All right, i am excited to welcome the gentleman from the advanced refrigeration podcast, the man's the myths, the legends brett wetzel and kevin compass, thanks for joining me guys how we doing tonight, brian thanks for having us on brian. So today we're going to be talking about identifying parts of a supermarket system um, but before i do that because both both of you guys are new to the podcast. I just want to go through and have you kind of introduce yourselves talk a little bit about your experience and then also talk about um. Just just you know why you started the podcast um and then, at the end, we'll kind of tell people a little bit more about how they can how they can find your podcast and everything you guys do.

But i'll start with you, kevin um, since you're gon na have to muddle through with your horrible internet connection, all right guys, i'm uh kevin compass. I am a supermarket refrigeration. Startup technician! I've done just about everything from air conditioning to um commercial, air, conditioning refrigeration to supermarkets, and now i spend the majority of my time designing controls and installing controls and starting up grocery stores all around the country. I basically you know, travel all around the country commissioning and starting up grocery stores and doing uh energy management projects and uh energy saving, optimization of grocery stores.

So i've been around just about everything from chillers to supermarket refrigeration racks, and i now we have this podcast that we also do that. Uh brings in the refrigeration side of it, so we're uh trying to you know, grow the refrigeration side of the podcast world and uh yep. It's basically uh. My story, awesome yeah, anything that uh that gets more people educated or interested in the uh grocery refrigeration.

Space is a good thing, i'm all for that. So how about you brett? So my name is brett wetzel, i'm the manager of technical, troubleshooting and training over at corsus i've been doing refrigeration. If you include my electronics background about 18 years, i worked on anything from a a small little self-contained up to a thousand horsepower ammonia screw. So i've done a gambit of different stuff um.

I worked on a whole bunch of ems uh. You know different programming, different systems and you know uh, like, like kevin said. You know, we started this podcast because we just wanted to help educate people and it seems to be doing its job yeah. Absolutely it's filling a really important gap that we had in the uh sort of media space and, honestly, you know like, even when we got into market refrigeration uh, which would have been.

I don't know six years ago, whatever it was um, we really came to the air conditioning side and a lot of this stuff. I wish your podcast was around because it would have made it a lot easier. Um we muddled through and figured a lot of it out and still to this day, are you know, learning a lot more about it, but it's really nice to have some of this uh some of this content out there and you guys really. Are i mean it's? It's advanced refrigeration, because a lot of it is pretty advanced.

I mean a lot of it is, is pretty in-depth, but today we're going to be starting with the basics, because we recognize that there's a lot of technicians out there, who are primarily air conditioning technicians. A lot of them are even residential, but who have an interest in maybe getting into some of these different segments and, honestly, you know my take on on market refrigeration, work or grocery refrigeration work. Is it some of the most interesting uh complicated? Yes, but but really just uh, elegant and interesting types of systems out there uh in the industry, so we're gon na kind of go step by step through each component and i'm just going to let you guys riff on it. I mean i i'll ask questions if i've got them uh i'll, ask the stupid questions, so you can deride me laugh at me.

You know point fingers, hahaha brian's, an idiot so but other than that i'll. Let you rock on with it so uh. Let's start with uh start with compressors and uh i'll i'll, let you guys take it from there, wherever you want to go with it in a supermarket in uh, a parallel rack application. So, instead of like a normal refrigeration or air conditioning system, you having one compressor and one metering device in one evaporator, one condenser.

Now we have this gigantic massive multiplex system. When i say multiplex i mean there is multiple compressors, multiple evaporators, sometimes multiple condensers, multiple metering devices across this whole supermarket. So, instead of having you know back in the day in this in the early 60s and 70s and 80s, they would have single systems. They would have you know, the meat cases would have their own compressor, condenser and metering devices, and it would be separate now, as things advanced, we started putting systems together, they become more efficient, more reliable, uh, more redundant because everything about refrigeration is about redundancy.

We wan na we're trying to keep food cold, we're no longer trying to keep people comfortable now we're trying to keep product cold and preserve product. Everything about this is about preserving product, so people could sell product instead of having one compressor for the system. Now we have multiple compressors on this on this refrigeration rack. So you start out, you have, you know multiple compressors of different sizes.

Some of them are the same size. Some of them have variable capacity, meaning vfds. Some of them have unloaders on them. Some of them have uh digital compressors, there's all kinds of ways screw compressors receive compressors scroll compressors.

It could be any of these um the way it's set up and they are piped with a common, suction and lick or discharge manifold. You have a common suction manifold and you have a common discharge manifold. So all the compressors are piped together. So you are able to meet the demand of the system, the saturated suction temperature you're able to meet that demand by cycling on and off, compressors or varying the speed of compressors.

So we are able to instead of cycling, a unit on and off on temperature. Now we are able to take that and we are able to manipulate the saturated, suction temperature of the system to meet the demands and load of the supermarket. So now this thing we are able to tailor this system to the demands of what we need. So we have uh just the standard compressors.

We have a suction header that your suction return gas is coming to, and then we come to a discharge. We come out of the compressors. We go to a discharge header where all your compressors tie into in a row. They all tie into a discharge - header, okay and after they all discharge together.

So now we have to deal with oil. Oil is probably one of the hardest things for guys to deal with in a supermarket and probably the most from problematic thing. Um of the supermarket rack refrigeration system, so we have to capture this oil because we have to feed all these compressors back the soil because we have oil coming back from the system. We need to get the oil back in the compressors so after it goes through this common discharge manifold and it's going to go into an oil separator.

This oil separator is going to capture the oil and return it back to the compressors. Now in a supermarket rack. Refrigeration system, you could have several types of oil separators. You could have a coalescent oil separator, which would be a filtered element that is going to cause the oil to aerate from the from the refrigerant and drop down it.

Basically, it filters the refrigerant and it causes the oil to separate by aerating it and the oil is heavier. So it drops down into the oil separator. Now you could have a coalescent, i'm sorry, nicolas and you could have a centrifugal type of oil separator, which is a screw type, so it is basically a screw inside of a cylinder. The discharge, gas and oil get forced up the screw.

The oil comes back down. The screw, because it's heavier and it falls and down to a reservoir in the separator or you could have it in what they call an impingement type separator an impingement type. Separator is a common. What you see on old systems? It is basically a cylinder.

The oil co or the discharge, gas and oil come through hit a screen, and in that screen it causes it to aerate kind of like the uh like the uh coalescent, and it causes it to drop out and fall down. Now. All three of these separators have different benefits: uh they're. All this.

The centrifugal is, you know better than the impingement type. The impingement type is probably the least efficient. The uh, the coalescent is the most efficient. It's going to separate the most oil and it is going to it - is going to clean up the refrigeration system as uh more than the other two would right.

You want to take the rest of the oil system, sure well on this uh part of the slide. We have you know, like kevin. Just went over the oil separator, which then is going to feed uh into the reservoir. This happens to be a low pressure type system um.

You basically have uh three or two different pressure drops, so you have flow because we can't have flow without you know having different pressures right. So you know going from the oil separator. Let's just say our discharge pressure is uh. 200 pounds uh.

You know it. You typically on the top of the reservoir. We have what's called an oil differential valve and that's what's actually going to uh, give us the reservoir pressure. Typically, this is either an ocv5 or 10 or 20 or 30..

You know, and what that's doing is basically wherever, wherever the ocv is actually piped into that's giving you a pressure, above whatever suction pressure, it's tied into on this particular system. The ocv is tied into what looks like the medium temp type type of the system. So what that's going to do is, let's just say, the medium temp side is running at 40 psi and we have an ocv 30.. That means inside that reservoir we're going to have approximately 70 psi of oil pressure, which then is going to you know, get filtered through the oil filter and then get delivered to all the rest of the compressors through the oil level, controls or sometimes they're referred to.

As oil pots, if you notice uh, you know the ocv is tied into the medium temp side of the header. The reason for that is because we do not want. We don't want the oil line off of the ocv hooked up to the lowest suction, because if we were to do that, we wouldn't have enough oil pressure to actually go into the suction header or i'm sorry to go into the crankcase of the compressor. Got it because you're uh just to clarify the reason that that is, and because i think again, a lot of air conditioning guys aren't going to catch this quickly? It took me a while to get this.

Is this idea that um your pressure that you have in your suction header is going to be the lowest pressure that exists within the system and obviously your medium temp suction header is going to be a higher pressure than any low uh low temp? And that's obvious because we're talking about suction saturation temperatures, when you have colder temperatures, you have freezers, you're, doing ice cream, you're doing frozen foods, that's going to be a significantly lower suction saturation, and in this case, if we were to have tied it in to here, Then our pressure wouldn't be high enough to push into the crank cases of our medium temp compressors, whereas if you're using medium temp suction, that will still be high enough, obviously to push into the low temp correct, got it yeah cause. Otherwise, i mean you know usually 99 of the time. It's always going to the high uh, the highest pressure. Header uh.

Sometimes you'll see it. If you have two medium temp racks, sometimes you'll see it piped into you know the lower of the two. That's not the correct thing to do, but you know the way it should be piped in is just like it showed it should be going into the highest pressure header to make sure that we have that correct differential pressure to make sure we can get that oil Supplied into the oil level controls to fill those compressors up, so they don't dry out, i'm gon na kind of step in and just play the the stupid air conditioning guy here, um every once in a while. Just so that way, we we don't get too far ahead of where everyone is, and i just want to state the obvious, which is that we're talking about oil, it's so critical in these systems, because you have all of these compressors that are sharing oil and so Obviously, you've got to have oil, that's continuously returning to all these compressors and it's so critical that that oil doesn't end up out in the system kind of getting lost out in these giant systems, because you have these, you know miles of pipe work, probably exaggeration, but A lot of pipe work going out into the store um, you have all these evaporators and if you've got oil, that's making it out, it's a little bit will but but very little amount.

But if significant amounts of oil is making it out into the store and not making it back, then you're going to have you know pretty severe issues and you're also going to have performance problems, because that oil is not good. We don't want it out in the store; we want it, just returning back to the compressors and that becomes so critical in market refrigeration. It's like the magic sauce and market refrigeration that, when uh, when somebody who's used to air conditioning, shows up it's like what is all this stuff and it's all about making sure that you get proper compressor lubrication after you leave the oil separator guys we get to A check valve so we're going to have a discharge check valve, so this discharge check valve does a couple things. It prevents refrigerant migrating back into the oil separator.

If the system were to shut off so say, the compressors were shut off for a safety reason or the compressors were some kind of some kind of uh safety situation they shut off or if the system was to satisfy, in the middle of winter time via low Load issue: you don't want all that liquid migrating back into the oil separator, because once it migrates back in the oil separator, the oil separator doesn't know if it's liquid or liquid, refrigerant or or oil. All it knows is that it's going to allow it to flow into the reservoir, then flow straight to the compressors. So obviously you don't want that, so that is going to cause um liquid to enter your compressor, so that check valve is there to prevent that migration of liquid refrigerant during a safety situation and a low load situation. So in other words, liquid oil in compressor, crankcase.

Good, liquid refrigerant and compressor crankcase bad, very, very bad. So after we leave that check valve now we're going to come to it. This isn't on every rack. This is just depends on the customer application.

You could come to a three-way valve. You could come to some automated ball valves if you have heat reclaim so heat reclaim is basically we're taking um the discharge gas out of this machine, this rack and we're using it to heat, something whether it be the snow melt system for the store like we Have in chicago we have a lot of snow melt stuff, so we're melting, the snow on the sidewalks or the in the gutters, whether we're using it to warm up a water heater. So we have a uh, refrigerant, uh, heated water heater, so we're picking up the it's using the refrigeration heat to heat up the hot water for the store or it could be using it for air heat, meaning we're heating, a coil on a rooftop or an air Handler or a uni heater in the back room where we're using the refrigerant heat to reject in a system. So now this becomes even more efficient because now the system's removing heat from the cases, it's refrigerating the cases and it's taking that heat and it's using it to heat the store yeah.

We see this a lot in in florida um for all the reasons that you mentioned other than all the snow stuff, because we don't know what that is, but we use it a lot for reheat for dehumidification as well. So you know when you have a need to dehumidify, but you don't have a need for comfort cooling. Then you can, you know cool the air drop the moisture and then reheat it using that uh excess heat that you had from the rack refrigeration system yeah. I wish we had more uh preheat around here.

We're not allowed to have that yeah any pla, any places that a lot of times that have high humidity when i was up in connecticut uh reheat was just it had to be there because otherwise uh you know these, the store would get super cold, but then Be just miserable humid uh because you know, basically it would reach uh, maybe 66 degrees in there, because it would pull down so quick. But yet you know it needed that reheat to stay running, to make sure you keep the store a little bit warm to keep a load on the compressor, so they didn't actually maintain temperature yeah, it's actually fairly rare in chicago now they make it very difficult for Us to have reheat with all our safety stuff we're using that we're using that either three-way valve or uh, automated ball valves or solenoid valves to reheat that so the way this works is this three-way valve. It rejects it. It sends refrigerant one way or the other.

So when it's energized, it allows a plunger to move inside of it and shift the way the refrigerant goes when it's de-energized, it's going straight to the condenser, it's going straight out towards the condenser when it's energized and it's in reclaim mode. It's sending all the refrigerant through that reclaim tank or coil or whatever it is, and then it's going back through a check valve, so it can't flow backwards and it is directing that towards the condenser that may not be on every rack. It just really depends on the application um of where what it is and how the customer designs it so after it leaves the reclaim if it's there, then it's going to go to our condenser splitting valves or three-way valve. So again we have another three-way valve or we have solenoids.

We have to control our condensing pressure. With this rack i mean you could be running, it could be sized for 115 degrees and it could be needing to run at a minus 20 degrees. This is this machine runs all year round, so we need to be able to tailor this machine to our conditions say in chicago. It goes from 100 degrees all the way down to you know.

Last year it was minus 20 for a couple days. So if we were to use say we have this massive 12-fan condenser on the roof, if we were to try to use that condenser when it's that cold, we would never have enough refrigerant in the system to operate that condenser. It would be so massively oversized. We would never need it, so what we do is we split the condenser in half.

We do this with us splitting controls so that we have a three-way valve in this picture. So in this example, so this three-way valve, when it's de-energized, it allows refrigerant to go to both sides of the condenser. The plunger is down or i'm sorry it's up and it's allowing everything to go and when it's energized it's in split mode. It only allows refrigerant to go to one side of the condenser, so in the winter time so usually, you know 40 50 degrees, most grocery stores.

They shut off one side of the condenser. So now we're able to better match the condenser operation to our actual ambient temperature. So, instead of having a massively oversized condenser, now we have a more appropriately sized condenser for the ambient temperature. Now, like i said you can have a three-way valve, some customers use uh, solenoids and they're always going to be normally open than they should be, because you always want refrigeration to fail on.

We would use normally open solenoids, a three-way valve electronic stepper valves to do this. Uh electronic stepping three-way valves, there's all kinds and actuated ball valves. There's uh multiple different ways to do this, but that is how we take the condenser and we split it in half. For winter time, if you notice in this pictorial, you'll see that there's two check valves on the outlet of both sides.

Now what he was saying before about you know having normally open solenoid valves on the inlet side. The reason why we have both those check valves there is because when it does go in a split, we need to remove that refrigerant from there. Otherwise, it will just log in there during the winter time and that's why we have uh the solenoid on the blue line coming off the bottom check valve. You know.

Basically, what that's going to do is when that three-way valve shifts it's going to stop the flow on the you know, summer side of the condenser that's labeled there. The check valve is going to prevent refrigerant flow from coming back up. The actual uh drain leg or drop leg is what we refer to it and then basically that normally closed solenoid line. That's on the blue line.

There heading to the suction line, which is on the green, is going to open up to remove that refrigerant. In the same the same hit, it's also going to pump out the refrigerant on that other line on the three-way valve in this instance and head out towards the suction line, to remove that refrigerant and basically that'll end up in the receiver yeah. Because you don't want a bunch of refrigerant just sitting, there absolutely makes sense, and then we have uh from here. We have the a8 pressure regulating valve.

That is a inlet pressure pressure regulating valve. So what all that cares about is the pressure on the inlet side towards the condenser. Basically, there you know, if you have in the middle of winter time, you might have the temperatures where it's going down to zero or even 30, like here in texas, will start having head pressure issues, and basically you set that valve to a certain uh psi to Maintain that certain head pressure, just like you, were on smaller commercial stuff, where you have a headmaster where it's labeled, 180 pounds or 150 pounds, which i know a lot of you guys have already seen out. But because these lines are so big, we need to be able to use two separate valves if we tried to use a headmaster on a rack.

Refrigeration, it'd probably be two foot big. So, instead of that, we use uh, you know the a valve for the inlet pressure regulator and the a9 as an outlet pressure regulator as the hot gas bypass. Basically, we refer to as a receiver pressurization valve um. So if the a8 valve starts holding pressure back, that means the outlet of that valve is going to start going down in pressure.

Well, we don't want that going too far down, because our expansion valves need a certain pressure in order to operate properly. That's when the a9 will start pressurizing hot gas into the receiver to help push that refrigerant out um, to push it out to our expansion valves or wherever it might be going yep makes perfect sense a lot of very specific purposes for each one of these valves And though they may look similar, they have very different uh, very different purposes, and i think that's, why being able to identify all this is so important because it can get confusing fast. So from the drain, leg or drop leg is what we referred to it earlier. Uh that refrigerant is then going to head into the receiver.

Typically, we try to maintain anywhere from you know, 15 to 30 percent, depending on what the manufacturer wants uh what the customer wants - and this is just to make sure that we get a liquid seal going out out of the receiver to ensure that we have a Full column of liquid, leaving uh leaving the receiver, which goes to the liquid line. This is very, very specific when you're talking with someone trying to diagnose something, there is a major difference between drain leg or drop leg and liquid lines, so just make sure that you understand you're only ensured that you're going to have a full column of liquid coming Out of that receiver, due to the way that the the receiver is actually piped, internally, yeah you're, going to have a very low sub cooling number like like a lot of guys, are used to seeing you know. Sub cooling, with an air conditioner you're gon na have a very low sub cooling number coming out of that receiver, maybe like two to three degrees. If you're lucky on a great day, it's going to be extremely low, that liquid receiver is ensuring it has a dip tube in it, and it's picking up liquid in there and it's ensuring that we have a full column of liquid going out to our expansion valves.

Because we can't maintain a sub cooling number, because our condenser is not backing up refrigerant in there we have a system where we're having a receiver, because our charge varies so much because things are shutting off. Things are turning on, things are going through. Defrost things are um affecting the system load wise. So that's why it's not a critically charged system.

It's a uses, a receiver to hold the access charge like a buffer tank. Almost you've got extra. You've got extra because you have a lot of different things that can go on in the system where you need a variable amount of refrigerant, and i also want to mention, because that was actually something that blew my mind: the whole the whole drop or drain leg. It's like that's the liquid line right, it's coming out of the condensers, we always say the line coming out of the condensers.

That's the liquid line! Well, no because it isn't necessarily going to be even full of liquid. You know it's not how it's designed the one. That's going to be have the full column of liquid is the one coming out of the receiver and also there's just if you confuse the two then uh when you're talking to somebody on the phone they're, not gon na, have any idea what you're talking about so Specifically in industrial systems, it's funny because, like uh you know, sometimes there is sight glasses on the drain leg and the you know they basically you'll see the refrigerant trickle down going into the receiver and vapor is actually going back up to get recondensed because obviously the Liquid is heavier than the vapor i'll. Take the super hard one so coming out of the receiver coming out of the receiver, we go down to the filter dryers.

This is to ensure any type of debris. Uh you know going through. The system is getting caught before it goes into, you know any of the expansion devices or you know anything critical that could, you know basically gum up um, which then in turn then goes to the sight, glass uh. This is just to you know, really just to ensure that you do have a full column of liquid um, going out from your filter dryers a lot of times.

You could have a receiver level of 30 40, 50 percent, and if you have a some sort of blockage in your filter dryers, you will actually see flashing in that site class. Unlike a normal system or air conditioning system, we want it with a receiver. We want to see a full sight glass all the time, so we want that side glass to be full all the time. If it's not full, then we have an issue whether it be like a low receiver level plug filters.

Uh plug screen that that sight glass needs to be full all the time in order for us to have proper flow to our valves. Now, after we leave the dryer and the liquid line sight glass, depending on the system, you're going to see this more on low temp systems and a lot of newer stuff, both low and medium temp, meaning, freezers and coolers, are starting to use sub coolers. So what we're doing on this? So since we can't gain sub cooling by backing gas up in a condenser on a trip on a traditional rack, because we have that receiver there. So now we have poor sub cooling going out there.

We have a solid comma liquid, but we have two to three degrees of sub cooling. Maybe five you're lucky going out to those valves well that doesn't lead to the best valve performance, especially when it's 100 degrees outside and that liquids 100 degrees. Your 100 degree liquid is not very efficient, feeding those valves so everything's about efficiency here. So especially when you get to low temp, when you start seeing this, you start seeing low temperature refrigerant.

It takes a lot of horsepower to do that. So, in order to make this system more efficient, we are mechanically sub cooling, the liquid. So what we do is we take a brace plate, heat exchanger and we are running the liquid line line through it and then, on the other side of it, we have a refrigeration circuit. This can be done a couple ways.

This could be say: you have a low temp, rack and you're using the medium temp rack to sub cool it, so we're using the medium temp rack to cool the liquid of the low temp rack. This allows us to bring our liquid temperature down to 40 50 degrees, whatever the customer design is - and this allows us to do a couple things - it allows us to run smaller liquid lines, because now we don't have to worry about the pressure drop as much. It allows us to have smaller expansion valves because now we're able to feed that with more efficient liquid and it allows the system to be more efficient because now you're feeding that expansion valve with say 50 degrees of super, i'm sorry sub cooling. And now you don't have as much flash gas going into that valve and that valve is going to be way more efficient.

So it makes the system more efficient. You could actually have smaller compressors. The whole rack could be smaller because you're running that efficient 50 40 degree liquid. Now there are racks that self sub cool.

When i say that they're economized they have economizers like you, would like some screws do with economizers. Basically, the compressor has an inner stage, meaning a second stage of it that is actually running the sub cooler. So the sub cooler is uh, no longer a parasitic load, it's a cancelization out, so you don't lose any uh btus by sub cooling it and you gain btus. So it's a it's a win-win on both sides, whereas if i was using the medium temp rack to do this, i increase the load on the medium temp rack now, instead of uh just keeping it all in the same rack.

So there's that's the two different ways that they're doing it so mechanical sub cooling allows us to uh, make the system all around more efficient yeah in simple terms, because we say brace plate heat exchanger and some guys like. Well, i don't know that is like this. Is an evaporator? That's what it is: it's a direct expansion evaporator and you you're using another evaporator in order to cool the liquid uh. You know on this particular rack using in this case we're showing it using another medium temp rack.

So it's it's really simple. The design it makes perfect sense, but, like you mentioned it does add, load because it is another evaporator coil. That's on that other circuit. Also, one more thing that i wanted to mention: you'll see that the you know any kind of bracelet heat exchanger, as you referred to as the evaporator you know basically always has bi it's it's doing counter flow.

So if you look on this actual pictorial you'll see that the expansion valve is there at the bottom and you're feeding the warm liquid at the top. That's to get the most efficiency out of that bracelet heat exchanger as humanly possible yeah, that's the same, even if you're doing um every time anytime you're using a heat, exchanger you're, almost always countering flows, whether it's water on one side and refrigerant. On the other, a some sort of secondary fluid like co2, regardless you're, almost always doing counter flow to get maximum heat exchange yeah. The only reason why i bring it up, because i know that you know sometimes when these things are put in aftermarket where you know they're doing a retrofit.

You know sometimes they're piped in incorrectly and they're, wondering why i can't i can't get it down temperature. Well, that's the reason why it's not piped in counter flow: this is the old r uh, the liquid differential regulating valve. This is placed on the liquid line coming out of the liquid header. The purpose of it is to maintain a differential during defrost, so that top evaporator, if you notice, underneath the expansion valve and underneath the liquid line solenoid, there are check valves in the opposite direction of where the refrigerant typically flows during defrost.

What will happen is off of the discharge header. There is a two-way solenoid valve right connected from the red line going into the green line. What that's doing is putting hot gas into that evaporator. Now what would happen is if that oldr did not exist.

Basically, that evaporator would end up just filling up with whatever pressure that the discharge pressure was currently running at. We would have no flow. It's not really the hot gas that defrosts that coil, it's the latent heat exchange. So basically, we need to have flow running through that evaporator in order to achieve defrost.

So what will happen is when that valve the old r goes into differential mode. It's actually creating a differential of anywhere from 20 to you know upwards of 30 pound differential. What that's doing is actually making the discharge pressure, 30 pounds or 25 pounds heavier than what the liquid pressure is. This is to ensure that we can actually flow vapor through that that two-way solenoid valve into the evaporator, bypassing the expansion valve, bypassing the liquid line solenoid and going back into the actual liquid header.

Because when we're doing this, we're actually creating liquid we're taking that hot gas we're actually desuperheating it making a latent heat exchange, which is really what's doing, you know most of the defrosting and then in turn, going back up to the liquid header itself. Yeah. That evaporator is becoming a condenser right, it's actually using uh, it's it's taking the ice, that's on that evaporator coil and the and the um, the lack of heat. That's in that evaporator coil and it's condensing that um that hot gas that's coming from the defrost header and that's really what's doing the work.

Like you said, it's a latent heat exchange and that's once you're going to get your head around that it's a eureka moment at ldr's. I i kept talking to nathan about it when we first started like what i don't. I don't understand, what's happening here and then. Finally, it's like oh okay.

Now it makes sense in order for it to get back into the liquid header. There has to be a pressure differential between this defrost header and the liquid header, and the ldr is what allows that to happen. Yeah, it's very similar to a heat pump with a few added components, see now you're speaking my language. It's very similar to the heat pump, see we we break apart our three-way valve and uh it's broken apart, so it's a couple, different components and then the old r is a added component.

Now you could replace that with a ddr which would be a defrost differential. So, instead of doing liquid defrost or a latent defrost, we could do hot gas defrost, meaning we're taking discharge gas. Just like a heat pump. Would we're taking discharge gas and shooting it back down the suction line and we're defrosting the coil that way with discharge gas discharge? Gas has more benefits to it.

I mean it's a faster defrost, it's a more efficient defrost, it's all around better and humid climates. To use that, but i mean it does drive up the head pressure so that that is the non-benefit to it all right, who's who's going to take the ever complicated ball valves. Oh, this is a difficult one. I'll do it! So i i just labeled this one ball valves because it doesn't, you know, basically it's going to dictate where ever you know, the name of the valve is going to dictate wherever it's actually placed uh the ones over on the green side is going to be your Your suction line, ball valves, uh, the ones on the blue line - are going to be your liquid line.

Ball valves. You can have ball valves all over a rack um, so i mean really wherever it is. I mean on whatever line that it's actually connected to and that's what you'll refer to it, that one is a liquid line. Uh ball valve that one's a discharge line ball valve yeah and the main thing there is.

Is that don't don't burn them up to begin with, so that way they actually do close when, when you need them to close, i i i don't know much, but i know that much because i've had enough of these suckers where you go to try to isolate And they don't isolate either that or they start blowing refrigerant out of the packing yeah exactly okay, uh. Let me take this one um on on the this solenoid uh. You know we have uh, there's the sometimes you can have bi-flow uh solenoid valve, so in the instance of that top solenoid, you technically wouldn't need that check valve. If that was a bi-flow solenoid, where basically, you could have flow in either direction.

But these are all you know single way. You know one-way, solenoid valves, um that are that are in this pictorial. So, depending on the system, you may have a liquid line. Solenoid valve you may not, so it just depends on the customer setup like where i was saying we have these liquid line, solenoid valves that we're going to have on here, depending on the customer.

Some customers don't have like a line solenoid valves at all and if they're there they're there for uh emergency shutdown and defrost they're, not actually controlling temperature with them. Usually we have after you leave that liquid line solenoid valve. We are going to come into our expansion valve, so we have a txv. We either going to have a txv, a a standard txv or a balance for txv, meaning it's uh.

It's able to a balanced 4txv is able to handle greater swings and pressure and conditions. So, like the tonnage of the evaporator can change a little bit more. It can handle that. So it has a greater control over that evaporator than a standard.

Txv um we're starting to see a lot more electronic expansion valves now so as they you know, become cheaper uh and controls become better we're integrating a lot. A lot of new stuff has a electronic expansion valve, so we have steppers. So we are able to control super heat to the you know, my new my nudist bit and then we're also using what they call pulse valves now, which are basically a orifice liquid line, solenoid that pulses on and off to feed refrigerant into the evaporator and control Superheat that way, those are going to be the three main metering devices we don't use any cap tubes or fixed orifices, or anything like that anymore. It is all going to be expansion, valves, thermal thermal expansion, valves, uh, eevs and pulse valves is what you're going to start seeing and all those of those are going to feed out into a distributor.

Now this distributor is just like you would have an air conditioning system. It is distributing refrigerant to multiple different passes in the evaporator coil. Now the things that are a little bit different about our distributors are systems that have hot gas, defrost or cool gas defrost for defrost. We have a built-in tee into these things, so it's not a tee, but it's a auxiliary side connector.

So what it is doing is it is taking the orifice that is inside of the distributor that creates the uh the vortex and makes it feed evenly it's taking that and moving it forward towards the expansion valve. So we do this because that orifice is very tiny. So we need to be able to move quite a good volume of liquid refrigerant back through that coil during defrost that hot gas is going to go through and condense into a liquid. And it's going to come back through those distributor tubes.

And then it goes into this asc and it's going to take a turn and go around the expansion valve through a check valve and then back into the liquid line. If that asc wasn't there and it was just a t, what ends up happening is inside the distributor of a normal distributor is the orifice. So what ends up happening? Is it hits that orifice and instantly slows down and you're never going to flow? The proper amount of refrigerant through that that augs, through that uh that t in order to properly defrost that coil. So that's where this auxiliary side connector comes in and allows you to move that auxilia or that uh orifice forward towards the expansion valve and allows the refrigerant to bypass that orifice and go around the expansion valve through a check valve into back into the liquid line.

So that's where our ours changes a little bit versus a normal distributor, orifice and distributor. Then we go through our evaporator coil, so we go through our evaporator coil, it's no different than a normal evaporator coil uh, except for fin spacing. So we have a lot tighter fin spacing because we're trying to main maintain these uh. Actually, it's a lot it'd be less, probably yeah greater distance between the fins yeah wider space, yes, low, low temperature, we're having a wider fin spacing and uh medium temperature, depending on it is, i mean some of the thin spacing is probably pretty close to a normal Evaporator coil, you would see in a house now i mean these cases have become so efficient that the fin spacing's like super tight on them, because they're trying to maintain that temperature difference from refrigerant temperature to air, don't forget to you know, mention the most important part Of the txv is the strainer in front of the txv.

You know these supermarket systems can be extremely filthy. You know whether it be debris from a compressor debris from you know, new systems being brazed in you know. This is the filters that are put in here. Just to ensure it's a small mesh screen that goes on the inlet of the expansion valve, not every single expansion valve has it, as you guys know, in air conditioning, but in refrigeration.

It's very just smiled upon whenever you have an expansion valve that does have a strainer in there to ensure that you can clean it. So you know the expansion valve itself does not become gummed up with debris. Yeah. It's it's pretty rare to have a bad expansion valve uh, most of the most of the time in supermarkets.

Most of your time spent cleaning stuff. Just like basic maintenance. I mean you spend a lot of time: cleaning, whether it's cleaning, evaporator uh, evaporators, cleaning, expansion valve screens, cleaning the pins on the expansion valves. You pull the expansion valve apart.

You clean the pins clean, the orifice uh they gum up. I mean there's a lot of oil in this system and a lot can go wrong. Real, quick with the oil and a lot of issues you know stem from that, so a lot of screens will plug up. I mean it just depends the more maintenance you do on a system like this.

The less problems you have, but i mean problems always occur, and i mean that's: that's why it's always so busy yeah for sure uh cleaning screens is like uh. One of the or swapping screens is like one of the most uh normal usual things that you have to do in the market. Refrigeration, it seems yeah, it's very satisfying, watching all that frost melt away from the valve all this uh. You start it back up.

So now we come out of the evaporator. Now we, this is where our entire temperature control control strategy - uh comes in here on a supermarket, so on a supermarket, we're generally not controlling temperature by cycling, a silhouette on and off that is a very poor control. There are certain applications where it gets used on some budget stuff, but what we are doing is we are manipulating the evaporator pressure and saturated temperature. So what we do is we have this device called an epr evaporator pressure regulator, so we are backing up refrigerant pressure inside the evaporator and setting the temperature of the evaporator.

So i can set this evaporator temperature to anything i want. I can make this uh evaporator a 20 degree, saturated uh temperature, a i could make it a 19 degree temperature. I could make it a 35 degree temperature, so i could vary this evaporator temperature, which is going to vary my case supply air temperature. So we are trying to maintain return, return, air temperature in a walk-in or supply air temperature in an open air case or a frozen food case.

We're trying to maintain that supply air temperature. We do this by changing the evaporator temperature, so every case manufacturer or store is going to have a legend, and it's going to tell you what the evaporator uh temperatures need to run in order to maintain a certain discharge, air temperature. So we're able to manipulate this system, so i could be running a minus 20 saturated suction temperature on my compressors and i could be running a plus 25 degree evaporator for some meat cases on that same header by using that evaporator pressure regulator. I'm able to change that pressure and manipulate it and change the actual temperature of the case with this device.

So long as you're going up from your suction header pressure, you can't the valve can't make it go lower than that. That's a common misconception. I've heard air conditioning guys have is that they think it can control it either way, but it's just increasing the pressure and therefore the temperature, from what the suction header is yeah. We can only go higher than what you know than what the suction the saturated suction is set for at the actual suction over the compressors that it's connected to.

If we refer to air conditioning right, we usually maintain a third, what 38 to 40 degree saturated, suction, right, yep and usually the discharge error is anywhere from 52 to 55 right. So usually that would give you approximately about a 15 degree. Td is what we that's. What we refer to in refrigeration step, basically the difference between your saturated suction and your discharge, air and that's what we're accomplishing here.

If we're trying to maintain 35 degrees, we would set the evaporator if it had a 10 degree td we'd set it for 25 degrees. Exactly the same premise that we do in hvac just with lower temperatures, yeah, that's another interesting thing because in um in hvac, we'll talk about td um. So we'll talk about design, temperature difference, dtd or td, and we refer to that as the difference between the entering air temperature and the suction saturation. And so we would say a common dtd would be 35, but in refrigeration they refer to it.

As the difference of the supplier, the air returning to the box versus the saturated suction, it's important that you, you know, get that distinction between the two segments. Otherwise, you'll be like what you know: 15 35. What is it yeah and i mean some of ours? Are you you see uh design, temperature splits is as low as like. I was doing some cases this morning.

They were four degrees, so we're maintaining four degrees from our evaporator temp. So i had a plus 27 uh degree evaporator and i'm four four degrees above that. So 31 degree discharge air temp and that's what makes all these cases more efficient now right. They you know years ago, the you know, that's the fin.

Spacing is really what does it um? You know the meat cases they used to be about maybe an inch and a half away from each other from fin to fin, and then they got a little bit smaller and then you know where the td was originally, let's just say: 15. The fin spacing then got less and they're like oh, we can get 10 degree td out of it. You know so we can raise our saturated suction they're like well, let's put a lot more fins in there and make it a lot more efficient, and then we can get it all the way down to three four degree: td, which means we can raise our saturated Suction a whole bunch more and actually save energy right, because then we're reducing uh. You know we're reducing the compression ratio, which means we're saving energy yeah absolutely and then out of here you just go right back into your suction header and reback, your compressors and all over again.

A lot of people who are listening to this are probably like man like they miss like a lot of stuff. There's. So many questions that i have it's like yeah. That's the reason why they have an entire podcast about all of it and not just a single episode um.

So this is like a lifelong pursuit, not something that you can cover and all the different exceptions and types of system infrastructures, let alone things like co2, and all this gets really really complicated. I'm going to kind of turn it over to you, brett. To kind of you know, wrap us up here and tell people how they can find your podcast, how they can interact with everything you're doing you're going to be at ahr any any stuff. You want to announce about uh about what you got going on and how people can connect with everything you're doing absolutely so i'll i'll, be at ahr in vegas i'll, be at the spoiling tent for the first two days, uh from 12 30 to 5..

You guys can come see me uh sportling's, doing a giveaway, uh i'll be doing a giveaway as well with some uh advanced refrigeration, podcast merch. I we will both be at your symposium down in claremont uh. Yes coming up, so you know we will both be there. Tickets are already booked um, they can find us at advancedrefrigerationpodcast.com uh.

We have a site where we have all our merch as well as uh. You know we're on almost every single major platform: uh apple podcast, spotify, google, you just look it up and you'll find it everywhere and we also have started doing heavy controls. Videos um on our youtube channel as well. Yeah people will always ask uh.

How do i find the podcast? Where do i find the podcast literally easiest thing in the world, go to any podcast app that you like it doesn't matter pick one and type advanced refrigeration in the search bar and it'll come up. You know easy and then also i i they didn't ask this, but i'll just say it leave them a review. You know once you listen to the podcast and you and you hear it and you like it, which you will um leave it leave a nice review. Leave a five star review, especially on apple podcast, because that really helps uh the podcast rank.

It helps people feel comfortable, um listening to the to listening to the podcast, and so do that subscribe um. You know again, this stuff is being given away for free for the benefit of the industry. The best thing you can do is just support them in that way. Tell your friends that kind of thing: it's it's good! It's good work they're doing, and i'm excited to that.

You guys took the time to to do this and i'm excited for what the future holds with you. You guys doing great things. Thank you so much for having us on man yeah, it's a pleasure and we'll do it again sometime thanks for watching our video. If you enjoyed it and got something out of it, if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click, the notifications bell to be notified when new videos come out, hvac school is far more than a youtube channel.

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