Uh today we're going to be talking about airflow, we're going to actually run the system, we're going to go through set up a profile and then actually make some changes to the system block off the you know, kind of simulate, a dirty filter, simulate a poor duct System and then actually show what it does, but before we do that, i just kind of want to talk through it a little bit and talk through some of the some more of the theory. What goes on in the system. We talk a lot about the same things over and over and over again, but the goal is to get you to a place where you both know what to do, but you also know why you're doing it, that's always the goal. So, let's start with really practical.

I always like to start with the actual practices uh that you do when you go up to a piece of equipment and let's say it's: a no-cooling call we'll use an oakley call as an example. What are some things that are airflow related that you should check every time, regardless of what the problem is versus the filter, what else blower wheel? What are you checking on the blower wheel, any build up on the wheel, yep, that's good! What else evaporative coil? What's specifically on the evaporator coil, though the underside, the inlet side of the evaporator coil, is what you need to be checking so just because you were in there with the blower and you looked down, you didn't see anything what else try to be a little bit More uh because those are things that you definitely go in with intentionality to check you're going i'm going to check the evaporator coil, i'm going to take my mirror and look on the underside. I'm going to check my blower, i'm going to check my filter. Those are intentional, but there are some other things that a good technician will always look for.

It may even just be subconscious. Look in the return grill every time you pass exactly. What are you looking for when you look in a return grill every time you pass? How dirty it is, or if there's another filter behind that there's another filter behind that aaron says if it's collapsed coming apart, those are all really good the sound of the motor, that's a really good one. So what are you looking for with the sound of the motor? I like this.

What are you looking for abnormal sound? So what are some things that can cause abnormal sounds with the blower motor static pressure, so what static pressure high low, too high of static pressure? So too, high of static pressure will cause what to happen specifically eric. That's all the type of motor depends on the type of motor. That's the right answer, that's what i was looking for. That's why i picked that area i didn't want to have to yell at anybody.

You probably would have said freon, you might have said um yeah, so it depends on the type of motor. So let's say that we have an old-school psc motor and you hear it making a noise. What are you what what would an experienced technician? Think i'm just gon na wait! Just gon na wait here standing here, i'm not in a hurry that it's over amping okay possible possible, but that's a symptom, not a cause, wired incorrectly and probably not as far as noise, probably not on a psc. Well, i'm not thinking you're, not thinking.

There's high static right because high static on a psc motor, the permanent split capacitor motor does what to system airflow dramatically lower system dramatically lower system airflow and the motor does? What, in response to that it does nothing. It does nothing. It's like a husband on the weekends. It does nothing true, so all it does is all it does is reduce its output.

It does not ramp up, and so it doesn't try to compensate there's, no there's no compensation taking place, so it won't be noisier because of high static pressure. A psc will not be noisier because of high static pressure, because it's not attempting to ramp up, but if it is noisy what are some things that could cause a psc to be noisy and do cause the psc to be noisy, not the capacitor right. Well, the capacitor. Doesn't it's a fine thing to check, but this is this is good because what you don't want - and this is something that a lot of newer techs do every time - there's a problem.

Every possibility is open, so you just check every possible thing that it could ever be right and that's okay to some degree, but what's better, is to be able to narrow down and find the problem. So if you have a psc motor, that's making a noise, it could be, could be the bearings on the motor could be the blower wheel. In fact, often it is the blower wheel and what often happens on a blower wheel that makes it noisy eli. It breaks.

Yes, it breaks the hub gets loose, yes, and so what will happen is. Is that either the entire larger hub, where it attaches to the blades disconnects or the internal hub, where the shaft attaches to that? To that larger inner hub intersection gets loose, and so when that happens, you'll often get a really loud noise. Sometimes, though, that noise will be intermittent so sometimes it'll, squeal really loud and then it'll stop and it's just a matter of if it finally caught for a second, but it can be an awful awful noise. So again i like having these conversations where we kind of go off on little rabbit trails, because there may be things that you pick up on that you haven't thought of before diagnostically.

The topic is airflow, though all right so with an ecm motor. If you hear it doing what matthew was describing, where you hear a lot of air sucking in the cabinet or it's making a loud whining noise or whatever, then you suspect static pressure? You suspect that your static pressure is high, and why does that motor? Do that? When the static pressure is high, why does it the air get noisy and the motors start to maybe vibrate a little bit more make more noise? Why is that just trying to maintain the airflow? It's programmed to be at it's attempting to maintain air flow or torque, depending on the motor type x13 motors, which is a brand name. Constant torque motors are going to attempt to maintain torque, uh, ecm or true variable are going to try to maintain airflow. So that's what you watch for when you see when you hear an air handler, that's howling or a furnace, that's howling always stop and look at static pressure.

First, before you even check static pressure, though what are you going to look for restrictions right, you're, going to look for the things we just mentioned, starting with air filter? Obviously, then, going to evaporator coil you're also going to look at the blower wheel, but blower wheel, loading doesn't make the motor function in the same way as other air flow restrictions. It's kind of a we won't get into that right now, but it's not it's not going to necessarily cause that problem. But then you look at things like burt said you look at the returns. What are some other things? What are some customer caused things? In addition to air filters that can cause low system, airflow closing supply vents, why do they do that? Why they're cold in the room, because, because they're cold in the room, trying to force more air into another room, exactly did i ever tell you how we used to do air balancing back in my prior company that will not be named? Did i ever tell you that? Well, no, that's that's yeah! That's how you check so the way you check for airflow, especially after you started up a zone, damper system, and i still stand behind this.

I don't have any. I have no shame in this whatsoever. You take a surveying flag and those are all over the place. You can pull them out from anywhere.

Nobody ever cares. It's amazing. You take a flag yeah, it's like hey. Look at this.

It's a gift. These are amazing. Uh you take a serving like you bend a 90 in it and you cut some cut, some cut it into little ribbons, and then you tape it onto a piece of pvc, see how see how fast the blowy blows, and that tells you whether you got good Air flow, so i so when i say stand behind it, i do not stand behind that as an airflow measurement tool really, but as a qualitative is a damper open or not. It's actually a great way of doing it.

We used to work in these big custom homes in iowa worth and windermere, and all this and you start up his own damper system or maybe two in a house and you've got to go through and make sure each damper opens and closes and that's an excellent Tool for that and i will not be ashamed. I will not. If you comment on youtube telling me i should be ashamed, it's not going to work, so don't do it because i won't be it's not going to work. It'll be ineffective.

You know if you diagnose this machine, and you think that trying to shame me about this is going to work. It's not going to you know. You're gon na have to put another txt in because it's not gon na work. The emotion! Sorry, i'm patting my mic now: that's gon na be noisy for the editor okay.

So what was i talking about? You were talking about your stealing survey flights. Customers survey. Flags. Oh yes, okay, restriction! So another thing we would do is if we wanted to force more air.

So if we had an area that was getting too much air, we wanted to force it to a master bedroom or something else. We would take a piece of duct board, we would cut it the a little larger than the internal diameter of the of the flex. We would then cut it in half, so it was kind of flexible and we could fold it over and we cut a smaller hole on the inside. Now the the trick was knowing how big to cut that smaller hole in the inside, and you know what science we used in order to figure that out handometer good old handometer, trial and error.

Yep should be like hey this this this laundry room. It seems like it's putting out a lot too much air, so i'm going to make the hole in the inside real small and then you take it. You take the grill down, you bend it and you force it way up in the duct. You know why you forced it way up in the duct might have been a reason.

No, the reason was because, if you put it right down by the vent, it would make a lot of noise because it would come through it'd, be high. Velocity would hit just a just a portion of the grill and it would make a lot of noise, so you shove it way up in there. So it had a time to become more laminar and fill the duct before it would come out, and so obviously that will cause low system airflow. It's not that it's ineffective at balancing, because you can actually improve air balancing and how it's doing that.

But along the way, what are you doing to your supply static pressure, you're, raising it right, just like crimping the end of a hose, if you pinch the end of the hose you're, building up more pressure and more static pressure in the hose itself? So, rather than that energy going towards flow, it's backing up and it's building up pressure, that's forcing against the blower and it's reducing the amount of air that can go into the space. What are some other things that customers do, that? We want to watch for furniture in front of the return. Yes, they move furniture in front of the return. It's especially awkward.

If it's a ceiling return, it's like man. Would you get that couch off the ceiling? I don't know what you're doing in here, but get that off the ceiling. No, so usually it's a usually it's a low wall, direct return and somebody shoves the couch up against it right or a lot of times, people with pets with a lot. You know very shitty pets that can even plug up if they have uh returns.

That are kind of you know tight. Maybe there's a stamp returns you'll. Actually the actual opening will get plugged in commercial you'll see it a lot with perforated returns called perfs. That's what we call trade, we call them purpose hey.

What do you got, what you got up there? What do you say? What do you say? What do you say you got it? No, that's not that's a whole different thing. That's a whole different problem that we have no, so because that, because the openings are so small, they get plugged up with dust and that can actually greatly impact system performance. Another thing to watch out for with perf grills is they glue a piece of like cardboard or they put a piece of metal in the center and the back is fiberglass and it's usually not supported well so over time it starts to sag down onto that piece That now obstructs the end of your duct, so you'll have a whole space that was cool and fine and then, like you, have to actually remove all those pieces of metal or cardboard to get it cool again, because it'll kill all your airflow yep yep yeah perfect, Turns aren't great they're, not the best um. What is something else that can happen to the system that you want to watch for that can result in poor system.

Airflow double filter, that's good! We talked about that. If somebody, but but yeah you're right, somebody could put one in a four inch media cabinet and then also put a filter in the cable guys. What cable guys watch out for cable guys crushing the ducks. You see all these dead ducks in the attic and that's those people guys it is always up there stomping ducks pulling off the supplies to pull themselves off in the attic yep.

I haven't seen that a lot, but i have i have heard talent. Yeah. Are you the one doing that not on camera collapse, returns and supplies, flaps returns and supplies that can happen the internal liner, especially if somebody made a duck splice and spliced it the wrong direction. So that way the internal liner starts to collapse.

In that can happen, you see that a lot on trailers, it's real common, a lot of i mean. Basically, you see everything on trailers, all the things you don't want to see. You know everything. It's like, oh, what is this a trailer? I'm going to see something.

I don't want to see you know i felt like i should just keep milking that joke, because i liked it, but then i didn't have anywhere else to take it. There's a lot of things. Bird almost ran into a pony one time. You know we also have the insulation in the unit sucking into the body.

Yes, i was waiting for that one insulation in the unit that sucks up against the blower yep. That's another, really big one. So actually, every time you take the panel off of a system and by the way, it's actually pretty dangerous to take the panel off of a running air handler like when i say dangerous, it's not probably it's probably not going to kill you, but i've seen people Pull panels off the insulation sucks off and then it goes and starts shorting out or gets into the blower or whatever. It can definitely happen.

Now, the more experience you get, the more you kind of make sure you get a corner and you kind of work it off, but you really shouldn't be pulling panels off. While the unit is running around the blower - and i know you're all rolling your eyes at me right now - the entire internet is rolling their eyes at me right now. What i'm just saying, that's so true brian and it's so true, so true i'll. Never do that again: yeah yeah.

What are some other things that cause low system airflow can definitely cause poor system airflow, exactly we're talking about like after the fact, though, right like after the installation yeah, but it could be, it could be poor design. Sure, what's another one: what can why do? Sometimes you have really bad system airflow right after you had a backup drain water in the return water supply water in the return yep, either way. If it's downflow, it could be water in the supply, but you will sometimes um, especially in cases where you have a flex return. Those flux, ducts, they'll, hold a lot of water: oh yeah, they'll fill up with water and that will block either the return or supply.

In the case, the downfall could block the supply either way it doesn't matter. If there's low airflow over that evaporator coil, it's going to result in problems right what else frozen, evaporator yeah i mean that definitely is going to cause low system airflow. Now often it's low system airflow that caused the coil to freeze up in the first place, but it could be something else. It could be a bad pxp yep.

You set an air handler on a platform and you don't want to hold it. That will definitely no. Let's not be ridiculous. Let's talk about stuff, that's actually going to happen in real life.

That means, of course, come on there's some things that just aren't going to happen forget to plug the fan back or if you plug the fan back in. What's it, there aren't nearly as many zone dampers nowadays that fail closed, because they're usually spring open power closed, so usually they're just going to blow all the time fire or smoke dampers fire dampers, that's a really good one yep and in commercial applications where at one Point in time, everything was fine, and next thing you know, like an entire area of a building. No longer has air, definitely look for fire dampers that are slam shot yeah. What else? This is really good.

We got a really good list here. We're going to compile this list because we're not even done yet we're not, i don't know we're not even what happens if you're working on a belt driven system - oh okay, so we're doing commercials too we're just going to go through yeah. Let's go adjusted, somebody went and messed with the shiv. So now it's not producing nearly enough airflow.

How did you just do that? Your belt sounds violent, adjust the shield, yeah yeah, that's after you stab somebody and then you're like you know what i didn't get it right. The first time. Let me do that again, that's adjusting a vfd could be programmed inaccurately. You could have a vfd, that's poorly programmed yep and that would be in commercial we'd call it that all right, i'm gon na wait for these these two knuckleheads to stop la yucking it up over here.

What do you think this is laurel and hardy? Nothing here. Uh wow so there's a residential version so hold on corey because he's a commercial tech talks about uh setting up a vfd programming, a vfd which a vfd is a variable. Frequency drive to spin motors different speeds right, so you're not stuck on 60 hertz 60 cycles per second, but in residential we have a version of that. That's pretty much exactly the same thing.

What is that called? What is the residential version of a variable? Frequency drive? Solid state i mean solid state means electronic. That's all that means well, you can get. You can use them for like a psg mode. Okay, all right all right speaking specifically of blower motors when we say when we say ecm electronically, commutated motor, we're basically saying a vfd driven motor and there is a vfd.

The the motor module on a ecm motor is a variable frequency drive. That's that's what it is right: you're, taking single phase in the case of residential um, ecm you're, taking single phase power, you're turning it into dc and then you're taking that dc and you're switching it in order to spin the motor at a particular speed. Now a lot of people will say: well, no, it's not it's not actually an alternating current motor, though it's a it's a dc motor. Some people say it's a three-phase motor, but really what makes it different is that, rather than having this true sine wave that we get from the power company you're, actually just energizing de-energizing at three different uh, three different poles there's three different faces.

What's that pulse width, modulation, pulse width, modulation, that's a word! You don't hear every day ain't, it good old, pwm we're not going to go into that right now, all right, but it's a huge one though, and it's one that we talked a little bit about last week and i want to talk about it again, because it's One that i know that we miss because you go in i'm gon na i'm gon na we're gon na go through a scenario here. Okay, you go up to a system, i'm actually gon na, throw out some numbers here for the senior text just so that we, you know all on the same page, go to a system. It's a 410a system. You've got 90 suction on it.

You've got 8 degrees of superheat outside you've got a delta t of 25 degrees, 26 degrees, something like that. You've got a head pressure, that's slightly low based on the outdoor temperature, i'm not going to try to come up with one right now, but it's slightly low. What is the root problem that caused their symptoms? It's airflow right, txt, meteor device. Sorry, i didn't tell you what meteor device it was because your super heat is normal to low your suction pressure is definitely low.

Your delta t is definitely low and your head pressure's a little low all right. Those are all indications of poor indoor airflow. So those are your symptoms, then, what do you do? Replace the txd several times you replace the tank over and over and over again, and then say it's probably the compressor and then say: i'm sorry ma'am this unit, just ain't got no more life left in here. Oh yeah, i'm placing your txv once when i drop the screw in the return.

Yeah screw out, never to go blue when it when it falls into the return right, hey the tfk again yeah. That's it yeah when a screw goes blue, something to look for um. So you go through all that now you so you've diagnosed that it's an airflow problem. Most techs are going to go through the list of things.

We've already talked about right, they're, going to check the filter they're going to look in the return they're going to look at the blower wheel, they're going to look at the evaporator they're going to do all that and when they get done, a lot of technicians are Going to call their manager supervisor and say i don't know, what's going on with this system, because i checked the airflow and it's fine right. Did you check the airflow? It wasn't fine right, you did because you connected tools to the system that gave you every indication that airflow was not fine right, they're, giving you they're telling you that it's not fine. But what do you do you go through your list and then at the end you say it's fine, but did you measure air flow? No, let's say you were really good and you measured static pressure and, let's say your static pressure. You're running 0.5 total external static.

It says right on the panel that that's what it's supposed to have, so my airflow is fine, but it's measuring static pressure measuring airflow nope. No, it's just measuring pressure right. So if this blower isn't producing what it's supposed to be producing, if it's not moving the amount of air it's supposed to move static is meaningless, doesn't mean anything right. So if, for example, somebody landed the yellow wire on the wrong terminal on a single phase unit, they landed it on y one instead of y slash y2, that's a carrier designation, but they landed it on the wrong terminal.

That system is going to run low air flow. Let's say that they pulled the dh to our jumper and they didn't wire it up properly to the thermostat. If you don't have 24 volt call on that dh, what's it going to do it's going to produce less airflow, and it's going to give us all these symptoms, everything's going to look pristine, everything's going to seem like it's working, fine static, pressure's, fine, everything's clean! What's the problem right, but it's that the blower's motor isn't producing enough airflow, because it is programmed in such a way that its inputs are telling it to produce less what happens if it's a four ton unit and somebody went and set the pin to three ton. It's going to produce less airflow than it should have right.

What happens if it's a heat pump unit in the green wire is broken somewhere? The g call so that way that blower never gets a g call in cool mode. What's going to happen to airflow on a lot of systems, it's going to drop a lot because that's a programming feature. You have a cool call without a g-call on a lot of systems, not all, but on a lot of systems it's going to produce lower airflow. So and again we i i beat these drums a lot.

I i cover this a lot, but there's a lot of things. You've got to check, and even then even after you do all that, even if you once you confirm that even once you look at the pin settings even once you test to make sure you have a 24 volt call on g and y y2. Did you check airflow? The answer is no, so i'm not saying that you did anything wrong because you didn't, but don't say you checked airflow because you didn't. What would you have to do to check air flow? You'd have to have some sort of a tool that measures flow, and there are a few true flow grid - is a really good one.

What are some others? Anemometer? You could use uh, you could use an anemometer, you could use a rotating van anemometer, but that's only going to go uh. Your typical large vein. Thermometer is only going to go at the vents, so you'd have to go to every vent in the whole house. Do a traverse on each one, which means you have to move it slowly across it.

Then time average it and then multiply it by all of them. But even then, if you have duct leakage, that number is not going to be right. You put that little uh cookie tray thing in the filter. There you go that you were talking about.

Yes, that's the true flow grid. Yeah, of course, that's that's, probably the best way in the most consistent way. You could do it with a large flow hood on the return. You could do it with a hot wire anemometer in the duct and do a traverse.

Do a log chebychev traverse and lay it all out with your different holes and measure it and take the time average and then calculate your velocity and then multiply that times the internal dimension of the duct right. You can do that. Are you ever going to do that? Nope nope? Not i mean in commercial, you might, if you're a test and balance technician, but you're not going to do it. We're not going to do it you're not going to do it right.

I've done it. You have, and in this scenario i'm not saying when i say you're not going to do it, i'm not saying it's those of you like well, you should do it. If you do it - and you are good at it, then great more power to you, but your average service technician is not going to do that right. So the point is: is that being good at going through all the likely causes of low system airflow being good? At that is the whole game right, but you have to go beyond the obvious.

You have to go to the next step and the next step, the next step and look at the way that the blower is programmed uh and then at the end, if you still really, you know, the readings are telling you your air flow's low, but the system Everything you can look at you're, not finding anything, then now's the time to get an advanced tool like the true flow grid and just see for a fact how much airflow is moving through that through that unit, because there's lots of weird things that can happen. Somebody could have put the wrong blower wheel in you know stuff like that. This can be hard to spot. Sometimes there's some there's some strange things that can happen yeah what happens if some? What happens if the motor is running backwards? That's one that a lot of people fail to catch, but we actually probably the weirdest diagnosis.

I've ever had and i'm only going to tell the story because it was weird it popped in my head. So it's probably not going to be useful to anyone and i'm sorry, but i had a uh ecm motor that was running backwards and it had been running the right way for a long time. This was not a brand new unit. It was like three or four years old and it was just running backwards, so i uh you know you know how to change the direction on a three-phase motor since you just switch any two legs right.

So i thought, oh well, a uh ecm motor is a three-phase motor, so i pulled the end bell off the motor module. I took the the three wires and i just switched the pins. I pulled them out and just swapped them and then it ran the right direction. Like i didn't i didn't.

I didn't think that that would work, but it did - and that was weird, so that's cool anyway, i'm not suggesting i'm sure i did yeah. I've always been very good at tending to profit, first, making sure that we quote for everything: uh, okay, so system airflow in terms of the average technician you're going to know that there's a problem with system airflow. First, by careful analysis of your system, readings and that's the point of today's class. More than anything else is to be able to spot an airflow problem and to know an airflow problem, uh separate from other types of problems, so that when you see the measurements as long as your tools are working properly, i want to talk about that.

For a second before we even get into it so long as your tools are working properly and you see certain indications, you know it's an airflow problem. You don't need to look at other, weird things. Okay, you don't need to replace the txv. You don't need to think.

Well, maybe it's the compressor. You know like that kind of stuff. You can know if it's an airflow problem or not based on the system, readings and that's what we're going to cover now before we do that. A couple ground rules whenever you're using instruments, um especially digital instruments or actually any instruments, but you need to make sure that at minimum they're zeroed and then also watch them against one another, and i just want to point out something uh.

If you look here at measure quick which we've got, you know a live, a live stream from the system. Here you see that we've got a slight difference between the high side and the low side, which is just going to be a calibration difference between them. But it's in the acceptable range right we're under one psi now. What is the acceptable range? It depends on how it depends on what you're doing, but for this, for these purposes within one psi is just fine right not going to make a significant difference.

Look here. Our return, dry bulb and our supply dry bulb are pretty different right. A return, dry bulb, they're, almost three degrees different now hypothesize. Why that might be before we jump to the conclusion that there's a problem, the supply dry bulb is 79.7.

The return dry bulb is 76.9. Are they mapped right? They're mapped right, they're right there right here. The reason is is because one is lower and one is higher. So there can be some some stratification there now.

Is it that much? I don't know, but we would know if we turn the fan on right. So if we run with the fan in the on position, then we would have a better sense now be careful because the motor does add a little heat to it as well. So it's not perfect, but the best way would be to take them both and put them both right in the same air stream, if you're in doubt put them right in the same airstream run some arrow roam and see even just having them with still air like This, it's not they're not going to be as accurate. These sensors are designed to have air moving over them, so putting them both in the return right next to each other, and just checking is going to be a good practice and we're going to do that.

But the thing i'm wanting to show you here is it's worth paying attention to right. If you just rush right in and start taking measurements and you're, not paying attention, if your tools have been zeroed and if they're measuring the same to each other, then you can make some pretty significant mistakes. You know five degrees of superheat one degree or one way or another can be enough to make. You think that you do or don't have an airflow problem and it's easy to get easy to get five degrees of superheat difference right.

So you got to know your tools and just pay attention to obvious things like that, the system's off, so they should be measuring the same right. Okay, why aren't they hypothesized put them together, run it? Let's see what we get right make sense so always always always double check your tools before we get running on the system. I do want to talk through quickly about our primary indicators of low airflow. What is our our number one primary refrigerant side indicator of low airflow, regardless of system type or metering, device, low, superheat, low super or low line temperature low, suction line temperature is actually a great indicator.

I actually prefer that over superheat, even because a txt is going to hold your superheat, where it's supposed to be right and that thc is going to start throttling, but your suction line temperature is still going to be low. Why? Because you're saying is what you have liquid refrigerant you're, not absorbing as much because you're not picking up as much heat right. If you don't have enough air you're, not picking up as much heat and so that drives down the evaporating temperature. So your evaporative coil gets colder.

So let's say that you have a 40 degree evaporative coil with 10 degrees of superheat. What's your suction line, temperature 55 40 degree evaporate coil 10 degrees of super heat is 40 plus 10 equals 50 right so 40 degree evaporator, 40 degrees, suction saturation, temperature plus 10 degrees of superheat equals 50 degrees. That's my calculator! It wasn't great we're just gon na pretend, like that, didn't happen, wow yeah too late, but now let's say that you have low airflow, and so, when you have low airflow you're going to have a lower evaporator temperature. So now let's say our evaporator temperature is 35 and we have 10 degrees of superheat.

Now, what's our suction line, temperature going to be 14 45., got it to the extent that this is kind of a neat thing if you measure a suction line tent now we're talking residential air conditioning here, this gets. But if you measure a suction line, temperature that's below 50 and the temperature inside the space is normal. I'm talking about outside temperature inside the space is normal and you measure suction line temperature below 50. Very good likelihood.

You have low airflow right, so an experienced technician will go up to a system, grab a suction line and feel that it is especially cold and you're. Looking for airflow, it really is kind of that simple. Now, i'm not telling you that! That's how you do it! You don't just walk up and grab a suction line, but if the suction line is especially cold, probably airflow or a low load low load, in this case, being an air conditioning system that would be a house. That's too cold right.

Somebody set the thermostat way down and let it run, but under normal operating conditions, having a section line below 50 degrees. More often than not is going to be an indication of low airflow, because if you had low refrigerant charge, what would your suction temperature be hi? If you had a restriction, what would your suction temperature be hi if you had a bad txt? What would your suction temperature be high right? All those cases is going to be high. So if it's low and the system's not operating properly, you have a you. Have low suction pressure you have low head pressure, look at pay attention to air flow first now we're talking about air flow on the evaporative coil.

But let's talk quickly about the condenser too, so in the evaporator coil. What does airflow do for the coil boils the refrigerant very good. So how does it do it heat transfer right? So, let's, let's really break this down. Okay, so air is what what is air made of molecules? Air is made of red molecules.

It's stuff little tiny, stuff right air has weight. It takes up space, it's stuff right, so as air moves over that evaporator coil, it comes in contact with the fins, the aluminum fins right. That's what it comes in contact with first and as it does that it creates some turbulence, so it kind of starts bouncing around and it imparts some of its heat to those aluminum fins. Why? Why does heat go from the air into the aluminum fins they're? At a lower temperature than the air right, and so what direction does heat move from hot hot to cold right? Let's just do a quick thought experiment.

What would happen if that ever coil had no fence what would happen if we took all the fins off of it, it would still work. Sometimes what would happen the heat transfer you'd have much less heat transfer right. Why would you have much less heat transfer? You have less surface area, you have less turbulence, so there's less time and turbulence. There's less, there's less dwell time.

Those molecules have less contact time right, so they just rush right, past they're not sitting there and contacting that those fins which then contact the tubing right. So, what's going to happen to the pressure inside that evaporator coil with no fins, it's going to drop? Why again the pressure temperature, because it can't because it's not having enough heat transferred in right, it's the heat, that's being absorbed into it! That holds up that pressure. If you're, not absorbing heat, that pressure is going to just keep diving and diving right decrease in temperature equals decrease in pressure right, we add heat to it. That holds the temperature up.

That holds the pressure up and we create this equilibrium remind me again, 75 degrees inside temperature residential typical unit. What's your coil temperature going to be about 40 degrees right? So if you have low air flow, what's going to happen to the coil temperature, it's going to drop it's going to drop, what's going to happen to the pressure in the coil, what's going to happen to your suction pressure, what's going to happen to your head pressure, It's not a trick. Question head pressure drops too right. What's going to happen to your compressor, when you have low airflow fly away, yeah, what's going to happen in your compressor and throws what the amp drops do drop? Why does the? Why do the ant draw? Why does the ant draw drop when you have low airflow doing less work right? Oh okay! Go ahead! Mass sampson mass, like i like mass! I like a good conversation about mass.

What's going on in mass when you have lower airflow, okay, the volume of what stays the same, the volume of refrigerant, where entering the compressor being cycled through the system stays the same, but the mass is decreased. Why? Because there's lower pressure right, there's lower lower pressure means in a contained system. Lower pressure means less mass. If the substance is the same, so it's lighter easy way to think of it is low.

Suction pressure means lighter gas. There's lighter gas coming back to that compressor. So, on the good news, the compressor doesn't have to do as much work right, so the amperage drops, but on the bad news, what else happens to the compressor? It's not getting cooled off as much as it should be. Okay, alex said it gets flooded and eric says it doesn't get cooled off as much as it should be, which one of those is true, the answer is, could be both them could be, could be, could be, could be cool.

I'm not saying they're both happening at the same time. I'm saying that if you actually have liquid making it back to the compressor, that's a flooded condition running flooded, but in that case your mass is not lower. Your mass is much higher to the extent that the compressor can't even compress it if it were to get into the compression chamber, and it would explode the compressor head right. So there's this fine line between light gas coming back and wet gas coming back that causes damage, but we're assuming here that we have some superheat, and so it is.

It is uh, dry gas, it's light gas and that's actually going to cause the compressor overheat. Even if the temperature of it is low, this is a tricky business because guys will say well look my return. Gas temperature is 45 degrees. You told me that it's the refrigerant that cools the compressor - and you also told me that low airflow causes lower suction gas temperature.

So why doesn't this lower temperature gas cool the compressor better? Wouldn't it cool it better? It's colder! The answer is no. It doesn't because there's less of it because it's light, it's light in the loafers you're still allowed to say that yeah, okay bird says it's fine. I've never heard eric doesn't know. Let's say that anymore: it's because you're wearing crocs.

That's why yeah you feel personally attacked by that parsley all right, so there is this fine line. Can you overload a compressor by having the suction gas be too heavy this on the other side, can you overload? Can a compressor actually do so much work yeah, because the suction pressure is so high that it overloads? Yes, the answer is yes, and where do you see that in grocery refrigeration? When can that happen? Freezers, you see a lot of pressure. Limiting txts and freezers overload. Compressors yeah, but when do they typically overload, there's two conditions where they are going to tend to overload without the pressure limiting exps or without the cprs, after defrost and and hot pull down.

So when they're under massive load - and that would be after defrost and hot movement when that suction pressure is so high that that gas is so dense, it's so heavy that that compressor has to do a lot of work to pump it. So compressors are dainty little pups, i mean they need everything to be just right. You know it's like alex's, mother, i'm saying oh, i can't do it. That's a good one.

I got a little off on the side tangent there, because the topic is airflow and the effect. So here's what we're going to do we're going to go through we're going to profile the equipment as we start it up we're going to get it running and look at where it stands with it running normally we're going to make sure that first make sure our Instruments are calibrated properly and then we're going to create some airflow problems. We're going to first block out the supply, see what happens, reduce it slowly see what happens to the system. Then we're going to throw some cardboard and place the filter to clog that up and see what happens to all of our system measurements as we go good old shopping bag.

You can find those in the filter, yeah shopping bag in the filter. That'll. Do it too or the customer who doesn't take the plastic off the filter when they put it in or uses a 3m filtrate, which is basically the same basically the same thing exactly yeah, i'm sorry, 3m! No! Don't sue me first thing: let's do is power. The unit up and let's turn the blower on and put both of the probes in the same location and just make sure that they even out we want to make sure that they're not too far off from one another, all right there we go so we're going To get the breakers on all right now, it's running, i guess that's fine! It might actually get slightly different yeah put them in the return, both of them all right.

So what we're watching for actually hold on i'm going to put on my i'm going to show you how to do something cool on this. You can show touch indicators, so i don't see that wow, so we're looking to make sure that our dry bulb and our wet bulbs are stay pretty close together and, as you can see, they were where they were quite a bit different, initially they're actually doing pretty Good now, but we're also one of them, looks like it might have gone off. No, i guess not. What does that red dot mean? Does anybody know okay? So the point is: is that we're looking we're looking good here so now warm one up in your hands? So we can make sure we put the right one in the right spot.

Okay, so this is the supply grade, so put that one up in the back up in the supply. Now all right try it try to get the probe a little closer to the to the vet. There we go that'll work all right so now we need to profile the system and actually tell it what type of unit we have here just uh. I don't think we can use that word anymore either.

We can't ask about what kind of unit we have that makes sense makes sense, so in order to profile outdoor temperature, because the after temperature is actually the same as the return temperature we're going to go ahead and just put that in there. So our return temperature is 76 degrees, so we'll go and we'll make our return out outdoor air temperature 76.. Now i already set the airflow to 700 scfm, which is something you can do uh measure quick. Is it doesn't allow you to set in the uh the profile for airflow anymore? So if you go back yeah the like standard airflow, so if you go back to the whole like cfm for ton where you can pick which one it doesn't, let you pick it like if you click the other ones, it doesn't do anything.

That's behind the paywall. Now, well, i don't know if i don't know, if that's why or not, but he was saying jim was telling me something about it, but then he talked for two hours straight and i stopped listening. So we do need to set the metering device type. It is a txt, the crating 13 to 16 sear, that's what we've got and then our refrigerant is our 410a.

So all that looks good outdoor measurements. We already did that. The only thing we don't have is discharge line temperature. If we had a different line, clamp another one, we could put that on the discharge line inside near the compressor indoor measurements we're pulling all of these in from the probe.

So when you see ones that set a calculator, that means that's a calculated measurement. So it's taking the relative humidity and the return temperature together and it's calculating the wet bulb same thing on the supply. Now i entered a measured cfm of 700, but that's just because it's a two-ton unit. I was just uh kind of bypassing the internal thing, but, as you can see, you see, they've got an estimated cfm of 340 and the reason why it's doing that is because the tonnage i always hit the wrong one system, id and system info seems so similar.

The tonnage is set at twelve thousand, so it should be set at two tons target sub cooling. It says ten, let's see if that's correct, on the data plate. It's taking me a really long time to find this. It's 11.

big difference all right. So now we're we're pretty much profiled we're missing a couple probes here, but we're pretty much profiled the way we're supposed to be so. You can see 329 cfm proton, pretty close in florida, 350 cfm per ton. It's pretty much.

What we're looking for so everything's! Looking looking pretty good now, you're going to notice that our target here is actually a little bit high and that's because we have a high efficiency coil and i think he also removed that that used to exist here. But anyway, let's just look at what we've got now, so you can see both of these are really close to being within the green zone. The only thing here is that our evaporator temperature is a little bit high, but that's actually pretty normal um, based on the way that measure quick works and our high of latent high moisture conditions. So our suction pressure of anything is a little high.

Let's go through our: we got our temperature split right right dead in the middle of what would be expected here, our delta t, and then our system capacity really really good system capacity. It's a two-ton unit and we're producing right. At 24, 000 btus we've got crazy, crazy, low, sensible heat ratio which, when your sensible heat ratio is low, your latent heat ratio is high right. So that means how much of the heat being removed is temperature change and how much of the heat being removed is water, turning it into condensation.

So we do need to make sure this thing's actually plugged in all right. It looks all right before it was dumping water all over the place, removing a lot of moisture. If we wanted to see how much moisture that we're moving 9.2 pounds per hour is how much water, i think, sucking out of the air a lot of water. You know how much volume a pound of water is.

Yes, how much one pound volume a pound? Is mass volume, evaporated, water or you've got about eight pounds per gallon? I don't know it's a pint, so a pint is a pound of the world around come on. Everybody knows that we had. We had a trainer come in here one time and he said that, like fifty thousand times, remember him saying that a pocket pound whirled around remember, that's not ringing anything else, that's just how he said it too. Let me do it again.

A pint of pound the world around see now you won't forget it either all right now. Why don't we have any of this data? Why isn't any of this showing up eer, s-e-e-r, c-e-s-p and fan efficacy? We didn't add in enough right we're not taking electrical measurements. So we don't have a redfish meter hooked up actually taking real-time wattage. That's the only way it's going to output that either i either either.

If i manually enter it or if i'm taking that real-time wattage, why don't i have total external static records? Because i don't have my static pressure probes hooked up right, but i i would have it if i had those hooked up and you've got your outdoor air temperature. Of course we're not actually outdoors, but this is what it is outside. This is pulled through an online service. Um atmospheric pressure, relative humidity outdoors, let's focus here.

Our suction line temperature is too low, just above 50 degrees yeah. So we can see our super heat is hunting a little bit. What's the first thing that you would do if you ran into this system - and these are the measurements that you were getting in real life? What's the first thing you would do let the system run for quite a while. Let it run well first yeah, then what would you do if you kept doing it? Sensing yeah, you checked to see if the sensing bulb was insulated and making proper contact or if somebody used zip ties to put it on section, especially if it's a ring just fine.

No it doesn't it does. No, it doesn't insulate it first. It works just fine for a few days yeah until you go sideways yeah exactly exactly you got it, so the bulb has to be making good contact, use a conductive, strap and then insulate it and make sure it's not in the right location, green equipment. Oh the same, it really doesn't matter, you can put it anywhere.

You want it's going down now, i'll put it outside. No, what eric explain what you're saying speak to speak to corey, because he's going to get into this argument again on certain equipment. People will mount it onto a place on the suction header, on the evaporator, where it's not sensing. After all of the return vents have entered the suction header, especially on reef equipment, because people are like.

Oh, let's just put it at the top right here, where it's only sensing, a third of the coil's return on the suction header, so eric's not saying that on a three-quarter inch, suction line and putting it on the top of the side of the bottom is going To make it huge, obviously, you've got to drill a hole through the suction line right. This is not the same temperature as the friction on the inside all right. So what do we call? What this system is doing right now? What do we call this? There's a term for this: it's hunting, that's the moving around, but low super heat is called what flooding flooding over feeding over the term leds. It's not actually flooding, because we don't have zero superpolation zero superheat would be flooding point one, but we're over feeding our evaporator coil.

In fact, superheat is an indication of how well you're feeding your evaporator coil high superheat means you're, not feeding it fully. Low superheat means you're feeding it too much. Sub cooling tells you how much liquid you're stacking in your condenser. I sub cooling means you're stacking too much low sub cooling means you're, not stacking enough.

I just came across this way of describing both of those, and i really like it. How do you feel about it? That's beautiful, say it again. No, i don't want to. I just said it.

I feel some kind of way i trademark some kind of what did you feel some kind of way feel some kind of way? Okay, good. I just said something way worse, but that's good all right so anyway, i don't like how low the superheat is, but everything else is really in line suction section line. Temperature is a little low, but that's because our superheat's low all right if we got our super heat up at our search line temperature. But you know what let's go ahead and let's go ahead and do this because we got we got plenty of time here.

Let's go ahead and see if we can figure out why this might be happening. So, let's, let's pull it, let's shut it off, let's pull it open and let's see, if we can, let's see if maybe there is a bulb issue or something else going on bulb. Is actually factory strapped with a zip tie? I've never seen that before. Maybe there's an is there.

Another strap underneath there's another one on the inside. Okay, all right, but this was open, so it's sucking air in which could be affecting and causing it to overfeed. So we're gon na seal that up and see if that fixes, the problem should always be zero when the system is off and that actually verifies it's a very interesting way of validating your tools calibration, because if they were measuring something other than that, that would show A miscalibration in between your potential, okay, okay, somebody needs a torque. We just need to make sure that we don't have any threads left on those screws.

There's that other hole sitting right there, that's exactly where that purpose is supply are very very low. Total external static is 0.2, the percent in that unit all right. So we want to watch this, but we lost one of our uh. We lost one of our probes.

There yeah we got the insulation's got to cool down. The insulation was warm a little bit lower than it was before a little bit. Of course, it hasn't run very long either. Yeah yeah, oh hey there.

He comes it's when the system is um unstable. You can bypass that now. So you can clear.