This episode of the HVAC school podcast is made possible by our sponsors, nav AK and navigable comm. You can find all the great nav AK tools by going to true tech tools, calm and use the offer code get schooled for a great discount, also air Oasis. You can find out more Eero Asus comm. They are makers of the bipolar and nano air purifier units made in the USA right in Amarillo Texas.

Also thank you as always to refrigeration technologies at refridge tech comm. Today we're talking about refrigeration and in refrigeration systems. We find that there's a lot of times that you want to use a little bit of thread sealant, especially on pipe thread. Now.

Log is great for use, especially on pipe threads is a little bit of a sealant and assembly lubricant, find out more by going to refridge tech, comm and finally carrier and carrier comm, who has partnered with us from the very beginning. Thank you to carrier, and now the man who thought dad jokes were funny before it was cool. Wait, it's still not cool Brian! Oh, hey, hey, hey! Yes! Today it's a special day. I have been chasing rusty.

Walker, since the very beginning, Jeremy Smith has been on the podcast several times and has written a lot of great articles for HVAC our school comm recommended that I talk to Rusty about co2. He said he was one of the best educators out there on the topic and I have been chasing him down for a long time and finally, he shot me an email and said he was ready to come on the podcast. So big thanks to rusty for doing this and we're gon na be talking about the three flavors of co2. So here we go rusty! Walker thanks for coming on rusty.

Thank you thank you for having me before. We get started into what we're gon na talk about today, which is the three flavors of co2. Tell us a little bit about yourself and where you work and what you do, I originally started at bone. I was a lab engineer at bone and became with the hill Phoenix I currently are in the corporate trainer.

I guess I'm an engineer out to pasture. So now, I'm just going around teaching and trying to have contractors understand anything from basic refrigeration and base literacy to your co2 booster systems, all right. So what is that job entail day-in and day-out? Most of what that entails is going from contractor to contractor, as they begin to work on different systems. The problem in our industry is, we all know now is we're not experiencing that game.

A lot of young people in so there's a new need to go out and teach some of these things at the Contractors level. If a contractor gets one of these new co2 work, I spend most of my time on I'd go out there I help with startups. I do the classroom teaching so that we can have a better understanding. So when we're out there in the middle of the night, we're not as lost as we were, we were trying to really get this as a mainstream product and trying to get guys on top of the curve and just spend a lot of time.

Talking and teaching them so for those technicians who maybe don't know much about Hill Phoenix and what Hill Phoenix manufactures or sells what type of products are included in their lines. Who finishes all the leading manufacturers of not only cases for supermarket, but we also manufacture large refrigeration rocks commercial use. We run everything from r22 still to 448, around 449. Now, with the changing in the refrigerants and or the leading manufacturer in the North America of co2 products and we're moving again into propane okay before we get into co2, because you just threw that propane thing out there, my understanding of propane is, is that propane is Only in really small stuff, so how does propane work in the larger grocery store segment? Well, we're still not ready to use it because of legislation and the limitation on how much we can use.

So we are moving into in the small cases so far, self-contained case a grab-and-go case that we can put anything from one and a half ounces to the maximum moment of five ounces. So this gives us the ability to take that off the rack and put it into the smaller. We can even put it in the C stores. We can put it in a small footprint stores so that we can eventually move more and more away from HFCS and HF o --'s.

Eventually, hopefully, we can start using propane in cascade systems, but that we're not quite there yet based on you out in the limit of 150 grams, so the move is towards Naturals and propane would be considered to be a natural. Co2 is definitely a natural start by just going over a little bit of the history of co2 and its use in our industry. Well, co2 is actually one of our oldest refrigerants first patented. In about 1850, it was one of the top refrigerants one of the main refrigerants used at the turn of the century, along with ammonia, sulfur dioxide, methyl chloride and some of these very toxic gases.

And what happened is there was a period where we had a lot of people getting killed because of the toxicity of the other methyl chlorides and the sulfur dioxides co2. So then, in the 1930s, GM patented r12 and once they patented r12 - and we got this low pressure non toxic, non lethal gas, all the other refrigerants, except for ammonia kind of went away and so the industry GM sold that patented DuPont DuPont called it freon. Then we came up with 502 and 22 and so all the natural they kinda went away because we had these low-cost, safe, refrigerants synthetic refrigerants. So all the national refrigerants kind of went away.

Then, when we started notice in the ozone depletion and we had a hole in the ozone sand, skin cancer rates went up and whatever's. There was a new push to come up with something that was just as efficient but was more environmentally friendly than the synthetics. We started looking back at co2 in the probably early 80s. It started seeing what it is.

It has better latent heat capacities and a lot of these gases has zero ozone depletion. So as we moved away from the chlorinated gases that are 12250 to the 22s, we came up with the HFCS, but then we noticed the HSCs had high global warming potentials. So we continued to move and look at the natural refrigerants and now we're finding that the BTUs, the capacities are better with co2. The cost is a lot less with co2 and what I really push is everybody always thinks the co2 is an environmentally friendly refer to which it is as a GWP of wine.

It's the base which we raid all of our co2 s against, but the really good benefit is the low cost of the gas it's running 50 cents to $ 2, a pound tens when, where you live geographically and the other thing is the BTUs per pound, I Have a latent capacity of 129 BTUs per pound of co2, comparing that to 448, which is around 97 BTUs per pound, and the easiest way to do that as now is challenge the technicians when they do a training classes. What I want you to do is start looking at the liquid lines when you go inside the store and you go into the cases and notice how small your liquid lines are. You're going to see a 3/8 liquid line on a 12-foot case where, when you start using your HMOs or you, agencies, you're, going to see a half-inch 5/8 liquid line, and that just tells me quite simply that I don't need as much refrigerant. I don't need as much gas to do the same amount of work, because the BTUs in the case doesn't change.

So if I can deliver less gas and just shows I'm doing more work with that gas, that's kind of how co2 came back, it was driven by a ozone depletion. It was driven by global warming, but now that once it's here, the capacity is really what drives and the low-cost. I want to add in a couple opinions here: real quick, so the listeners know that when I'm given opinion, I want to caveat it that this is not like solid fact, necessarily, but there's so much talk in our industry by technicians where they think the global warming Stuff is BS or whatever, and they get all worked up about that, but there's so many reasons to be excited about co2 that have nothing to do with that side of it. Obviously, that's a big reason and that's why it's kind of got the ball rolling.

But one of the big reasons is is that co2 does require skill to work with and as guys talk about, you know, they're taking the skill out of the trade they're, dumb and everything down. Well, co2 is something that there is some additional things that you got to know it's a good refrigerant for people who know what they're doing, which i think is kind of a good thing for the trade. But the other thing is like you mentioned: it's a really good refrigerant and it has low production costs. So when you think about being tied to other countries to bring in our refrigerants and for our raw materials, co2 is something that we can do right here in the US.

It's very simple: it's inexpensive. We don't have to worry about it for years and years to come from an environmental impact standpoint and it really kind of brings home a lot of the skill that it takes to do the job and also the US manufacturing side. I think there's a lot of things to like about it. Yeah there's some challenges, but we're going to talk today about how some of these challenges are being overcome.

Okay, you have any comments on that. I agree with that. It does take some getting used to and one of the biggest problems I find with technicians is the internet because they read all these different things. They go on these different blogs and they start thinking that co2 is something that it really is not because at the end of the day, most of these systems are just another referral.

It's just another DX refrigerant, especially when I'm talking about cascade or booster systems. It's just another refrigerant that happens to run at a higher pressure that has a high triple point all right. So before we go into the three flavors. Let's just address quickly.

That high triple point thing we're going to talk about this in some future podcasts we're going to more deeply, but there's a couple things you got to know about co2 when you first start working with a triple point, is one of them. So, what's the abbreviated version of that real quick triple point just quite simply says that every gas will have a point where that'll be in all three states, both liquid vapor and solid, all three with co2. The triple point is at 60, psi G. So if I'm servicing a case - and I allow the pressure to drop down to 60 pounds - 60 pounds gauge any liquid - that's in that evaporator in that receiver or wherever will turn immediately into dry ice.

So the key is just quite simply how to get rid of the gas. How to boil off the liquid. Before I hit that 60 pounds in another broadcast, we'll go ahead and cover that the other kind of side of it is the high limit talked a little bit about that when it comes to the supercritical fluid side. What's the quick cliffnotes version of that co2 has a very low, critical point, a hydro point in the low critical point, the critical point of co2 is going to run around 87 degrees once I reach 87.

If I looked at my pressure, enthalpy diagram when we say it becomes a supercritical fluid, there's no more relationship pressure temperature relationship, I can't look at my PT chart and tell you at the temperature, because what happens as I go above 87 and this changes into a Supercritical fluid the densities, the liquid and vapor densities now move along the density chart and they become equal, and so once the liquid densities and the vapor densities are equal. There's no way to distinguish: is this a liquid or source of vapor? So that's why we say it's an undefined gas. It's now supercritical and everybody wants to come up with some other term. Well, is it really superheated? No, it's not superheated, because if it were superly did that mean so it would be a pressure and a temperature relationship, and I can look at a saturation point and say it's above that.

But since there is no saturation point because the densities are equal, the only thing I can call it as a supercritical fluid makes sense. So we've got the critical point at the top end and then we got the triple point at the bottom end. What makes co2 different than a lot of refrigerants we work with is the fact that the two of them are pretty close together, whoo all right, so now we're gon na dive into the specifics of the three flavors of co2, so I'm gon na. Let you just take it from here: go down the list, what are the three flavors and what are some of the differences all right, so the main three systems or flavors of co2 that we have out there now and these again are the base flavors, because then, On one of them and I'll kind touch on that a little bit, I can do something kind of a hybrid, and we will talk about that as well, but the main flavors are the first one we started doing in 2006 was co2 secondary with co2 second day.

I call this a gateway system in a way it gets us to the booster, because, with the secondary system, all we do is we have an HMO or an HF, see on top, as any secondary system would do so. I'm going to have the HF. Oh up here I have in between the upper section of the system and the bottom section of the system, which is me co2 portion. I have a heat exchanger, so we'll start with how the system is going to look.

It's going to have a giant large receiver inside that receiver is going to be both liquid and vapor co2. This system, currently that you see currently you're, going to see a lot of this in a wetlands water you're, going to see it in a Walmart. These are just a few that's chosen to secondary, because I'm going to have it it's a low temperature system, I'm running it at minus 20, which was co2. Minus 20, is 200.

Pounds was a low pressure system, at least in the co2 world. So what we have is we had this giant receiver, where I have liquid and vapor inside there I'm going to come off the bottom of the receiver and I'm going to send it to a multi-stage centrifugal pump. This a triple pump has, when I say multi-stage, it has three separate impellers that allows me to step the pressure up across there so that I can move the fluid all the way into the evaporators I stepped it up. I've got about a 25 pound differential across this very small centrifugal pump.

I push the co2 out now. I send it to each one of the evaporators. This is a moot type system, so I have a large liquid loop and by large and co2 numbers. That's probably 7/8, I send the co2 out to the evaporators in the the walk-in or the cases and for a metering device.

All I have is a solenoid I'm going to cycle that solenoid simply based on discharging our temperature. So we look at the temperature I'm trying to run 0 minus 10 minus 20. I simply open the solenoid and close it based on that temperature. Now this is where we stole right out of the ammonia handbook, we're going to use a two-to-one over feed system.

So the pump is going to push out actually more co2 that I'm going to boil off inside of the evaporator, so the solenoid is going to open up when the discharge air goes up. I allow the liquid to come into the coil that liquid is going to, quite simply because of the BTUs per pound. The discharge enter temperature is going to drop, really quick. The solenoid is going to cycle off and you're going to actually see on most systems.

The soy's going to have more off time than on time, but as that slowly closes, I still have that liquid sitting in the coil. So as my discharging air, my fans move the air across the evaporator. The discharge comes in any infiltration and like an open case and some of our stores, where we have open low-tech aces. We allow that air to come across the coil that air that load, that heat that's coming off the product infiltration and appending somebody opens the door all that heat simply boils off the refrigerant now our flow rate, since it's an over feed system, is very slow and What I'm doing is, as that liquid begins to boil and becomes a vapor I'm bringing back both liquid and vapor.

We like to say it's a wet return, quite simply as saturated. I have liquid vapor in both on the return line. So the return line brings that liquid vapor mixture back into the receiver, where the liquid, though we didn't use, will fall to the bottom to be ready to be reused. But the vapor is now going to move and we have a heat exchanger very large you're, saying it kind of looks like a chore heat exchanger.

If you were to see it for the first time, you would think. Oh, my god that looks like chill are very similar, but what we do is we use a thermal siphon now, so we have a line that comes off of the receiver comes up to the inlet side on the top side of the heat exchanger. This is vapor we'll bring in this paper. This paper is attracted to the cooler for 48 or 22 or 407.

That's on the other side of that heat exchanger. Now we begin to bring that in now the temperature drops, as we begin to change state. One of the other things about co2 is for every one degree. I have a six-pound pressure drop, so I have six pounds per degree change.

So as I begin to refrigerate that refrigerant, it creates this natural siphon, a thermo siphon right out of the ammonia handbook. So we create this thermal siphon that allows the vapor to come out of the receiver into the heat exchanger. Chilled heat removed. Put that heat into the upper system, the 148th or the HFO system we put that heat over there.

We condense it if you will and they condense liquid or that liquid comes back into the receiver, and we quite simply send that liquid back to the evaporators. The nice thing about this is that you're not going to worry about superheat. You don't have to worry about how to set the expansion valve out off you simply control it with the solenoid, then on the upper cascade or the upper section of the system, the age of CHF, both side of the system. We've put the heat into that refrigerant.

That he quite simply takes it from the compressors to the condenser and discharge that heat outside using the HSC or HFO refrigerants. And all that we see inside the store is the co2 and a lot of people like this system. Because the simplicity of control and the lower pressure, the whole system is going to run somewhere between 200 and 250 pounds based on load, of course, by the power outage which we could cover later. The pressure would go up, but as the normal operation, I'm somewhere between 250 and 200, pounds based on load.

So that's the second first thing that I'm thinking is okay. Maybe one of the big advantages of this is that if you really want to reduce your total HFC charge or HFO charge, this is a way to do that, because now you're keeping all of the primary refrigerant inside a motor room, for example, for us, I'm trying To draw a picture in my head, this is one of the disadvantages of a podcast, because we don't have a diagram to point at, but a picture in my head is I'm thinking of this a lot like a water loop or a glycol loop system, and that We may see in an air conditioning, for example, where you're using a secondary refrigerant, which, in a glycol water loop system that would be the secondary and you have the primary. That's then cooling it, but you're still leveraging that high heat content of latent phase change that you have in co2. So co2 is advantageous because you can move a lot more heat less of it than you would with other types of mediums that we're staying in a single form right doing a podcast is very difficult for me because I'm usually having the graphic but you're, absolutely right.

The only difference is, it is actually exactly like a glycol system, except some of the differences between this and going calm on a glycol system like we do a glycol in a supermarket using +20 propylene glycol on the pump on that system will be on the return Line pulling the refrigerant or the glycol back from the cases here, we're going to have it and push it's going to be on the supply line. That's going to push it down, the other difference is, and the biggest difference is with glycol. I'm going to have sensible heat transfer, so I'm going to Center as a liquid, I'm going to leave as a liquid, and I should see about a 78 degree TD based on how he'll Phoenix the size of our ecosystem. Here I'm going to get latent heat transfer because I'm going to enter as a liquid through that solenoid and I'm quite simply boiling the refrigerant off that sensible heat transfer where I'm entering this liquid leaving is liquid.

I'm getting the advantage of the Laney transfer or I'm boiling it off, I'm absorbing the heat and I'm changing the state. When I take a quick second and talk to you a little bit more about refrigeration technologies, if you listen back a couple episodes John Pasteurella came on and talked about additives and systems, and if you listen to that, podcast you're gon na see exactly why I love Working with refrigeration technologies, because they're from the trade for those of us who are working with our hands in the trade, you know that most of the people in the tray - they don't pull any punches right. We don't have time to screw around. We don't want to be sold with the sizzle without having mistake and that's what I like about refrigeration technologies.

They make good solid products to do what they're supposed to do, and one of the big things that they do that they're supposed to do. Is they make products that are non-toxic as much as possible? They make products that are safe to use not only for technicians but also to have in customers, homes and buildings. They make really good cleaners and chemicals. They make an excellent, even acid, test kit.

I didn't even realize this, but they make some excellent acid test products and you can find out more on their website, like I mentioned refrig tech comm, but kind of the mainstay products, the ones that I really enjoy - big blue. They low temperature, big blue. You get the big blue and the spray bottle that we've all seen, and then they also have one with a swab. If you prefer the swab, it's an excellent leak, reactant, so bubbles for the uninitiated in the terms its leak reactant.

That's the fancy word for it, but it's great stuff. If you've used a big blue, you know it's great nyah log is excellent. When we're pulling vacuums, we use it on all the seals and on the threads to help pull the deep vacuum that you can also be used as an assembly lubricant, it can be used on pipe thread and flares. It really helps to get a nice tight seal, helps prevent galling when you're putting metal parts together and it's refrigerants safe.

It's made from either POA or mineral oil, depending on which one you use, and so it's okay to get a little bit of it in the system. It's not gon na hurt anything in comparison to some other products that you definitely would not want to get into. The system dialog is non hardening also, which is also an important thing if you're working on it with refrigeration. So there's a lot to like about refrigeration technologies products and you can also find their products like many of the things that I talked about here on Tru tech tools website.

So if you fight it at your local supply house, that's best, but if you can't find it there, you can always go to true tech tools. Calm and use the offer code gets cooled for a great discount all right here we go back to rusty. I'm here talking about the interesting the glycol loop system and the latent he the additional advantages that you get by using the latent phase change with co2 Christ. You mentioned that it was very similar to vikon, that's true, it's just.

I get the advantages of latent heat transfer instead of sensible heat transfer like I'm a glycol system or I'm just looking at sensibly grabbing sensible heating. Just changing my delta T going through the evaporator, and you also mentioned that the metering device is the solenoid now. Is it actually a metering device? Does it change diameter at all, or does it just basically open and close? It basically just opens and closes so it's a metering device in the fact that it allows and it meters the amount of flow in there based on discharge air temperature. So it stops and starts of it's kind of binary.

It doesn't get a change of stained internet pressure drop going through that it's pull ported, so it's just a metering device in the sense that it allows the co2 to enter the coil as needed, because once it goes in there's an over feed system. It's just right out in the ammonia Hamlet is an over feed system. That means that liquid, since there that I've allowed into it - and you could say if you wanted, that the heat mode itself helps meter the matter flow because as the mode and the heat comes across, that corner on boils that refer turn off and brings that liquid. Vapor back into the receiver, I don't have to worry about superheated, I'm not going back to a compressor.

So I get a point flooded coil. So there's liquid all the way through the coil glycol system would have, and so I get heat wrestler throughout the entire surface area of that coil. It's also interesting because you use a couple terms that are just intuitive for you, but I think a lot of text may not know the difference. You talked about it being circulated using a centrifugal pump and it's a pump not a compressor, because it is moving liquid and not a vapor, so it can't compress you can't compress a liquid at least not at any significant amount.

That's why it's a pump, not a compressor. That is correct, and it's just like you mentioned for those air conditioning guys to do this air conditioning it's the same type of pump, I'm going to use there! It's a centrifugal pump of Belling gossiped or a Paterson pump. So the only difference here is when I say multistage, I have actually three impellers instead of a single impeller and it's much much more, that's a third of the size and then on the primary side. Another interesting thing that probably blows a lot of guys Minds which you mentioned is that that refrigerant that co2 moves through that coil or through that heat exchanger, I should say just based on the thermal properties alone: there's no pump, that's driving it through there's, nothing! That's forcing it through other than the pressure drop that occurs within that heat, exchanger right and that's correct.

So here's one of the things that's critical for a technician to understand, because since I'm using that thermo siphon, if I get any little bit of non-condensibles and there'd be at nitrogen or hare, because somebody had purged their hose when they put the hose on the system. Those are American, decimals are always going to go to the highest spot and the highest spot here is going to be in that formal siphon that comes up to the heat exchanger. So if I can't bounce a little bit of nitrogen or a little bit there, then I lose that entire thermal cycle, because it's if you want to say vapor locked if you can say that, because I've lost that sight, I'm not taking it and co2 vapor in There so those non-condensibles will just sit right, so one of the things we always look at is if you're running one of these secondaries neo2 systems, if your expansion valve and if you think about that, if they put vapor on that line, that means I've lost. My look: I have no load to that heat to the vaporators on the floral, the HSC side, so the expansion of that's going to be an electronic expansion.

Now nowadays because is mechanical. Are they end on that expansion? I was going to begin to close down. So I will see it I'll be looking at the controller and I can see that it's down to 10 % open - and I know I have a lot more load than that. I have a lot more heat.

Well, that's a quick indication to me that I've lost my load. I've lost that heat exchanger, and so some co2 can be vented. There's no recovery, no reclaim! I can vent it. We always install an access port, so I quite simply just open that access port and then down any non-condensibles that I have in there.

So I'm going to go in there, I'm going to personally get good perch on it. Then I'm going to close that valve that I'm going to look over and see the expansion I'll begin to load back up as that thermal siphons reestablished, and I now have load to the age of CHF both side of it. The expansion valve on the HFC side will begin to load up, it'll, be open up and I'm bringing my co2 temperature down, because the first thing that we've gotten you out there is it's going to be cases, run warm of course, and you're going to walk in There and you're going to see your bust pressure. 300 pounds 350.

Well, the first thing you're say is I've lost my load. I've lost one of those heat exchangers and so you're going to start looking at those expansion valves and then you're going to see one or more of them only shorten 10 or 20 % open. And that's going to be your indication that hey, I probably have non-condensibles talking about this. It reminds me it's not exactly the same, but it reminds me when we're talking about thermal cycling and the sort of lock that you get.

I remember back in the old case. My grandpa used to tell me if you had one of those ammonia refrigerators in your RV or whatever he said. You know what you do to fix those if they stop working. Is you shut them off? You turn them upside down.

Let them sit for 24 hours and then set them upright again and light them and then they'll work. It just kind of reminds me that we're just not used to seeing these types of systems, at least most of us in the industry, then just use thermal cycling. Just use Heat essentially as the engine to drive that refrigerant around, but it's a very interesting system and, as you mentioned, it's beautiful to be able to vent the co2, because now you can easily remove those non-condensibles without having to worry like we normally do. And again.

I always like to tell people if you really want to get a handle on this particular system. The half of it comes right out of you, so the ammonia guys are like oh yeah, okay, because thermal cycles and the overfeed systems come right out of the moon handbook. So that's an interesting thing. If you want to go to research, a little more.

Just look on some of the ammonia books that settles type number one, which is the secondary system right yep. What's the next labor, so the next one is our cascade system we've been doing cascade refrigeration for hundreds of years? Well from not that long, but so what I have is like, by definition, the cascade system is to complete refrigeration systems tied together at a single point. So I'm going to have an HSE and when a de HFO system that's going to be less a 448 or whatever the refrigerant is, and it's going to have a compressor or condenser or a receiver. An expansion valve it's going to have an evaporator and then back to the compressor on the lower cascade, which is going to be my co2 side.

Of course it has a co2 compressor and has a condenser. It has a receiver. It's going to have expansion valves out of the cases kind of evaporators, that's going to be my caseload or my walk-in, and then i'm going to bring that superheated vapor back to the compressor. So what you want to picture in your head are taking these two systems and let's put a heat exchanger in between the two systems: let's put a brace plate, heat exchanger and on one side just like on the secondary side.

There's going to be my four oh four, my four 48 and that's going to have an expansion valve, and that is the evaporator to the upper cascading. The heat exchanger is the evaporator for the upper cascade. The other side of that heat exchanger is a condenser. It's the condenser for the lower cascade.

So that's why we call that heat exchanger our term, for it it's going to be the evaporator condenser, because it's on one side of its the low side for the upper cascade and on the other side, it's going to be the co2, that's being condemned, and it's Going to be the condense room so now that I kind of set the stage here, I think it's easier to understand. If we start on the Laurie cascade, the Laurie cascade is the refrigerant. That's going out into the store it's what's going to be, removing the heat from my cases from my walk-in and I'm going to use that as co2. That's typically, a cascade system doesn't have to be, but typically our main manufacture.

These we use co2 as the lower cascade or the low temp system, so we'll run it again at minus 20. Minus 20 is 200 pounds. It's we get that on our P teacher. The compressor is going to compress it's going to run.

It's either going to be a Copeland scroll or a Bitzer reset. Those are the only two that we typically use in the US. So I take this. I compress the gas just like any compressor ever design.

The only thing different if I were to open them, pull the heads on this compressor as I'm going to see Pistons for a low temperature system like this and we'll see, Pistons there's a size about maybe a little bigger than a quarter because of the sweat volumes In the link capacity of the gas, I don't have nearly the size compressors that I would for a normal DX system and also, I imagine your compression ratios - are going to be pretty low in comparison with other types of refrigeration, because you're so accurately controlling that condensing Temperature right, that's exactly right, so I don't see a lot of fluctuation. So it's a very stable compression ratio because when I discharge out of here - and I send it up that heat exchanger - that heat exchanger, the upper cascade - is going to be running out about a + 15 ish, because I only have a four degree TV with co2. Not a 10 degree TV, so I'm going to run that at a 15 degree saturated on the upper cascade, which is going to allow me to condense. The co2 at a plus 20 nice thing about that is everybody's, always concerned about pressure with co2, and they hear all these four stories and unfortunately they read it on the internet.

But here I'm going to condense it plus 20 plus 20 is 400 pounds. So I am going to compress around 100 and that's going to vary based on load a little. But since the mode of the upper caste is relatively stable, I'm going to be somewhere between si plus 18 and maybe plus 22 at max you're. Not going to see that ambient temperature that the upper caste gave we'll see, so I condensed it plus 20 I bring in a superheated discharge, vapor go through there.

The expansion valve is going to open. It is the load from the evaporator, so it'll open up the electronic expansion valve on the HFC side will open up. You will begin to remove he downs that condense it into a liquid. I now send that liquid co2 that plus 20 into my receiver, like I, would on any other system when I approach it from a service standpoint.

I want to approach it as a normal DX system, with a little higher pressure, I'm going to go through a heat exchanger and then I need exchanger between the liquid and suction on the lower cascade. I send that sub cooled liquid. Now I send it into an electronic expansion valve now there are no mechanical valves in co2, none of the co2 systems. I don't even know if there's one that exists anywhere, I don't think anybody's ever wondered, assign one cuz.

Why can't or not the mechanical valve is going to go the way of the dodo? So I have this electronic valve. I can hi there use a pulse valve which is manufactured by Dan Voss, primarily, but spores just released their own pulse valve. Typically, those valves are going to have a six second window they're going to look at four superheat through the case controllers, they're going to say I need a hundred percent of the mouse for six seconds, I'm going to be open if I need fifty percent of that Valve based on Sabri, then I need to send that valve on the pulse valves. I'm going to be open for three seconds on for three seconds on a stepper valve or on stepper about it's simply going to drive that auger screw.

If you will two percent open, how many steps do I need to open up or close based on super II? Because when I leave the case here, I have a liquid line and a suction line, not supply and return like they did on the secondary. So now coming out of the evaporator, I need to have that super heat. I need to have that eight to 10 degrees superheat, so that I bring that suction back into my low-temperature co2 compressors. Like you said earlier, I can't compress liquid at least not very long, and so I need to make sure I have super deep for the protection of the compressor.

So I bring that 10 degrees about 30 degrees back at the compressor, based on what Bitzer tells us bring that suction back that superheated suction back to the compressor. I compress it again back to the condenser and I have a nice little DX system on the upper cascade system. On the other side that heat exchanger, I have an expansion valve, that's going to open up as the load and the heat from the condensing from those more cascade. Compressors enter that heat exchanger the upper test, Cade expansion - I was open.

I can control superheat once they open and allow make sure that I have superheated vapor going back to my upper cascade compressors again those could be Bitzer, those could be Coppola and resets or Scrolls. When I do, co2 Copeland really doesn't have, or Emerson really doesn't have a reset for co2, but on the upper cascade I quite simply could use Copeland research fits or Scrolls, and then I go to that. I take the heat that I picked up in the water cascade. I bring it into my compressors, compress the gas, take it to my hair, cooled or adiabatic or whatever condenser.

I want to have this drugs that he condensed that superheated vapor back into liquid sand. The receiver to another heated, just a little bitty inline heat exchanger, a little sub, cooling and superheating fact that I'm trying to expansion up and there I go and that's the DX co2 cascade system. In a nutshell, yeah. It seems like really simple.

Honestly, I mean once you get over the idea that you have this heat exchanger, that is simultaneously the evaporator for the upper cascade and the condenser for the lower cascade. After that everything kind of falls into place. The upper cascade is like every other system. We've ever seen it I mean it's got like you mentioned your air-cooled condensers or water-cooled adiabatic or whatever, so that there's some variants there, but their refrigerants were used to seeing.

All of that is the same on the co2 side, we're essentially just running a really low or very controlled compression ratio just doing the math in my head. It sounds like it'd be between 2 to 1 301 compression ratios, which means that those compressors are going to run really efficiently. They're, not gon na have to have like you mentioned, they're gon na really small cylinders in them. It kind of falls into place and it makes sense because now you're moving co2 out into the store most of your charge is gon na be co2 and you're gon na have a much smaller upper cascade, refrigerant charge, which is useful because now you don't have to Worry about chasing that all down throughout a store, especially when it's a controlled refrigerant and that's again, one of the goals here.

What are the goals for all of these systems? The first two anyway, is: how do I reduce if I'm not prepared to go to the higher pressure booster type systems, then how do I reduce the amount of each of season each of those? How can I get that as well as I can try to comply with some of the EPA regulation, some of the things that's going on in the California and that's where it starts, but then once you get used to it and one of the things I always Tell technicians when they walk into a co2 store, specially-made, not seen one. The first thing. I always think to tell them it's debris: it's not that different dude. We haven't changed laws of thermodynamics, and it's just like you said it's very simple.

It's just a DX system with a little bit higher pressure and if you want to think of it as a water, cooler, referer cooled condenser yeah, that's a good way to think of it. A refrigerant cooled, condenser yeah. That is exactly what it is. So anything else to hit on the basics of Cascade.

Before we move on to booster there's a really clean system, I'm going to come back to the second day and DX after we do the booster, because I like to introduce to what you're gon na start seeing in Florida, Publix was already started. Moving to this hybrid system and if we can we'll come back and visit that after we do the booster all right, so let's jump right into booster, then because there's a little bit more complicated, I like to think of this system is the sexy system, because this Is where you're going to separate the boys and the men as far as technicians go? This is where you have to pay attention, and this is where I live now, because there's so many customers, all these Trader Joe's just everybody is moving to this system because, let's start with, why would you do this system? Why would you go to a booster versus the other two? The other two are simpler, lower pressure, but now with booster I have zero hoc or hfo. I never have to retrofit this system. I never have to revisit this system you're not going to get better than a global warming number of we number better than zero.

It's still one of the better performing refrigerants because of its latent capacity. So you always say the salesman and other people say this is a future-proof system, because I am NOT going to have to retrofit this. That's my sales pitch. Maybe I buy it.

Where do I sign rusty yeah? See I'm not only. I know that we drinking the kool-aid. I make it absolute though, since I can't really show a picture. What I'm going to do is kind of give you a little bit of a visual and as we go through this for those of you who worked on a Carlisle to stage compressor, where I have that inner stage where I bring the suction in, and I compress It once and I can press it again - bass ending that enter stage discharge into the suction of the other set of headers if you've done that before try to keep that in your head.

So I always like to start at the upper side. The high side of this - and that's going to be so - I have a series of medium tempo. I'm going to take one of our smaller systems. It has to medium.

Temp is one we call it two bit. It has to medium tempo pressures too low, temp compressors. I have these two bits or Copeland. No on this one on the medium temp, it's going to have to be bitter.

That's the only compressor we have in us right now for the medium temp, transcritical state. I come out of here and I discharge out of these compressors, I'm still using peely oil, like you did on the other two I haven't had in any kind of exotic, weird oil. It's still going to be the best or approved pou oil, I'm going to send it or oil out of the compressor, I'm going to send it to all separator. Now I like to think of the system is operating in three modes, so I'm trying to go through all three modes very quickly and then maybe we can revisit it later but let's say wrote: one is 41 degree ambient between say 77 78 degrees, ambi droplet.

So I come out of the oil separator and I go to it's 70 degrees right now. That's what we're gon na do for our discussion, so I send it out at 70 degrees, I'm gon na run it a fairly low pressure at nine hundred and thirty pounds, and once you get used to see it is a booster systems. 900 pounds. I got no biggie low pressure inside the copper hair.

Now I'm going to use high pressure, copper, which is going to be about 10 % steel with the rest of its coppers, was heavier, but it's rated at over 2,000 pounds. I come out of the compressors. I go into my condenser. It is a condenser right now because I'm entering it with superheated vapor that conventional could be air cooled, it could be any about.

It could be water-cooled whatever I sent it into that condenser. This is a condenser. That means my fans are running, I'm cycling, my fans and leaving that condenser. I have a sub cooled liquid.

I come out of there through the drop leg or the liquid line come through there into what we call a high pressure control valve. This is a valve specifically for these systems and it begins to help me regulate my it's going to operate in three different modes. It has its own controller that is going to manipulate it, and this controller is going to look at droplet temperature and drop leg pressure. So that's liquid, coming out of the condenser! So if I can read liquid pressure and at the temperature, I can calculate sub cooling.

So this bow. What is it going to regulate in this mode? One! It's going to regulate sub cooling! It's going to regulate the liquid coming out of that condenser. To give me three to five degrees of sub cooling, leaving that condenser it has to leave it in there a little bit to help cool in the fans right across it. So it's sub cooling leaves that's what I'm going to do.

Then I'm going to go through that valve that metering valve and I'm going to go into a flash tank, but think of the flash tank is a receiver. So I'm going to enter into that flash tank and receiver and what I say 930 pounds well. My evaporator is really good for 650 pounds, so I can't send that liquid out of that receiver into the store so off the top of that receiver. I have a flash gas bypass valve now.

What this valve is going to do the same little controller, same Damphousse controller that is controlling the high pressure control valve is going to control a flash gas bypass valve CCM bow that valve is going to regulate, because my controller says: okay, I want 500 pounds or 33, liquid in that receiver, coming out of the receiver into a store, as the pressure goes up in that receiver, I will open that flash gas that flash gas is the inlet goes to the receiver. The outlet simply dumps into the medium temp suction, which is going to run across 20 or 400 pounds, so I have plenty of pressure drop, so this is a stepper valve. The CC valve is a stepper mouth, as the pressure and receiver goes up. This valve opens up and dumps whatever vapor is on the top of the soil.

I get paper and I allow the vapor to enter into the session so think of it as load on to the medium construction. So I've now managed the pressure in this receiver at 500, pounds 33 degrees. When I look at my PT chart, then I allow it's a loop system, so I come off. I send all my liquid out the loop.

I have branch circuits that are going to feed both my medium tent cases and my low temperature cases on these cases on each one. So I've got this nice cool, beautiful, liquid co2, the headed in my cases, at 500 pounds. Let's start at the low temp. I go to the low temperature cases, I have an electronic expansion valve, it could be a stepper or it could be a pulse just like on the cascade, the exact same expansion valves they used on the cascade and what a monitor each case has its own case.

Controller in this case controller is going to look at discharge air to open the valve up once the bobbins up. It now becomes a super ii controller. It's going to control 210 degrees of super e, so now I bring that vapor load tap is going to run nominally of course, 2200 pounds. My brother system, Anna past March 20, I operated expansion valve so that I have about 8 degrees of superheat leaving those evaporators.

I come back through an inline heat. Exchanger, maybe picked up a little more superly. I come back to my compressors. Come back those compressors 30 to 40 degrees of super e into the low-temperature reciprocating or scroll compressors.

Those could either be Scrolls or resets on the sub. Woaaa temperature compressors: I charge that out of there some run at minus 2,200 pounds i discharged now. Here's where you have the try to picture this system a little differently, so the discharge goes by discharge, this gas into the medium type suction medium times, such as running the plus 20. So again, my compression ratios are low.

My compressors are low and I'm running a plus 20 discharge and a minus 20 suction, okay, so 200 and 400 pounds. If you want to talk pressure, but I always like temperature says, pressure to me - is just insignificant, because it's really temperature that I'm trying to control temperature of the case temperature of my suction line super II, so I've got a minus 20, no plus 20. I think that discharge line that discharge line is only maybe five because they come right off the compressor right into the medium temp. So I bring that in now that vapour enters into my medium temp suction.

So already, my compressors have two lows: the vapor from the flash tank and the heat actually coming from the low temperature cases, because that Letendre days and he enters in my suction line and there's my discharge line into my medium-tempo now also on my medium time. Suction. The wick, where we talked about earlier, goes to the expansion valves on your medium tempo walk-ins or your medium temp Casas. Again, it's going to be a pulse or a stepper.

It's going to open just like any DX electronic expansion valve. Would it's kind of control superheat and it's going to take that superheated, medium temp vapor back into the suction of the medium temp? So it's critical to understand that I need to make sure one thing that you can already figure out is when I start this up. I must I have to start my medium temp up. First, there is no starting your low temp up, because if you start the motor up, you discharge in medium depth, suction medium temps, not running you'll, kick off on high head high discharge pressure within 10 15 seconds.

If that so we always start the medium tent, we always run that system. That, in a really quick, nutshell, is how load one works. Now, let's talk about the sexiest part of it, the part that everybody was always asking me about dude I've heard it runs at 1,200 pounds, that's scary, okay, it could run at 1,200 pounds. So, let's enter into mode.

I like to think about is anything above. Let's say 78 or on say 85, because I'm transitional between 77 and 78. That's where my fans start to go up. I haven't run supercritical yet so 90 degrees.

Critical point is 87. So now I no longer have a condenser, because once they go supercritical, no matter how much surface area I have I'm not going to be able to condense that into a liquid, because it's undefined gas with the same densities. So what I do is we now call it the gas cooler, because all that's going to happen is my fans are going to come all the way on and I'm just going to get rid of. If I were to look at my high sand therms on my pH diagram, all I'm doing is getting rid of as much heat as I possibly can.

My fans are running wide out if I'm using the adiabatic with a pre-cooler the pre-cooler waters on I'm doing whatever. I can do to get rid of that heat and the easiest way. I always tell technicians, if you want to know if you're super critical or not reach over and touch with the back, your hand touch the discharge line, it's hot. If you reach over your drop leg and your drop leg is just as hot as your discharge or almost as hot you're super critical, because you didn't condense into a liquid.

What do I do now? My controller, not the case controllers. Not the controllers are controlling everything, but the standalone little controller is going to go to the high pressure control valve and what he begins to do is regulate that valve to be open, not a hundred percent but regulate that valve. To kind of create a point where I can create I'm going to open it to a point where, once I come through there, just like a metering device would on expansion, I would going through that bow. I drop the pressure into the receiver, the receivers right at 500 pounds when I go through this device.

Let's call it a metering device and mode when I go through that orifice and I create that pressure drop, I'm no longer above the enthalpy dome, where I'm super critical but now entered back into the enthalpy chart and now I've changed it in our change state and I'm able to change my state, the condenser by cooling it, but by dropping the pressure through that high pressure control valve and now I have liquid, it's actually gon na be a saturated liquid going into the receiver. Now, of course, the flash gas bypass valve it's 90 degrees, so I may be running 1150. I mean be running at 1200, so that flash gas bypass valve he's going to be almost all the way open because he's taking all that high pressure vapor and he's dumping. It into the medium temp suction and, to be quite honest with you, this is where, when people say, transcritical systems aren't as efficient as long as I'm subcritical.

As long as I can stay out of the supercritical state, I win the energy war because of my gasps. My efficiencies of my gas, but once I go supercritical, of course, I'm going to lose a little bit of that energy benefits because I'm bypassing a lot of that load back into medium depth, compressors. So that's why we will go south and go to Florida.