Latest / The Refrigeration Mentor Podcast / Episode 298. CO2 Experts: CO2 System Troubleshooting and Fine Tuning (Part 2) with Chris Brown of Danfoss

Transcript

Episode 298. CO2 Experts: CO2 System Troubleshooting and Fine Tuning (Part 2) with Chris Brown of Danfoss · The Refrigeration Mentor Podcast

• 0:00
  Trevor: Welcome back to the Refrigeration Mentor Podcast. This is part two of the episode I did from CO2 experts with Chris Brown from Danfoss. We dove into controller troubleshooting and CO2 racks, and this one here is really, I. The technical side of starting up, some technical tips, the things you need to look for on a startup to really be proficient on getting that rack up and running, or getting to a point where you can start adding gas.
• 0:01
  One of the nice things about the pack controllers is we make it pretty easy where maybe even in our own devices, historically it was, you're, you're talking about PID algorithms and so you have your integral your gain, these KPTN settings and people are saying, well, it's a unitless value. What number do I put in there?
• 0:02
  And that's when you start to talk about reliefs and, and we don't want to ever have that conversation when it comes to the, the, the receiver pressure or anywhere else in the system for that matter. And then on the low end you can see that it was the, it just is a concerning of a problem that we were getting down to 400.
• 0:03
  Chris: Yeah. And, and this is on a, in a per area, this setting, you're, it's not just one common one for the whole system. It is. You'll have one of these selections for the receiver bypass. You'll have one for the gas cooler fans, one for medium temp selection.
• 0:04
  It's really, if you, you, you can dolly systems in and see this large of a difference in performance where, what was over a hundred PSI swings in pressure. You're, you're getting these down to maybe 30 pounds swing, which is much more manageable. Reasonable. And, and it, yeah. Like you said, it. It, it stays in line with how some of the other components were selected from a sizing standpoint with something like your expansion valves
• 0:05
  Chris, maybe you can correct me, Brian, you could have changed this to say seven faster, just easy PI selection. But if other things are not working properly, you're not gonna fine tune this properly.
• 0:06
  What is your top end? What is your lower end? What is your actual set point? Why are they there? You know? 'cause I, I love the graph and then we walked through it. We did a, a training last year, the year before, walking through. Out of the ECK 3 26 manual. That graph is a beautiful graph for, for that controller.
• 0:07
  It all depends what you're trying to do. 'cause with heat now trying to get heat, doing heat, reclaim heat pumps with CO2, it's a huge different dynamic and I love it. I love it learning so much.
• 0:08
  And just starting at the top left here with troubleshooting, it's the rack superheat. And so again, maybe this is one of the ones that's more on the, the front end of the, the license lifespan or lifecycle of the rack. But we talked a little bit earlier about how do we go about troubleshooting If the rack is getting alarms for low super heat, are we concerned about flood back?
• 0:09
  And this is where the history logging that's happening taking place really helps. Is the low super E only happening in certain parts of the day? Does it go away at certain parts of the day? Maybe where that, that case that is problematic is in defrost. So you, you can really use the data in the system to try to pinpoint where, if it is gonna be something from an evaporator where that that issue lies with the super eat so that you can address it at that case and, and, and not sit there scratching your head trying to figure out where it's coming from.
• 0:10
  Make sure you clarify what they actually mean because there's a lot of terms out there that aren't misused but aren't, they're not always talking about the same setup. I
• 0:11
  So both of these hot gas and the liquid injection, now you're, you're not looking down on the sales floor at the cases. Now it's what up at the rack could be potentially causing low super heat issues. And these are things with CO2 systems that we see utilized pretty regularly in the designs with the liquid injection.
• 0:12
  So the, these are two areas within the rack that you want to focus on if you're having super eat issues. It can be a simple checkup manually driving these valves in both directions, monitoring your rack superheat, and seeing if you see an effect from them changing state, because if you don't, then that might be a sign that, hey, something's wrong here.
• 0:13
  So really important to take a look at these and the sequence of operations, this is not Chris or Danfoss setup. You gotta go to the manufacturer that is designing the system. 'cause it could be different. It's not gonna be the same. I've seen a lot of setups from different manufacturers from all around the world and they do it differently and there's reasons why they do it lift differently.
• 0:14
  What we are controlling is between the separator and the reservoir where we have a solenoid valve. We are controlling the flow of that oil out of the separator into the, the reservoir through a, a setup in our controller. And it's primarily dictated based on level switches in the separator. So when you look at these oil separators for the CO2 systems, it can have either a high level switch, a low level switch, or both.
• 0:15
  So you could do things like jumping out the level switches or manually forcing them into a position through the controller and then watching the solenoid, which it's usually going under a pulsing strategy, but making sure that solenoid really is opening and closing and then that, that, that oil's getting over there.
• 0:16
  Trevor: Yeah, and that's key. I was with Ernie Lynch last week. Shout out to Ernie. He's on here talking about oil management set up in the Danfoss controller, and he walked and explained it.
• 0:17
  But, so this, this is our service tool software here. And you can see we do have an area that's dedicated to oil management here. And within this setup, here's kind of a screen that you really want to focus in on for how we control that solenoid. And so we start let's start at the bottom half. We've got a number of periods, period, time, and open time.
• 0:18
  Trevor: So on startup, if they put this in and all of a sudden that separator was still seeing a level, they would have to upgrade the periods or should they upgrade the time? What would your recommendation, because now you get big oil separators, you get small oil separators depending on the size of the system.
• 0:19
  We start to run through however many pulses we've defined here or periods. And at any point in, in that sequence, if we see that we drop below the low level in the separator, it'll just stop what it's doing and stop feeding oil into the reservoir on the spot and, and cancel the rest of the periods again, until we show another high level.
• 0:20
  And then if that level switch in, the oil separator still shows high. After we've run through these three periods that we have here, we've got this repeat function. And this just simply says, if I'm still showing high, I'm gonna wait the defined period of time that I have here. This is one minute. You could actually make it instantaneous if you want.
• 0:21
  Chris: So this would be related to that high level switch again. So if we go through this period of time, and you can see we, we kind of extend this out. We don't necessarily want to create nuisance alarms off of this, but this is essentially saying if the high level switch in the separator has stayed high for this period of time, this is when we would eventually generate an alarm in the pack controller to say, which might have a problem.
• 0:22
  There are times where we see, maybe it's a nuisance alarm, maybe it's not a nuisance alarm. Maybe there's something a bit more realistic or, or something that actual, that needs to be addressed. But we do see issues where we'll get these alarms because the low temp discharge pressure has gotten too high.
• 0:23
  It's more so focusing on making sure the media temp compressors are doing what they're supposed to.
• 0:24
  We are gonna shut off load temp compressors. And obviously in turn with that, you would start to see load temp suction alarms and then your, your alarms for high temperature on your load temp cases if this is happening. So. Again, this could be anything for medium temp compressors. Maybe we have one or two of those that got locked out.
• 0:25
  The advantage of doing this is it reduces the cycle count and that median temp compressor, and we also are a bit more prepared for a load that could be coming in from the load temp side. If we, maybe we have a freezer that just came outta B frost and there's a quick increase in the load from the load temp side.
• 0:26
  We're starting to see some implementation of that on the CO2 system. So maybe we were running 400 PSI medium temp for six months or a year, and everything was fine here, and then all of a sudden the suction floating strategy got turned on, and now maybe our medium temp suction is climbing up a few pounds higher than that because of the suction str or the floating strategy rather.
• 0:27
  Yeah. So right now customers are paying money for these features that aren't being used. And I've seen this for over the years and years, but as we talked about, as the shift happens, we're gonna see more people start to embrace this stuff and get understand how it works. Because that there's a huge amount of savings there.
• 0:28
  And so when, when you walk in and everything's down, I think just again, based off of past experience, one of the, the first checks I think that's worthwhile is knowing that most of these jobs do have a phase loss monitor wired into our pack controller so that we can shut everything down if we do lose a phase is checking to see if that's the case or not.
• 0:29
  But that, that phase loss monitor is, is definitely something that you want to, it, it's a quick check. Most of 'em have an LED on it. And then with our controller, our pack controller set up, it's a quick check there as well to see if we're showing that we're shut down because of that phase loss. And, and that could be the, the magic answer to everything there.
• 0:30
  How do I properly shut down a CO2 rack versus HFC? Because in CO2 systems, you don't go and just shut all the breakers. You cannot do that. You're gonna pop releases. There is a sequence of it. It's built into the. Danfo controllers where the manufacturer will step their sequence in how they wanna shut down the rack and start it back up.
• 0:31
  Where did I lose my charge at so that I can try to understand what's going on better and see if it's something that I, I, I do need to address. And so this is where the history is gonna help you out. I mean, just tracking the pressures throughout the system, it's which pressure exceeded the limits of, of the relief valve first or at all period.
• 0:32
  You gotta figure out what act, what's the story, you know? And I don't think, I think a lot of the time we're, as a technician, we're out there, we need to get up and running, we do whatever we have to to get it started. And, and since it's new, we're doing some things maybe we're not supposed to do. I've even seen it on HFC racks even now, still.
• 0:33
  This is where I see a lot of issues with systems. A lot of popoffs happen, or relief events happening. Systems like we showed earlier. Those, those that flash tank up and down. When you understand the sequence of operations from that specific manufacturer, why it's supposed to do what it's doing, it's a game changer for your troubleshooting out there and calling up Danfoss and asking, what is this manufacturer's set points?
• 0:34
  He's got a whole team that wants to help you out there. So you want to get to that right person on that right day who understands that system. They can help you a lot quicker. That's why they got the support lines. Chris, how can people find out more about your support team if they're working on this product and and they need to learn something?
• 0:35
  This is something we've had out for, for multiple years, but really in the last 12 months is where we put a lot of time and effort into it so that this website we have, it's dan false.com/supermarket support for guys that can, can remember that or want to write that down, but. This is really what we've tried to make a one-stop shop.
• 0:36
  These are anything from standard documents that were already created by Danfo to more regional and customer specific US and Canada. Documents that my team has made up based on questions that they're getting asked by the customers here in the region. And then maybe the most time and effort that we've put into is this video section.
• 0:37
  Yeah, this is an area that you can kind of lean on as well in addition to what we can offer directly with, to, to supplement that some and say, Hey, I, I know this resource is here. Let me go check and see if what I, what I need an answer to is here real quick before I pick up the, and give somebody a call.
• 0:38
  And this is what you want. What I would love for you to do as a technician is to learn and grow and help uplift the industry. Any final thoughts, Chris? For the technicians out there who are listening today.
• 0:39
  Because it's, I mean the, the technology's not going away, right? It, it's just gonna be become more mainstream as we move forward. Yeah.
• 0:40
  And Dimitri, I'll get back with you on that. I think it's the MOP Is there MOP settings in your controllers like. I'm pretty sure there is. So your suction pressure gets so high, it stops the valve from opening anymore to cause a high pressure situation. Is that correct with your A KV?
• 0:41
  Chris: I know just to, to, yeah. With our case controller specifically, that is not a hard cutoff where if we have, let's just say a medium temp 450 PSI for that max operating pressure, it's, it's not a, we got the 4 51 PSI and that valve is gonna go to fully closed.
• 0:42
  What did he think about that episode? Like that? There was, there was so many gold nuggets in there. Definitely, definitely. You're gonna have to re-listen to that, especially if you're doing startups. This is key. And those tips that Chris gave us there, man, I learned a ton from, from that session. And I look forward to hearing from you.