Latest / The Refrigeration Mentor Podcast / Episode 332. 7 Transcritical CO2 Refrigeration Service & Maintenance Tips

Transcript

Episode 332. 7 Transcritical CO2 Refrigeration Service & Maintenance Tips · The Refrigeration Mentor Podcast

• 0:00
  Speaker: What's up everyone? Welcome to the Refrigeration Mentor Podcast. So glad you're here. We're gonna be diving into some CO2 today. , Heavily involved in CO2 for almost a decade now. I think it's, yeah, it is a decade now where I've been learning, growing, getting better, but I'm always learning. Be honest with you.
• 0:01
  The biggest thing is though, is I want to talk about some of the. The service and maintenance tips and I, I think this will, hopefully this will be helpful for you because I really want you to be confident in what you do with CO2. I know it's new to a lot of people, but it's not new to a lot of people as well.
• 0:02
  What is that baseline of a system? Because when the sy something's going wrong, how do I, I know what to look for And that's the biggest thing. What is that baseline? And so why does this really matter? Because CO2 systems are very dynamic. , Without like a clear baseline, you don't know because at that point you're really chasing ghosts, you're chasing, you're chasing your tail potentially, if you don't know what that baseline is, at least a clean baseline.
• 0:03
  And I want you to talk about this with your team. This should, you should do a toolbox talk. So if you're a service manager or your lead technician, you want to talk to 'em about this, maybe even listen to this podcast with them. , Because what I think this is just from me. There's many other podcast episodes I did with different snapshots and, and different lung.
• 0:04
  The level percent, so how much CO2 is in there. And then as well as that opening presented of that flash gas bypass valve, that constant pressure valve. Some people call it the receiver bypass valve. There's many different terms for it. I think number six would be getting the medium temp suction pressure, and temperature and header superheat at least.
• 0:05
  So in your, the summertime would be a baseline, and then the wintertime would be the baseline. And then you can compare to weekly trends. So, 'cause now you have a baseline. And a lot of the controllers today, which is great. Like the microthermal, the E threes, the IDMs, the Danfoss. You got lots of great grass.
• 0:06
  So those would be a couple of red flags in that one. So I think that that would be number one. Get a baseline for your store, your or your team. And this should be actually done. After the commissioning, then after they do the, the filter replacements, and then they do all the cleanup that the recommended manufacturer does, and then you get that baseline.
• 0:07
  That's a seasonal tool. It's not an always on crutch. So you gotta remember that. So one of the things to do is it's something that you can take action on at one of these checks in the field is measure the approach in dry mode. So you really co compare and compare that to the baseline that we talked about earlier.
• 0:08
  You wanna make sure that you're, when you're looking at the, the coils, they're not scaling up. And if you have the pads, like Paul Noreen from BAC, he actually came into my CO2 course, which was super cool, gave me lots of great feedback of the course. But he was like, Trevor. One of the big things is, is that they, we need to clean the, the pads properly.
• 0:09
  We've seen it many, many times. And then you want to inspect the nozzles too, like I talked about the pad earlier. But on the, the misting or automizing systems, you gotta check those nozzles and make sure that they're clean. You scale flush any of the scale and, and check for any damage on check confirmed drainage on the, the gas cooler, the atic gas cooler, make sure the, the float working and then the drains are working, and all those things that, that's something that you really want to check out.
• 0:10
  So if you clean the pads, but you still have that high approach, , your gas cool out versus your ambient, there's something else going on or there's something going on, you gotta dive in deeper. Okay, another one. I think the next one could be high pressure valve optimization and control. Really control sanity.
• 0:11
  He's the guy who owns SEP Tech now. They're owned by Ref Plus. But we were working on the trainer and we were looking at the trainer. Yeah, and we kept running pressures super, super high. And what was the problem was that high pressure optimization that, like, that limit that we had in there was too low.
• 0:12
  A long way. But when we were sitting down looking at it, and there was this one set point that was set for, I think it was 1,250 PSI, and we had, we turned to 1450 PSI and then all of a sudden that whole unit just. Just was not running as hard and it just started running. It wasn't tripping off on hot, on on high pressure.
• 0:13
  This is on the roof. It could get the temperature change. It could go from minus 30 all the way up to 110. What I mean? Or it goes from, the minus 20 Celsius, all the way up to 40 Celsius, ambient outdoors. So you wanna make sure that the insulation on there, you could cover it and make sure it's on there.
• 0:14
  Once again, anytime you see like a saw to up and down, up and down hunting you wanna make sure that you address any sensors. And filters, and you check all this stuff before you start playing with the PNID or tuning the PNID because. You have to, you have to start doing some of that. There is, with these systems, if you want them to run the most efficiently, there is some PID tuning you gotta know how to do this stuff.
• 0:15
  So that's, that's something really, really to understand. I think another one could be like flash tank stab ability, , that liquid quality cases is so, so important. All these valves work in sequence. They're all working as a team. Like I said earlier, if you have a bad high pressure valve, that one's hunting, that's gonna make your flash tank hunt, which is gonna make your cases hunt.
• 0:16
  System is running efficiently and effectively, but really think of that, that flash gas bypass valve, that bypass valve, that receiver bypass valve, that, that constant pressure valve, whatever you want to call it, as like a controlled leak. And think of it as like if it, if it's pinned, , something upstream isn't right.
• 0:17
  You wanna avoid hitting the top and bottom. 'cause that, once again, that's hunting. If you're going 60, 70 PS, I, , five, six bar up and down, up and down, that is an issue. The, you gotta look at what's going on. Why is my valve my flash tank reacting like that? If it has a strainer, you gotta clean that, that flash gas bypass strainer.
• 0:18
  CO2 going inside these, these gaskets, when you take them out, they're gonna swell. So you're going to have to have the replacement par it's there. Make sure you check the differential at each case. Realistically, if you run an issue, what is that differential? So it's really that flash tank pressure versus that ca that, that case pressure, , and anytime you have a low delta P across, you gotta check for the liquid filters or if any lines are undersized, something that that can happen.
• 0:19
  That receiver line, going back to the median temp suction header doesn't get liquid up that high. Okay. So that's something that you really want to make sure. And then I, yeah, I think that that's so important. If your pressures do start to reach or you start to get close in the flash tank to having a blow off or popping that relief valve o open it back up.
• 0:20
  If you have a lot of ex vs hunting, , is there a vapor in the liquid lines? Are you getting alarms or cavitation at the EVs? This can happen, what I mean? You have flash gas at those EVs that that could cause some cavitation. I think another one I would say this would be number five would be, you gotta understand superheat.
• 0:21
  That's a bad. Sensors give false confidence. So really, really what you wanna do is trust but verify. , Compute the super heat with your own instruments at the pipe. This is what you gotta do. You can't always rely on the electronics. Like I said, trust, but verify it. A lot of people get into situations where the high pressure valve is not working or it's acting erratic or the, the.
• 0:22
  And if that soup breed, that those compressors not right, that you're going to damage the most important component, one of the most, they're all important, but the, the most expensive component usually in the system and some of the things that you can do in the field to check this is, . Pick a medium temp or a low temp case and measure the evaporator at lead temperature and press and pressure.
• 0:23
  It could be that your soup eat set point is too low. It could be that the PNID or adaptive soup eat setting is not. Set correctly. There's quite a few different things somebody could have played around with a maximum opening, minimum opening set points. There's lots of different things that you can take a look at.
• 0:24
  You just gotta understand. You wanna make sure after defrost you confirm that superheat gets back to target range promptly not, it doesn't take a half an hour to get back to the proper superheat. You want to make sure that, to check any heaters and terminations and fan delay, you gotta check that stuff.
• 0:25
  Okay? And this is where you gotta get into the bits or software, the Copeland software, the box software. Oh, Darrin software. You gotta get into their, their softwares and check that out. And one of the things that could be a red flag for sure is like frosted suction headers. Okay? If you have a frosted suction header, sweating compressor shells or any reoccurring low suit, low super eight alarms, that is something that would be a flag for me.
• 0:26
  So just, just make sure that would be a, a flag for sure. I think number six would be oil management, , and that, that separator and but oil re return hygiene. Okay. Getting that oil back to those compressors. And this is super important because CO2 density and the operation range makes that oil really finicky.
• 0:27
  Just putting the, the compressors to the limit, , and the flooded start just, just smash and smash it away. Short cycling, sorry, not flooded. Start short. Cycling and just putting these compressors to the test. So when they do fail, just like if a COPA fails or a bitzer or a Bach, it's that we potentially.
• 0:28
  Temp, right? Whoever the manufacturer of the coalesce is separate, you want to get that delta B no different than in su like supermarket refrigeration. We want to get to delta B. The delta B is the same, and you look at temp, right, and Western ma, you want to keep it really below like that. 13 PSI Delta P from the internet out of the separator or one bar.
• 0:29
  Log each compressor oil level at like a steady state. Anytime you see higher, low oil patterns, what, what is that? What is causing that low oil in those compressors or the high oil? We gotta figure that out. Check the coalescent pressure differential, like replace that element if you need to. And then always , trend.
• 0:30
  You wanna always observe the sight glasses. You always wanna look in the reservoir site. You wanna check the, the the sensors on the oil separator, the oil reservoir receiver. You want to check the sight glass on, the oil level controls, if it's O-M-B-O-M-C, om five, what Cree want. It doesn't matter what, what it is.
• 0:31
  If you have a lot of oil carryover, if that's chronic you gotta check what that suction gas velocity is. Okay. Really look at any long horizontal runs or anywheres where pipes might need to be fixed. I've heard a story there a few, I think it was a few weeks ago, where someone said, yeah, the.
• 0:32
  You gotta follow, follow up, and if you're unsure, if you are the lead foreman and you're unsure, size it yourself. There's tons of calculator. You can go right to, to Danfoss for easy one. There's tesis, there's HVAC advisors. There's so many different easy single software, virtual engineer by spoiling.
• 0:33
  Or even noisy starts up on the compressor that, that there would be red flags for me. Oh, okay. And one of the checks that not enough technicians, I see more and more doing it now, been preaching this for seven or eight years, a long time. So ever since I started really heavily trained compressors back in my Copeland days is that discharge tampon check on every compressor, not just on the header on.
• 0:34
  Gotta be safe out there. We're working with chemicals, we're working with electricity, we're working with oils. , We, we want to be safe out there. And this is so important because CO2 is high pressure. And if you mishandle it, it can create dry ice and blockages. You can over pressurize trap sections for sure.
• 0:35
  Or seven bar for sure. What I mean? There's different set points. They're not gonna go through that right now. You can come to the intro to CO2 course and we can walk you through that. But where it will happen though is when you're changing an oil filter for an example. And we definitely talked about this in in the CO2 training programs that, so if you need to change that liquid line filter or dryer, you're gonna hook up your, hook up the proper gauges first.
• 0:36
  Say a recovery unit and you'll pull that 200 PSI out there and put it back in the system so you're not leaking any CO2 out of the system. A lot of people ask me, well, is there a CO2 recovery unit? Well, I don't know of any yet, but four 10 is a, a lower pressure than 200 PSI. Vapor. So find out from your manufacturers.
• 0:37
  Just say in that filtered dryer. Second, I've seen it lots of times. It's not always easy to do and sometimes you just gonna cause dry ice. There's certain parts. Sometimes if a strainer is is damaged or bust it in the liquid line, you gotta isolate it. You only can isolate that part, then you gotta cut it out to get it back up and running.
• 0:38
  Make sure that they're up to date. Ensure any anything is clear. You don't want anything in those pressure relief valves that could plug it up. And you always wanna make sure that the they're pitched properly and are properly vented to the outdoor safely. What else? You want to make sure you always follow lockout tagout and PPE, what I mean?
• 0:39
  'cause when you're on call and you have a rack down and what the startup procedures are on, just say 'cause of a fuse blown or a phase monitor trip because power issues, what those startup procedures are and you can feel at least a little bit more confident when you have that rack down.
• 0:40
  Like have it at that store and here's the baseline, here's the date, here's what it looked like, here's what all these pressure baselines work and, , and, and then write that down, , because. Having a, a stable system really is your friend. It really, really is your friend. If, if this helped, , share this with a tech who is new to CO2, that's what I asked you.
• 0:41
  Okay? The first one would be that ambient dry bulb at the gas cooler inland, what is that? Ambient dry bulb. Okay. Second would be that gas cooler outlet temperature. Actually go check this stuff. You need to use your tools and go check this stuff. What is that approach? So they do that calculation, gas cooler outlet minus the Ambien.
• 0:42
  You get that. The level of the flash tank. So what, what is the liquid level in there, as well as the percentage of that flash gas bypass valve. The next one would be the medium temp suction, pressure, and temperature. And this. The header Sube, at least the header. It would be great to get all the compressors as well 'cause that's really important, but at least the header sube.
• 0:43
  But once again, you gotta check the calibration of those sensors as well. So if you verify the sensor work good, you can use it. You can go off the, the, the controller. And I think number 10 would be that liquid filter dryer, Delta P. Hope you enjoyed this list. Hope you enjoyed this podcast, and if you took a few things away and if it helped your day out or helped your team out, that is super, super important to me.