This video is an excellent class from the 2023 Hvacr Symposium from Joseph Joe Henderson Joe is a great guy I Got to talk to him quite a bit at this Symposium Got to know him a really great instructor and this is a class on airflow and airflow Diagnostics which is just an important thing that anybody can learn. Joe's are really down to earth guy, a long time instructor and I know you're going to enjoy it. Big thanks to everybody who came out and supported the Symposium Big thanks to Measurequick and Akka for being our title sponsors and everybody else who came out and spoke and who supported it. We have another one coming up very soon so make sure to go to Hvcr School.com events to find out more.

The fifth annual one is I would say right around the corner but it's not. It's still a ways away it is in February 2024 but you are going to want to get it on your calendar and if you haven't gotten your tickets yet, you're going to want to do that ASAP because it is almost sold out as it is. Joe Henderson Talking about airflow and airflow Diagnostics This is a airflow measurements and Diagnostics So I'm really excited to be here. I've been following Brian Orr I've been following uh Craig and several others for years Jim Bergman and when they started doing these symposiums, I was just like I want to get this in positive you know and I never couldn't get there and so I was so excited that I was able to not only come here and attend it also to be able to be a presenter.

And so I Hope you guys are excited too because I've been traveling across to conventions across the U.S and this is a very unique there's uh, conventions for Distributors there's conventions for you know companies to go out and see all the new Jazzy products and there's conventions for instructors to learn how to train. but for technicians, there's not been a whole lot of them you know. And so this is fantastic and for them to make it so affordable. Really appreciate it.

Glad to be there So it is an honor. all right to be here in front of you guys and also uh, I am just a little grasshopper walking among these educational giants that are here today. You've got some of the biggest names in the educational industry for HVAC here today and it is truly amazing. Hopefully you guys will look back and appreciate what you've gotten and so being that you don't know who I am and I'm just a little grasshopper I thought I would tell you a little bit about who I am.

my name is Joey Henderson I've been doing this for 34 years. I Started in the Navy I was a nuclear submarine. the USS greenling we called it the USS green thing out of Groton Connecticut I Actually attended nuclear power school right here in Orlando we're not right here, but nearby Orlando Florida When there was a Navy base in Orlando Florida 100 years ago and had a service company called comfort Zone and then later on I started another sold that one started another one called HVAC Design Services and a total of 15 years between those two I've been a carrier and a trained technical rep and trainer for South Carolina did that for a total of 15 years between the two. So I was a tech guy and trainer for South Carolina and then I worked at Uh when they were building nuclear plants down in Southgate up in South Carolina I was on part of the team there to be an HVAC mechanic for the nuclear power plants, but that project never got completed.

So we was there for three years and threw pencils up and ceiling tiles and never got anywhere. But if I would have got that job, we had a million ton Chiller that I was going to be overlooking. it had a few more zeros behind it than I was used to, but they all cool in heat right? So and I've also been an instructor via part-time and now full-time Uh for 30 years I've been Nate certified I've been with Nate almost since they started. We got Nate certified there at heat pump installed and service.

I was also a geothermal Nate certified for quite a while to let it lapse I've got HVAC certification Master HVAC I hold a state mechanical license in South Carolina I've been an active member of our local heat and air Association South Carolina I've been an educational chair and several other things. Put together conventions and got an associate's degree from Midlands Technical College I'm also a full-time instructor there I run the program and one of our students I don't know if he's in the classroom here, but is up here. It's pretty nice to see that I also run an HVAC consulting company where I do independent presentations like this I've done it for uh ahr I'll be doing it this year ABM for our Scalt iConnect training I went to the Bahamas did some training there and also for Esco and now finally I can add to my list that I actually made it to the Symposium and here I am so I am a die-hard airhead I Love air and it is a very, very passionate thing for me I Love duck design I love zoning. Uh and a lot of people don't like zoning because they are not properly designed in the ductwork.

Okay, uh and but I've got zoning in my house I've designed many Zone systems I've redesigned many Zone systems out there. They work great I Love everything about airflow. Why is it that I care so much about it and why should you whenever I was uh the first time I had my install business uh you know I came out of the Navy understood the mechanical side of things I didn't We really didn't study about the airflow side of things water flow a little bit and so when I went out there and started installing I kind of followed what I saw? you know? so when we replaced the unit, if it had a box and duct work on it, I put a new unit in there with a box and duct work on it and turned it on. It ran great right.

The handiometer said everything was fine. everybody got a handometer, use it all the time, right? Okay, all right, so the hand armor. super good air. All right.

let's go all right. Had no clue that I was screwing up duct systems all the time and I was putting in units. Do you think any unit That's rated? Of course back then it was 10 and 12s here. All right.

But any unit, no matter what the serial rating is, do you think you're getting that when you put that an existing duct system? Not at all Never impossible? All right Now of course. I Love the CR2 that came out because it exposed what I said was going on all along. See, the first year ratings were based on no ductwork. Y'all know that that's the reason we're going to see her too.

No ductwork, no resistance. It was a 0.1 static total. That's no duct work the minute you got any static on that duct system. The Seer rating was here going down.

so I saw this happening and I took a manual J Dtns Anybody ever take that kind of a class before? All of them. Okay, when I took that, my eyes were open and manual D just glared at me. Manuel D is the standard for duct design covers all aspects of duct design. Uh, Jim Bergman threw those all those manuals up on the screen this morning, you know.

And Manual D was in that list. Manual ZR was written later for zoning because of the fact that zone systems were so screwed up due to duck design, not because of the zone system itself. and once I took a hold of manual d it changed everything. All my units started working better.

Uh, all the performance went up and when I sold that company and I became a tech rep for carrier and that was carrier and Bryant and Payne back then and I was a Bryant dealer I didn't have any troubles with my brain system not one I didn't have any compressors I've never lost a single compressor in any unit I ever installed and I never lost a replacement compressor in any unit of somebody else's that I replaced that compressor in. Okay, and it goes back to installation practices, but a lot of it goes back to airflow. Okay, and so when I started hearing about people losing compressors and having all this problems with equipment that I installed, I started going out and checking out installs. The number one problem was airflow.

Nobody understood it. Nobody I mean can you see air? All right? Well we can measure things that we can't see. We all know how to use a Volt meter I Hope. All right.

If not, finger works good for you know, quickie. All right. So you know we can measure. We got Volt meters to measure, you know, voltage, right? We got gauges to measure pressure, we got temperature sensors.

but how many people got something to measure air up until recently? All right, You know, not many most of the time how do we measure air? The hand Domino right? All right. put it up there got good air. Oh got good air. You know we're done.

we're out of there. Well oh it was screwing up a lot of systems and when I went out there and started redesigning duct systems, explain to them how it works. All of a sudden everybody's call back started dropping off, light bulbs started going off and people they paid what 10 12 14 000 for systems. We're actually getting more what they paid for.

Think about it, a customer. If you if I paid a thousand dollars for something do I want somebody to say hey works pretty good you'd say well thanks. You know now well I want that day to work Perfect. If I pay a thousand dollars or something, what do you pay twelve thousand dollars for something And they said ah, pretty good.

Came on, got a good airflow. bye see you. What does a homeowner assume that you've already done a thorough job of checking electrical, refrigerant and airflow right? Did we? most time we did it? Why didn't we do it? Didn't know how? didn't know how to? how do you measure airflow right? We don't know. Uh I Taught all across Tech schools.

As a carrier rep, the number one subject that was the weakest on teaching was airflow. Most of the time even the instructors didn't really know much and everybody that had a deculator it only needed one setting point. One, that was it. And that got everybody going right.

Okay, that was wrong too. All right. So you should care a lot about this because in the end, if you don't get it right, if you don't check it, you don't know what you're looking at. You just robbed a customer.

You just took twelve fourteen thousand dollars out of their pocket. You don't think that way. I Know you didn't wake up thinking that way, but that's what we end up doing right. You're like a mechanic.

They're just kind of halfway, put some screws back into the starter and you walk out of there. What happens, right? Same thing. So let's talk about how to do it. First of all, what happens up inside of a duct system? This is just a representation right here of how the air flows through the duck.

We've got two kind of pressures that we work up. Okay, we got velocity pressure, but we got static pressure. The thing that I want to talk a lot about a static pressure today? I'm not going to I'm not talking about duck design as far as how to use a ductulator and all that. I want to talk to you about what happens inside that duck.

Now when I talk to customers I Explain that the fan motor here. that's just like your heart. What's your heart doing is pumping blood through your system, right? It's circulating blood all through the system. That heart's just moving.

Well, that fan motor is like the heart of this system. Guess what the ductwork is Our Arteries right? And then the air is like the blood flowing through Our arteries. If you've got restricted arteries, was a duty high blood pressure. what's the silent killer Anybody ever heard that call high blood pressure is a silent killer.

You can have high blood pressure right now and not even know it, and die of a heart attack, get a stroke and you had no symptoms, no signs. That's what happens when a lot of times the airflow. we think just because this thing's turning and this thing's running, we got good airflow, right? I Mean we figure everything came on so it's fine, but it's not and it's a lot to do with this right here. So when you look at these lines right here, this is the air moving through the duct and air is always trying to expand.

It's always pushing out right. You blow up a balloon. What's it Do right? right? Well, the metal ductwork can't do that, can it? So the air is pushing against that ductwork and that's creating resistance. Okay, so ductwork's got resistance going through it all the time.

and these arrows are pointing that the resistance is on the outside edges of the duct. So this is called our static pressure. It's the pressure that's pushing against the outside edge of the duct. Now, what's going through the center here is velocity.

Okay, and a lot of times. that's what we're dealing with on this motor. This motor can only push and pull so much air against so much resistance, right? Okay, so if you got a car got a little beep beep Four-cylinder car, right? It can only go so fast on a road, especially when it starts going uphill. What about if you had a six cylinder car, would it have more horsepower to do the job right? What about an eight cylinder? Even better.

Okay, same thing. These motors are rated to only handle so much load or static pressure against them. And so what we've got to do is, we've got to make sure that that motor is operating in its proper static. How do we know that? How do we measure it? Well, This is the uh, the standard way of measuring now.

We've also got the the air grid out there now, right? and that'll measure total airflow at the unit. What I'm looking for is I Want to measure what the static is to get a balance of static pressure so that we got smooth, quiet, return air and a good throw of Supply Air Okay, and I want to know where my problems are with the static pressure probe I can actually start hunting for problems. Okay, all right, got that word from Rob Faulk All right, hunting for problems with a static pressure. So you know we've got these kits right here.

We've got. you know, different kinds of manometers, but you got to have a manometer to measure static pressure. Okay, anybody remember this guy? All right. Okay.

had to have a level. had to zero it out. It was perfect as long as you mount on a wall. All right.

But these days this is about where we're going. We're going on the digital side of things and we've got to have what's called a static pressure tip. Anybody know about static pressure tip? Good deal. all right now.

The most accurate way that I have learned to use these is: you want to be sure that you point this tip into the airflow because what happens, you see, it's a bullet. There's no hole right there that's totally closed off. So when you got that tip and it's pointed to the Airstream here comes the air and when it hits it, it expands around it. Okay, so what does it create on the outside edges of it? The static pressure.

And that's what these little holes right here are measuring is the static pressure so you always want to pour it into the airflow. That's really important. if you turn it the other way, you'll still get a reading. but I've seen it go off a little bit.

so I Always recommend you go this way. and the one thing this is not. it's not a pedo tube. Okay, Keto tube has a hole in the center and another line to it so it can read static and velocity and give you Cfms.

So this is just a static tip and they're out there and you need to have one right? Okay, another way you can do it if you don't have a static tip. and I've tested this in the field is you can take a straight piece of tubing and if you run it at a 45 degree angle with the airflow, this will create a static reading in that tube and that'll almost get you almost as accurate as a static tip. So if you don't have a static tip, you got a little straight tube. so you know you've got your little flexible rubber tube.

You know that might work. Just make sure that it's at that angle and check it out. And the next question is, where do you take it? Well, you want to make sure that you are catching every single thing that motor is having to pull and push against. Now this right here is just a nice little illustration.

right? A little straightened up. You know, straight duck coming in, straight duck coming out. But what do we? What do we know happens to this right here, right? That's it. There's our supply, duck right there, the whole thing, and then what do we do? You know either we come off left and right with big 14 16 inch hard pipe duck Bullhead Tea right? or we come off over the what about 15 Flex runs all right I call it the Chinese water dragon, all the house, All right.

and this motor cannot push against all that stuff. I Think we know that we just don't want to believe it. but it's true. So what happens is we start taking our static pressure readings.

Well, you get over here and the evaporator coil in the air handler has already been configured into the static pressure reading of that motor. That motor's already been designed for it. Okay, now most of them say a dry coil and where I'm from that does not exist in the summer. South Carolina There is no dry coil in South Carolina All right, they're all wet.

I Think they're wet before we even start them up. Okay, all right, but uh, you want to take it If it's got a filter right here. you want to take it after that filter if you take it over here in a little more convenient spot. But they got a filter.

Guess what that right? There is more restriction and it can be a heck of a lot of stretch. A furnace. Uh, completely filter. We call them furnace.

Killers All right, All right, you got to be careful. Filter pressure drops are massive and if you're not imagined after that filter, you're going to get wrong readings. Now here's the other thing too is that in order to get correct airflow readings, you've got to have straight air. All right.

I'll give you new party word so you can sound real smart. Okay, it's laminar airflow. laminar airflow. All right.

So next time you're the party, go I wonder if you got a level of airflow cool in that bit right there? All right. All right, Laminate airflow. It's got to be straight. and if you look at the readings before you can get straight duck airflow out of the duct, you've really got to have three to five feet of straight duck before you do anything to it.

No changes. Okay, so when you do a bullhead tee, you got a plenum box here that may be 24 inches long and you got two 18 inch runs off of it. or two 16s or 14 whatever you got. Here's what happens is the air comes out of that blower and it's it's whirling around coming out of there.

Okay, and it's coming out and it hits that box. And where does it go back this way and it just creates this turbulence effect. You can't get airflow reading in a turbulent box because it's like little Eddies. You know, like the water comes off a waterfall.

All right, comes out at the bottom. What is it? It's a mess. all right. Water is just swirling everywhere.

It's they got dead spots. they got areas where the water doesn't move at all. And then finally, what happens when you look way down the Waterway it Smooths back out. Okay, well that's what you got to let airflow do.

before you get an accurate reading. you've got to let it straighten out. So what I started finding is that guys were if I was happy. If they're taking static pressures readings, that was a great thing.

All right. But they weren't getting accurate readings. they were reading low static I thought they were in good shape. All it was is dead air.

It's dead air. And if you've got too many turns too close to the outlet or the inlet, even the inlet counts. So when you come right here to you know, return Right here in the back of this box. it creates turbulence there.

What we get is called system effect. That's a term system effect. Too many turns, too many twists, too close to the unit, and you get so much turbulence, no reading will work. You can throw your static pressure readings in the garbage.

They're not accurate. It's got to be straight air. So there is another way to see if your motor is over working. To see if it's producing, you can take an amp draw of the motor itself.

Okay, an amp draw of the motor. What about a PSC motor? If you got a PSC motor, What do you think? If it's pulling too much load on it, too much static, what's it going to do that? Yep, the amp goes up because it's not moving that much air. What do you think it's going to hunt around Or the amperage is okay. What about you? What do you think you want me to say it? Don't you? I can't say it.

All right. All right, you're not gonna. A lot of people don't really understand this. So if you've got a PSE motor and a PC motor has a fixed horsepower, right? Okay, I mean you got to go with speed test.

But you're on one of those speed tests. If you've got too much static, Does it move more air or less air? Somebody answer: less Right Moves less. There is that more work or less work for that motor? Let's see. 50 50.

All right. more less more or less. All right. if it's moving less air, it's less work.

So does it pull more amps or less. amps in this Rated Less less? Yeah. So it's a dead giveaway before you before you even pull out all the bat gear. Okay, you just turn the fan on, go up to the disconnect, make sure the heat strips aren't running all right.

Look at what the rated amperage is on our right amps not motor, and take an Amber drain on a motor. If it's pulling less than rated amps, it's moving less airflow. period. Now you can go start finding out why if it's pulling full load amps.

PSE motor. Now with a capacitor, right? We know we're loaded up. We're moving the correct airflow, right? It doesn't mean that we're a balanced static duct system. That's the next thing I Want to talk about Now, let's talk about a ECM motor.

All right. How many types of ECM Motors We got? what's there with them? You don't care. He's my other instructor. X13.

All right. What else? Constant speed? All right. So the X13 is the constant torque, right? and then the other one is constant. CFM Okay, now anybody remember the old term variable speed and I grew up with that one.

Okay, because there was no constant torque that we knew of at the time. All right. But now that we got the two types, A Lot of people think that an X13 works just like a variable speed motor because they look kind of similar, right? Okay, they're both three-phase DC wound. Motors They both have a module on the back of them.

All right. Biggest difference is constant. C of M has what 5000 wires going inside of it, right? Okay, constant. and the constant torque has less wires.

but a constant torque is a high efficient motor. But does it have any more airflow capability than a PSE motor? Yes, No. What do you think? All right, Who doesn't like them? Technician? somebody? Nobody wants answer? All right. It has the same air flow capabilities as a PSC motor.

On average, it just does it more efficiently. but the minute it hits its static limit around 0.5 Guess what? it starts doing? losing airflow? Okay, now it'll start losing airflow, but not not near as fast as my time over or so far I Know time flies when you're having fun. But really, all right. So what happens to the amp draw of a X13? Okay, it actually bumps up just a little bit at first because it's holding on with that constant torque capability.

All right. And then it'll start gradually dropping off as well. so it's not as immediate as a PSD It has a little bit more of a hang time after it gets past its limit before it starts dropping off. Now, what about a constant CFM You go over there and you pull Amber on a constant CFM You do not want to see Max Amps on that bad boy.

All right if it's pulling Max Amps You can definitely take the sear and throw in the tank because it ain't efficient now. Is it giving you right airflow? As long as it's at now. Remember, you can go past the static of a constant CFM It's not a guarantee, but if it's pulling Max Amps That joke is ramped up like our hurricane. All right, you'll be pulling the three-year-old off the return.

Okay, they'll be like Poltergeist Help me help me. Okay, all right, all right. it'll sound like it's raining in the events everybody walked ever heard of when one's ramped up like a hurricane. All right.

I Walk in a bonus room and we'll be like dang. I'm ready. I'm ready for the events just to fly off the Diagon ceiling. All right.

And of course, whose problem is it? Saturn Variable speed, right? That's the problem. Nope, it's too high a static. Okay, so you can quickly. If you've got a duct system that's not the straight air, you can do an amp draw just to prove to yourself whether it's really moving the right airflow or not.

Okay, so a PSC You want to see it. Full load amps, an X13 Full load amps a constant CFM You want to see it about half to three quarters all right now. I've been saying this for years and years and years and I'm real good friends with Chris Mahali Hope I said that last name right and uh I verified that he he gave me his green light on that discussion. All right Now if you're moving Max Amps On a con CFM Are you still moving the right airflow? Most likely yeah, but at too much money and you have no room when coals get dirty.

Okay, so you can do this. Use your static tips But Be sure that you've got straight airflow. So here's your PSC motor. Most of them are going to be rated at a maximum of 0.5 Has anybody looked at a blower table and seen them rated at 0.3 I Promise you there are some air handlers out there been I Used to work in the industry in the manufacturing side of things.

The way they could get you an inexpensive air handler is to give you a very low horsepower blower motor. Okay, and you go look at them. Tables: 0.3 was where you got your airflow now I could go to 0.5 but you might not be getting 800 Cfms, You might be getting 600 Cfms. Okay, brand new right off the bat.

so be sure you look at your blower tables, but on average 0.5 Now that also includes X13s. Like I said before, they're not. They're not a variable speed motor. They look like one, but they're not.

Now here's your variable speed. now. variable speed depend on the manufacturer, can go from 0.8 to 1 inch of static. Now if you're not sure what in the world good static is because like you go get like I go get my blood pressure taken right when they get done they say oh, okay, well yours is such and such over such and such.

All right I Have no idea is that good I always ask, is that good? Is that bad? Am I going to die? What is it You know and then you say good, Oh, it's a little high. Well, it's a little low. It's okay. All right, you know and you know if I go back the next three times.

It's usually different stories, right? But what you're looking for on duct system static depends on the motor. Okay, and we'll talk about that in a minute. So what are you looking for? All right on yes, please question So What at what? Amps Do you start becoming concerned that there's a low airflow problem I Said right? Okay, all right. so it all depends on the motor.

If it's a PSC motor, Oh oh got yourself, it's a PSE motor. You know you're going to be looking. Uh, within 10 of this rated amps would be a good number to look at. Okay, all right.

so I think that's what they're looking for on a PSC When you start having trouble I like to see it and remember your meters are going to read differently depending on the quality of your meter then on the battery of the meter. Uh I got where I was changing batteries every season when spring came I changed batteries and everything when fall came I changed batteries and I mean it was a I didn't care and uh, two reasons. One, the the weaker your battery gets, it can get inaccurate. You don't know it.

Okay, Secondly, if you forget and you got an instrument, you don't use a whole lot. What happens? That battery after a while corroded? I've lost a 350 dollar meter because I had a two dollar corroded battery. Not dirty thing. All right.

and trust me I had Emory Boulevard and I had Q-tips and everything else gone all right from then on. Buddy I changed batteries I like nobody's business I just kept a whole pack of them. Okay, so and it's nothing worse when you're out in the middle of nowhere and the battery goes out and you ain't got no Replacements no backup. Okay, all right, so thank thank you.

Hope that answers the question. All right. So on non-constant CFM Motors Okay, PSE and x13 operating static startup static in my opinion based on what I've seen and in my own duck designs when I've measured myself, you want to? You want to start at about a 0.3 Don't get a 0.5 and go woohoo. All right, that means you're already maxed out.

If you got a 0.5 you ain't got no room for a dirty filter. You ain't got no room for dirty coil. That's the best that you know will ever be that day. And after that, it starts collecting dirt, starts collecting dust, and it starts getting dirty.

and that if you start at a 0.5 you got nowhere to go. You're going to start losing airflow from the minute you started it up and you'll never get it back in most cases. Okay, so point Three is what you're looking for on. Uh, so yeah, so why gives you good thing? so 0.3 no more.

Now when you look at the Supply Plus The return. When you have a manometer because they what you hook up on, the return is the negative is the minus sign on your manometer. What you put on the supply side is the positive sign on the denominator, but the two you add together it's not a subtraction. Okay, it's not like the supplied static is say 0.2 and your turn stat to be 0.1 which would be a lovely reading by the way.

All right, you don't say 0.2 minus 0.1 Here's my total static. You add the two numbers together. the minus sign just tells you to put it on the return side and the plus side just tells you put on the supply side I Wish somebody would tell me that when I was turning it out All right, that's how it works. I Had the Dern magni Helix I was like well which one goes where you know? did anybody remember did everybody get a new one and get the instructions out of the different thing? Well, there was none right and there was no Google to go find out what it was supposed to do.

All right. That government, All right. So you want to be sure that when you measure Supply and return, you measure them separately, don't measure them together Because what if out of that point three, all point three was on the return. You don't want all your static built up on the return.

What's that? A good indicator of a restricted return? All right. And now your stat on the supply side is probably nothing All right, because it's conservation of energy. If it's all on the left, there ain't nothing happening on the right side. Okay, so you've got to balance it out.

You want the return static to be less than the supply static. Okay, you want to balance there. So an ideal setting. What I'd be looking for is about a point one on the return and about a point two on the supply.

Okay, if you've got that balance which you can by Duck design, then you'll get a good air flow rate. Yes sir. Yeah, I Never have two hoses in my duct system because I don't know where the static is. So let's say you read the 0.5 you know and you go well at least I Got that all right? Yeah, but if 0.4 is on the return, you've got to undersized return.

all right? you. Because Remember overall, you may be getting the airflow across the coil to get capacity, but your distribution your duct performance is going to kill it. And if you've got any duct leakage on the return, if you've got all your static on this on the return side, what are you gonna be doing? You're going to be sucking in everything through every single crevice on that return. I've seen a 10 degree drop in the wintertime in a crawl space from the return air.

Entering the return Grille through a single piece of flex, it was no longer than 20 feet, went straight into the ductwork and we were getting a 10 degree drop of temperature before it hit the furnace. Okay, we weren't getting a good performance. I was like where is this going on I promise you it was an inch Gap in the return pan. but why was I sucking so much air through there? Because that during Flex was like all the static.

Okay, yes sir, good question. The question is is why would I want them different rather than say what exactly equal? All right. The reason I would want the static lower on the return is because it's slower airflow I want to get it low and slow All right. just like I like to cook all right I Love cooking all right.

So I like to do a slow cooker so but you want that air to come at a slower velocity to keep it quiet. Okay, and so that way if you keep the static down, you can ensure that it's going to be quieter. If you keep the static up on the supply, then you get a little bit more velocity and a better throw out of the vents. That's that is my reasoning for it.

Okay, uh, and by the way I came out with that rule just from field measurements I haven't seen that in a thing I don't even know if NCI teaches that or not. Do they do that sir? No, they don't teach that. He's sad, but they will now. So there we go.

All right. So now, what about a constant CFM All right constant CFM gives you a little bit more leeway, but if you started out about a 0.35 to 0.5 total with the same rule Supply A little bit higher than the return, it's going to be pulling about half or a little bit more rated amp draw. Which means it's going to be running sufficiency. I Don't know if when I worked for train train actually put the wattage of the constant CFM motor along with the static pressure reading and the reason for that is that the real serial reading is what? How many BTUs per watch you get? All right and the higher that CFM constant CFM had to ramp up to get that airflow, the more money it costs that started eating into the efficiency.

Okay, so you want to get that balance? Well, if you started off at about a 0.35 to 0.5 and you can go up here no problem, then now you've got room for dirt with that one so it keeps it quiet and it keeps it efficient. Okay, the higher it has to ramp up, the more money it's going to cost. Now let's talk about how a constant CFM model Works in general. Okay, it's like a cruise control in your car.

Okay, so you know David over here when he like sets his cruise control at 90. you know, when he's running late. you know you know you set your cruise control on the in your car. You're going down a flat interstate.

Everything's fine, right? But the minute you go uphill, right? What does it do? Does it speed up? it does I Thought it was cruise control I Thought it kept the speed constant. The engine increases right? The RPM of the engine increases. We're maintaining that 70. it's tapping into the available horsepower to do it now.

if and if I'm into what I used to have a little four-cylinder Ford Ranger All right, you know. the minute I went uphill I don't care. All right, that thing's through the floor and I'm still I ain't going nowhere. All right, because all my horsepower was used up just to go down the flat part of the street.

All right. And then I went uphill I had no horsepower. Same thing with a constant CFM It's like that. Beast Okay, it's like that big Deezy.

you just crank that thing. Oh, you, back it out. and if you put this up against maximum static, that'd be like you having to stomp that ginormous diesel truck just to get out of the driveway. and they'll And you had to keep it that way everywhere you went.

What do you think the gas mileage would be on that thing? All right, All right. So, but that's not the case, right? you've got available horsepower. So when you're in a bigger engine, you got it on that cruise control and you go up that hill. What does it do? Ramps up it Taps into the available horsepower to maintain constant speed.

Well, that's how variable Speed Motor works. Okay, the variable speed motor reads the resistance so the duct work and it speeds up to overcoming. So you want to be sure that you're keeping that at about a 0.35 to 0.5 So here's some key points to keep the static pressure down. Okay is you want to keep the trunk line as straight as possible, straight as possible.

Now, if you've got the wire off to the left and the right three to five feet, you know those Supply ducks that you take like one foot off the air handler right? because you got that that Supply duck like right there. All right. You know it sure is convenient. Supply Boot done all right.

but I promise you you're creating a lot of turbulence. not only for that one I've seen it actually pull. You know anybody ever did the highly technical tissue paper test. All right, All right, All right.

hold it up there. All right? Well I put this. that's how you go check returns right? Okay, it's working. It's sucked in my day, you know I really worry when I put on it Okay, we're not working all right, so you know, but you go over there to the supply.

All right. it'll do a little tissue test well. I had one job and I mean I was I was telling I said it's too close areas Ah that's kind of working. you know? well I put that tissue in there.

The tissue went fool. The air was turbulating so bad in there it was sucking air in and pushing air out about that far off the grill. Okay, so it creates a lot of problems. So you want to keep that straight duck if you'll get three to five feet of straight duck on the return as well as a supply.

I Promise you you'll get better airflow performance. period just doing that. Okay, the other thing is and one of my mottos is you can make small changes and get big results and the small changes are with the duct fittings. Okay, now straight Supply runs and low loss duct fittings so you want to pull your flex duct or run your pipe right? Well, hard pipe.

You can run straight because it's hard fight right? but Flex you want to pull that stuff straight and tight I would reach in and grab that knife outside. outside looks beautiful, you know, but it's not like an extra six feet of flex up inside that thing. All right. So you want to reach inside there and grab that inner vinyl lining.

What I do is I'd hook it up on one end and I would reach and I would grab that vinyl and I would try to pull it off the boot and I pulled a straight tie in heart and Cooley and the other manufacturers. The way they get their airflow Rings through their flex duct is they put on the machine and they go all right. pull this dirt and tight all right and then they measure and they say haha I got good airflow. Is that how it happens in the field? Oh you know I'm running around and everything you know.

This is a good little illustration of how the air flows through a duck. uh and uh, you know I you know, don't don't have any money to do all that high dollar animation. So here we go. So um Here Comes Air flying through the ductwork here on the return.

Here's something that's really, really interesting. It's pretty neat is that if you can see right there, all right as the air takes this turn, it creates a little Bank of air right up in here and it actually creates a smooth turn. So the outside turn curves all by itself. Okay, it's the inside turn that kills you because all the air.

Five minutes. oh there it all the years. Yeah, all right. So I got all that all right.

Air turns really tight right there, creates a turbulence. Let me just let me cut to the chase here. You want to miter the inside turn, not the outside turn miter the inside turn and it will cut the static restriction by at least a third or a half. Okay, and then up here, you want to be sure that if you, if you come up here with our straight duck, don't do a bullhead tee unless you got turning veins all right.

But if you ain't got turnip veins, use a Y fitting, use a squared around, don't do the cap with a hole in the center of it. I Got time to explain all the problems with that? All right. If I could ride around with a big sign on the van or walk around with a big sign down All right I would say Square the rounds round round wise. okay, hard elbows when you make a turn, every flex run I had two elbows all right, one of the take off and one at the boot.

All right. Now if the takeoff was straight up to the boot. okay I didn't need elbow there but the minute I got to angle it I put a hard elbow on there if you do those things I swear it'll make so much different and the last thing is you want to up and I have time to show you this how this works. but if where you used to run a six inch flex, run a eight.

we used to run an eight, run a ten and I promise you you will create a lot less restriction and I went to where I had no six inch runs in my duct systems. All right, it's because what happens when you get in the field, it's not straight diet. It's going to have some sags and turns without a little extra flex. Duct sizing will help overcome that.

Okay, so just a little tidbit there. All right. I Want to go? Okay, don't do that. All right.

All right. Don't do that. Don't do that. Don't do that.

Now let's look at some problems here. Um, okay. 510 air handler I Wish I could tell you about the whole job I Took that picture. All right.

How about that one? I didn't take that picture. All right. I Thought that was a good one. just wanted you to see real one good one.

All right. Looks like a big stick bug in the Attic All right, Oh yeah, we see any problems there. All right. Uh, probably that was no flash.

All right. How about that one? Oh yeah. And then of course I got a zoning duck on it and they couldn't figure out this was at a half million dollar? No. a million dollar home.

All right. This is a five ton air handler with a two foot flex box. Uh, that was a mess. All right.

By the way, not only does it cause airflow issues when you get all that high static like I tell you about on the return, your drain lines won't work, they'll hold water the whole time they're running. And I went on a lot of drives where it was me, the contractor, a lawyer, the homeowner, and the installer. When I was a tech rep. it's because of a Dern drain line not draining when they opened up the unit.

Guess what was all up in there two three years later? That that big uh word, right? We can't say that. that. Really bad looking stuff. All right, So you know.

Yeah, so it was a problem. Lawsuits occurred. How about that one? Yay! I Want to say all the time? All right. that was nice.

Hey, but they used 10 gauge wire. At least that was nice. All right. All right.

how about that one Silicone fixes everything. If you ain't got duct work deals on that, literally, it's a Nike box. All right. All right.

You know how many ding ding ding ding ding ding ding All kinds of problems out and poor old. Lacy you got two small duck working out. All right. All right.

like that one. Yeah, all right. yeah, that's good, huh? Oh I Love this one here. This is one of the jobs.

I went on big old pleated filter, cut off half of it. Okay, all right, how about this one? you better watch Teletubbies I did when I was okay. nevermind. but I look like new new vacuum cleaner kinked a little bit.

Maybe so. I used to go through all the exercises. how to fix that too late? All right. Ah, no crawl space? no attic? Who cares? All right.

Oh, how about that one? Hey, they won't sweat. Probably that. Okay, all right about now. what are people thinking? All right? So now, uh, I took this one.

All right, this little top of a hotel. They've been losing multiple compressors I wonder why? All right. So how about this 7.5 ton package in it? Guess what? Those are 14 inch flex duct. Wow.

All right, how about that one? Okay to their defense, I was a temporary unit sitting out there. All right, but they look really wild. Okay, my favorite that's been around for a thousand years. Anybody ever seen a picture before? All right.

Okay, so we always call it that lowest bidder. And today I heard a new term from Jim Bergman that's called two stage equipment. That's exactly right. Okay, here's some things right out of manual: D which do straight and tight.

Don't do the Chinese water dragon. All right. use hard elbows. Don't kink that off to the side you might think.

oh no. big deal that creates a lot of turbulence. Straight and tight, Straight and tight. So there you go.

By the way, this presentation is on a PDF for you guys. And here's the duck fittings. Wish I could go over that some more, but duck fittings will kill you. That one torpedo Booter By loves to use that's worth 50 feet of duct restriction.

All right, that's a ton of stuck restrictions. Don't do it. Yummy. You fix those a lot.

All right, All right. now, how about these duct board? You might use duct board God Bless you. All right? So now here we go. Just got to do it right.

That's the correct why. Duck board. Not that one. Okay, all right now.

who can spot the good better and best other than the fact that it's labeled. Okay, all right, this is bad because we got these hard inside turns. This is better because we got inside turns at a curve. This is better because we got turning veins.

This is the best because it's inside all top and bottom. You throw some turning veins in there and who knows what's that drop to be on that thing? All right. So, but this is the best way to go if at All possible. Or you got tournaments Bullhead Teeth bad, Bad Bad.

All right. So here you go. These are rough numbers depending on how close they are, but roughly that's about a five to ten foot restriction and that's a 10 foot restriction compared to 50 feet. Okay, all these add up Believe It or Not Your Takeoffs are 35 feet of restriction.

35 feet. Here's an underlying problem that a lot of people don't even think about. Doug says it was all together and we got poor airflow. We're checking everything.

everything. What the heck you know? well is anybody, you ain't got to raise your hand. anybody ever done that before? All right, you know, kind of, uh, bad. I'll tell you what that causes airflow problems.

Stop He said. all right and there's a good one. Okay yay Operation person, Yay! have a good day. Big thanks to Joe Henderson for doing this.

Much appreciated and once again thanks to everybody who came out to the Symposium We look forward to seeing you again in February 2024. 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 in 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! Thank you.