June 2, 2025 • 32 mins
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In this episode of CO2 Experts, we’re shifting from advanced technical concepts back to the foundational principles of CO2 refrigeration by diving into basic keywords and terminologies. We cover entropy diagrams, saturated lines, subcooling, and the critical point, as well as plotting system parameters to troubleshoot more effectively. We’ll also discuss differences between global terminologies and give refrigeration technicians practical tips for mastering transcritical CO2 refrigeration systems.
In this episode, we cover:
-CO2 refrigeration keywords and terminologies
-The entropy diagram
-Saturated points and vapor states
-Flash gas and system dynamics
-Critical points and supercritical fluids
-CO2 safety
-Plotting and troubleshooting CO2 systems
-CO2 system design strategies
Helpful Links & Resources:
Episode 130: Decoding CO2 (R744) Phase Diagrams w/ James Seabrook & Parham Eslami Nejad
Episode 285. CO2 Experts: Transitioning to CO2 as a Service Technician Q & A with Andrew Freeburg
Episode 299. Basic Refrigeration 101
Episode 115: Understanding Compressors: What You Need To Know
Mark as Played
Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
(00:00):
Well, welcome to another CO2 experts. This week we're gonna be diving into some of the basics of CO2. I know we've been diving deep into some of the heavier technical stuff over the last , four or five weeks. And now we want to, I want to dive in, go back to the basic talk about some of the keywords and terminologies I, which I really believe is super important to.
(00:01):
Some things that are, are used in Europe aren't the same here in Canada as, or the US or Australia or New Zealand, so it's really un. Getting the foundation of those key words. And I think this is really, really, really important. So if you're listening to this on the podcast, after it's recorded, you might want to go to the YouTube channel and check out the slide.
'cause we build customized supermarket programs, customized CO2 programs for contractors to really level up your team. So what we, what, what do we have here? We have. Entropy diagram. And for all those of you who are joining, please share where you're from. Calling in from. I love seeing where you're at in the world, learning, growing.
So as we can see right here, this is called, some people call this the bell curve. This is the saturated lines. First step is understanding what's on the left side of it. So if you're looking at a diagram on the left side. Saturated liquid or the bubble point. So that's very, very important to understand because as that refrigerant transitions to different states.
There's, , 10, 12, 15 degree glide in some of these refrigerants. It's like to design like an SST and design a coil for that is very difficult for CO2. It's not that difficult, a single blend. You wanna understand what that I. Dew point is, or the vapor point. So, 'cause we always wanna make sure that we have vapor, going back to those CO2 compressors, the booster compressors, or the trans-critical compressors, we wanna make sure that we always have a specific amount to surface the super heat.
And we'll talk about that in a little bit on the left side. Of the log diagram, we have what we call sub cooled liquid. So anything past this saturated bubble point, saturated liquid line will mean that we're subcool. And the further we go is the more sub cooling we have. We know a lot of controllers when you're designing a system.
And understanding where to plot that on this diagram is super important for anyone that's working in CO2 or any refrigeration system, to be honest with you. And there, as we continue to move along the system, we have the gas and vapor side. So I've talked with engineers. They drew lines for me. Oh well this is actually gas.
As we can see them, all that go down, there's this correspondent temperature. So as that compressor, so that CO2 compressor compresses that refrigerant, it's going to have the heat of compression and it's gonna take it up along here to change that temperature. And when you're plotting this. You can go into your system that you're working on now.
We, we want to know, or how much flash gas is coming out of that high pressure valve coming down the drop leg from the condenser. This is super important because this is gonna tell us how that system is running. A lot of the times in the, the CO2 programs that I'm doing and the training technician is like, well, why do I really need to understand that?
And it's important as a technician to understand, well, I'll get way too much flash gas. This is no different than working on an HFC system and you and your liquid line, you're getting flash gas. That's the way I think of it is 'cause the more flash gas you have, the more energy penalty or tax that you're gonna use.
Critical point. This is a term that most people know, but what, what does it mean? The critical point is when you're above that, it's the CO2 is an undefined fluid, or I. Any refrigerant, it's an undefined fluid when we're above that, 'cause all refrigerants will have a critical point and it's important to understand, 'cause I didn't, I didn't even know that.
One of the things that I learned maybe after about six or seven years of training, CO2, 'cause I've been training CO2 since 2015 and maybe even longer, longer than that. Well, no. 2015 I started training, but I learned this about CO2. If you're not above both the critical pressure and critical temperature, you're not gonna be in super critical.
It's calculating in these high pressure controllers, the best coefficient of performance. It is trying to maintain the least amount of flash gas or the, not, no, I shouldn't even say the least amount of flash gas, the best amount of flash gas going into that receiver to maintain, to the amount of work. For those trans-critical compressors or the parallel compressor, depending on the, the system.
The left side of the te critical temperature, but we're above the critical pressure, like I talked about already. This is compressed liquid. And where did I learn, learn about this? Well, really I was, I was chatting with my friend uh, a good friend, James Seabrook. He owns a company called Vitalis, and they built CO2 extraction machines.
Is looking to design trans-critical systems. This guy's a game changer for knowledge on designing system, but he was like, Trevor, that is a compressed liquid. And then I put the two, two together. It was like, because we don't see that in refrigeration. We don't see , above the critical per pressure really and below the critical temperature.
Can dry ice happen? It can happen in a system, but it's very rare. Where I would see it the most is on the safety side is engages when someone's charging. So if someone never charged CO2, but they charged a lot of refrigeration HFC system, they've gotta really understand what is happening when you're below that 61 PSI or 4.2 bar I think it is.
Which is, could be around, let's say 200 PSI or , 14, 15 bar, just making sure, maybe not even that high, but making sure you get to that suction vapor. We know we got no liquid in there. Now we can open up that after we release the pressure down to atmosphere, now we can open that up. So there are situations where I talk with technicians in the, our training program, say, Hey Trevor.
But when you're charging or adding gas, that is something that needs to be a concern. And if a technician's shown once. It, it'll, it'll stick with them. But it is important to understand how it happens. Okay. I've seen systems be charged from evacuation with liquid cylinders. It takes time though.
So how would I really plot this? What would it really look like? So here's a, a system just a basic booster system. Let's plot it. And this is how when I'm doing a training and I'm talking to the technicians, is getting them to understand how does that really work? ? 'Cause their P and IDs are gonna look a little bit different than this, but you can plot the PNID right on on this chart.
If this is why this three-way ball valve is switching, it's not to do with anything but temperatures or pressures or voltages. And understanding how to plot it. So let's do this quick example here once again. So here's our trans critical compressor. I got here on, on here a Bach compressor. It could be anybody's compressor, but what happens, that energy comes in, that starts up that compressor.
We're above that critical point. So what we're doing, we're cooling it down as much as possible. So when we go through that high pressure valve, when that fluid hits that high pressure valve, that we have as much liquid in that vapor as possible, or the least amount of flash gas as possible coming through that valve, which is so, so important.
It's just more work. More work for, for those compressors. More work leads to more energy. More energy leads to higher costs. And if it's too much work and if it's overwork, that means that now we're working the compressor in real hard to the point where now over time, it's reducing the life instead of those 10, 15, 20 years, five years or six years getting together, that because we're working the compressor too hard.
(00:22):
Or a atic cooling or parallel compression. There's lots of different strategies that are out there and I've seen it from the designers in the course doing different approaches, , coming up with different things to try to make sure we get the least amount of flash ass going into that receiver.
That's, that's all when you can, it's a restriction in the pipe. My, my good friend Kevin Mo from the uk, he, he's like, that was multiple times on the podcast. He said, it's just a restriction in the pipe, and that's all it is. When you can get your head around that, it's a restriction in the pipe. We're opening and closing, trying to change the flow of that.
So as you change that vessel pressure, that flash tank pressure, receiver pressure, it's gonna change the amount of work that this valve is doing. Then that means if there's more flash gas going through or less fast, it's gonna change the amount of work on these compressors right here. That's a big deal.
And that's where the game changer is. I see multiple times technicians coming into their program. They're like, I kind of understand the sequence of operation. Well, no, let's understand. There's no kind of, let's understand exactly way that's supposed to work. So you understand when a problem happens, I have an oil issue because that receiver is, I.
We're dropping the pressure and we drop the pressure because we know we need to drop the temperature and this is all electronic valves are doing. So what we're doing here is we're dropping the, the temperature to one point. So we get our all, we're pulling the heat out and we're actually dropping the temperature to remove heat.
So you'd have liquid coming down the drop leg, not fluid, down the drop leg. Okay, so, and then right here we push out a little further. What does that really mean? So in this example, we must have a sub cooler in here. We're pushing that out a little further. So when we drop our temperature down for our low temp to remove that heat.
It wasn't only, it was with CO2 systems, but I didn't really, I couldn't see inside the pipe. I could get the pressures and temperature, but I couldn't really visualize what's actually happening in that pipe. Now, I, I can't, I can see if there's going through this discharge line. What is it? It's actually a fluid going fluid in there.
So systems that are designed correctly, I. They're installed properly, they're service and start. They're started up and commissioned properly and in they're serviced and maintained properly. Nobody has issues with them. I talk with people that the system's been running for years and all they've done is their simple six or one year maintenance.
And I see it all around the world with the people I'm working with, the, the systems that have issues that I see, there's one, one or two parties left out. I. One or two parties left out, and it could be anyone. It could be the retailer left out. It could be the contractor left out. It could be the manufacturer left out.
And this goes for designers. This goes for technician. This goes even for the retailers. The refrigeration leads on that. Those of you that are putting the work in today are benefiting tomorrow. 'cause I see this in our CO2 design course. I see this in our CO2 intro course. I see this in our CO2 advanced course.
Please share this with others. We're here to uplift the industry by helping each other. That's what we do here at Refrigeration meant that we're helping people all around the world to level up. So if you're interested in one of our programs, reach out to me. Send me a message, send me an email trevor@refrigerationmentor.com.
Well, welcome to another CO2 experts. This week we're gonna be diving into some of the basics of CO2. I know we've been diving deep into some of the heavier technical stuff over the last , four or five weeks. And now we want to, I want to dive in, go back to the basic talk about some of the keywords and terminologies I, which I really believe is super important to.
(00:01):
Some things that are, are used in Europe aren't the same here in Canada as, or the US or Australia or New Zealand, so it's really un. Getting the foundation of those key words. And I think this is really, really, really important. So if you're listening to this on the podcast, after it's recorded, you might want to go to the YouTube channel and check out the slide.
'cause we build customized supermarket programs, customized CO2 programs for contractors to really level up your team. So what we, what, what do we have here? We have. Entropy diagram. And for all those of you who are joining, please share where you're from. Calling in from. I love seeing where you're at in the world, learning, growing.
So as we can see right here, this is called, some people call this the bell curve. This is the saturated lines. First step is understanding what's on the left side of it. So if you're looking at a diagram on the left side. Saturated liquid or the bubble point. So that's very, very important to understand because as that refrigerant transitions to different states.
There's, , 10, 12, 15 degree glide in some of these refrigerants. It's like to design like an SST and design a coil for that is very difficult for CO2. It's not that difficult, a single blend. You wanna understand what that I. Dew point is, or the vapor point. So, 'cause we always wanna make sure that we have vapor, going back to those CO2 compressors, the booster compressors, or the trans-critical compressors, we wanna make sure that we always have a specific amount to surface the super heat.
And we'll talk about that in a little bit on the left side. Of the log diagram, we have what we call sub cooled liquid. So anything past this saturated bubble point, saturated liquid line will mean that we're subcool. And the further we go is the more sub cooling we have. We know a lot of controllers when you're designing a system.
And understanding where to plot that on this diagram is super important for anyone that's working in CO2 or any refrigeration system, to be honest with you. And there, as we continue to move along the system, we have the gas and vapor side. So I've talked with engineers. They drew lines for me. Oh well this is actually gas.
As we can see them, all that go down, there's this correspondent temperature. So as that compressor, so that CO2 compressor compresses that refrigerant, it's going to have the heat of compression and it's gonna take it up along here to change that temperature. And when you're plotting this. You can go into your system that you're working on now.
We, we want to know, or how much flash gas is coming out of that high pressure valve coming down the drop leg from the condenser. This is super important because this is gonna tell us how that system is running. A lot of the times in the, the CO2 programs that I'm doing and the training technician is like, well, why do I really need to understand that?
And it's important as a technician to understand, well, I'll get way too much flash gas. This is no different than working on an HFC system and you and your liquid line, you're getting flash gas. That's the way I think of it is 'cause the more flash gas you have, the more energy penalty or tax that you're gonna use.
Critical point. This is a term that most people know, but what, what does it mean? The critical point is when you're above that, it's the CO2 is an undefined fluid, or I. Any refrigerant, it's an undefined fluid when we're above that, 'cause all refrigerants will have a critical point and it's important to understand, 'cause I didn't, I didn't even know that.
One of the things that I learned maybe after about six or seven years of training, CO2, 'cause I've been training CO2 since 2015 and maybe even longer, longer than that. Well, no. 2015 I started training, but I learned this about CO2. If you're not above both the critical pressure and critical temperature, you're not gonna be in super critical.
It's calculating in these high pressure controllers, the best coefficient of performance. It is trying to maintain the least amount of flash gas or the, not, no, I shouldn't even say the least amount of flash gas, the best amount of flash gas going into that receiver to maintain, to the amount of work. For those trans-critical compressors or the parallel compressor, depending on the, the system.
The left side of the te critical temperature, but we're above the critical pressure, like I talked about already. This is compressed liquid. And where did I learn, learn about this? Well, really I was, I was chatting with my friend uh, a good friend, James Seabrook. He owns a company called Vitalis, and they built CO2 extraction machines.
Is looking to design trans-critical systems. This guy's a game changer for knowledge on designing system, but he was like, Trevor, that is a compressed liquid. And then I put the two, two together. It was like, because we don't see that in refrigeration. We don't see , above the critical per pressure really and below the critical temperature.
Can dry ice happen? It can happen in a system, but it's very rare. Where I would see it the most is on the safety side is engages when someone's charging. So if someone never charged CO2, but they charged a lot of refrigeration HFC system, they've gotta really understand what is happening when you're below that 61 PSI or 4.2 bar I think it is.
Which is, could be around, let's say 200 PSI or , 14, 15 bar, just making sure, maybe not even that high, but making sure you get to that suction vapor. We know we got no liquid in there. Now we can open up that after we release the pressure down to atmosphere, now we can open that up. So there are situations where I talk with technicians in the, our training program, say, Hey Trevor.
But when you're charging or adding gas, that is something that needs to be a concern. And if a technician's shown once. It, it'll, it'll stick with them. But it is important to understand how it happens. Okay. I've seen systems be charged from evacuation with liquid cylinders. It takes time though.
So how would I really plot this? What would it really look like? So here's a, a system just a basic booster system. Let's plot it. And this is how when I'm doing a training and I'm talking to the technicians, is getting them to understand how does that really work? ? 'Cause their P and IDs are gonna look a little bit different than this, but you can plot the PNID right on on this chart.
If this is why this three-way ball valve is switching, it's not to do with anything but temperatures or pressures or voltages. And understanding how to plot it. So let's do this quick example here once again. So here's our trans critical compressor. I got here on, on here a Bach compressor. It could be anybody's compressor, but what happens, that energy comes in, that starts up that compressor.
We're above that critical point. So what we're doing, we're cooling it down as much as possible. So when we go through that high pressure valve, when that fluid hits that high pressure valve, that we have as much liquid in that vapor as possible, or the least amount of flash gas as possible coming through that valve, which is so, so important.
It's just more work. More work for, for those compressors. More work leads to more energy. More energy leads to higher costs. And if it's too much work and if it's overwork, that means that now we're working the compressor in real hard to the point where now over time, it's reducing the life instead of those 10, 15, 20 years, five years or six years getting together, that because we're working the compressor too hard.
(00:22):
Or a atic cooling or parallel compression. There's lots of different strategies that are out there and I've seen it from the designers in the course doing different approaches, , coming up with different things to try to make sure we get the least amount of flash ass going into that receiver.
That's, that's all when you can, it's a restriction in the pipe. My, my good friend Kevin Mo from the uk, he, he's like, that was multiple times on the podcast. He said, it's just a restriction in the pipe, and that's all it is. When you can get your head around that, it's a restriction in the pipe. We're opening and closing, trying to change the flow of that.
So as you change that vessel pressure, that flash tank pressure, receiver pressure, it's gonna change the amount of work that this valve is doing. Then that means if there's more flash gas going through or less fast, it's gonna change the amount of work on these compressors right here. That's a big deal.
And that's where the game changer is. I see multiple times technicians coming into their program. They're like, I kind of understand the sequence of operation. Well, no, let's understand. There's no kind of, let's understand exactly way that's supposed to work. So you understand when a problem happens, I have an oil issue because that receiver is, I.
We're dropping the pressure and we drop the pressure because we know we need to drop the temperature and this is all electronic valves are doing. So what we're doing here is we're dropping the, the temperature to one point. So we get our all, we're pulling the heat out and we're actually dropping the temperature to remove heat.
So you'd have liquid coming down the drop leg, not fluid, down the drop leg. Okay, so, and then right here we push out a little further. What does that really mean? So in this example, we must have a sub cooler in here. We're pushing that out a little further. So when we drop our temperature down for our low temp to remove that heat.
It wasn't only, it was with CO2 systems, but I didn't really, I couldn't see inside the pipe. I could get the pressures and temperature, but I couldn't really visualize what's actually happening in that pipe. Now, I, I can't, I can see if there's going through this discharge line. What is it? It's actually a fluid going fluid in there.
So systems that are designed correctly, I. They're installed properly, they're service and start. They're started up and commissioned properly and in they're serviced and maintained properly. Nobody has issues with them. I talk with people that the system's been running for years and all they've done is their simple six or one year maintenance.
And I see it all around the world with the people I'm working with, the, the systems that have issues that I see, there's one, one or two parties left out. I. One or two parties left out, and it could be anyone. It could be the retailer left out. It could be the contractor left out. It could be the manufacturer left out.
And this goes for designers. This goes for technician. This goes even for the retailers. The refrigeration leads on that. Those of you that are putting the work in today are benefiting tomorrow. 'cause I see this in our CO2 design course. I see this in our CO2 intro course. I see this in our CO2 advanced course.
Please share this with others. We're here to uplift the industry by helping each other. That's what we do here at Refrigeration meant that we're helping people all around the world to level up. So if you're interested in one of our programs, reach out to me. Send me a message, send me an email trevor@refrigerationmentor.com.
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