This episode of the HVAC school podcast is made possible by our sponsors, one of those sponsors being carrier and carrier comm thanks to carrier for investing in technician training by investing in the HVAC school podcast. Also, thanks to refrigeration technologies at refrige tech, comm talked a lot about them and a they make big. Blue okay haven't use a big blue, then, what's wrong with you big blues, good stuff, finding leaks. If you are raising and pressurizing and not bubble testing your joints, then you need to start doing it and you should use big blue, also air Oasis air, oasis.com /go.

For you to find out how you can use air Oasis in your company for indoor air quality products, there american-made no nonsense. Iaq company the company i've been looking for for many years, the one it's not full of fluff, but rather it just makes good quality indoor air quality products. That's arrow, Asus, comm, /go, also Navigon navigable comm. You can buy nav act products now at true tech tools.

Comm TR you tech tools, comm offer code, get schooled for a great discount, I'm especially enjoying the NRP 8 di vacuum pump and the NEF 6li flaring tool. Those are two tools that I've been using recently and I really like them and they make a lot of different types of things and XK like every machine's leak, detectors, swedge tools, all that kind of stuff, and you can find it all. That's your tech tools. Here's the guy who talks about test Oh 6:05 eyes and delivered capacity in his sleep and maybe Jim Bergman, but he swears.

It was just one of those I'm flying and my friends were all there sort of dreams, nothing weird Brian or hey. You found the HVAC School podcast. You are one of the few, the proud, the HVAC school podcast listeners, so one of the ones who wants to learn more about some things that you might have forgotten along the way as well as remember. Some things even forgot to know in the first place and good on you for doing it today, I'm talking to Chris Stevens and we're talking about commercial refrigeration, temperature controls on the basic side, we're not going into the really fancy stuff, just the basics of commercial refrigeration, Temperature controls - and those are one of the first things if you're gon na be working on a refrigeration system, and you are mostly an air conditioning technician that you may be a little thrown off by so hopefully, you'll find this helpful.

So here we go Chris Stephens, talkin refrigeration, temperature controls. Alright. Thank you, Chris, for coming on the podcast. Thank you for having me Chris, has written for the HVAC school website written some tech tip articles, and this particular podcast that we were doing is sort of based loosely around an article that he did on reaching temperature controls.

It's interesting because as simple as temperature controls are or refrigeration, controls are there's a lot of questions about them and I think it stems from the fact that the way that they function is so different than the way that we do air conditioning controls, even just from The voltages and everything, so I think that's where a lot of that confusion comes in, so I like to hit on these topics, because I know a lot of you are obviously air conditioning technicians primarily and it's just good to kind of get a refresher. So some of this is gon na, be really basic for some of you, but I think some of you it'll be a good refresher, maybe even for your first introduction into it, but before we even go into that, just tell us a little bit about you and What you do about your company and the type of work? You do, I'm a service technician here in Southern California. I call myself a service technician, I'm technically the part owner and a service company here we're a commercial refrigeration company that specializes in restaurants. So I'd say: 98 % of my work now is restaurants, so I work on reach and refrigerators ice machines, air conditioners.

I work on it all pretty much. I've been in the trade for over teen years. I kind of lose count, so I'm also very much involved in my local RSES chapter here in Southern California. It's actually the arrowhead chapter they're actually joined that chapter, because I wanted more information about the industry.

I wanted to increase my technical skills and be able to talk with other peers that work in the industry, and that is something that our SES really does help out with. I think that it's definitely a lot easier to find information about the industry. Now, with all the YouTube pages and HVAC our school, the information is actually a lot easier to get than it used to be, and with that being said, I actually started a YouTube channel. Also, the start of my youtube channel is actually for my employees.

It really wasn't to post the videos and make them public, they used to be private, and I would just film the things that I thought were interesting that I used to talk to the guys about. I figured hey. I've got a camera phone, so why not start filming them that kind of worked out for the guys really well, so I just decided to make it public, and so now I have a YouTube page called HVAC our videos and I post videos about just the interesting Stuff that I see reach-in refrigerators, there's some good examples of misdiagnosis in there from myself and from other technicians there you go and that's actually very similar story to how HVAC school got started. By the same thing, I started creating stuff for my own employees and then thought I should just put that out there just to benefit the industry, and then it turned into something.

So for those of you who don't follow a Christian channel, it's a really really great channel and just and we're gon na mention it again at the end. But if somebody wants to look it up, what's the name of the channel, it's called HVAC our videos yeah. It's an excellent channel. It's in my two top favorite channels that I watch and that I use with my employees.

It's you and a keg Rives or aka HVAC. Those are the two channels that I enjoy the most so well done on that. Thank you. So, let's get into these controls here.

So, let's start with just talking about temperature controls and how they differ from HVAC controls or a/c controls. I should say air conditioning thermostats. What are some things that can make them different? Well, I would say the biggest thing is: is just the temperatures at which were controlling. I mean when you're looking at a standard air conditioner.

What are you looking at, like 45-degree, vaporators temperature 55 degrees out temp? Is that about accurate yeah? I mean anywhere from a 35 degree, evaporator temperature, they're, very cool up to ya - maybe 55, if you're in a really high load or something like that yeah so on. The refrigerators were basically just bringing the box temperature down we're. Trying to keep legally federal law says we have to keep our product temperature under 41 degrees for a refrigerator. So with that being said, you've got an evaporator TD that is going to be a lot lower than that box, temperature typically 20 to 25 degrees below the actual box temperature.

So if you're running a 40 degree box, temperature, subtract 25 from that and you've got a pretty low, evaporator temperature, so a lot of these controls are essentially just bringing the box temperature down. Now I will say that, unlike an air conditioner, the refrigerators oftentimes will disconnect the compressor directly instead of running it through a thermistor. I mean instead of running it through contactors. That is something that is changing slowly, but you can get some of these basic, simple coil sensing temperature controllers, that literally the power wire for the compressor, runs right through the control.

There's really not a lot different about an air conditioner, except for the temperatures at which we're controlling, but you do think a little bit differently about evaporator temperatures, coil temperatures, that sort of thing - and you stated it right off the bat we talked about TDs whenever we Say TV in air conditioning engine bergman and I've been working with text to try to get them to think differently about this, but a lot of times, texts automatically think of delta T, which is the difference between the air temperature going into an evaporator coil versus out Of an evaporator coil and they don't necessarily always think of their suction saturation, which is what we compare for super E. That's the temperature we use for when we measure superheat, they don't necessarily think of that as the evaporator temperature, whereas in refrigeration, refrigeration techs, have a much better sense of that that your suction saturation pressure correlates to an evaporator temperature or they're measuring the evaporator temperature directly And it's that difference between that evaporator temperature and the temperature of the air entering the evaporator ie, the temperature of the air in the box, that refrigeration technicians think of quite a bit. I would definitely agree with that, but I also don't make us sound to be anything special, we're just technicians and we make the same mistakes as everybody else. I would say that a lot of the videos that I've made - I'm pretty honest in my videos - that a lot of the examples and advice that I give is because of the mistakes that I've made.

I've made a lot of mistakes. Luckily, there wasn't severe consequences for those mistakes and I corrected him and righted him with the customer, but I learned from them we're just normal people we're the same as everybody else. I mean I work on air conditioners, just the same as I work on refrigerators. I will say, though, that you pointed out a good thing about the TD in that people tend to confuse that with the delta T.

That is something that even confused me when I was in trade school, because I would go at nighttime. So I could literally have one class where I was taking an air conditioning class and the teacher was talking about delta T, but he kept calling it a TD and then the next day, I'm in a refrigeration class and he's talking about the TD. And I would question like what do you mean and then I would get frustrated when we would take a simple test and I would get the answer wrong and it's like we'll wait. So it is very easy to get confused on the two.

I think, even with air conditioning, if you can stop looking at pressures and when I say stop, I mean you're still gon na consider your pressure. But if you start looking at saturation temperatures, it's gon na make your life a lot easier. I agree I mean it's one of the first things that I think new technicians should be transitioned into is thinking of every pressure that you take is really just correlating to a temperature. It has a temperature meaning because then you can start to make sense of temperature readings alone, which is what Jim and I have talked about a lot on the podcast about checking your system without taking pressure measurements on every single case, and that's something in refrigeration.

You see all the time I mean you're, not always connecting gauges to a piece of equipment, correct. That is correct. There's a lot of times, you're not going to we're talking about Jim Bergman. I will also say that he had a great point that he made something that we all think, but you really need to understand.

You have no business attaching service gauges to anything. If you do not know what those pressures are supposed to be before you put those gauges on there and I'm not talking just pressures, I mean saturation temperatures you need to understand. If this particular box is going to have a 20 degree TD, 25 degree TD, your pressure should be about this. So that way, when you connect them you're not looking at them going huh.

I wonder if those pressures are correct and that applies to air conditioning and refrigeration, so rubber meets the road when we're talking about a TD. If you're looking for a TD of 20 and you have a box temperature forty degrees, then that means your suction saturation. Your evaporator temperature that you're measuring on your gauge should be about twenty degrees. That would be accurate now.

I will also say that a lot of times we do not know exactly what those t DS should be, because refrigeration manufacturers sometimes beat to the tune of their own drum, and it seems like they make things up on the fly. Their refrigerators work, but a lot of times, even when I'm talking to technicians or guys that are working with me. I hate this word, but I do use it as we use a rule of thumb. I have a general idea that my TD should be somewhere within 20 to 25 degrees somewhere in there.

There's no specific documentation saying this is what it should be we're unlucky. I tend to think that we are have a little more accuracy when it comes to some air conditioning systems, because some manufacturers do publish what the sub-point should be or what the superheat should be, or the target superheat should be refrigerators we're not very lucky, especially when It comes to reach and refrigerators. The manufacturers tend to kind of hold some of that information yeah and today we're gon na focus more on the reach inside and it crosses over into walkins for sure at least some of what we're going to talk about, but we're gon na stay on the simple Side, obviously, when you get in a grocery store, refrigeration, parallel systems, then your controls are going to tend to get more complicated. I wanted to start with exactly what you already covered, which is there are a couple things you need to think about.

You need to think about the temperature of the box and you need to think about the temperature of the evaporator coil and those are two things that you need to understand: first and how that even relates to pressures before you get started. And that specifically applies to this first control that I want to talk about, which is the standard pressure control, just the basic, simple pressure control. So how does that work? The basic, simple pressure control in its infancy is just a control that it can either open or close when the pressures fall or rise. The standard, low pressure control is going to open on a pressure fall and then close on a pressure rise.

We can use it as two functions. We can use it as a loss of charge switch. So if the pressures get so low because we're running out of refrigerant because of for some reason it can open and shut the system off. So it can be a compressor protector or we can use it with the idea of a temperature differential from the evaporator in mind.

We can use it as a temperature controller, because if we know that at a certain temperature, let's just use our twenty two refrigerant r22 refrigerant is going to be this pressure at a certain temperature. Well, with that logic, we can control temperature. That way, we can say hey if the box is running and the pressures are this much on the low side, this control we can set it to do whatever we want it to do, and therefore we can use it to control temperature, and so that is that Basic connection between pressure and temperature and we're specifically talking on this kind of control scheme side, mostly about the low side of the system, right we're talking about the suction side. That is correct.

I'm gon na say typically because I'm sure there's some weird situation, but typically we're gon na control, the temperature by monitoring the low pressure side of the system. As an example, you mentioned in r22 system, and so in that case, if we wanted it to shut off at a 20 degree, evaporator temperature, then that correlates to a 43 psi pressure setting then. But how do you set because of course, it doesn't come on and off just at a single temperature? So how do you set that differential? How is that setup? Well, first off something we have to understand when we're using a pressure. Control is pressure.

Controls are never 100 % accurate, they are actually very inaccurate devices oftentimes. They will have a number on a little readout or a dial on the control that says: 20, psi 30 psi or sometimes they're a differential control where it'll say cutting cut out minus differential. Those numbers are never set in stone, accurate. The only way to know if it's accurate is to field calibrate the control use.

Typically, the easiest ways is to use some nitrogen apply, so much pressure to the control and write down when it's set at 20 psi. Where does it actually turn on and off at and record those? So then that way, you have an idea of how accurate the control is, and that is critical. Not only that you don't trust your control, but also that you don't trust your tools. You did a really good job of showing how you calibrate even your k-type thermocouple, using an ice bath in order to make sure that they're measuring what they should measure before you rely on to measure box temperatures talk a little bit about that.

That's a pet peeve of mine in that people tend to rely on their digital gauges. Let's just talk about a k-type thermocouple clamp that you're gon na use to measure - let's just say, suction line superheat. It's really easy for people to just throw those on a system pull the insulation back, clamp the clamp on there and hey my service gauges say that that clamp is measuring 45 degrees. Well, there's a couple things you have to think about number one: k-type thermocouple'z tend to be very inaccurate if they're not calibrated properly, okay, so in all reality we should be calibrating those every time we use them now in a perfect world.

That's not going to happen me personally, I like to calibrate my thermocouples at least once a week and verify their accuracy. The next most important thing that I can't stress enough is, is that once you calibrate a thermocouple to a port on your thermometer or your gauges, it has to stay in that port and when I say stay in that port, you can unplug it. But you have to plug it back into the same port again, it is calibrated for that port. Only.

You cannot plug it into the liquid line side of your gauges or the t2 plug on your thermometer without calibrating it again. So that's very important is checking the accuracy of our measurement devices yeah, because when you're making an adjustment to the k-type thermocouple you're, not actually making the adjustment on the k-type thermocouple you're just adjusting your meter or thermometer or a gauge or whatever it is. So that way, the k-type thermocouple reads correctly, and this is a really common thing that you see guys do. They'll have a t1 and t2 say on a really nice quality to say a fluke, two channel thermometer, or I have one of those a long time ago or even a field piece or whatever the case may be, and then they pull them out and when they Reconnect them they swap them around, and now they could be wildly off and so for this type of stuff, especially in refrigeration, where you're really trying to hit it to the degree as much as possible.

I mean you don't want to be two three four or five degrees off in a lot of cases. You need to make sure that the measurement devices you're using to confirm your settings are correct and then, like you mentioned, because these things are historically inaccurate. You can't just set it and forget it: you've got to set it and make sure that it cycles on and off there are correct temperatures talk a little bit just from the standpoint of refrigeration. What kind of things do you do after you do set up a control to make sure that it is going to work properly before you leave, as in verifying that the box is coming down to temperature? Is that what you're, asking yeah, just meaning like because in air-conditioning, for example, we'll talk about like make sure that the drain drains and make sure that the equipment is running when you walk away from and that sort of thing? But in refrigeration generally, we want to be a little more careful to actually watch the thing come down.

You don't want to just take a hot box set it up, confirm you just set the dial and leave. You want to be a little more thorough and making sure that all the controls, defrost everything is all working before you walk away from it right, yeah. Definitely so after I set up a control typically now this is me personally. I am gon na watch that box operate now.

If I felt the need to put service gauges on the system. Again, that's a very important designation. If I felt the need I am going to watch the pressures watch, the system operate and I'm typically gon na watch. It satisfy and then turn back on, probably two to three times so.

I'm gon na watch a full cycle on the system to see the actual cutout temperature, so the temperature at which the system shuts off and then the cut in temperature at which it turns back on and I'm gon na watch that two to three times and that's What I was gon na suggest is that you want to at least watch the thing cycle once before you walk away from it, because I seen a lot of guys do this and it's kind of a standard way of doing it. Where, when you're setting up a control, you kind of cycle it on and off, and then you test it against what the actual temperatures are, but you driving a dial up and down, isn't the same as allowing it to actually cycle naturally, and especially when you're talking About analog controls, your basic electromechanical controls or pressure switches, they can be very, very inaccurate, so you want to make sure that it's set in properly, which brings me to the next type of control. So we talked about the standard, basic low side, pressure control, suction pressure control. Now what is the next option? There's something called a constant cutting control.

How does that work on the low pressure control, once we've verified that it's accurate or we've compensated and made it accurate? We're always going to want to understand that the way when we're using it to control temperature in a system is that we're going to keep the evaporator TD in mind when we're setting up the pressure controls, but that you also want to account four line set. Lengths in how the system's operating and what I mean by that is is, let's say we have a remote condensing unit, that's on the roof and it's got a 75-foot line set. You really need to watch that box operate. You cannot just set it and forget it, because I bring out the way to set up a pressure control as a temperature controller by using the TD.

But when you have a long line set length, you're going to have pressure drop, that's going to become part of the equation. You're gon na have a lot of factors inside there. So it's very important that we monitor the system and there is going to need to be field adjustments. You can actually find on some of the old school literature from to come, so you can find an old pressure.

Chart that'll actually tell you if you're using when I say old school, a lot of the information is going to be for our 12 or our 22. It's gon na say if you're using our 12 and you want the box to be this temperature. Here's the pressure control settings, that's just an easy way for someone to do it, they're, basically just doing the math for you, but those settings kind of go out the window when you have a long line set length. So that's something always important to remember is is that you have to watch the Box operate.

You can't just set it and forget it. You really got ta fine-tune things once you install them yeah exactly and also and again we're talking about smaller systems here. But then you also have to consider with some of these types of controls, you're actually working with a pump down solenoid and then that even adds and a whole nother thing. And that's again we're not to that point yet.

But you talked about length of line and refrigerant capacity, and all these sorts of things. You really have to make sure that you know the type of control scheme that's being used and that it's set up properly and that you test it and make sure that it is functioning before you walk away from it, and that is corrected. I would also say that, even in the article that I had written, the pressure control used as a temperature controlling device is not very common anymore, there's only a few instances. I still do see it today on certain manufacturers, but there's only a few instances.

It's only on self-contained regions anymore, so the line set length is free fee and there's really not too much involved. So they are pretty simple and when you think from a manufacturer's standpoint, it's really a very easy way of controlling temperature and it's very economical for them. Because thinking that we're using the pressure of the system, thinking about the saturation temperatures and we can use that pressure control as a defrosting device, also because if it's turning the box on at 40 degrees or whatever corresponding pressure, that is every time we brought the coil Temperature above 32 degrees, so therefore we've self defrosted it. So they are an economical feature for the manufacturers, and you tend to see that they're doing that for a reason to save pennies, basically in the long run, because when they manufacture a million boxes in a year.

Those pennies equate to be a lot of money. One of the big challenges that we always face is there are a lot of ways of doing this, but money does always come into play. So now let's go ahead and talk about the next type of control, and that is the constant cut in control and we'll start with just the basic electromechanical control, and this is very, very common control strategy. I would say the most common refrigerator controller is a simple coil sensing temperature controller, or we may call them a constant cut in control.

Okay, they're, very simple. In theory: essentially, you have a sensing bulb that is embedded in your evaporator coil. There's a couple different methods of doing that and that control is directly sensing evaporator temperature, as close as it can without being a pressure control. So they've got the sensing bulb embedded in the evaporator and they have figured out the temperature difference between the surface temperature of the evaporator and the internal refrigerant temperature.

They've done the math for you, but that control is monitoring the evaporator temperature and what it does. Is it basically just turns the system on and off instead of using air temperature, it essentially just uses evaporator temperature and it's a little bit more accurate in my opinion, but there's a problem with it number one. It's very susceptible to the system, operation assistant, vital signs. Your evaporator superheat has to be absolutely perfect for a coil sensing temperature controller to work with a lot of technicians.

I hear in people that I talk to seem to say those controls are no good. I don't like those controls, they're, always faulty, there's, always a problem with them. Well, we can step back and think about it. Those controls are actually very accurate controls and they work really well, but a lot of things can affect the way that those controls work.

If you have a dirty condenser, your temperature controllers not going to work right because your system operates as one whole piece. So if you've got high head pressure, it's gon na affect the evaporator temperature and so forth. If you've got low refrigerant charge that coil sensing temperature controller is going to see that before you do typically before things start happening, so you're gon na get a service call about that temperature controller or about that box and you're gon na say. Oh man, the box is not turning on until it gets to 43 degrees.

Well, it might not be the control, so they are very accurate and they're very good controls, but they can be very difficult to diagnose yeah and the system needs to be working properly. I mean that they rely on the system functioning properly for them to function properly and in one sense I think technicians would say well that's a problem. They should just do their job, but if you think of it in a broader sense, if there's a problem with the equipment, then you're gon na need to fix it anyway. So really, what's the issue so we're in the evaporator coil, do you want that? Coil sensing probe to measure is it just anywhere in the evap coil or is it a particular place? This is another interesting point.

Manufacturers tend to be to the tune of their own drum, like I've said before, and they kind of all differ in different ways. Okay, if you ask my opinion, I typically want it to be closer to the outlet of the coil, so you're, seeing the full function of the coil you're, seeing the refrigerant go all the way through the coil and you're sensing, the temperature of the refrigerant as it's Leaving the coil, so then you know that this has happened inside that coil, but I have seen other manufacturers do some weird things where they put the sensing bulb in the front of the coil. They kind of all have their own theory and way that they do it. The important thing is to remember is that that system has to be working 100 % correctly, to the way that the manufacturer designed it now.

That is also another point of contention, because if we don't know exactly what that thing should be doing, how do we know how to diagnose it right and it does make it challenging, and you - and I actually had a conversation about this sort of a theory of This setup after you wrote this article because I was having some struggles with it, but what it comes down to is a lot of these electromechanical kind of basic coil sensing controls. They don't have necessarily even temperature radiations on the control just has like numbers. In some cases, some cases just like dots on it, there's not a whole lot of information on that dial, and so, where my mind works, I'm used to thermostat. So I think I want to set this box to 40 degrees and that's what I the box to be, and this control should do that.

This control is specifically set up for this equipment, because a particular coil temperature relates to a particular box temperature. As long as everything's working properly as soon as you kind of upset the applecart and things aren't working properly well, now everything can be off and it's and it may not do what it's supposed to do. So it is important, like you mentioned in the article, that it's important, that you have the right control for the manufacturer when you have these simple controls, because if you were to put in a different control, then it may not be set up in the same way. Not designed in the same way, and that can be a problem and that's one factor there and then the other side.

You got to make sure everything else in the equipment is working properly. The super heat set properly the system is clean and well functioning. That's correct! These controls - you had mentioned that a lot of times they have dots or numbers on them again. This is going to be a general rule of thumb.

I kind of cringe when I say that, but the controls typically have numbers on them from 1 to 8. For the most part, that's pretty common most manufacturers. That control should usually be set between 2 and 5. That's typical! That's the starting point.

I sometimes go in the middle somewhere of 3 and start there. But again it's not one of those things you can just set and forget. You've got to watch the Box operate a lot of these systems. I will say that they can be difficult to diagnose when they have a constant cut in temperature controller or a coil sensing temperature controller, because, let's add another factor into there, a lot of times the refrigerant charges on these are very minimal.

We're operating with 1/3 horsepower, compressors or condensing units and the refrigerant charges can be of lowest 6 ounces, so they purposely don't come with service ports on the system. They usually have process stubs. So basically, it's just a port. Coming off the liquid line.

Dryer, that's welded shut. So before we tap into that system, we have to really evaluate the entire system to make sure that we actually need to put service gauges on that system, because we can run into some problems if we go put a gauge with even a 2 foot hose on It we could lose a lot of refrigerant when you're dealing with 6 ounces, so that is an argument to be made for smart probes or small service gauges. Yeah and again I mean a lot of what we do in refrigeration is common sense assessment. I mean Chris talks about this.

All the time in his videos goes through and he's noticing things as he goes. Okay, this is dirty that needs to be cleaned. The seal isn't good on this door so on and so forth, and a lot of the diagnosis is visual and common-sense stuff. But it does creative challenge, sometimes when you're wanting to confirm 100 % that it's working properly and you really don't want to put gauges on it.

Unless you absolutely have to let's touch on the idea of constant cut-in and what that phrase means what makes something constant cut in so the idea of a constant cutting temperature controller - or we can call it a coil sensing temperature controller - is that it's pretty simple? Actually, it's gon na constantly turn on at a set temperature. Okay, so most constant cutting temperature controllers are going to turn back on or cut in between 38 degrees and 41 degrees. The idea behind that is that you are making sure that the coil temperature is 38 to 40 degree or 41 degrees, and if you understand how refrigeration system works, with the TD in mind, my evaporator temperature is going to get well below freezing. So, with the constant cut in control, what we're actually doing we're maintaining the temperature in the box, but the second thing that it's doing is it's making sure that that evaporator coil is clear of ice before it turns that compressor back on and that's important to understand, Because, as that system operates again, if we have a 20 degree TD on a box, that's running 40 degrees that evaporator temperature is going to be 20 degrees when that control or when that system is running.

Okay, obviously, 20 degrees is below 32 degrees, which is our point at which we're gon na start to build frost on that coil. So if we don't have something to defrost that system, we're gon na start to build up ice and slowly over time, that ice is going to make the box stop working. So the constant cutting control actually serves two purposes and that it controls the temperature of the box, but then, at the same time it's a self defrosting control. It ensures that there's no frost build up on that coil every single time.

That compressor turns on again make sure that everybody who's listening to this, you want to know that, when we're talking about this strategy, we are talking about refrigerators or talked about refrigerators. Coolers, we're not talking about freezers at this point because we're not talking about a defrost strategy where you have heater those sorts of things we're talking about just off-cycle type of defrost here. I think a way to think about this when you hear constant cut in so that means that the cut in is fixed. It's constant, it doesn't change, you can move the dial and you're not changing the cut in.

So that means that when you move the dial you're changing the cut out, so it's constant cut in a variable cut out, depending on how you set that dial right. That is correct. You can also call that your differential of the temperature controller, but yes, that's exactly what it is. So I like to try to tell people that, no matter what you do to that dial, I even tell customers this because a common service causes I keep turning a colder and it's not getting any colder.

We can also relate that to an air conditioning call it a residence, but, like I tell the customer, don't turn the dial, because that particular refrigerator has a constant cut in control. So if it's not working, there's something wrong. Turning that dial really doesn't do anything for us as technicians, we can tweak some things by turning that dial, essentially by turning the dial, we can increase or decrease the start and stops of the compressor, because if we can turn the dial colder, then we can make The compressor run longer and we have less start and stops on it, but there's a fine line. There then there's also digital controls that do similar things.

So how do those work order? Some differences so one of the newer strategies that we have coming into the market - and this has a lot to do with energy efficiency requirements by federal government - is that we have got a new type of temperature controller, and that is, I call them a digital, constant Cut in control, we have those controls, there om controllers, and they typically can do a broad range of stuff. They can still be a constant cut in control. They'll have two sensing probes, they'll have one for the air and one for the coil, and it will still operate as a constant cut in. So it's looking at evaporator temperature, but it'll have a second probe that we can do all sorts of features with.

We can see air temperature which can help us with defrosting. We can have really the sky's the limit, because if you have a computer programmer, they can program that control board to do just about anything. We've talked a lot about the ERC 213, which is a Danfoss control kind of a universal refrigeration control that can be used in a lot of different applications. A lot of different defrost strategies are available to that control, but there's a lot of snow other controls made by other manufacturers.

But the one thing that you'll start to see as soon as you get a digital control is that you, as the technicians, start to become responsible not just for a dial setting, but also for those temperatures and that's where a deeper understanding of that temperature difference. That design temperature difference between the box temperature and the evaporator temperature becomes more critical, whether the manufacturer tells you or not. If they don't tell you, then you sort of have to make a good guess at it or your best guess, because otherwise, again you're still sort of just doing trial and error a little bit. You're testing it on off in order to get the box temperature that you want and to set up the need for a strategy that makes sense, but when you're dealing with the digital control, you're, actually looking at a readout that gives you numbers versus just some numbers.

On a dial that really don't have a deep meaning, so on these digital controls, I want to point out that they have some weaknesses, but they also have some really good things about them. Ok, one of the things that I really like about the digital controllers is we're no longer looking at a number on a dial we're looking at a digital temperature readout. So that can be very beneficial for us because it can be easier to diagnose. If we can see that that control is turning on when it's this temperature in the box, then that helps us to diagnose them a little bit better.

That is definitely a plus. Let's just say this is a plus. Some of the other things we can do with these digital controls is is because they can program to do just about anything they can cycle. Evaporator fan motors on and off to quote, unquote save energy, but at the same time there can also be some weaknesses in these controls and I'll say the number one weakness in a digital control is the sensors or the thermistors.

All manufacturers of every control are having a very difficult time, making sensors or thermistors that are not susceptible to water, intrusion, okay and I'm not talking dipping in bucket of water and they fail. But if we've got a sensing probe, that's mounted in the evaporator coil and that evaporator coil has frost on it all day long. That sensor is around that moisture and the moisture intrudes into the sensor and becomes a problem. So I would say one of the number-one weaknesses: is it bad sensors, that's a huge thing and on the digital controls, I think often times they're diagnosed as being bad, when, in fact, it's just the sensors another issue that I run into with the digital controls, and This is also you can call this.

A good thing about them, too, is that they can have actual defrost built into them where they actually have a timed defrost. So that could be a good thing, because not only are you looking at coil temperature, but on top of that the unit, basically it can be programmed by the manufacturer, but typically six times a day. It looks at the coil temperature and it says hey. I don't need a defrost or hey, I do need to defrost, so it can actually skip defrost and just keep running, but at the same time a problem is especially in restaurants that have a very high volume.

Is that sometimes we need more defrost than that controller? Can handle, or sometimes we need longer t for us. A typical strategy in a restaurant is to defrost for 45 minutes in the middle of the night when nobody's there. So that way, we can really clear that coil of ice on one of these controls - they typically don't have the ability to do that, typically, whatever defrost it uses. It applies that same defrost time to every single defrost, so you typically set it up for a 5 or 15 minute defrost.

You typically can't set it up to do a 45 minute defrost at a certain time in the middle of the night. So I'd say: that's a weakness about these digital controls, and so, when you're talking about doing like in the middle of the night to defrost, which is an interesting thing to do in a busy restaurant, it makes a lot of sense. You're talking about like with an analog electromechanical time clock you can go in and set the pins so that way every night at 4:00 in the morning or whatever 2:00 in the morning or whatever the case may be, you can set it so that it stays off For 45 minutes is that what you're, referring to with that more analog strategy? Yes, definitely again, working in restaurant refrigeration, it's it's own little demon. One of the major problems about restaurant refrigeration is that the volume of use those refrigerators use.

We go through starting components like crazy. Our compressors are run to the bone because they're starting and stopping multiple times an hour on a residential air conditioner, you can set the thermostat to say hey. I don't want that compressor to start more than three times an hour. Five times an hour or whatever it is without knowing for sure, I could tell you right now that, within an hour period, my refrigerators compressor is going to turn on probably 10 to 15 times on and off on and off.

So we tend to have problems with evaporator coils freezing up on these refrigerators, because the reason why they're turning on an office because we're opening and closing doors and drawers and we've got a lot of intrusion from outside air. So these things are running hard and oftentimes. We have issues where, even with a constant cut in control, just a standard electromechanical, constant cutting controls, we can still run into freeze-up problems, which is very interesting because you're looking at coil temperature, but you can still have freeze up problems. So in a situation like that, we might install a electromechanical defrost module that I can say hey at 2:00 in the morning.

I want this thing to defrost for 45 minutes so where it turns the evaporator fan motors on, and it just shuts the compressor off now. It's important we do that in the middle of the night and the reason why I say that is because there's nobody there and so your product temperature typically isn't going to come up above 40, but we can defrost the thing for a nice long period of time. You actually get to a really good point, which is when you're dealing with refrigeration - that's very active, meaning people are opening and closing doors and pulling out product and putting in product that maybe isn't the all the way down to temperature. Now you just have these constantly varying loads.

That's part of the reason why coil temperature measurement is so critical. Is that you're measuring on something that has some mass? The coil has some mass. It's got refrigerant, it's made of metal, and so it's not gon na jump up and down like crazy, whereas box temperature is going to jump up and down. It just is - and I think some people have a misunderstanding - that box temperature and product temperature and coil temperature are all the same thing and they're, not those are all very independent things.

Your product has mass, the actual walls of the box or of the inside of the freezer refrigerator has mass, but then you have the air which easily can jump in temperature. Somebody opens that door. You remember when you were a kid. My grandpa used to always tell me if you open up the refrigerator that the Penguins will get out.

Maybe like you all that hot air rushes in and it can very quickly change the air temperature, which i think is one of the big reasons why it's not a great idea to just be measuring the air temperature alone, because you don't have that thermal ass. I would even say that I've done some scientific refrigeration work. I don't do it anymore, but in the past I've worked for hospitals, doing refrigeration work or we're cooling medicines. I mean you could be cooling anything Edison's vaccines, all kinds of stuff in in those situations they actually control the system off of product temperature.

So we'll have a vial of glycerin sitting inside that refrigerator that the thermostat is sensing, the actual glycerin temperature and what they're doing is they're simulating the temperature of the products, not even looking at the coil. Well, actually, they will look at the coil too, because they have these controls that run. These things are very complex, but they'll actually sense the product temperature to make sure 100 % sure that that product temperature never gets above their thresholds because a lot of times in the scientific industry you've got no joke a box that has over a million dollars worth Of product in it - and this is a tiny little box and to them a loss on that product is not acceptable. Yeah and it's also not acceptable to your insurance company either, and I imagine yeah.

It was definitely a very, very stressful time and the reason why the customer we don't do service for them anymore, is because it put the stress on me, including myself, we're a small company. So I have four people, including me that are working, but it got to the point that I had to be the person that go to that hospital every single time and even on me I mean I could work on it, but the stress level was just through The roof because, oh you know the temperatures one degree above four it's supposed to be, and they would call me out there at 2:00 in the morning and we don't care what it costs. I mean we could make all the money in the world. It wasn't worth it because it was just too stressful, yeah trust me.

I understand the feeling we're getting into more stressful stuff as we move forward in kalos doing more commercial refrigeration and it is pretty wild. I can only imagine what that's like yeah, I'm downsizing with all that right now I cut all that stuff out and we're letting go of customers and I'm actually reducing the stress level, even though they, of course the money is not great. I mean it. Don't get me wrong, the money's fine, but I mean we're basically evaluating the way things are, and stress is a big factor in it for me, so I'm cutting back yeah makes sense, makes sense.

So one of the types of controls are there. We've kind of talked about a constant cutting control, which typically tends to be an OEM replacement control, meaning that that's an original equipment manufacturers control. You can get those on the aftermarket supply houses, but typically you're, going to see those in om boxes. We've talked about using the standard pressure control as temperature control.

That's a kind of an antiquated control, but it still is viable. We've talked about the electron constant cut in control, now kind of similar to the electronic constant cut in control, and you can already touched on it a little bit. But we do have a universal control, such as your dick sol controls, or your Danfoss crc 213, which you made the video on. That is a aftermarket control.

Now it's important to understand too. Just because you see a danfoss control or a dick sol controller. It doesn't necessarily mean it's aftermarket or it's om. They do make specific controllers Danfoss will make a custom one that you can't go buy at the supply house and vice versa.

Okay, but the universal controls that we can buy at the supply house. They typically are pretty broad and you kind of explained it in your video. When you did that Danfoss control I mean the sky is the limit. You can do so much with those controls.

If you have the mindset and can really think it through. I would caution you to be careful about using those things, because you can screw some things up, but if you really know what you're doing man you can make, those things do all kinds of cool things. Staging evaporator fan motors. You can make them turn on alarms that send signals that set up auto dial systems that call people when the refrigerator goes down.

You could do all kinds of stuff with the universal digital controls. You can also use the universal digital controls for freezer controls. Also, you can set them up to do electronic defrost. You can pretty much like I said the sky's the limit on those we have other controls too.

We have basic electromechanical controllers that sense air temperature. We really haven't covered those ones, yet those are very common refrigerator control and walking, coolers and even walk-in freezers that are simply just a standard temperature controller that you mount in the return air stream, and it does one thing: it just turns it on and off dependent On air temperature, we do see those I tend to see people using those a lot on reach and refrigerators when they really really shouldn't, because when you pull out a constant cut in control and you put in one of those air sensing temperature controllers, if you don't Know what you're doing, which I tend to think that a lot of people don't understand how the constant cutting controls work, they've, just a limited, a defrost out of that system, there's no more defrost in there unless you put in a mechanical defrost timer. So you do have to be cautious about using those air sensing temperature controllers yeah because with the constant cutting controller because you're seeing the coil temperature you're building in that temperature increase, where it's gon na wait until once that thing cuts off, it's gon na wait until It gets to a temperature, the fixed, constant cut in temperatures, so it does have a chance to defrost, whereas when you're using an air temperature controller, it's gon na cycle on and off like an AC thermostat, I mean it's just gon na go on and off, and It's never gon na pay attention to the evaporator coil temperature, and it also seems like with just the air temperature and these more Universal controls where they're set up to just measure air temperature. It seems like you're gon na sort cycle quite a bit more as well.

Definitely - and I can guarantee you without adding a defrost to that system, you're going to have more freeze ups on that system, you're definitely going to get a lot more calls on it. Now, they're, simple, the simplicity of them is easy. I mean it's just really easy to know that hey when the temperature gets to this this thing's going to turn on and it's going to turn off. I really think that we as technicians need to investigate a little bit more and not be afraid of certain things.

Like a constant cut in control, people tend to bash them or say: oh those things are horrible. They insert name of whatever manufacturer of a refrigerator. Their controls are no good because they're constantly breaking, but I think that we as people. Naturally, we tend to be afraid of change in a lot of us are actually afraid to ask questions, we're actually afraid to say hey.

How does this work? Can you explain it to me because, once you understand how those constant cut in temperature controllers work they're really simple? Now they really are complex at the same time, so I guess that's kind of a problem there. Well, I think it's complex. I mean this goes back to a meeting that I have consistently with my technicians, but I just had again last week or it's like look making a mistake with how you understand how something works happens. All the time I mean I've made so many mistakes with things like thinking it's one way and it ends up being another, but you eliminate a lot of those mistakes and you learn how to eliminate a lot of those mistakes by not leaving until you've fully tested The equipment and you'd solve so many problems when you do that.

Even if you don't fully understand everything about the piece of equipment, if you just test it every possible way and watch it go through some cycles and you're gon na be much more likely to say. Hey that doesn't seem right and then you're gon na have a chance to rectify it and, of course, with refrigeration, no matter what type of refrigeration you're working on you have. Temperature control, which is you want to keep your product, your box at the right temperature, and then you also have to think about defrost. So you've always got to keep those two things in your mind and as long as you're thinking about both of those things all right, how's this thing going to turn on and off and maintain the proper temperature of the product and B how's the thing gon na Defrost, and is it gon na defrost enough, or is it defrosting too much if you're constantly thinking about that? Well, then, you're, probably gon na eventually come up with a good strategy depending on the application.

Definitely my company had a service call recently on a refrigerator, not working at a restaurant, and it was not myself that diagnosed it. It was another technician he went out to the restaurant and this was a two-door reach-in refrigerator. That was a sealed system, so you could not put service gauges on it unless you absolutely cut into the system, so he diagnosed the system as having a bad temperature controller. The symptoms were when he got there.

The customer was complaining that it was maintaining 44 degrees. He walked up to the refrigerator. He noticed that it was indeed maintaining 44 degrees. He put his calibrated digital thermometer in the box and he noticed that the box was maintaining 44 degrees, so he diagnosed it as a bad temperature controller.

The temperature controller that the manufacturer sent us was a giant digital conversion system, so it was taking out the old electromechanical temperature controller and it went to a digital control. Because of that, when I saw that that control came in, I decided that I was going to be the one to go out and do the conversion just because it looked kind of complex. So when I first got to the restaurant, I kind of wanted to confirm the diagnosis, so I went through the refrigerator and I noticed sure enough that it was turning on and off at the wrong temperatures and it was a sealed system.