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Rector seal rector seal is a sponsor of HVAC school podcast. In this episode and one thing that we've been doing on our trucks here at Kalos services and Central Florida, my business we've been trying out the leak freeze product only in a very specific use case. Older systems, with very small format, carry leaks with customers who really don't want to spend the money in order to get it fixed right away. We've been doing some tests with it, and we've been pretty impressed by the fact that this leak, freeze product is reducing leak rates or eliminating very small form of carry leaks.

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Air washer, if you want to read that and kind of see the engineering that went behind it, I mean it. Willis carrier was really a smart guy, like he did a lot of work, but mostly what he did work in was humidity really psychometrics is, is what Willis carrier brought and that's where the term air conditioning when we say air conditioning before that there was refrigeration, refrigeration Existed but people weren't thinking about the entire picture of air and that's what Willis carrier really did was invented systems that could handle all of the ventilation and dehumidification or humidification and cooling or heating of the air. All those things simultaneously, because that's truly what air conditioning is so, if you want to, if you want to find that that historical document, you can go to HVAC our school comm forward, slash Willis, that's HPC! Our school comm forward, slash Willis episode, is also sponsored by Parker zoom lock, meet zoom, lock the 10-second flame free refrigerant, fitting from Parker reduced labor costs by sixty percent with no brazing no flame, and no fire spotter discover how sumac can help you be more efficient And productive visit zoom lot comm for more information there once was attack from the south was always running his mouth. He started a podcast boys ego was vast, but it can't find another rhyme for South Brian are like hats off to those of you who can write a limerick right off the top of your head.

I I was trying to find a good word other than mouth to rhyme with south for like half an hour. I couldn't think of anything, but I said heck with it. I'm just gon na go with a limerick anyway. Today, on the podcast, we have dick words from refrigeration training services and dick is one of the few people who I really really really went out of my way to get on the podcast, because I'm a huge fan of dick.

I think he does great work. He's a technician at heart and he really understands technicians he's one of the premier trainers in the industry, especially when it comes to refrigeration and he wrote, wrote the book on refrigeration for air-conditioning technicians because it's it's called commercial refrigeration for air-conditioning technicians and today that's what We talk about commercial refrigeration for air-conditioning technicians, so here we go dick, worse, commercial, refrigeration for air-conditioning technicians. It's in its third edition, which I didn't realize, because I had the second edition and I didn't realize how much could change in a book until I went to the third edition, and the third edition really is tremendous. I mean there's so much added into that edition.

It goes into co2 and I'm gon na open my eyes and a lot of things. I was shocked at how much I learned, having already read the second edition going to the third, so a third edition is great and then also the name of your organization. If I'm not mistaken is refrigeration training services, that's correct. If you wouldn't mind just telling us a little bit about where you you know where you came from how you got into this business and then how you got into teaching and being an author.

I started out in air conditioning actually in sheetmetal, while I was still in college and eventually went to work for the company and was in the engineering part of things later on, transferred into installation service and became the service manager, and a sister company was a commercial Refrigeration company - and I was fortunate enough to transfer over to that company and the first couple of days in commercial refrigeration was just awesome for me, and I said this is where I want to be, and eventually set up my own company, along with my partner, and We went into business in 1974. Twenty-Five years later, I retired, sold out to my partner who's still running the company, and I got into teaching before I retired. I knew I wanted to go into teaching eventually. That was something that was important to me, because I had gone to a factory school at Copeland.

I think that was about 1991 and had some awesome instructors and I realized, even though I'd been in the trade for 15 to 20 years. I realized how little I knew and I came back to my company and started giving half-hour classes once a week, because I realized that my technicians needed some help as I had done and while teaching my technicians, I realized that's what I wanted to do when I Retired and I went to a community college and started teaching at night part-time and really enjoyed it, but once again I had an eye-opening experience about. There was a lot more that I needed to know before I could answer questions from my students. When I first started.

I thought I knew everything and after the first semester I realized there was a lot more. I needed to know so I spent the next couple of years going to factory school seminars, both on air conditioning refrigeration and then came back to the classroom, my better prepared. Then from there I developed some powerpoints at first. They were just to keep me on track, but I had my wife, who is a graphics person on computer, come up with pictures and drawings and so forth to illustrate what I was trying to teach and we would get refrigerant flowing through a pipe or electricity going Through a wire or something like that, and when I started using in the classroom, students were saying: why don't the other instructors have this one thing led to another and we started making instructor CDs everything that I put in the instructor CDs that I eventually started selling Where things that I used in the classroom - and so we would use them edit and get them the way we wanted before, we would allow them to be sold, and so that's what we've been doing since about 2005 is primarily selling the instructor CDs to instructors across The country and we have them in all 50 states and internationally as well, and then I got involved in a book that was kind of crazy, but a publisher convinced me that I had done a course in commercial refrigeration.

All I had to do was take. That course, and put it into the proper format, and I could come up with a textbook well, I thought that would be a good idea, because I was trying to help air-conditioning technicians have a resource that they could use to at least get them off of the Ground, as far as what the similarities and differences in commercial refrigeration and air conditioning are so that they could expand their scope, they started out in paperback, black and white, and it took off so next thing was hardback color and we did the third edition which came Out in January, but I've got a file full of things ready to do on the fourth edition, so that just keeps expanding because of things that not only I have found, but questions that others have sent me as far as needing to understand better certain things in Commercial refrigeration, so that's basically it yeah. That's a really - and you know what's interesting - is that such a consistent story with the best trainers out there, the best trainers out there always had a measure of field experience you have more than most. I think, but in talking to you, know guys like Jim Bergman or Dan holohan as a guy who I've had on the podcast or Jack Rhys.

You know these guys they've been in the field and so they've had that sort of hands-on experience and then they're able to translate it in a relatable way to the people who are actually doing the work and that to me seems to be different than people who Come maybe for more from the engineering side, who have very valuable information, and it's very important and very useful, but it's hard for them to translate that to the technicians, mind because they haven't been in the trenches experiencing it in that same way. I agree with you. Yes, so I want to highlight a couple things about this book. There's two things that make it different.

The one is is that you have been fairly unashamed about giving what you call t ro t, which is rules of thumb, basically for technicians, when you don't have data to reference from a manufacturer which is a bold move. And I want to talk about that. In a second here, but also you have some excellent graphics, I mean it's not just good photography, but also really good graphics. That show I mean everything from the flow of refrigerant and the different temperatures and pressures at different points, even in your diagnostic examples, but then also even some of your electrical diagrams.

Like your defrost diagrams or excellent, I mean they're they're unrivaled in the trade. From the standpoint of a technicians, mind they're not necessarily traditional schematic diagrams, like you, would see in a traditional textbook, but they communicate what a technician needs to know who's actually out in the field working on the actual product. So I want to I just kind of you went over this briefly, but what mine sent? Did you take into writing the book when I started writing this book? It was from my classroom perspective, looking into the eyes of my students, who were often technicians and trying to understand where they were coming from and trying to relate what they already knew to what I was trying to teach them. I'm not the smartest guy in the world and I did have difficulty understanding, air conditioning and refrigeration just like everybody else, but I think I was able to remember what was confusing to me and I think I utilized that memory of what were the tough concepts.

For me to helping me to learn it well enough to explain it simply as if I were talking to a new technician beside me on the job trying to explain to him what this concept was about. I didn't realize how important the basics were until I went to that Copeland school. There were two people that were teaching that it was George story and Glen Hannigan and I'll. Never forget those guys.

There was a class of about 30 of us at the factory in Ohio, and I thought I was going to learn about compressors, but out of the five day course, the first day and a half was nothing but basics. Super heat, sub cooling things like that. I raised my hand the morning of the second day, and I said you know I was kind of bored yesterday when you were going over the basics, but then I realized, I didn't understand the basics and I really appreciate you taking a step back and doing it That way to help me understand it better and Glen Hannigan smiled. He said: that's why Copeland asked us to start giving these courses, because people were complaining that Copeland was making a bad product when, in fact it was the technicians did not understand.

The basics did not understand what the compressor was supposed to be doing and that really helped me and I looked at how they presented things and that's how I presented them to my technicians at my company and started the training program yeah. I think there's with training and so for anybody who's been in two different manufacturer training courses or you've been to trade school or whatever. There's a couple different categories that I put things in one is the engineering side and if you've ever read a lot of the ASHRAE documentation. You know what I'm talking about stuff, that ASHRAE publicity publishes it's very important stuff, but it's highly engineering driven and there's all sorts of numbers.

On a page I mean formulas, numbers charts all that sort of thing, and I'm not discounting that, especially when you're on the design and engineering side, but for a technician. A technician sees that and they get overwhelmed pretty quickly and so in a classroom environment. That's generally not super effective and then there's the other side, which is the very simplistic I mean most of the manufacturer. Training that you go to nowadays is you know, teaching you how to hook up a BCD to their particular interface and the and the different things to consider with their particular product and the problem with that is it's good information.

It's also very good to know, especially if you work on a particular product, but it isn't general enough that it gives you a real understanding of how things work. It's so much more of the what and the how and not really the why but the sweet spot. I think that the industry needs especially right now at this juncture that were in with the skills gap and everything that we're facing is training that really teaches us, the wise and not the wise, at the math and engineering level, but the wise at the technician level. The wise at the Installer level, you know this is why, when a compressor fails, here's the reasons why a compressor can fail and here's what it looks like when you break this compressor down for the people who are the mechanical minds, the visual learners out there in Your book does a really really nice job with that.

I wanted to address this question of rules of thumb, though, because this is one of the things that I really appreciate about your book. Most most books aren't bold enough to do this. Did you get any pushback in putting these as they're listed here the TR, oh T's, the rules of thumb? Is you get any pushback from the industry on that? Yes, I did and the attitude was well. You can't actually say that ten degrees of superheat is the normal superheat, because it varies based on equipment, application so forth, and I agree with that.

But the trouble is the industry for years seems to like, let's say, you're reading something and it says: well, the you should have the appropriate superheat for this application period, and that leaves the technician in the dark. Well, where do I find this information so in training? My technicians, I had to come up with rules of thumb and I actually use them on the job, and I said well: is this accurate enough to get them in what I call the ballpark, in other words, get them close to what it should be and if Nothing else if they understand what the approximants are when they are talking to a knowledgeable factory, rep or an engineer, they are able to either ask questions or to understand what the rep or the engineer is telling them. If they have no idea of the approximations, then they're completely lost and they'll be confused, because one engineer will say one thing: another one will say another. For instance, we talked about superheat but is superheat taken at the evaporator or is it taken at the condenser and the answer is is taken at both places, but it's tremendously different because copeland, if you ask them what proper superheat is they'll, say 20 degrees superheat and If you ask heat craft what the proper superheat is, they will say 10 degrees superheat, but the difference is that heat craft is taking it at the evaporator at the evaporator outlet and Copeland is saying we want you to check it at the compressor Inlet because by The time it gets up to 20 degrees of superheat, we know we're not going to have a problem with flooding, and it's only through these rules of thumb that we are at least able to ask the right questions of the people that we're trying to network with Yeah and that's what you have written is exactly what the industry I remember.

I created my first training program for technicians. I think it was probably in 2002 or 2003 in that range, and I was looking at great great resources like the ract manual, a modern refrigeration. These types of manuals and they and they were excellent, but they even in those books. There are some rules of thumb.

There are some of those things, you know general design, conditions and those sorts of things, but I still struggled because I was attempting to communicate ideas like design temperature difference on an evaporator coil or a condensing temperature over ambient on a condenser, and they were buried in These tomes of very important works that cover the entire. You know depth and breadth of the industry, and so I attempted to make a lot of this stuff on my own, and a lot of it was wrong. You know cause I didn't know what I was doing, but over the years I've learned that a lot of the best trainers you would fall in this category and I think Jim does a lot of the same sort of thing is that you use what you see? What you what's being experienced out in the field and then what you test, what you can prove through testing and you put that in a way that's beneficial, because truthfully in this business and we're gon na talk about this in just a minute we're dealing with temperatures. I mean that's largely what we're doing, even when we're looking at pressures or converting those to temperatures and if we can get within a couple degrees of what it's going to be.

Even you know there will be some variation manufacturer to manufacturer, but if we can get ourselves within a couple degrees, we're gon na be in a much better position than if we didn't have that information at all. Exactly close may not be good enough, but it's a whole lot better than not being close at all correct, correct, yeah and that's an important distinction, and it's also important that technicians don't just stop with rules of thumb. You know and - and you would say that Jim would say that, and I would say the same thing: you don't just stop with a rule of thumb. You get into the manufacture data, especially if you have access to it, but a lot of times.

The rules of thumb are going to get you in the ballpark, like you mentioned before enough fit as a perfect example of this, when you talk about hot pull down on a piece of refrigeration equipment, you really need to get to a certain level before you can. Even accurately start to dial in a super heat say, and if you don't have any idea what you should be at even in a hot pool down, then you're. You know you have a new technician who has literally no clue what supposed to have they're, not gon na even be able to get to close box temperature. So actually, let's, let's do that, though.

Let's talk a little bit about the idea of conversion of temperatures to pressures and how an AC technician, because we're largely mostly honest, is going to be air conditioning technicians who are out there. Fixing air conditioners day in and day out and they're overwhelmed by. The idea of working on refrigeration equipment, because the Box temperatures are different and the refrigerants are different and and all those sorts of things. So what are some of the first things that you tell a technician as it relates to maybe they're overwhelmed with their feeling about working on refrigeration? Well, let's start out with the temperature I'd like to call it the evaporator keyd, because it's the temperature difference between the inlet air temperature and the temperature of the saturation temperature of the refrigerant that's inside the evaporator, and that is something that you can depend on.

As far as being very indicative of what's going on, the problem with just standard TD usage where the inlet air and the outlet air are being used is a lot depends on air flow, and this is especially important in air conditioning and of course, it does translate To refrigeration as well, but let's take air conditioning which most people understand when I came into the industry, there was one refrigerant that was being used. That was our 22 and the experienced Tech's who were teaching me did not understand refrigeration temperature. They only understood pressure and when I would ask them well, what does the suction pressure supposed to be, or what should the suction pressure should be? They say well about here based on it's a hot house, and we got a lot of humidity here. So it's gon na be up around this area and I said well what about the head pressure? Well, it's a hot day out here we got a load on the house, so it's gon na be up about in this area and he's pointing at this set of gauges, and I'm going on.

You know shaking my head like. I know what the heck he's talking about, but it was all kind of guess what I didn't realize until later on is number one. They had no idea about refrigeration, temperature and saturation temperature, and this, of course, was back in the 1960s when a lot of this was very new and there wasn't a lot of training going on and these guys in the field were basically thrown in there and they Were trying to figure it out for themselves, so I don't blame them, but I realized that they were able to finally get around to the point where they could say if it was working right or not, and of course, those old systems being seven and eight sear. You know you just they had gas to them and they seemed like they would run.

They're not like things are today, but when I did get into refrigeration, I no longer could depend on a pressure being in a certain area, because at the time there was r22 being used in commercial refrigeration. There was our twelve and there was our 502 and we had a wide spectrum of ambient temperatures. As far as the box was concerned, everything from fifty five degrees down to minus forty degrees, and so I had to learn about evaporator temperature, condensing temperature and how it relates to the air that's going through it. And this is the difficult and the scary thing for air conditioning technicians who are trying to get into commercial refrigeration.

It's like what the heck is it supposed to be. So once again, let's go back to air conditioning now we know that in air conditioning most of the time the evaporator t-d, the difference between the air coming in and the refrigeration temperature is approximately 35 degrees. So if I have 75 degree return air, I should have a 40 degree evaporator temperature. What happened? Let me add real quick there, because this is one area, the technicians, I've heard, get confused and you're explaining it very well.

But when we're saying TD, a lot of technicians will say: TD temperature difference and they're thinking delta T so from here on out when we say delta-t we're talking about the air temperature difference across the evaporator coil, exactly right, meaning rule of thumb. A lot of guys, sir around is 20 degrees, even though that's not always the case either. But that's the rule of thumb. A lot of guys say we're talking about TD, as in the difference between the boiling temperature of the refrigerant inside the evaporator, coil or suction.

Saturation is what we're looking at the comparison between that suction saturation temperature and the temperature of the air in the box. That is correct, so in the case of refrigeration or in the air and the return in the case of air conditioning, I just wanted to make sure that everybody is on the same page with what dick is talking about yeah and I'm not saying that using delta T is bad. I'm just saying that there are a lot of misinformation and easily made mistakes by going with delta T, and it boils down to in air conditioning delta. T can be fairly accurate because you've got a mixture of the air coming off the plenum into the first length of duct, so that is pretty good, whereas in commercial refrigeration, we're dealing with unit coolers or what I call a coil type evaporators that have a propeller Fan on them and to try and get an accurate measurement coming off of propeller fan is almost impossible, so we couldn't use a delta T very easily, even if we wanted to so.

The evaporator TD is so much more indicative of what's going on and that's what we use now on the other side which air conditioning people usually recognize is your condenser split and condenser split has to do with the ambient air. The air surrounding that condenser. That's coming into the condenser and once again the saturation temperature or the condensing temperature of the refrigerant inside that condenser and on 10 serie quipment for years it has been approximately 30 degrees. So what should it be? Well, if it's a hundred degrees outside, then I should have a condensing temperature.

That's approximately thirty degrees different than yeah, so 130 degrees is what you would expect, your condensing temperature, which is you take that on your liquid line? And that's you know if you have the? If you have the gauge built in or you have a test o or something that shows you, it's that's gon na, be your condensing temperature, your condensing saturation temperature, your liquid saturation temperature, whatever you want to call it it's what you're, seeing on your high side gauge? Not looking at the pressure, but rather looking at the temperature that relates to that particular refrigerant at that pressure, that is correct, and so we take that a step further. Now we know what the temperature of the refrigerant inside that condenser supposed to be. Let's just now take a temperature of the liquid line, that's leaving the condenser and let's say that the liquid line leaving the condenser is 120 well, it's 10 degrees cooler than what's going on in the condenser itself and that's what we call our sub cooling and for Years air conditioning was diagnosed with one or the other, either the head pressure or the suction pressure and too many in the old days it was like gee you have to take both into consideration. Then we moved on to understanding what sub cooling was about, how it was such a great indicator of the amount of refrigerant usable refrigerant in the system and about superheat superheat was slow and coming because we didn't have digital thermometers that could actually read the proper temperature Of the suction line, if we use pocket thermometers, it was a guess so that wasn't even taken into consideration.

Even when I started in the business in 2000, we were still using vodka thermometers. I mean it's crazy. We were measuring superheat with pocket thermometers, either jammed underneath the armor flex, or you know some guys with electrical tape it with a piece of armor flex over it. You know that was the typical thing and in my company I was the first one to buy one of the flu clamps with a k-type thermocouple, and when I got that everybody you know, thought it was the greatest thing since sliced bread.

It's amazing how much that's changed even in the last 20 years. I know it and those guys you're coming into the trade right now or like well. You know why didn't you use this before, and the old guys that have been in and for 20 years said? Well, we didn't have it and hopefully they've gotten on the bandwagon, but anyway so in air conditioning. We had that 35 degree, evaporator TD, in the cooling side and the low-sided system, and we had a 30 degree, condenser split in the high side of the system, and that was pretty much what we dealt with, because those would go up and down with the air Temperature that was coming in if I had a 75 degree return air coming into my evaporator.

I should have a 40 degree evaporator temperature. If, however, the air temperature coming into the evaporator was 80 degrees, then my evaporator TD would still be the same 35. But now my evaporator is running at 45 and once my students understood that concept of what it was supposed to be doing, they were better able to diagnose what the problem was when it wasn't doing that, and it's amazing how that evaporator TD will hold for about Five or ten degrees on either side of the normal area, based on the loading just as condenser will do the same thing when that 30 degrees, if it's a hundred degrees outside it's going to be 30 degrees higher than the outdoor temperature at 130. If, however, I have 70 degree, ambient air, I'm gon na have again 30 degrees above that will be my condensing temperature or a hundred degrees that works very well between 70 and 100 degrees.

Once you go over 100 degrees or you go under 70, some other things take place and it gets a little bit screwy, but still you've got a rule of thumb of 30 degree. Condenser split to work with you have a rule of thumb of a 35 degree. Evaporator TD, to work with you have a rule of thumb of 10 degrees of sub cooling, and you have a rule thumb of 10 degrees of superheat. You are now ready to do a pretty good job with air conditioning yeah and that's in same thing, in refrigeration.

That there is an air conditioning. This is what I talk about all the time in the podcast that you're always better off to have a concert of readings that agree that the system is functioning properly or they can alert you if something is functioning improperly than to just rely on single reading sets You know so many and air conditioning, so many technicians and the guys are probably getting sick of hearing me say this sort of thing on the podcast, but so many technicians will hear. Will you set the charge by superheating on a fixed orifice and you set the charge by sub cool on its exp and while that may be true by manufacturer, specs checking everything checking your superheat, your sub cool, your suction pressure, your head pressure or your better way Of staying at v, -- your condensing temperature and your evaporator temperatures, and then also taking your delta T, taking the concert of all those things on an air conditioning system gives you a really good look into the functionality of the system, and the nice thing with refrigeration? Is you check many of those same things that the exception being delta T on a refrigeration system and as long as you know, what's different in the case of a refrigeration system, how those kind of fixed numbers that we look at how they change then you're gon Na be in a really good position to tell the same thing about a refrigeration system. Exactly so, let's talk about some of those.

Let's, let's go through some of the common evaporator tds that we see and so again, when we're talking about evaporator tds, we're not talking delta t we're talking the difference between, in the case of refrigeration, the box temperature, the temperature in the box and the temperature of The refrigerant boiling inside that evaporator coil, so the saturation temperature that we're seeing on our suction gage. So what are some of the common rules of thumb that you can that you can count on pretty well on a walk-in refrigerator when you're sizing up the system? You're? Looking at an evaporator that will produce a certain BTU requirement and if you look in the manufacturers specs on their coils it'll, say either 25 degree evaporator for medium temperature or it'll, say a 10 degree TD and they're designing that coil at a 10 degree TD. But they've got other BTU capacities at other temperatures at a 5 degree TD, at a 50 degree TD, at a 20-degree, but on my rule of thumb, most walk-ins from a manufacturer's standpoint are set up at a 10-degree TD, are designed for a 35 degree box temperature And therefore, at 10 degree TD on a 35 degree box, the evaporator temperature should be running at about 25 degrees, that is my saturation suction temperature and that's a TD we work with on medium temperature now on low temperature. It's exactly the same.

It's at 10 degrees. However, we're working at a box temperature of minus 10 and we're still dealing with that 10 degree TD, so 10 degrees lower than minus 10 is minus 20, and that is the design conditions for the evaporator is running at minus 20 degree, suction temperature, no matter what Refrigerant you have, if you're using our 12, our 34 502 452 404. I don't care what refrigerant you're using those temperatures will be the same. It's just the pressures that are different, yeah absolutely and that's what is so relieving as a technician.

Once you understand this because the condensing temperatures you don't have quite the variation say you have a you, don't have quite a bit variation. What the outdoor temperature is. Obviously, whereas in the case of the actual evaporator, the box temperature varies quite a bit depending on the job that it's doing, and so, if you understand this, this is the primary point of variability as it relates to the refrigeration circuit, at least. Is the design temperature of the box and the TD? That's designed for that of Aperta call in that box? Is that said correctly, yes, and I was thinking why the change from r22 to 410 a was so disconcerting for many air-conditioning technicians.

Well, that was because, originally you know our TDS we're going to be the same. I mean if we used our 22 and our 4, a in a system that was designed with a 35 degree TD, evaporator and a 30 degree condenser split, condensing unit. The temperatures would be the same, although the pressures were different. What happened, however, is when we went to 410 a we increased our efficiencies, and we went from 10 seer up to 12 14 16 and on up from there, what happened with our condenser splits, our condenser splits dropped down.

They went down from 30 degree, condenser split down to 20 degree, condenser split and a lot of the air conditioning technicians were confused by this. They understood that 410 a was at a higher pressure, but the temperatures didn't relate to them, and so they got very confused and that's why? If you understand refrigeration concepts, you're going to be able to understand your air conditioning concepts, much better, because it's only going to get more technical as we learn how to make things more efficient and it's going to be a fun ride. I'll tell you that and you've got to understand those basics, the TDs and that temperature splits and so forth to even keep up. But at our school I taught at Northern Virginia Community College and when I first went there they were teaching commercial refrigeration.

First, in the first two semesters of the tritscher, it was commercial refrigeration. I'm going wow, that's kind of strange. These kept most. These guys are going in to air conditioning.

However, I realized after teaching that a couple semesters that was fantastic because by the third semester, they went into air conditioning they were much better prepared than if they had started out with learning about our 22 and just one type of system. So, very simply, if you're gon na focus on one thing, if you're converting from air conditioning to refrigeration and there's one thing, you really want to learn first and just wrap your head around. It is this idea of evaporator TD evaporator temperature difference difference between the indicates of air conditioning the return air temperature and the boiling temperature saturation temperature inside that of Aperta cal, and then the same is true for refrigeration. But in addition to that, there are some other things that you want to at least understand about a refrigeration system when you walk up to it and one thing that a lot of technicians will notice if they go into a commercial refrigeration, rack house, for instance, or If they were working on a small region, they'll notice that in a lot of cases, they'll have frost on the suction line, going into the compressor and, of course that scares the bejeebers out of a lot of technicians.

So can you speak to that quickly? Certainly frost. Only indicates the fact that the temperature of that pipe is below freezing. That's what Glen Hannigan said in the one of the first series of classes. I was in, and I didn't really understand what he was saying until I saw a picture of a compressor at the Copeland factory that was completely encased in ice.

It apparently didn't have any defrost going on and they took a picture of and they said does this indicate flood back and everybody in the class goes yeah? Of course, you know - and I said no check your suction line temperature and then compare that to the saturated suction temperature that you're going to see on your gauges, and we were looking at that and the saturated suction temperature was minus 10. The temperature of the line was at zero degrees and the difference was 10 and it was like hold it. There's 10 degrees of superheat there's no way it could be flooding well. It was because that that line temperature was 0 degrees and over time it just built up a heck of a lot of frost.

So for me and the people in the class that was really an eye-opener. However, a lot of air-conditioning technicians see that and they have a heart attack, because you don't see air-conditioning lines frosting and why is that? Well, go back to that 35 degree: the evaporator TD, if I've got 75 degree air temperature coming into the vaporators. My evaporator is running at 40 degree temperature. I pick up 10 degrees of superheat.

My suction line coming out of that evaporator is 50 degrees, 10 degrees higher than the 40 degree. Evaporator 50 degrees is never going to form any frost, but let's say for some reason or other. I have flood back and I'm not boiling all that refrigerant off in the evaporator or let's say that somebody has not changed the filter. What happens to the evaporator temperature when you restrict the air actually that TD of 35 degrees holds? In other words, it thinks that maybe it's um, let's say 50 degrees, because it's full of ice on that coil, the air that that's touching.

It is 50 degrees and you take 35 degrees below that. You've got 15 degrees doggone. That suction line is going to be really cold and it's gon na start frosting. So frost is just an indication that that line is below freezing.

Is it normal or is it not that's what you have to determine and that's something that I think technicians if they think about that they'll. Look at a cooler, for example and they'll, say well yeah, but the cooler is supposed to only maintain you know, 35 degrees. So that's above freezing right well true, but the evaporator coil has to be lower temperature. Then the space temperature in order to transfer heat out of that box, and so if you have a as an example, let's say you have a walk-in and you've got a 35 degree box.

But now you have a 10 degree TD. That means it's 25 degrees that suction line, if it's exposed, if it's uninsulated is still gon na, tend to freeze over time, and so you have to have some form of defrost and pretty much every type of refrigeration that exists. There has to be some way to deal with ice because you're dealing with evaporator temperatures that are below 32 degrees as soon as you're below 32 degrees for a sufficient amount of time. You're going to have ice as long as there's some moisture in the air and so talk about the different types briefly of defrost that go into refrigeration and kind of how you can tell which one is appropriate for different circumstances.

Well, in a walk-in walk-ins. They have that 10 degree TD. On a 35 degree box, you've got about 25 degree evaporator. You are going to be building up a little bit of frost in there, but under normal circumstances the thermostat will be satisfied because the compressor is going to bring that box temperature down cycle off on the thermostat.

But the fans continue to run, and this is something to remember in commercial refrigeration. We keep those fans running all the time because they are helping us to defrost our evaporator during the off cycle off cycle, meaning when the compressor is off. So let's say that the unit runs for 10 minutes and it cycles off one thermostat and it's off for five minutes. During that five minutes.

The evaporator coil, that was a 25 now relatively quickly, gets up to 35 the box temperature that is above freezing and it will defrost the frost. That's on those evaporator coils. Usually they start forming where the pipe touches the fins, and we really don't see evidence of that out at the end of the fins. So we don't really recognize it as such.

But let's say that they're using the Box all the time, in other words the doors open all the time or they're, putting the hot product in there or something and the unit does not have time to cycle off. And it runs for two or three hours straight and there's no time for it to shut off, while that frost build-up between the pipe and the fins will start migrating out to the edge of the fins and it'll, eventually bak the airflow. Now it stops cooling because it's not getting the air across the evaporator properly and it continues to run until it freezes itself up. In those cases where we have that happening.

There's a couple things we can do and one of the simplest is to add a defrost clock that manually shuts that unit off usually at night for about an hour, sometimes as much as two hours and that's when nobody is around. That's when the doors are closed and the product temperatures have come down, the box temperature will go up a few degrees, but not that much. It will give the coil time to defrost itself at night and that's one of the ways that we do it in reach. In refrigerators, the evaporator TD is 20 degrees, so let's say that we have a reach-in refrigerator that is designed to maintain 40 degrees.

The evaporator is running at 20 degrees, 20 degrees below the box temperature, because the coil temperature is colder than we had in that medium temperature walk-in. We have a tendency to freeze up a little bit faster in there. A lot of manufacturers actually put the thermostat bulb into the coil fins, because they are sensing that temperature in the fins so that, if it does freeze up because they keep you opening the door and closing the door and putting in warm product which you have a Tendency to do if it does freeze up and it does cycle off on the thermostat thermostat is not going to come back on until that Frost has defrosted completely. So that's the way that usually the reach-in boxes are done again.

If that doesn't do it we'll add a clock to that 1 2 and have it do another defrost at night and then, finally, when you have freezer applications, then you actually have to add heat and because the box temperature itself is lower than 32 and when that Occurs, you actually have to have a defrost that adds heat to the coil to to get that ice off yeah, it's a little bit more intricate because we have there several things going on there. Like I said, we had the fans running continuously and in your medium temperature boxes. However, of course, when it goes into defrost on a freezer, we have to shut the fans off while those heaters come on and usually their electric heaters that are embedded in the coil and then we have to have something that tells it to go back in to Defrost, when all that frost is melted, then we can't bring on the fans right away after defrost, because we'll blow some of the residual moisture off of the fins into the box, which will turn into bicycles and also it'll blow some of that heat. So we have to delay the fans and we delay the fans until the temperature of the coil gets down to a predetermined amount.

So there's a little bit more to freezers, but once it's explained it's it's very logical and all of them are done the same way as far as wiring as far as how time clocks work and about the different controls for both the fan and the defrost termination. So it's not as scary as you might first think, and that's actually one thing about refrigeration. That I've noticed is that in some ways when you're coming from air conditioning, it seems may seem overwhelming. But in many ways the controls related to refrigeration are more consistent than the controls that you see, even in a residential air conditioning where you could deal with.

You know ten different manufacturers, proprietary communicating controls, especially nowadays and all sorts of different thermostat manufacturers. Obviously, you'll run into cases where refrigeration equipment is tied in to you know: energy management, equipment or building automation, or something like that, but in general, most of the controls that you work on in refrigeration tend to be more consistent. Would you agree with that? Definitely, as a matter of fact, air conditioning has gotten into some very fancy controls, especially proprietary controls, which makes it very difficult for a technician: who's working on three four: five different brands of equipment to figure out what's going on, whereas in refrigeration we've kept up with The old-school stuff and we're just now coming into the demand defrost, which has been used in heat pumps for a long time now we're just getting into it in commercial refrigeration, which is strange. It should well.

I should say now: it's been out there for fifteen years, but it's relatively new and like anything else, when you first see it it's scary, what you have to do is to go to seminars that are given by the manufacturers and learn about it. Any company that does not do that is really losing out. Yes, it takes their guys off the road for maybe four hour, but they're gon na spend 40 hours worth of wasted time if their technicians do not understand the latest things that they're working on. So once you get a feeling for that, even though a lot of it is proprietary, it will transfer over to other manufacturers and it'll make it easier for you to pick up those you'll say well so, and so does it this way, how do you do it And you can relate, and that's one of the biggest things that I found is beneficial to technicians, whether it's in a book or it's in a classroom or it's on the job is relate to what they already know or understand, rather than try and bring in a Whole new concept, but I digress, I'm sorry! No! No! That's that's exactly, and in fact, that comes down to the root of what learning is anyway.

You know when a baby learn something that's what the human mind is doing. Is it's relating something that they already know to something else in order to make sense of it? Contextually, that's how we learn how to read: that's how we learn how to drive. That's how we learn everything all those things that we now kind of consider as just a sixth sense. We just know it.

We learned through contacts taking what we already know and injecting some new things into it and relating those two things together and that's that's. What all the teachers do and I think you've you've recognized that and you put that into writing very well. So let's say: let's have it: let's give an unidentified themselves in so you're an air conditioning technician and you end up getting thrown into a situation where you're expected to work on some simple refrigeration. Let's say it's: a convenience, store application and you're supposed to work on a walk-in or a reach-in cooler and one of these applications.

What sort of mindset tips would you give a technician, who's walking into this and feels a little nervous or overwhelmed by that? By that prospect, I think we have a tendency to diagnose what we don't understand as being a problem, because we don't understand it by that I mean, let's say that we replace the part first, that we understand the least. So if you don't understand how a refrigeration system is supposed to operate, you are gon na blame, the compressor first off or the expansion belt first off and you're not going to look for the simplest things like I tell my students when you actually go on a Job most of the time it's boring, ly simple, dirty evaporator, dirty condenser. What happens in air conditioning? You usually run into a problem that was a result of a clogged up filter and you don't get as many of those difficult problems as you might think. So.

Look for the simplest thing. First, are the fans running? Are the coils clean you know, does it have refrigerant in it? Is it off on high pressure? Is it off on low pressure, simple stuff yeah I mean that does seem to be true in most of the industry. Is that guys will diagnose the I think, the most the most common one that we see is the board. You know there.

It's got a bad board in it, you know, and they don't understand what the board's even supposed to do, or the inputs and outputs. I think what I would add to that is that if you don't understand how something works, then you have no business condemning it. So if you think it's this thing, but you don't understand how it works, then take the time to understand how it works or get someone on the phone who does understand how it works or something you know bring them alongside you whatever, before you go ahead and Condemn this part or say that this is the problem or start to rip things apart. That ought not be ripped apart, and I think you know like I keep quoting Jim Bergman here, but he says the same thing and as so often it's cleaning and when guys start connecting gauges even two pieces of equipment that they don't understand at all.

Or they don't know what the way he puts it is. If you don't know what the pressures and temperatures should be, then you have no business connecting to it because you're not going to know if they're correct, even if you, even if you do see something on the gauge, and I think that's a really good, really good Point so for technicians out there who have no perspective on these things. I think a great place to start is probably your book honestly. Well, it is, and I think another thing is that we need to build up a network of people that we can call.

I remember, as a service manager, the guys were calling me at the office when they had questions. However, when we got into everybody having a cellphone, they were calling the guy who was on the call before or one of the lead technicians and talking to them, and it freed up me a lot. But what we did is every Tuesday when we had a service meeting. We encouraged people to bring up things that they stumbled on during that week.

So we all learn together and once you start learning all together, whether it's in your company or whether it's as an industry, then everybody benefits so building up a network of people that you can contact quickly is extremely important, and one thing that I told my technicians. I gave them phone numbers of the service reps for all the equipment that we were working on, but I was emphatic about. They were only to call them if they were completely flummoxed with what was going on and they had to have all the information. Ambient temperature, superheat sub cooling pressures, temperatures model number serial numbers.

Everything had to be right there and by getting all that information nine times out of ten, they solved their own problem. They didn't even have to make the call, but when they did make the call it was a matter of when that service tech saw that one of my employees was on the phone. They knew that they had the information they knew. They had already checked all the easy stuff.

It was going to be an easy call for them. Yeah, that's so important because it's not only important like you said, because a lot of times you find the answer before you even call somebody, but it's important to have a reputation in the industry as somebody who does the due diligence and isn't just looking for isn't. Looking for hand-holding, you know this is not an industry that works well with people who want their hands held all the way and - and you, as you know, we're facing a struggle with this with it with a new generation who's kind of used to having their hands.