Rack Refrigeration Intro & Discussion

this class is kind of wide-ranging we're going to talk about a lot of refrigeration stuff we're not going to cover like really small refrigeration systems like pump down systems but Corey and I have some good good stuff coming here shortly when I say Corey and I it's mostly Corey but um good good 3D video that we're going to be making on that actually already working on that but this class is uh kind of for folks who work in big retail uh all the stuff you kind of need to know if you really don't have a background in it but for those of you who are like all right I'm going to check out this isn't for me this is got stuff in there that's really for for anybody who wants to understand more about the basics of how things get made cold and hot and uh ventilated which is sort of what we do here so to start with I want to introduce a couple folks who are going to be on the mic here as they have stuff to share um Corey Cruz a uh Market Refrigeration Tech all around good guy I saw you wave um hi it's Corey a lot of you probably already know Corey Chad minir um another uh kind of lead Refrigeration HVAC guy working in the market in retail space uh Christian Maitland Christian I don't know what do you what do you go by like what's the title for you same thing Refrigeration Tech yeah refrigeration service tech and I'm sure Bert won't be able to keep his mouth shut at some point and all of you already know him so I mean we'll see we'll see how it goes we'll see how it goes [Music] to start with we're going to go over just some some Basics that everybody everybody's familiar with if you do this sort of thing but it's always good to good to cover it um it's one of the first things that I learned whenever I went to HVAC school and made me write it over and over again on the board this is an illustration that's widely available that we created um and kind of kind of covers the basics so to start with evaporator um I prefer to call it the boilerator and the evaporator's job is to absorb heat that's what it does picks up heat in the case of refrigeration it picks up heat from product cases um and the case of air conditioning is picking up heat from the air that's traveling over it from the return side of intake into the home and the reason it can remove so much heat from the air so again it's absorbing heat so it's removing heat from the air and that's the process of cooling removing Heat the reason it can remove so much by volume is of the refrigerant of the fluid is because that fluid that we call a refrigerant is changing state so it's changing state from liquid to vapor and in that process it's able to absorb a lot of additional heat we're not going to go into a ton about that but that's the that's the basic so I always call the evaporator the heat absorber the compressor is the pressure increaser so its job is to take low pressure gas it's coming back from the evaporator coil and increase its pressure and in the process you'll see that you have Vapor or gas coming into it at a very low temperature and a very low pressure with the large line and it comes out at a very high pressure and a high temperature with a smaller line the reason that happens is because you're taking molecules and you're jamming them together you're taking molecules that were kind of moving slowly just floating through space and you jam them suckers together and so uh they get a lot more jiggly so when you think about temperature temperature is a measurement of how jiggly the molecules are when they're mashed together they move a lot faster if you want to be real fancy about that you say the average molecular velocity that's what temperature is it's a measurement of the average molecular velocity which just means that higher temperature stuff means that the molecules are jiggling a lot faster and lower temperature stuff means they're jiggling slower so it comes out of the evaporative coil if they are uh they're less packed together and so they jiggle less and then we throw it in the compressor and compressor jams them together increases the pressure and it comes out as a very high temperature gas goes into the condenser condenser's job is to reject Heat so uh we're generally in most of the systems we work on it's rejecting heat to the outside air but in some cases like self-contained systems that may be rejecting it to the inside space or in the case of water cooled systems uh it may be rejecting heat into water or some sort of other secondary fluid a metering device is what I call the pressure dropper uh pressure decreaser if you prefer to not use the dropper word um and its job is to reduce the pressure on liquid refrigerant uh again I didn't really mention it's a condenser but obviously condenser not only does it reject heat out evaporate absorbs and then condenser ejects that but it also changes state once again it changes it from a vapor to liquid and that's why it's called a condenser and it does literally go into the top as a vapor and it changes state and then comes out the bottom as a liquid so if you pay attention you'll notice that evaporative coils are fed from the bottom and so it starts as liquid and ends up vapor in the top and condensers are fed from the top starts as uh starts as vapor and then ends up Liquid as the bottom goes up the liquid line it goes to that pressure dropper or metering device which then allows that refrigerant to boil once again which now absorbs more heat in that evaporative coil people who get really confused by this idea of boiling you think of boiling as being you know boiling is always boiling hot right well that's just because we're used to water boiling at 212 degrees but actually boiling water is actually absorbing heat from the burner so it's actually picking up heat and then rejecting it into the into the space as that water leaves in the case of a closed loop system the the part that does the boiling is the part that's actually cooling what's around it and the part that does the condensing is the part that's actually heating Once Around It Go ahead Bert okay fine all right you got me I just want to point out that the names of these four major components are what they do like the work that's being done it's often something that could be easily overlooked but like really helpful for anybody new is trying to learn it like you start memorizing the names of these things and that one day when you finally connect like whoa that's actually their job like the name of the thing is it's jobs so honestly that's genius I never even put that together that changes my whole outlook yeah it changes everything uh which is why Bert's title at Kalos is the annoying guy you know assistant right on his right in his business cards uh yes good point good point evaporator evaporates compressor compresses condenser condenses meter and device meters uh and a lot of you may not even experience text you may not hear a metering device a lot but a metering device is a couple different common types so txv's electronic expansion valves um Pistons capillary tubes a lot of different types of uh standard meter devices hand valves yes yes in case of the manually set metering device but again it's always taking a higher pressure coming in and it's metering it to a lower pressure coming out so it's decreasing pressure um and it's resulting in that evaporation again in the evaporator Clow some simplified principles here that are always worth covering um energy is neither created nor destroyed so we're kind of summarizing some of the Newton's laws and some of the laws of thermodynamics so energy is neither created or destroyed we're just moving heat around that's all we're doing so heat is a form of energy and we're just moving it around heat moves from hot to cold or higher temperature to lower temperature and that's really key because when we say hot to cold and we're not talking about total heat content we're talking about temperature and the best example I can give is if you you think about a swimming pool versus a coffee mug the swimming pool may be you know 70 degrees and you'd say if you jump in that swimming pool be like oh it's cold in your coffee mug uh maybe you know 100 degrees 120 degrees whatever it is and you would say well that's hot but which of those two actually contain more heat in the fluid so in the in the liquid which contain more heat well the swimming pool actually has more heat because it has a lot more water in it right so overall the heat content of a swimming pool is much more significant than the heat content of a coffee mug if you take that coffee mug at 120 degrees 130 degrees and you Splash it into the pool it's not going to change the temperature of that pool at all even though it's a much higher temperature so when we talk about heat It's always important to know are we talking about units of heat that would be BTUs British thermal units which is the overall amount of heat or are we talking about the intensity which is temperature and again we already already mentioned temperature is average molecular velocity which just means how fast are the molecules shaking inside of inside of that substance and so that's actually what we're measuring with a thermometer right actually measuring the average speed that those molecules are vibrating inside that substance um really you're not making code you're just removing heat exactly you're not making anything cold you're moving heat around and there really is no such thing as cold um some people will point out well yeah there's absolute zero which I think is negative 490 something like that I never remember what it is and that is the point at which it can't get any colder but cold is not a that you can't measure units of cold we measure units of heat uh or the absence thereof of heat so we're really just uh we're really just moving heat around that's all we're doing solids liquids and gases those are our states of matter um in a air conditioning refrigeration system we really don't like solids and we see it sometimes when we allow our evaporator coils to get a low enough temperature that the ice builds up on them but that is not a design feature unless you're working on an ice machine but we also see it uh in some rare cases if we work on co2 systems and we allow the pressure to drop low enough uh below that triple point and now it becomes solid inside the system so that's a that's another kind of bad thing um you'll notice it kind of talks about the different types of heat here you'd have to really zoom in to see what it says here but you have latent heat of fusion that's the heat that goes for to change something from liquid to solar solid to liquid gas to liquid you have latent heat of vaporization if it goes from liquid to gas and liquid latent heat of condensation if it goes from gas to liquid and then you have the latent heat of sublimation which is when something changes directly from a solid uh to a liquid to a vapor or a vapor to a solid that's what we see with CO2 CO2 has kind of that weird property at low pressure where it does that and in the past we wouldn't really care but actually nowadays we work on quite a few CO2 systems where CO2 is being used as the heat transfer medium is being used as the refrigerant is not a state of matter well okay well this is actually an interesting all right interesting point there are actually indefinite states of matter um when we say when we say something has a particular state of matter we're we're saying it has some properties that we combine together and we give it a name but there are actually tons of different states of matter that we don't list here um when we're talking about uh fluids that we traditionally use for air conditioning Refrigeration these are the big boxes um that we that we place them in but uh yeah when you get things that are really high temperature really high pressure really low temperature uh really low pressure you get all kinds of crazy states of matter that exist within that I heard a physicist talk about this one time that really everything that we're uh calling different states of matter are really just simplifications that make it easier for us to understand but there's essentially indefinite indefinite states that you could say well this slight property changes or that slight property changes you can also get solids and um some some refrigerants similar like CO2 um glycol you know they have like burst pressures and stuff like that so you can get them inside the line yeah good point especially when you're working with the secondary fluid I mean water being one of the most common secondary fluids we ever work with meaning that you're using water um so just to be clear what we're saying in many cases we take refrigerant and we uh expand it in the evaporator coil we evaporated uh boil it whatever you want to say and that's how we absorb heat but sometimes we'll use an evaporative coil or heat exchanger and we will cool another fluid and then we'll take that fluid and pump it around and it doesn't actually necessarily change State when that fluid is water obviously you have to be careful not to freeze it you you really got to be careful with that um obviously if it freezes it expands um water and a few other liquids actually create a crystalline structure when they when they become a solid and so they actually expand and Converse things so you got to be really careful with that as well how do these thermodynamic principles apply to refrigerants I don't like to I don't like to uh read slides too much but this is basically you know just a definition of something so when we take air conditioning is basically and really when we say air conditioning the original definition um this really comes from Willis carrier Willis carrier started using that term air conditioning and I think he defined it as the simultaneous control of temperature humidity and filtration I think is uh the three that he named but we can really say you know it's when we say AC we're usually talking about the cooling process but conditioning the air really could mean a wide variety of things but we generally just mean Cooling and so generally speaking when we're using these types of systems that we're talking about that utilize compression refrigeration and evaporator coils uh what we're absorbing heat from inside the structure and we're rejecting it outside the building in order to make the the temperature of the structure inside a lower temperature in the case of refrigeration we're doing a similar thing we're just picking up heat from product picking up heat from inside of a case and then we're rejecting it somewhere else in the case of a self-contained product obviously or self-contained case that's inside of a store think of a soda machine and you are you know rejecting heat from those those cans of soda inside the machine you're rejecting it to the space around it so which in most cases would be inside the store what makes a refrigerant a good refrigerant is that it can change phases and reject a lot of heat in doing so and we call that typically we call that the latent heat of vaporization so when we look at what makes a good refrigerant a good refrigerant we say how much heat does it absorb and reject per pound uh within that kind of Target design temperature range it's a really good refrigerants that we've used for a long time would be like R22 r410a you know those those sorts of refrigerants R12 being one that was originally used in in refrigeration as we've gone on sometimes we've had to make sacrifices but sometimes we don't for example ammonia is an amazing it has pretty much the highest heat of vaporization that uh latent heat of vaporization of any refrigerant that we work on still used today in ice rinks and things like that downside of course is that you know it'll kill you CO2 has great great latent heat of vaporization but it has this challenge challenge of you got to kind of keep it in this particular range of temperatures and pressures in order for it to be effective propane has amazing latent heat of vaporization uh better even than R22 with the same pressures but again you know kind of explosive so we always have to think about you know the safety of a refrigerant it's latent heat of vaporization how well it carries oil we've changed the oils with modern refrigerants because of that because we want to make sure that that oil circulates with modern refrigerants that don't carry traditional oils as well as the old ones did but those are the things that we rely on with uh with a good refrigerant those are the characteristics um and then temperature pressure relationships so this is a really common one and this is and this is actually uh fairly Universal so as pressure increases temperature increases and as pressure decreases temperature decreases a lot of people say well yeah that's true when you're changing phase so in an evaporator coil you know we drop the pressure and so it begins to begins to evaporate and that's when we pick up a lot of heat but it's actually true universally so if you take even something that's just vapor and you drop its pressure its temperature is also going to decrease in fact the very first ice machine or very first Refrigeration machine again it's this is a disputed territory but we're from Florida so we like to credit John gory as being the inventor of refrigeration used essentially air and water it didn't use a true refrigerant to change state but just through pressing and decompressing pressurizing and depressurizing you could absorb and reject heat without a phase change we use phase changes nowadays changing from liquid to Vapor in order to move more heat but pretty much universally you decrease pressure you're going to decrease temperature you increase pressure you're going to increase temperature comments anybody no all right all right yeah no I do want to say though uh the thing that you said a while back of you know how they came up with the term you know like one time yeah yeah actually that's yeah that is a kind of a fun thing to think about so when we talk about BTUs we can use 12 000 BTUs per hour um or what is that that's uh 288 000 BTUs per 24 hour period somebody can do the math real quick and see if that's right 12 000 times 24. that sounds right where that came from was when they initially were uh designing refrigeration systems one of the very first applications for that was to be able to cool product in refrigerated box cars and so when you would send meat or you would send any sort of perishable uh across the country you would have to pack it in blocks of ice and you'd pack it together with blocks of ice and sawdust usually is what they would use as an insulator and you'd send it across the country well when this uh compression Refrigeration first came out and had to design them they would say all right well how big do I need to make this thing yeah how how big how big do I need to make it in order to cool the product and they would say well before we used to use three times tons of ice and so okay so I need to make it three tons worth and that's where we that's why we still use that today so literally a a ton of cooling capacity whether it's Refrigeration air conditioning whatever it is that 12 000 BTUs per hour or like I said I think it's 288 whatever it is um times 24. uh that 24 hour period that's the same as it would as a block of ice would take uh or absorb in completely melting so I'm going from a 32 Degree one ton block of ice to 32 Degree completely melted water um that is one ton of equal to one ton of refrigeration and that's where it comes from a little fun history lesson a lot of things are very simple like that um like when you think about American wire gauge like we say number 12 wire you know like well where did that come from why is it number 12 wire well that actually started out as fencing wire so when they would do fencing they would say number 12 that's how they rated fencing wire and so you just get wire that was the same size as what you would use for a fence that's how it started because actually some of the very first distribution Electrical uh that was used in the in the country was actually just running along fences that's how you do it if you wanted to get electricity from here to there you already had a fence so to wire up and fire up Dems was the good old days let me tell you when you could electrocute someone not blink an eye yeah I'm just kidding that's not we don't want to electrocute people I don't want you to get that idea um at least not usually all right the lines we talked about this a little bit already so each line is named between the components so your suction line um we'll start with that moves between the evaporator and the compressor so it moves that cool superheated vapor from the evaporator coil to the compressor and when we say superheated once again everybody freaks out just like when we say it boils in the evaporator coil and they expect it to be hot because we think boiling's hot and they find out it's cold it's like what's going on here what's wrong with the language it's because we're used to water and what we hear superheated that sounds oh man that must be super hot but the air around us is super heated superheated just means that it's a vapor that has increased in temperature above its boiling point in the case of air well of course what's the boiling point of air I don't even know it's really cold you know it's like negative something 200 something degrees and so the air above us is highly superheated above its boiling point in the case of refrigerant we're just saying if it's superheated that means it's completely boiled in other words there's no liquid left it's completely Vapor so when we say the suction line moves cool so it's still low temperature to touch um superheated vapor from the evaporator to the compressor that's what we're saying we're not saying it's super hot to touch we're saying it's heated above its boiling point discharge line goes between our compressor and our condenser again it's still Vapor compressors are vapor in Vapor out unless you want them to blow apart on you um so very hot superheated vapor from the compressor into the top of that condenser then it goes through that condenser desuper Heats begins to condense until it's fully liquid at the bottom and the liquid line is going to move warm to touch sub cooled liquid from the condenser to the metering device so the liquid line better be full of liquid that's what it's supposed to have in it and that's going to move and that liquid line transports that liquid to the metering device uh again we're going to talk about receivers here and a couple more slides in Market Refrigeration it would go to the receiver before it goes to the mirror device uh superheat again we already talked about that it's just the temperature of a vapor above the saturation temperature and sub cooling is just the temperature of a liquid below the saturation temperature in other words if something is sub cooled if it has if its temperature is below it's condensing temperature that just means it's liquid that's what we're using that measurement for and superheated that just means it's vapor all right so we got some other uh things that we kind of add in these are some of our basic accessories that you see you know regularly the receiver basically is a tank for liquid so rather than it coming out of the condenser and going straight into the mirroring device you have this receiver in between which acts as a storage tank and this is especially important important in systems that don't have consistent load on them so especially cases like grocery stores where you've got multiple evaporatorial coils and you don't know you know how much is going to be operating at one time or how many will be in defrost whatever you needs it to have some excess refrigerant to work with sight glass is just a way to kind of look into your liquid line and see is it a full line of liquid and this is a shortcut that that essentially has been used by lazy Refrigeration techs forever because they don't like to measure sub cooling but uh but it is a it is a good visual way to see whether it's effectively when I first when I first ever went to a refrigeration system uh the guy who was training me he said look at the sight glass and see if it's clear all right if it's bubbling I I honestly and I don't know if anybody else had this issue but I was like okay it sounds simple but I didn't know what I was actually looking at and there's actually no difference between a Clear Sight glass and an empty sight glass so I have seen where people are like oh yeah sight glass was clear it should be working and it's like okay would you put gauges on it no and it's actually empty and so uh it should you should be able to see right through it yeah so the point is is that both vapor and liquid are both clear and um if it's full that could mean that it's full it's full of liquid means you don't see bubbles that's a better way of saying it rather than saying fully say is are there bubbles or not but you also you won't get any bubbles if it's off completely too so like you know it's uh it's a very uh kind of narrow band of things that are gonna where you're really gonna see Bubbles and that's when you have a functioning system it's got refrigerant in it but you don't have a full line of liquid and it's running obviously uh filter dryers uh filter dryers are commonly installed in both the liquid line and the suction line um kind of for different purposes your liquid Line Filter dryers generally tend to be there um for operation purposes they're going to catch things before they get into your metering devices or your screens since it's very important that you know they keep they keep that liquid line clean your suction line dryers filter dryers are there to protect the compressor and especially become important when the system has had massive amounts of contaminants in it for those of you who kind of wonder why we don't have suction line drivers on more systems or why that's not uh more regularly used when you use suction line dryers they produce a little bit of a pressure drop even if it's just tiny even when they're clean and this comes down to some basics of moving heat around and how these systems work we want to keep our compression ratios as low as possible and when you're hearing they'll say oh that's fancy dot compression ratio what is that it's very simple it just means that if you take your your discharge line pressure so the the pressure on this on the line coming out of your compressor and you take your uh suction line pressure coming into your compressor you want those two to be as close together as you can you don't want a lower suction pressure than you need and you don't want a higher discharge pressure than you need because either one of those means the compressor's got to do more work right and so if we drop our suction line pressure by even a small fraction that impacts the ratio more greatly than even a significant increase in head pressure generally does and especially in refrigeration because in refrigeration we run very low suction pressures those pressures are low to begin with so even something like a one PSI drop can be a significant percentage change which means that your compressor runs harder and gets hotter and you don't move as much refrigerant because again whenever you drop the pressure on your stunt line an easy way to think about this is when the the gas coming into your compressor when that pressure is lower the gas is lighter stands to reason right if you have less pressure on it there's less molecules packed together so the gas is lighter so for every rotation of that compressor or orbit of the scroll it's going to move less gas if there's less stuff there it's going to move less of it not only that because these are refrigerant cooled compressors in almost every case what we work on if the if the gas is less dense coming into that compressor it's not going to be able to cool the compressor as well also so all of this to say that's the reason why we don't like suction line dryers to be in and if we do have them in we want them to be the lowest possible resistance we don't want them getting dirty we don't want to put in really Mack Daddy restrictive suction line dryers any longer than we need to so it's for those of you who have worked in the trades for a while and you're like why do we you know why do we cut them out in the case of like residential systems or if you work in grocery stores why do we replace these burnout dryers and go back to replace some of the more simple ones later on or why do we pull them out completely that's the reason why we don't want to have additional pressure drop in the suction line whereas something like the liquid line where the gas is already very dense it's under higher pressure it's not nearly as much of a consideration it's not going to be a big impact on their compression ratio if any at all in most cases can I add something Brian yeah go ahead So for anybody who's looking to get into Commercial Refrigeration beginning of the job we go and we put in such filters I would recommend it says in the scope you're only supposed to put them in the beginning and take them out the end of the job but definitely check on them after about two weeks because those racks aren't serviced as much as we service our racks and those filters can get really dirty really fast and it can cause a lot of problems and unnecessary service calls yeah so to the to kind of the point of what Christian's saying um there's a lot of reasons why especially when you're doing you know it's some sort of major work on a site why you're going to see the suction line dryers start to start to plug up and a lot of it has to do with if compressors have been running hot for a long time the oil can get really kind of gummed up and messed up um and then another reason is if people when they originally uh piped the store if they didn't flow nitrogen when they brazed you're going to have all this carbon throughout the throughout the system and especially when you do a retrofit or an oil retrofit which we're not doing as many of those as we used to but when you go from mineral oil to Poe oil um that Poe oil is much more of a solvent than the mineral oil is so if you had any of that cupric oxide on the inside of the tubing because they didn't flow nitrogen while brazing all of a sudden that's all going to start coming and anybody who's done a retrofit from mineral oil to Poe on Old racks you know you see that you get all this carbon starts to come through and that's where uh not only just changing a before and after but like Christian said just you know replace it just check on them basically look at the pressure drops uh suction line dryers are always going to have some way for you to look at the pressure drop across that section line drier and generally speaking and again it varies depending on the refrigerant but but anytime you start to get over 3 PSI you know like you really need to need to look at that again anything is bad but the more is worse and so you know just just follow the specs on it go ahead bird I'm just wondering if you guys are uh is there always suction line dryers on like Market systems because we put them in maybe after certain kinds of repairs in residential but is that something they're always there there's always going to be a shell for them now most of the time you there shouldn't be any in there sometimes they get left but um yeah what what basically like the standard practice to help people know if suction line drivers are in there is uh because they're cores they're not just like a sweat and dryer they have Springs and so you would leave the springs for those like somewhere at the rack that's easily visible so you would know hey you know there's three suction cores or shells on the rack and I have two Springs maybe one of these still have a suction core in them you know or I have three Springs okay well should be good you know so there should be equal amounts to whatever uh filter dryers or however many uh uh suction line dryers shells there are uh so if you don't see them definitely it's it raises red flags immediately also as Brian said uh if you have any question about instead of taking everything apart check your pressure drop across the canister yeah and it also doesn't even take that long to pump down that header and pull them and you know so it's not like a huge ordeal but uh it's significantly less work to pull a suction line dryer on a rack than it is to cut it out on a uh on most racks instead to cut it out on uh you know a commercial air conditioner or even a residential air conditioner so it's just bolt-on a little side note since we were kind of talking about correctly drop a little bit about oil now I don't know if there's a slide but like like on a rack oil system uh that oil separator you want a pressure drop but not more than the manufacturer recommendation I think like Western Meyer I think it's like yeah like five PSI is what you should have and it's more than that obviously you need to check it and I think separate is a I think I think it was temporary is you the temp right as you replace it with Western Meyer our friends at Western are like to hear that um but again that's on the your oil separators on the discharge line so uh pressure drops on the discharge line aren't nearly as big of a deal as pressure drops in the suction line just because of the of the ratio so for example if you think about you know let's say you're let's say your suction pressure is I don't know I'm just going to make up a number let's say your section pressure is 10 psi right and you have a one PSI pressure drop that's a that's a one that's a ten to one ratio right if you have a uh you know 200 PSI and you have a one PSI pressure drop that's a significantly lower ratio fraction and so you can afford pressure drops under discharge line in your liquid line that you could never afford uh on your suction line and so it's just a just a good thing to remember um and again G2 I think I really like what Christian said uh to once again it when in doubt just check the pressure drop across your suction line drives even in residential if you don't have a pressure drop it doesn't matter people will often say well you got to pull the second nerves out you got to pull the secretaries out no you pull them out if they have a pressure drop that's that's when you need to pull them out if they don't have a pressure drop don't worry about it it's not going to hurt anything it's all about that pressure drop well not even suction filters but a lot like your your line dryers as well always check those it doesn't work yeah for sure in the case of residential you don't have pressure Taps across your liquid line so you you can't necessarily check it but that's where you check for temperature drop so on liquid on the liquid Line Filter dryers you have that Advantage because if there is a pressure drop um you're generally if it's bad enough you're going to see a temperature drop now again with liquid it gets tricky though because if it is if it remains fully liquid and you haven't eaten up all your sub cooling you won't necessarily see a temperature drop across the liquid line filter dryer so not every restriction across the liquid line dryer is going to show up in terms of temperature drop Birds laughing because I got into a fight with Joe Shearer about this and uh I was wrong and Joe Shearer was right I wasn't fully wrong though and we're not going to explain that here it's fine but I can admit I can admit uh Joe's smarter than me it's fine I I uh I know we gotta we gotta move on but real quick uh I was uh coming from Air Conditioning to Refrigeration especially uh I was always used to just doing a temperature drop because it's faster more efficient however um I quickly learned that you can have like as little as maybe like a one degree drop across a differential or uh differential across a dryer specifically liquid line dryer but your pressure drop across that can be 10 12 PSI sometimes I mean it's like ridiculous amounts and uh it's just so when if you have access to put pressure ports um you know or if you have the ability to to take the pressure readings I would always take a pressure reading over a temperature reading temperatures are fine if that's all you got but always pressure that is more reliable way to tell so that's all I want to say about that yep that's that's true um and then uh oh and also to point out on instructional under our temperature is not going to do you any good um so that's it's you got to use pressure um accumulators uh I don't know that we see very many accumulators in refrigeration in rack Refrigeration uh yes uh older ones on your smaller one smaller Refrigeration units yeah but you're going to see a lot of accumulators out there on air conditioning and like like Kerry mentioned on some uh Refrigeration units and an accumulator's job is basically to catch any liquid refrigerant before it makes it to the compressor that's its job and so it's got this YouTube in it and um it's gonna you know it would have to be super full of liquid before that would ever come back and so it just allows that system to sort of manage some liquid coming down the suction line now that's not the design we don't want liquid coming down the suction line but there's some reasons that can happen especially on things like heat pumps and air conditioning where you don't have control of that evaporator temperature because you're the evaporator is goes outside and the heat pump what was the artist formerly known as the condenser coil becomes the evaporator coil and heat mode and you have this really low temperature uh space outside and so sometimes you will get some liquid that's coming back especially with fixed orifice metering devices which some people still use and so uh that's what that's that but but the thing to realize about accumulators is they can cause you a lot of Heartache because um the oil also needs to get pulled back to the compressor and so we're kind of relying on that oil settling down into the bottom and getting picked up by an orifice down at the bottom of that tube because as that oil travels back because you know a little bit of oil circulated through the system at all times we can't let that just get trapped in the bottom of the accumulator so it has a screen and an orifice down to the bottom that picks up that oil and brings it back to the compressor if that screen gets plugged or if that orphan orifice gets blocked for any reason that compressor is eventually going to start for oil and die and the problem is a lot of technicians don't think about that so whenever you're working with a system that has a compressor failure and you can replace the accumulator easily and inexpensively I generally recommend just doing that otherwise you want to empty it and uh and clear it out now again it's a good idea to empty it anyway because if you empty it in like very little oil comes out well then it's probably safe but again when you're going to diagnose it you're not going to be like all right you got a bad compressor time to empty the accumulator you know like that's that's not going to be a normal practice so that's why it's it's better yeah part of our standard protocol is every time we find a failed compressor we just cut out that accumulator immediately um I mean it wouldn't be a terrible idea but it's not something anybody does that I'm aware of so just some things to know about that we are getting pretty technical here far more technical than we would have gotten if we didn't have a bunch of me feeling like I've gotta make it a little bit more interesting all right motor rooms Corey uh what are what are some of your top motor room uh pointers so ear protection is crucial uh that's the number one thing that uh especially people who aren't used to the noise already are going to and when I mean use the noise I mean the people whose hearing hasn't been damaged by the noise already to where it's not that bad um they are loud so uh headphones uh that are semi or fully noise canceling or earplugs are a must um there is a lot of things that look scary so if you don't know what you're looking at ask before you touch but um you know just it's it's not as uh intense it's intimidating but it's not as scary when you break down the racks even to this day I mean you know I'm not the greatest Refrigeration guy in the world but I still try to break down racks uh especially ones that I'm not 100 familiar with in the little pieces uh as far as instead of looking at the entire motor room saying oh my God you know there's all these pipes and wires and everything like that say okay well you know what just like an air conditioning you know it's it's all the same stuff more or less um so you know break it down this is for your oil this is your compressor this is your breaker this is your lines and then Trace Out Lines um you know to see what goes where uh because it you know you're always going to have and a DX rack you know for uh regular Refrigeration you're always going to have your suction line you're gonna have your discharge line you're gonna the refrigerator the refrigeration cycle never changes so especially people coming from Air Conditioning to Refrigeration um I I always find it helpful to try to find uh Common Ground between the two and it makes it uh in my opinion at least just a lot easier to not get overwhelmed by everything in a motor room particularly all right Chad you got any top motor room top tips there are some motor rooms the compressors because they kind of push them against the wall so sometimes it's a tight fit and just be aware of that um but I think Corey pretty much explained it pretty well uh you know they're loud I do want to point out uh because I just read the safety considerations on the bottom where it says Exit the motor even cases refrigerant leak that's actually very good um but one of the things that you want to make sure too is that uh all or all the ones I've seen at least we'll have exhaust fans um keeping fresh air and so on the right of that picture that's like your intake for fresh air that's important to keep the motor room cool but it's also important uh for ventilation and stuff like that you don't want to ever have uh it's an overlooked thing and you know people like ah it's just an exhaust fan but those are actually really important port safety as well as the health of the rack to always make sure that your exhaust fans are running and if they aren't running uh it it needs to be more common to make that more priority to figure out why and repair those because in case of uh a refrigerant leak that's gone undetected there are refrigerant Leak Detectors at the racks usually with varying accuracies uh most I'll be honest with you I hardly ever look at those but um if there was a refrigerant leak and there was a high concentration of refrigerant in there particularly when you start getting into more dangerous refrigerants like CO2 you want to be very mindful of that and that's with anything walk-ins motor rooms you know you want to always make sure that you leave yourself plenty of ventilation I was going to say one of the best things to do when you're going into a motor room especially if it's a new store of yours pull out your leak detector and look for things that just don't look right if you see oil on the ground investigated if you see a part hanging hanging somewhere even if you don't know what it does ask someone try to figure out what's going on if it's supposed to be like that go ahead and research everywhere make sure you don't have any refrigerant leaks just try to control the things that you can control now the thing with safety uh you know it's not all laid out there but just kind of a rule of thumb that I like to go by is a any copper line in the motor room that's not insulated just imagine it's hot don't touch it no imagination it is hot Chad has all the marks to prove it too yeah I've got a scar on my arm myself again I keep I keep giving too much props to Christian but I really do like the look investigate anything that looks looks suspicious in terms of oil anytime you see any oil anywhere always investigate it um anything that looks like it could be leaking always investigate it making sure that you're leak free and clean in your motor room so I would also say again this presentation is kind of more for Basics people who really maybe even shouldn't even be in the motor room kind of some things to make sure you know but if you're a technician who's responsible for a motor room one of the best things you can do is just keep everything really clean because then you can see if anything's changed much more easily if you if you leave everything oily and messy as it is um then it's hard for you to tell when a leak is developing um it's more difficult to notice all right I'm gonna go through some basic here I'm not going to spend a lot of time here um when we talk about open front bunker and glass door refrigerated cases that's that's the bulk of what we uh what we work with inside of a set of a grocery store and really what these are is they're they're ways of displaying product but they contain your metering device they contain your evaporator coil they often contain you know your whatever your mechanism is for defrost and they have a fan or a set of fans that then circulate that air parallel rack systems we say parallel rack we're just talking about you're allowing multiple evaporator coils out on the floor to utilize multiple compressors that are mounted on a racks when we say a rack that's what we're talking about the the frame that all of this is mounted on that also in generally include the controls and a lot of the electrical as well as the oil management system allowing multiple uh multiple different systems out on the floor multiple different evaporative coils or cases out on the floor to kind of share that capacity that those compressors are producing obviously ice machines we don't need to say what a nice machine does because I think it's pretty clear we have these oil return systems which is a really big or oil oil management system sort of you want to call it this is a really big part of rack Refrigeration or really big HVAC systems that you don't deal with in the smaller world in the smaller world you don't have access to it it's just it's just kind of like circling through the system but when you have these large distributed systems with a lot of piping and a lot of different evaporator coils getting that oil back can be very difficult so as much as possible we want to keep that oil there with the compressors and that's where we utilize oil separators to kind of keep that oil from even leaving the rack in the first place is just as little as possible we want to make sure it stays in that in that rack and then we're also managing the oil in the compressors we're actually you know using oil sight glasses or some sort of uh sometimes it's just sensors that you're utilizing but we're making sure that we're keeping that oil proper in the uh in the compressors yeah oil is the airflow of refrigeration so often overlooked often misunderstood but when you get down to it it's not as scary as it looks um I oils repairs as long as it's not at night are my favorite repairs um it's the sexiest part of Refrigeration in my opinion most people hate it I love it um you can really get in depth with it and it's surprising how how easy it is to overlook things but how simple it all is it's it's all a it's all science so get good at oil and you you will be much better off uh just like if an air conditioning if you learn oil or if you learn airflow and understand airflow um very early on your career is going to be a lot easier makeup air units um see a lot of these uh these basically replace exhaust there so when you have um kitchens or anything like that where you're exhausting a lot of air you're pushing a lot of air out you have hoods whatever um you have to replace that air in the space otherwise the space is going to go in negative pressure so we actually talked about this recently um restaurant that I go to a lot I I always has like this awful smell in the bathrooms and I noticed that the doors were really hard to open so I didn't have to use any fancy tools I just you know bathroom smells really bad doors are hard to open um so I let the owner know I'm like well what's what's happening is your your floor drains are drying out and so when you're floating dry out it sucks sewer gas back up or wherever that floor drain is discharging which is likely some are nasty and it's making the bathroom smell terrible um he just kept putting different like Glade plug-ins all over the place thinking that would solve it and it was just because you didn't have enough makeup there so you got to match that air coming back into the air leaving and that's what makeup air is for in many cases you know for years uh makeup air is literally just drawn outside air and dumping it in but outside air is unconditioned so you're not dehumidifying it you're not cooling it often you're hardly even filtering it nowadays there's a lot more requirements to actually condition that air before you bring it in into kitchens and all that which is a reason why for a really long time there's a lot of condensation issues in restaurants and you'd see the around the vents there would be sweating and there'd be all these all these issues because you're bringing in all this unconditioned air uh and then HVAC rooftop units are really common I think it's probably more common in our Market than maybe just because our outside conditions are pretty reasonable generally and so uh rtus are really common in our in our Market um some things that you will see uh kind of uncommonly but from time to time you'll see economizers and economizer is a system that basically uses outdoor air as a first stage Cooling in cases where the outdoor air temperature is lower than what the indoor air temperature is which can happen pretty often when you have commercial spaces that are generating a lot of internal heat um so you can kind of use that at times and then we do see in grocery stores quite often um reheat and so that reheat comes in from um often the refrigeration equipment the Rack you're bringing in that heat and uh running it through a coil in order to reheat past the evaporative coil in order to make the system act as a better dehumidifier because sometimes you need more humidity removal but you don't need as much cooling capacity and so you run the air over an evaporator coil which drops the moisture and then you reheat it again so that way you're not over cooling the space allows you to keep running the air conditioner even in times when you don't necessarily need more cooling capacity all right so now we're at controls I'm not going to talk here I just we got some things listed here I'm going to let whoever wants to whoever wants to talk about this uh take it I um all right so let me look at this picture here all right so in this particular um photo it looks like there it looks very Compact and very confusing but basically there's just several different controls um again we're talking about the basics for supermarkets so first off your temperature controls your epr sort valves epr is evaporator pressure regulator um since this is a parallel rack system you have multiple compressors that are sharing a common suction a discharge line and maintaining a set uh suction saturation temperature or set suction pressure um now at evaporator pressure regulator's job is uh to regulate the pressure on the evaporator so each circuit usually will have some sort of evaporator pressure regulator uh whether it be a sore it um uh CDs valve you don't have to worry about um what type they are right now they're just they all do the same thing it's different different ways to skin a cow is that what they say uh skit a cat yeah that would be a cat yeah yeah always cat or whatever but um yeah so you have your evaporator pressure regulators your low pressure controls are I mean that's pretty self-explanatory low pressure um if it gets too low it will uh cut in or cut out excuse me uh and I'll let you guys take it the three-way valve when I say a three-way valve it's similar to a reversing valve um but instead of shifting it to let's say heat uh it is redirecting discharge gas for a separate purpose uh usually a reclaim uh to a water heater or an air conditioner for uh reclaim dehumidification um if anybody else wants to take constant cutting control defrost control electrical control whatever or whatever else all right here we go evaporators um so I kind of want to clarify uh what these things tell us so when superheat tells us uh about feeding issues it says charge issues here but how well are we feeding this of Africa are we feeding it with enough refrigerant so low superheat are less than five degrees Fahrenheit means that you're flooding it so you're over feeding it we say overcharge likely these are in cases of systems that don't have receivers and where you only have a one-to-one type of configuration but in a grocery store generally when you're over feeding an evaporative coil it has to do with the setting of the meteor device is that that meteor device is over feeding the evaporator coil um and that's generally because you're using txvs or electronic expansion valves high superheater superheat over 20 degrees Fahrenheit and again we're talking about at the evaporator coil or even you know it doesn't have to be that high uh means that it is starving so you're not feeding enough refrigerant through so I always talk about superheat the easiest way to think about it in my mind is when you have a low lower the superheat the more full the evaporative coil is a boiling refrigerant when you have higher superheat that evapor coil is less full of boiling refrigerant and that is actually very that that is what's happening um and so we want that evaporator coil to be nice and full we want to have a load of superheat but it needs to be low enough that it's it needs to be high enough that it's under control Jamie kitchen from danfoss um taught me this term in a podcast a long time ago of minimum stable superheat which means that we want our super heat to be as low as we can possibly stably keep it which is where electronic expansion valves have an advantage because they don't become unstable until a lower superheat than uh thermostatic expansion valves do thermostatic expansion valves as you start to get kind of at least your typical ones you start to get below about six degrees of superheat they start to get unstable you start to get hunting and all this which is why if you get a case where you are getting hunting or you're getting like kind of intermittent flood back then just increasing your superheat a little bit sometimes can stabilize everything out and then high temperature in the refrigerated space so we would say you know it's not making temp um dirty or frozen coils low air flow on a externally equalized dxps that are in some of the most of the cases I've seen they'll have screens in them that you can replace you don't have to unsweet anything it's just it's all right there you can check that screen of where your Inlet of your refrigerants go and if that's all blocked up it's going to cause you know high superheat and uh like newer cases as well um not always are they shipped with the right cartridge size which is just you know the different size orifice for you know how many BTUs you're trying to make with that case so usually I just call them and let them know what I'm using the case for and the manufacturer will let you know like what size orifice you need to appropriately get that case set to how it should run yeah which is another key point for anybody who is used to air conditioning we talk about replacing valves well in in the market Refrigeration at the very worst you're swapping a screen or cleaning a screen and maybe replacing a cartridge if it's the wrong one or the cartridge is messed up in some way the internals so you basically have the screen and you have the guts those are the two things you're going to potentially replace or change on a valve if you have the wrong ones you're not replacing the valve itself which is kind of kind of nice the not nice thing is is that because they're longer piping and there's just more that can go wrong the screens do plug up more yeah or the power heads two most common things you're going to run into with the expansion valves are obviously a dirty screen uh that's gonna be your by far your most common but the second most common in my experience is a uh is a stripped out uh stem adjustment stem so people will have superheat issues they will crank on that thing until they can't anymore as soon as you feel any resistance like stop because I can't tell you I literally I should I should have taken a picture I have a bin in my truck of stripped out stems and spoil them if you're using spoiling valves they have a part number where you can actually get those uh but yeah over adjusted stems are horrible because they will get stuck they always get stuck all the way closed or all the way open depending on what somebody was trying to do with them so if they're trying to close it all the way they over adjusted it's going to get stuck closed if they ever um trying to open it all the way and they open it too much it's going to get stuck open and you're just gonna flood all the time so those are the two most common I've seen or the push rods that are seized up yeah oh yeah I I think that has a little bit to do also with you know the over adjusting and all that too yes Corwin has a nice kit uh that comes with push rods you got all your cartridge sizes and a nice little bottle of oil so like it is always important to just always oil everything when if you're rebuilding a valve from making is you will feel them and if you're having issues with not getting proper superheat or it's not feeding properly don't try to push that valve or grab some some other sort of problem and I've seen people think well maybe I just open it or you know two currents or so I'll get a little bit more Super uh or less super heat out of it um in the case of you know you're just going to end up breaking the valve and then it's an expensive car to just be replacing willingly all right so uh compressors um you know anything that is uh out of the ordinary in terms of noise or or um you know shaking around uh that that's what you have to pay attention for and then also another good thing to pay attention for is high discharge temperatures I I like the idea I've taken um thermal imaging cameras into motor rooms before and you can actually do a lot of comparison there now obviously they all have to be on uh and at full capacity but you can kind of comparing one to another is one handy thing in a rack room it gives you that context um but you want to pay attention to that and then obviously slugging uh or flood back so flood back is just just means that it's that liquid refrigerant's making it back to the compressor slugging means that liquid refrigerant is actually making it into the cylinders or into the compression chamber so if it's actually making it uh into the into the space where it's truly being compressed that's when massive damage uh can occur and kind of blow everything apart yeah compressors superheat and discharge temperatures are very overlooked when you're just doing regular debate and service calls um or uh anything for that matter each manufacturer of compressors I don't care what it is they all have a factory recommended uh compressor superheat to make sure that that compressor is staying nice and cool Copeland I know prefers like 20 to 30 degrees of compressor superheat and measuring it uh I think they want like 10 inches or something from the from the compressor I don't know but um yeah so compressor superheat is uh vitally important and discharge temperatures as well you can't really use a thermal imager to see discharge temperatures like line temperatures because of the copper but uh you got to put like tape or something on it I don't know but uh a regular pipe clamp or thermocouple uh it works just as well and uh again Copeland and really anything it's pretty Universal I mean you don't want anything over 225 degrees I mean once you get 200 over 225 degrees discharge lines have uh you're you're going to start cooking that oil which is going to lead to massive problems with both the compressor and the rack itself if you've made a some sort of alteration especially something at the case level and now all of a sudden you're getting flood back go and look at what you just did because if your valve is wide open or something else is going on some something's going on where liquid refrigerant's just flying through that evaporative coil um you need to rectify that because again this flood back happens because of something that's going on at the case level in rack Refrigeration so figure out which ones which one's causing it it's most likely the one you just worked on if it was working fine before and now you're having now you're having an issue to the point of uh yeah I like what Corey had to say about checking discharge temperatures it is true that when you are checking the actual discharge line temperature with a thermal imaging camera doesn't work because of the emissivity of the copper tubing but you can still tend to you can still compare like compressor to compressor on the actual heads and all that uh even the oil pumps and all that you can get a good sense of if you have an outlier in terms of um high temperature but it's critical to understand that in rack Refrigeration because you have multiple compressors sharing the same oil uh it's really dangerous to have um issues to allow issues to occur that can break down that oil because or or cause or cause damage because now that can get shared among multiple compressors and really cause a catastrophic situation so it's another reason why it's really important to do maintenance and keep an eye on all these things make sure you're tending to oil make sure you're not slugging or flooding um just making sure you're keeping that all uh all in check I was just going to add to starting up new cases if uh like if you're starting up a new case or if you just replace an expansion valve on a case and you're not it's a good a good starting point is to kind of feel your feel your valve out I usually which we deal with spoiling valves more than anything and it's like I think it's four and a quarter four and a half Turns full turns it's going to put your valve like right in the middle and that's usually a good starting point not always but typically that's a pretty good starting point to prevent you know immediate flood back I don't know if I should get into it but another good thing to keep in mind about flood back too is it doesn't necessarily need to be just at the it is at the case level but in a in the event of like a wreck that has been down for any prolonged period of time you're going to uh have the potential when you start that rack up of massive flood back so you have incredible load heat load on your uh on your rack when you have multiple circuits all warm and you just kick on all the compressors uh so to negate that you would anytime you have a rack down like I said for any for a long period of time you're going to want to valve off the suction lines to uh those racks and kick everything on very nice and slow you don't want to go you know Tesla super speed mode 0-60 you know reset all the oil and kick it on because you will take out a compressor guaranteed um it's very easy to do well you do your oil reservoir are you going to wash your oil out well yeah yeah that's why that's what I'm saying is you you take all you're going to valve off your oil reservoir but um you know the circuits and kick one compressor on now put it put a valve on the suction lines and just meter nice and slow all the circuits off you know gradually on as well as the compressors and then yeah like Chad said the oil uh that's been sitting in the bottom of the separator it's gonna it's cold uh it's gonna be high pressure and you know open it up Let it Flow a little bit close it and you can feel the lines how cold they are it might be saying it's on like but you feel the heads of your compressors like if they're not warm or like hot like it's not running and then also a good thing to check too to make where you can see if you're not like bleeding by a discharge gas through the reception side you can feel the bell in each compressor they should be cool sweating if they're warm and it's running then you gotta miss you and that will also increase your suction pressure which is not going to help out your cases or really anything normally if you feel your suction Bell head is warm this picture is a good description of it you usually have a bad valve what were you going to say Carrie oh I was just gonna add to uh if you come to a rack and you really and it's not running at all and you're not sure how long it's been down I mean probably the safest thing to do is is just go back to the truck grab the recovery machine and try to get the Liquid you know like Corey said battle off your section going back to your cake or coming from your cases and pump pump that liquid into the liquid line and just so that you you know and then slowly valve your cases back on you know turn the compressor on to slowly valve those cases back on so you know for sure there's not any liquid or any chance of liquid getting back to that rack when you're starting it up this is what happens to your Val these this is from a 6D compressor uh that I pulled the heads on Wednesday uh if you notice all that right uh sorry I'm plicking everybody off but if you notice like all that right here these are uh your discharge uh pucks or valves whatever you want to call them Reeds uh and they're all blown out so it's it's bypassing that's that's no good liquid was on the head it was started up at some point and liquid does not compress and that's your end result uh and your Pistons are all bent too as Carrie said making sure that when you go to Star of a wreck it's going off for a long time making sure that there's not liquid in those compressors if you're not sure you need you need to make sure because you will kill all those compressors almost instantaneously trying to just shove them one with well being full of liquid like that I might have done that before a couple times me too me too bad boys one compressor at a time oh yeah for sure and then the next one especially especially especially on bitsers pictures do not like liquid at all oh yeah yeah dancers are the worst with that I mean any event thought back they cannot tolerate thank you guys uh for taking the time to do this and uh we will we will follow up and wrap this one up I do appreciate the engagement I kind of like doing it this way it's it's fun thanks for watching our video if you enjoyed it and got something out of it if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click the notifications Bell to be notified when new videos come out HVAC school is far more than a YouTube channel you can find out more by going to hvacreschool.com which is our website and hub for all of our content including Tech tips videos podcasts and so much more you can also subscribe to the podcast on any podcast app of your choosing you can also join our Facebook group if you want to weigh in on the conversation yourself thanks again for watching foreign [Music]

Channel: HVAC School

Views: 22,964

Keywords: hvac, hvac school, Rack Refrigeration, Discussion, Intro, market HVAC, facilities staff, supermarket refrigeration, HVAC/refrigeration, circuit, main components, evaporator, compressor, condenser, metering device, vapor, laws of thermodynamics, subcooling, suction line, discharge line, Accumulator, leaks, motor rooms, evaporator pressure regulators, SORIT valves, three-way, defrost controls, commercial, hvac technician, supermarket refrigeration systems, supermarket service tech, Parallel

Id: WTinJMl0rMY

Length: 64min 47sec (3887 seconds)

Published: Thu Nov 17 2022