valve itself, you'll read in the manuals, you cannot jump a remote to run 24 7. Because they don't have the feedback signal.
• 2:07
  So over time, over months of just running and running, you can start to lose steps. So sometimes you have to reset them and it drives them right to their original position. Or even has extra steps to drive it even further. Yes, yeah.
• 2:08
  Speaker 2: Yeah, um, a few mayors will say to drive it like, um, X and O percent over.
• 2:09
  Um, closed or open to, you know, fully reset it and get it back on its pace.
• 2:10
  Speaker: Yeah. And that's, that's important to understand because you could be looking at no electronic valve should be a hundred percent open if you're almost satisfied, you know what I mean? If you're almost satisfied and that valve is still a hundred percent open, is it blocked?
• 2:11
  Why isn't the flow getting through? Is it lost percentage? You know what I mean? Because if it's If it's a, after a defrost, if it's a hot pull down for sure, it could go to that a hundred percent, but when you're close to make them that, that temperature, it shouldn't be at a hundred percent open.
• 2:12
  Speaker 2: Yeah. Then you got to start looking forward and, you know, your supply, are we getting our liquid refrigerant to it in the first place?
• 2:13
  And is that why it's, it's wanting to be 100 percent open? Is it actually open? Like you said? Yeah.
• 2:14
  Speaker: Yeah. And one of the things we were talking about, we're talking about now, maybe it's flooding back. You could get that call in the middle of the night and you go up and it's compressor one or two or three just say washed out, there's no oil in there and it's an oil failure control and you go reset it and it runs totally fine, but come to realize it's really has nothing to do with the, the oil failure control, it all has to do with that electronic valve flooding.
• 2:15
  Sending too much liquid back to that rack, that primary rack and washing it out. Do not just go and reset oil failure controls, because if you do, you might not be able to figure out the problem. You got to look in the compressor. Is there oil or is there not oil? Yeah, a lot of steps there. Have you ever come across that?
• 2:16
  Speaker 2: Oh yeah, um, I think as you know, like oil fail calls are like, you know, a big issue in the industries because there's so many different possibilities and stuff like that. And you know, there's many different steps that you should be going through before you just press the red button and then, you know, walk away.
• 2:17
  So that's all dependent on the type of system you're working with and, and stuff like that. So that's, um, based on what system components you have is, um, is to some of that based on some of the things that you go through on those oil fails. Thanks.
• 2:18
  Speaker: Yeah, I totally agree with that. Um, there's lots of, lots of stuff.
• 2:19
  And oil was really difficult for me for the first five, four or five, six years, honestly, until I really. Spend the time learning about all these different possibilities. Um, so getting back to the liquid overfeed system, we checked the evaporator. We kind of understand if you run into a pulse valve issue or a solenoid issue or a filter dryer issue flooding back.
• 2:20
  What are some of the other things you may see on one of these systems as an issue?
• 2:21
  Speaker 2: Um, I guess the most common is low CO2. We have, um, a low CO2 level and then that's just, um, getting back to, you know, our basics, um, verify we have a proper refrigerant level inside of the side of the vessel. And, um, if, if not, where to go, find the leak, add it as necessary and stuff like that.
• 2:22
  Speaker: So one of the big things that I've seen many, many times is where, um, a pump. And I've heard this from lots of manufacturers, a pump would fail. And like, why these are 10, these are expensive pumps. They're way more expensive pumps than the glycol pumps. Yes. Okay. So you have this 10, 000 pump, uh, fails well, and then you replace it and all of a sudden it fails again.
• 2:23
  Why? Well, sometimes, or not sometimes on them have the, um, a level liquid level control for the CO2. And so they'll have sensors, they'll have sensors inside this level control where, and I don't know if you've seen these before, but they're measuring, um, How much CO2 is in that system. And then all of a sudden one of them could be full of carbon and it thinks that there's liquid CO2 in there, but actually there's no CO2 because it's plugged up and it's sensing that there's stuff there.
• 2:24
  Have you ever come across where those eyes are, are dirty or plug?
• 2:25
  Speaker 2: Luckily we haven't had any pump failures in my time here because, um, you know, some of the, the PMs that we do, um, hopefully. Yeah. Um, allow it not to happen. Yeah. So, um, luckily we haven't had that misfortune yet, but, um, certainly I want to make sure any of those features are operational.
• 2:26
  Speaker: . A hundred percent. And so, cause that's a, one of the big things is sometimes something fails in the system, but it's due to something else, you know, and if you just change the part where they'll follow through. Following that root cause or that, that process, everything's a sequence. When you understand that sequence of how it goes, where does the sequence stop?
• 2:27
  You know what I mean? And figuring that out. , okay. Let's talk about your low on gas. How do I get CO2 in the system? What is the process there? Because if that's one of the biggest things that first step is you got to find that leak, you know what I mean? You got to find the leak. Uh, I think this is one of the biggest issues in all refrigeration and HVAC industries is there's a leak.
• 2:28
  You got to fix that leak, find it. And it's not just, uh, an access fit, you know? Oh, it's just a little access fitting. I lost 200, 300 pounds. They're Schraders. Yeah, Schraders. So what is your process? You come to a store, it's low on gas. Cause everything's starting to warm up a little bit. What's your process on charging?
• 2:29
  Speaker 2: Um, usually in the, uh, the skids that we have, have a, uh, charging ports designated that, um, charge here. So, um, a lot of times, um, these are, um, On the, on the second story or the roof. So, um, hopefully there's, um, there's, it's a charging line going to the roof. We actually have been to some, we have some locations that don't have that charging routes, that charging line.
• 2:30
  So that, that gets things a little more complicated, but, um, we usually charge at, uh, at the pump skate at where they, the designated charging port.
• 2:31
  Speaker: . And one of the things is that you already have CO2 in the system. Usually you're not empty. You're not below your trip. Oh, yeah. Right. 61 PSI, uh, you know, four, 4.
• 2:32
  3 bar, whatever you're, you're above that. You still have CO2 in there. So you don't have to charge vapor. First you're charging liquid, but these, these cylinders, they're different than the standard HFC cylinders. You get like 60 pounds of CO2, but the cylinders are like 200 pounds. They're way heavier. Way heavier cylinders, you get way less refrigerant in them, so just be aware of that, um, when you're moving these.
• 2:33
  Speaker 2: Yeah, for sure, um, um, you got guys that'll walk up to it thinking it's a regular 160 pound, um, HMC cylinder, and it's 260 pounds full, and stuff like that, so, um, definitely gotta be cautious of that.
• 2:34
  Knowing actually how much refrigerant is inside of it, like, like you mentioned, there's only about 60 pounds in there.
• 2:35
  So, um, be mindful of that, it's not a hundred, it's not a hundred pounds, it's not a hundred and forty, just, just around sixty.
• 2:36
  Speaker: Yeah, because you go, okay, well I need three hundred pounds, let's grab three bottles, well, no, you actually need five bottles, you know what I mean? So that's a, that's a big, big difference there.
• 2:37
  Awesome. Awesome. There's, there's lots of, so many great tips. Any, anything else you, you can think of for the liquid overfeed systems?
• 2:38
  Speaker 2: Yeah, basically, um, most issues I see are with, um, the heat exchange in the EV or a case issue, particular to like the dryer valve that we talked about. Um, And then just like the, the, uh, primary system, the conventional rack that we all, we all know, and that's, they're, they're really not that complicated.
• 2:39
  Um, when I first was introduced to them, I'm like, what is this? Why is there a solenoid with, you know, CO2 sitting in this coil, boil it off. But then once you just like do a little bit of research and break things up into pieces and, um, and go from there, it's, it's not too bad. And the big thing is
• 2:40
  Speaker: it's, it's refrigeration, you know, this is the stuff, if you spend a little bit of time researching and learning, it's not difficult, but you do have to spend that time to do it, you know, and it is intimidating and it is overwhelming, but if you're curious about it, you know, you can get through that call, you know, and just like Patrick said, these calls are not DX rack that you're going to get.
• 2:41
  Maybe it's different components on there. But it's the same thing, you know, frozen up coil, issue with maybe a valve, the metering device, compressor, like system flooding back, you know, all these calls are no different than what you're going to get on a regular conventional system.
• 2:42
  Awesome, Patrick. I want to, I want to thank you for taking the time. We're going to do this again. I really enjoyed chatting about this, but I think this was a really good point of, uh, that we made and then some great technical, uh, tips there. Any, any final thoughts for any technician going out to work on a liquid overfeed system, CO2 system?
• 2:43
  Speaker 2: Um, just to make sure that, um, Like I said, I, I tend to look at that primary system, like conventional REC first to make sure that is, you know, that's kind of the heart of the system I look at and make sure that that's operating, um, as it should, um, and it's even a little easier for most of us because that's what we've seen.
• 2:44
  So, um, start with what you know first and then, and then branch off to the liquid overfeed side.
• 2:45
  Speaker: Patrick, I want to thank you for taking the time to chat about, about this. I learned a ton and I appreciate you taking the time to chat with everyone here at Refrigeration Mentor and we'll do this again.
• 2:46
  Speaker 2: Alright, thank you Trevor. I appreciate it.