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Ed Janowiak of ACCA gives a presentation about fan and duct design, system testing, and Manual D at the second annual HVACR Training Symposium. Learn more about the 2022 HVACR Training Symposium at
Ed has over 35 years of HVACR experience, both in the field and through teaching. He has lived and done business in New Jersey, which has a variable climate, and he has experienced a wide range of temperatures.
When designing ductwork, we obviously want our static pressure to be close to our calculations. However, lower static pressure is usually more desirable than higher static pressure. When static pressures exceed our expectations, we have to start removing elements of our design.
The real key to good duct design is managing the occupant’s expectations. Understand what the client wants, but you must be up-front with what they can and cannot expect from their HVAC system.
Manual D requires that you pick a fan and design the ductwork around the fan. Ducts must accommodate fan pressure. (Manual Q is the opposite; you choose the fan based on the duct resistance.) Manual D’s goal is to calculate the critical path, which is the longest circulation path in the system. It’s also a good idea to comply with local codes, but it is not responsible for a design’s predictability.
To design a duct system, we also need to know how much BTUH (BTUs per hour) and CFM (cubic feet per minute) need to be delivered. We can get these figures by finding the BTU gain and loss (Manual J), and we can use Manual S to calculate our target airflow. Take the SHR (sensible heat ratio) into account, and you use all of that data to find your capacity.
We should refer to the friction rate worksheet to develop a good duct design. You initially take your external static pressure and CFM readings. Then, you discover and note the component pressure drops. You also take available static pressure and total effective length into account. In the end, you will figure out your friction rate. The purpose of that worksheet is to determine the friction rate based on the duct system’s critical path.
We use manometers to take static pressure measurements. Static pressure is NOT velocity; it is the measure of pressure against the walls of the duct. You can use static pressure as an airflow indicator.
Several components can contribute to pressure losses in the critical path, including heat exchangers, UV lights, grilles, and dampers. However, the filter is the most notorious source of pressure drops. When sizing a filter, you need to know CFM, velocity, and area. The system must have enough pressure to overcome those drops in the system.
Once you have calculated your external static pressure and losses, you can subtract those losses from your external static pressure to yield your available static pressure.
You determine your total effective length by adding the supply and return-side total effective lengths together (including trunks, runouts, and group fittings of each one’s critical path). Then, to get the friction rate, you multiply your available static pressure by 100 and divide that product by the total effective length. (You should also be able to find that value on a chart on the friction rate worksheet.)
Humans feel comfortable when they don’t notice their surroundings. So, excessive fan noise can be an unexpected source of discomfort for occupants. Watch your air velocity to avoid creating that humming sound with the fan. Don’t start off at high speed! Manual D gives us maximum air velocity guidelines to avoid comfort issues. Manual T also covers terminal velocity and grille selection, which heavily contributes to comfort. (A grille should be located in a sensible location and should have the proper throw. Grille size will determine the distribution box size.)
You must determine your heating and cooling factors to begin working on your duct design worksheet. The heating factor is the blower CFM divided by your Manual J heat loss; your cooling factor is the blower CFM divided by your Manual J heat gain.
When you use effective length charts, you must keep in mind that those effective lengths will only contribute to duct behavior predictably under a certain set of conditions. If you’re running at a slower fan velocity the friction rate will change, and you will need to do some more calculations. As friction goes up, effective length goes down.
Our external static pressures may end up higher than we anticipated due to excess length (with flex duct).
Ed also discusses:
Alternative ways to measure static pressure
Height-to-width ratio of ducts
Design software pitfalls
Return drop sizing
Sizing for flex duct systems
Round registers
Grille air velocity and sizing
Filter sizing
Standard test airflow rates for MERV ratings
Read all the tech tips, take the quizzes, and find our handy calculators at

This class is by ed jonah the new proud to announce manager of design education with akka. It's a pretty big deal that he got that position as well deserved as you'll see in this video in this class. Ed covers duck design manual d. This is from the second annual hvacr symposium in claremont florida.

If you want to find out more about how to attend this year, go to symposium. I think you'll enjoy this class. It's a long one, but you will definitely learn a lot about duck design. If you stick through it, this may we went over this stuff before i was in a current life previous life, i spent 15 years in a service truck, so i don't get up here and tell you stuff, because i've read it in a book.

I've lived it uh. I've done the things that you're not supposed to do. I've put screws into things that let stuff out. That's not supposed to i've.

Put my foot through ceilings where that's where the new return went. You know there's some stuff, i'm not necessarily proud of, but you know you do what you got to do we're in a house in tuckerton billy's in the attic i hear the plywood starting to crack and without skipping a beat i'm sitting at the kitchen table across From the homeowner she's every bit of 80., his foot comes through the ceiling and lands on the top of her refrigerator. She takes a deep drag off her palm all. It blows it out and says how you going to take care of that honey, and i said we're going to take the heat off the back of your refrigerator and put it right in that return and help distribute it throughout the whole.

The entire house and i'm not making this up because that's exactly where we put a return in her kitchen above the fridge, so i've done as much stuff. That's wrong as right. It's just that i've learned the math behind doing it right. I've done the the bad duck systems, and now i make duck systems that don't require the occupant to turn the tv up when the system comes on and isn't that our goal right people are so callous to the fact that the air is supposed to make noise.

I have had people call me after the fact and say: i'm not 100 sure if this is working right, because i can't hear it run. I've taken pieces of string or ribbon and tied them to diffusers. So they do this when they run so they know it. But i i can i'll, never forget it.

I had this woman go through that whole explanation. Her son was there ma? Why don't you have the air on? I do i'm not sure you can't hear it oh and when i got there, i'm like what do you have thermostat set at well at 76 if we keep it 73 now it's too cold in here we took care of their humidity problem. It was the first time i had a a comment: i'm not gon na call it a compliment because she didn't realize she was complimenting me. I went outside and i can't dance, but i was dancing baby.

It was a big deal. Not only did we do her house, we did like three or four other houses on that street and that's what you know the word of mouth. We were talking to somebody over the course this week about them, starting their own business and advertisements and stuff in the 15 17 years i own my own business for actively contracting for three or four. I never paid a penny in in advertisement, so yeah, it's the word of mouth is when i had my business.

I ended up doing more of this than that which i like talking about it better than doing it. I've never done a class in a hot attic. So, there's that right all right, so i don't want to, i think it says chuck in a truck in the hvac industry. I still do some work.

I try to avoid it, but i still do it. Oh, i wanted to wait until we were we were live. I wanted to tell you my shirt story, so i bought these shirts that when uh we're warm when i get warm they're supposed to unwrinkle - and i just went use the bathroom and that one has a mirror in it - and i was like my shirts wrinkle and I went to iron it this morning, but when i plugged the iron in at the hotel, it smelled, like grilled cheese and i'm pretty sure, whoever the bleepity bleep was in there before me, made some dinner because i pulled the coffee pot out and i wouldn't use That because it smelled like chicken soup, so somebody was having a smorgasbord with stuff that i don't know why. So, if my shirt's wrinkled sorry but it's wrinkled for a reason - yeah, oh i'll, be there next year.

No doubt all right, that's me, and this kind of goes a little bit more of an accelerated uh uh version than what you saw this morning. Even though i like talking about myself, it's kind of gets kind of boring, but i got more pictures and these down here just show. I do local stuff for my utility programs. I do local stuff like for cash or from for pay actual system installs and that's that's the uh esco thing the last time they had it in vegas the train, the trainer stuff they're, my favorite events, especially talking about these kinds of topics.

Because again i don't want to exaggerate the numbers, but i bet i have supplied manual s and manual d. Information to you know directly, not through classes but them contacting me. I give everybody access to my drop boxes, i'm stealing most of this information from somebody else. So i'm just sharing the wealth, if you will so it's good stuff.

Actually, that's not true. Most of this content is my saying, is mine, but who cares i'm not in competition with anybody if you're on social media and years, i i kind of that name or whatever and you've seen that picture. That's me right, and that literally, is me in 1966.. That's uncle leon and he was a bit of a weird dude and i kind of take after him and that's a compliment to him and i think to me, but he thought it was funny to put a lit cigarette in a kid's mouth that wasn't two years Old, yet so, finally quit last week after all those years, but actually i quit about 15 years ago, but i'm actually one of those weirdos that can have like one cigarette a month.

If i want, i always wanted to be that person, and i kind of am now so i'm going to be finding you house later and mooching to smoke all right, my market, this we didn't get into last time, and i want to elaborate a little bit more On this i live in new jersey and i live in the good part of new jersey where it's not city-like, it's very well, it's a garden state. I live on the outskirts of a million acres of pine trees that are like little pine trees around here. There's just no palm trees near them, so it's not that much different. These are the markets that i'm actively working in right now, where i live, is considered mid-atlantic, southern new england, so i don't have cold like the weirdos that live in minneapolis cold.

No thank you, but it gets cold. I've seen minus six in my car driving through one of the colder sections, so it gets cold. Where i live, we we test our furnaces and they only run 20 of the time out of the hour. Even when it's minus six, like everywhere else in the country, we don't know how to size them things either it gets hot once in a while 104 is the hottest i've ever seen it in the town i live in, but we've had stretches where, from summer to Summer, we might only see 10 or 15 hours above 90 degrees.

So why would you want to size a piece of equipment for 104 when you might only spend 20 hours in an entire summer above 90 and obviously the answer? Is you don't want to trust the math trust the process, all that and you can enjoy those predictable results? That's what we're after and we see some real ugliness. We see conditions that are akin to what takes place right here in claremont, not with the duration, but enough that we have duct work that drips and it's i'm a bad person because i love it. I preach this stuff. Do this or you're going to have a problem? Do this you're going to have a problem? I go to an akka meeting and i got guys saying that stuff never happens.

Uh. Let's see it's gon na be the summer of 20, which was kind of humid. 19. Wasn't 18 was, and i would be in a crawl space or an attic or a house with one of those contractors, and you believe me now because i'm in the house, because the ductwork's dripping right - it's this stuff is eventually going to happen.

You you guys don't have to wait that long before it happens right you do something wrong and two days later get over here. It sometimes it'll take us 18 months. It takes a while for us to get a string of that wet it's common, but it takes a while. So i don't, i don't think i live in a unique area, but i think i live in an area that represents about two-thirds of the country right.

So i i feel everyone's pain, so to speak about what you deal with. Do we want to avoid the problems? Yes, can we avoid the problems? Yes - and we do it by following the guidance right and the guidance is not just manual j, not just manual s, not just manual d, but using them all together, that's the again the predictability. I i really like that word, i'm not a big fan of sandy. That's exactly where i live.

If you guys are familiar with sandy uh, what do you think that is yeah? That's sand! That's that's! Not snow! Uh! That's what 30 of the houses in my area look like after that storm, so they've been replaced with these right. Our customers have money right and they want to spend it baby. You take one of those houses that exists like that: real quaint, looking place and you knock it. You pay 800 for it and you knock it down.

You spend 500 and you build that and it's worth two. They have two percent three percent of their total budget to spend on mechanicals. If they're going to be there 12 months out of the year, they're getting radiant heat man, if they're only going to spend six weeks of summer, there they're going with low bid and they're getting three oversized furnaces and three oversized air conditioners. But the good thing is they oversize the air conditioners? They don't last that long, so they only have to deal with it.

For a shortened period of time, sandy came ashore in 12 right. These houses were all fixed in 13.. Most of those condensing units need to be changed in the next year or two already yeah, it's pretty cool man, oh yeah, the furnaces will last. You know 20, 25 years you go through three condensing units for for one furnace, so it works out pretty good and who doesn't like doing a condenser change out for 18 000 right during the summer when they're renting that house for ten five a week.

It's like. I don't know if i can get there today. Oh ten great yeah. I can get there today so a little bit of a.

Maybe i'm, not maybe i am. I don't know, i'm a dad. I'm very proud of this uh. That's my kid! It's a few years ago, but that's one again.

I say i live in jersey and people, oh oil refineries that was right down the street from the house. I was living in at the time, so it's pretty nice there she is in the house. We presently live in. She knows how to measure air flow she's quite adapt at it.

Adept adapt adept. She worked at the contemporary. What's a half hour, 40 minutes away. She did the disney college program a couple years ago.

Oh look at that we're in the same shirt in that convenient it's wrinkled. There too. I bet they were making cheesesteaks in the room that day, one of the best days of my life right there. You do to take your kids to work day.

That was the first time i ever got to do that. The college she attends, which is right outside new york, city, montclair, state, university or msu, has a lot to do with this class. I talk a lot about make up msu, not montclair state university, but it's makes it up, don't make up right so anyway, they asked me to do a not the college, a distributor, rented rooms at the college said you come to a class. They give us free time in their training rooms, so i had to say yes and i'm like all right i'll.

Do it. Here's my kids schedule no conflicts, and that was good. Anybody use uh ewc controls for the john brown name ring a bell. John was sitting next to my daughter, and i was doing my same stupid joke.

She got to do the punch lines to my jokes. That was a cool day that was a big day for me and whoever the photographer from that's from universal. That's who rented the stuff they uh, they had a good uh photographer there i was. It was a big deal and that's her in the boy she's known as the kid that's the boy and that's the most uh recent picture i have of all of them.

My wife, that's me, he's currently a cop in baltimore, so he's a a pretty ballsy guy, i guess is a good way to say he's probably going to end up down here, he's been doing some interviews, so if any of you guys live around here, i might Be calling you asking for advice as to where i should move or where i shouldn't so we'll see what happens all right? That's enough of that stuff! I i i could get away with just talking about that stuff. I would. I got ta have some fun too. All right, this is what we're gon na.

Do we're gon na talk about selecting fans, we're going to look at what happens when we try and make a good duck system, and then it's all going to wind up at the end, where i don't think acca does a good job of forcing you to follow Up - or at least it's not in the book right, i got people in here that use external static pressure to estimate airflow right, yes right and that's also the same information that we use to design our duct work. How often do you look for those numbers to match right and you should be, and some people do but a lot of times they don't and we're going to walk through the process. I'm going to show you why they come out good and i'm going to show you why they come out bad. I think he split, but house was in here before i've seen a couple of his things where he's using numbers that just make i twitch every time.

I look at him, but he's not taking some of the stuff into account the exact same way. I don't take stuff into account because that's my safety factor, but i end up with external static pressures or that are lower than i anticipate, which is fine, because we can always make that work exactly how we want. But when we have external static pressures then are higher than desirable. We got to start giving stuff back and sometimes that hurts or we just can't do it.

So i'm going to explain that so i'm going to go through the design part of it at a pretty rapid pace. Again, we can't teach manual day in two hours i'm going to try, especially if i waste all that time showing you pictures of my kid. It's a good thing. We have a computer because i'd be here with my wallet: yeah i'd be going up in there.

You see it. Isn't she cute? You know that kind of stuff. So again i haven't looked at this a while. So i got to read this and figure out what i'm doing next, so the testing after the fact some of the stuff, you already know yeah, and i want you to use this stuff and i'm thinking that you're not completely proficient with manual d.

At this point, that's why you're here and you're in the right place. So thanks for hanging out with me all right, we got to manage expectations of the com for the customer. When it comes to this, you can't have a 70 degree house on 100 degree day and have a good dehumidification on part load days. I know when it's going to be 90 degrees in my market.

I can make a house comfortable rather easily because the system runs a lot when it runs a lot. It does all the good stuff dehumidification is taking place. Air mixing is taking place, that's easy. So what is the the struggle right? Part load conditions, 82 degrees in gray.

What's the driver behind making the system run right, sensible btus? If they're not there, the system isn't going to run. Have you ever told a customer to open the blinds when it's only 80 degrees out? I have think about that. For a second hottest day of the year at your own house, do you close the blinds? I do because i'm smart, i don't know it says about you, but i know these guys, so i can get away with that. But don't tell anybody, but he couldn't figure out what a pound of airways before so just keep that they got to figure it out now.

So it's a strong comeback. I like that, but we got to manage the expectations of the occupant. If somebody doesn't have a point in conversation with, what do you think is going to happen or what you can expect to happen, you're already putting yourself in that butt kicking line and we're trying to stay out of it right. So that's how that goes.

I want to remind you that it's important to manage your expectations when you come to an event like this. Also, you know where this is going. Don't you keep in mind who's up here right now, all right got a little snow, i'm out there with the torch best with a coupon i ever spent at harvard freight man. You want to feel like a superhero.

You pull the trigger on that thing. Man, you get a flame coming out of it, that's good stuff, right there i'll! Let you decide it's one of the two yeah i saw him. I did this before he copied me yeah all 18 people that saw me on tiktok told him about it and he put his up there. All right remember.

This is how it appears. Are you ready, because that's what it really looks like all right? No, it's a is it no, that's the tan one. So i told brian when i was going to do this, i said i want a boom mic, i'm going to sit down and do my class and i'm going to do them exactly like i do at home. In my basement he said i don't care what you do and i said i'm always in my drawers when i'm doing the classes, because i think that's funny and he laughed pretty pretty good for a while and then he said well, what kind do you wear? I'm like it's, it's definitely pg.

So if you ever see any of my youtube videos or any of that you're not going to scrub that from your brain, because that's it man, it's just. I guess the first time i wore pants since the pandemic set in you know why i have like three different shirts. That's all i wear and just it's the same shirt. It's not that's! Actually, a tan one from the cabela's cabela's collection.

Yeah, it's same brand. It's a sipowicz shirt. Is there anybody old enough to get the sipowitz nypd blue? There was the real gruff guy called everybody a scumbag. He always had a plaid short sleeve shirt and a tie on and he was the yeah simple witch.

It's my sipperwood shirt. So you never remember simple andy sipowicz yeah. He was a little gruff all right. We already know that this system is going to move a thousand cfm because we went over it in the last session and i blew through it quickly, but it kind of lends itself.

We are going to cover it right now, eventually, manual d manual d requires that we pick a fan and then what are we going to do after we pick the fan, we're going to design a system around our fan manual q, which is its counterpart for commercial Duct design is the exact opposite. We just make up a duck size, and then we pick a fan big enough to overcome the restriction of the ductwork in commercial duct systems. Do we care about noise? No, it's part of it. We want the background noise in a commercial application.

We want that constant air flow. Remember before you're talking about air coming in non-stop we're going to treat it we're going to address it, so we can let it run all the time. Webster defines comfort as not being aware of your surroundings. If a fan is coming on and off, if it makes noise we're going to be aware of it, that's not comfort.

If a system runs non-stop, it blends into the background, it can be a little bit louder and it's acceptable because we're not going to notice it because it's always there in an office environment, it's welcomed. It gets rid of the noise of these people outside here. That won't shut up. You know it's it.

It kind of takes it so that those noises kind of blend into the background with white noise is generally what it's referred to. So it's on purpose yeah and he said about an office building. That's a perfect example of it exactly and if i really wanted to be that guy, i was going to repeatedly say what, when you said that, because he started off, you can't hear and again there's something wrong with me, because that's just funny all right. So we got to take our pressure losses into account.

I'm old enough that man, the friction rate, worksheet and manual d, said device losses now they're called component losses, but i'm updated. This is the only manual d presentation that actually says component losses, and you got to be a big old dork with this stuff to even know what i'm talking about right now, but i'll point it out. When we get there we're going to design ducts to accommodate our fan pressure now, a couple of you guys are going. What is that? Does that help you all right, all right that looks more like what you're doing okay code compliance we're back to this whole code thing? These are my local codes and they talk about where, specifically, all this information is coming from so mechanical code or energy conservation code, they specify the akka design series again, i don't care if you want to follow code or not, but i want it to be a Conscious decision, if you want to get into the purposeful defiance and all that, i want to warn you that you can never say i didn't know, because if you are at the discovery phase or you actually end up in court, saying i didn't know you might as Well just say: here's my checkbook write yourself a check because it's not a plausible defense, you're responsible for doing your due diligence.

Again, i want to emphasize that code is a minimum standard. It is not solely responsible for predictability that we seek, but it's the path to it. It's the minimum stuff. We should be doing all right to design a a quality duct system.

We need to know how many btus and cfm need to be delivered. In this example. Right here i got a heat gain of 22 000 btus with a sensible heat ratio. 0.9.

I got a heat loss of 31 000 btus. Does that sound like something that could be in your area? Not yours! Your your loss is double your gain pretty similar to mine. I don't know where these com numbers came from, but i don't know i just made them up manual. J gives us the btu loss and gain manual.

S gives us guidance on that airflow. I do more stuff right on this little dry erase board that i bought at the dollar store than i do anything else. I it because it looks more like a piece of cardboard that i picked up off the ground on a job site and i think that's where that it. It feels right to me i'm doing the math here.

The math tells me that my total btu gain was 22k and they're. My sensible btus. It tells me that my sensible heat ratio is 0.9 and i'm doing the math as per manual. S tells me a 1011 cfm is my target air flow.

So that's close enough to 11.. If you don't understand that shame on you, you could have learned it a couple hours ago or you can use the password that you got for attending here and look at that class and i've already done it. It was pretty good. I watched it and the me walking up to that camera is quality content.

I like, i actually did look to see if the whole thing worked and while i was standing in line to get the what was it, what did brian call? It god's chick, the lord's chicken yeah. I was waiting in line for that. It worked that fast, so they got that whole thing working out, uh fairly; well, not 400 cfm per ton, just putting that out there. In case you were curious.

That's our gain! Our starting air flow, where we're going to look at the extended performance data, is at a thousand. My heat loss is here using a rule of thumb, it's a quality rule of thumb, but it's a rule of thumb. Nonetheless, that's what my heating airflow is going to be again, at least to start before i make some massages to it. It's something i can't come up with words, so i use whatever pops into my head and that's weird that i said that that's what popped into my head, but i digress.

This is the equipment that we selected. It happens to be a vrv system with a bunch of numbers. After it, its capacity is 26800 btus. My heat gain is 22 000 btus at a thousand cfm.

I look at the correct spot. Excuse me on my extended performance data, and it's telling me my total capacity is 26 8.. If i take my total capacity and multiply it by 130 percent, it tells me that my ceiling or my limit for this vrv technology falls within the 30 percent limitation. That is the guidance of manual.

So what are we going to get a thumbs up right? We're there? I'm sorry right! I had to cover that everything else. Moving forward is going to be about ducks and i promise or i pinky promise, no more equipment, selection stuff. It's all going to be at duct work. Yes, sir, the definition of comfort get the dictionary out.

Webster he's the dude who writes the dictionary right. The definition of comfort is not being aware of your surroundings, so it's just not temperature or humidity. It could be. If i hear it, if it's blowing on my neck, you know it's all part of the design series.

Daca design series has specific language that talks about the occupied zone two feet in from the exterior walls from the floor to the ceiling. I think the number is 40 feet per minute velocity. We want to keep the air under that, but above and out at the exterior walls. It's like animal house man there's a party going on.

You can have that air moving at any velocity. You want because well who's the tallest person in the room. I get this guy with the beard. He's a big.

Are you ever six foot? Okay? Oh yeah? He might get it in the forehead, maybe even in the nose that air that's moving too fast, but he's just going to have to walk closer. I got my ponytail down the back of my shirt. I don't want to show off. You know it's.

I need this. A little bit longer so i can do the twist and tuck it back up underneath. So it's tight, it's just not there. Yet my daughter thinks it's cool, my wife hates it.

So i'm talking to this this company about something and i'm like yeah. They want me to cut my beard. My ways like yeah, like they didn't say that or you look like one of the founding fathers come on the friction rate worksheet. I somebody brought it up before they have any music on here.

I got ta cue, the music right now you ready i'm kidding. No, it's not anything you're gon na do i'm gon na. Do it the friction rate worksheet or how about that? Is that too much? I think it's pretty good. That document right there forces you to do everything that you need to do to do a good duck, design right, look at step, one.

What does step one ask for external static pressure and it asks us what our air flow is step. Two are pressure drops step? Three, if you didn't know what a st available static was before you're going to find out, because all you got to do is fill in the blanks. Everything about that document forces you to do a good duck design, because if some of the numbers come out where they're not big enough, you can't proceed it's why you can't randomly say that your friction rate's supposed to be 0.08 or 0.05 or whatever magic number you Want to use if we don't have enough available static right there, it's not going to work, it doesn't mean no air is going to come out of the vents, but a predictable amount isn't, and we seek that predictability right. So we're going to go the whole process.

Let's do it step one like i said that is going to be external static. Pressure versus my cfm are component losses. I always called them device losses, because that's what the old sheet said available static pressure. We got to go through teo, the longest circulation path.

We got to cover that i'm going to go under the assumption. Everybody already knows what effective length is, we're going to apply it to ductwork we're going to take that duct work and look at some charts, and it's going to tell us what our effective length is for each individual fitting. Some of these are yeah. It makes sense and some of them are like whoa.

I had no idea and there's stuff that it's nothing short of bizarre. You can go to the supply house and they'll sell some of these fittings and they're, not the better choice and the one. That's a better choice, they don't sell. But what do you sell? You sell what people are buying and people are buying the wrong fittings.

It's bizarre. I did uh training for a company and i won't mention them by name gray, metal and i was at their factory doing a class. They have a duck slide with the wrong effective length on the fittings and a couple of their guys that work there. I'm doing my things what you're saying is wrong.

No, i i wasn't going to touch this, but now that you brought it up what's on your duck. Slide is wrong because, when i looked in here, it agreed with me right and oh, oh geez. Well, they're giveaways! That's a suspenseful thing, isn't it? I warned you i'm like a 12 year old, but i want to see three happy people, everybody look under your seat and see. If you got a piece of blue tape, you might have to stand up and look.

I got one got another one. You picked the right seat there, you go anybody else there. It is my name ain't in that one, my name's an s, so it really is page four see. I know the page, thirty right! That's where that that yeah, i kept thinking about that, because i forgot to give them out the same way.

First go around so the lucky guys that came up to talk to me. Afterwards they got him so that worked out pretty well anyway. Again, i'm like a 12 year old. I can't help with that a little insight to the world of ed.

It's a little scary, all right we're gon na go through this excuse me we're gon na go through this entire process. There's our friction rate worksheet. We already determined that our target air flow is a thousand cfm, because we were able to meet the sensible meet the late and not exceed the total by 15 20 or 30 percent 1000 cfm. We're gon na go and find a furnace.

We needed uh. What was it 31 000 btus, this 40 000 btu furnace has enough capacity, and i'm looking at something with this constant torque, ecm motor. The dip switches are set like this. I got .7, that's where i'm starting off with for my external static pressure, very close to that thousand cfm number that i need wait.

A second. Are you guys cool with the external static pressure thing? Did you sit on steve's thing before or do you need a little more? Let's do a little more, and i want to talk about this one for a second, because it relates to something again that i like to talk about with this stuff. Does anybody recognize this drawing where you might have seen it? Does anybody go on true tech tools at all? Have you ever seen some of the free downloads they have on truetech, i'm guessing at this? The first part, but i'm going to say bergman, originally put this on true tech tools back 10 years ago 12 years ago. But i know the guy who originally drew it and he was using it in a class here in orlando two years ago.

And when that drawing popped up, i almost said: why are you using my stuff until i realized that i got it from him and i started using it like 15 years ago. So if you guys have ever been to the chris mahali is the ecm trainer for gen tech. He was the original person that drew this. So if you ever see this one and him again, he was the original.

He did that. I think before he worked for gentech so anyway, i stole the diagram, because chris's original diagram had an incline manometer on it, and do you even know what an inclinometer is? You don't need to it's like? Are you using an abacus or your phone to do? Math right, so it's modern stuff. If you want the really cool one, go talk to captain america over there about getting the dg8 i've been playing, one of them for a while. I got one on the the leg of my crappy table in my basement and i have a hose that goes into my bill co door, so i can measure stack effect in my basement and talk about that.

I have another hose that when i built the house, i ran a piece of pex into my attic, so i can look at the pressure in my attic at any given time just by holding it up, because i have a tube yeah. It's it's good stuff. Anyway. Jim was very nice at the lunchtime thing when he said that some of these other manometers that's a good manometer for measuring static pressure.

That's a good manometer for measuring the combustion appliance zone pressures and things of that nature. That's a random number generator. If you stick it in the vent of a water heater, that's a micro, manometer that'll, give you an accurate measurement. So that's the difference between the two static pressure.

Real simple first word describes it in its entirety. It's static. What's that mean not that it gives you a shock, no saying motionless, what was it motionless yeah? He got it stagnant, not motion, so our our fan, it blows up the ductwork and creates pressure, and then it also gives us flow that static pressure right outward force within a duct external static pressure. The way we use it is to match it to blower data and the manufacturers were nice enough to put the furnace on a table and hook a contraption to it.

You can estimate your airflow based off of that pressure and sometimes they weren't real nice to us. Sometimes they make up numbers they'll, take it at two or three points on the the chart, and then they extrapolate the other numbers. I don't like that. I want these things to be accurate.

So, and you already guys, you know what a pressure drop is. So i won't even say that one static pressure: how do we measure it or external static pressure? How do we measure it well with a manometer, the uh incline monomer. That's it yeah! If you, if you forget to open the the one end right on your shirt, hopefully not the customer shirt good way, good way, good way to take all kinds of measurements right better way. If you want to take those real small measurements, uh most cost-effective way to take those real small measurements that you might be interested in, there's chris's drawing and chris was very impressed with himself when he made that wheel spin.

I have a real blower wheel in mind that makes it spin so again. Fourth grade baby, i'm up to that. Well, that's not it! That's one of them! Old-Fangled things, not one of them newfangled things, so manual d helps us with this stuff. What does it do? It tells us don't allow the air to move greater than 500 feet per minute across that return, that stamped steel grill.

Why don't what why don't we want the air moving faster than that noise right? Those girls will start to hum. Everybody knows why they hum right, because they don't know the words come on when my kid was in that class. She got to do that punch line and it was a big deal to me so filter girls, 300 feet per minute. Keep that velocity in check so to speak when the air goes across the filter, we're going to talk about filters and what a bunch of dirt bags the filter manufacturers are for not telling us the truth and then i'll i'll.

Take that back and say they're just following the rules, but we have to watch how they're following the rules. 52 2, the ashrae standard for filters, they have to publish merv and pressure drop at one of seven different velocities. The lowest velocity is a 143 or 149 feet per minute. It's a frigametric system again because it's something about some milliliters or something i don't know what it is, but they're, not numbers we're used to.

I'm used to 300 feet per minute, but it's 297 because of metric, but they will publish their numbers at velocities that we've rarely achieved, and we see these numbers that we like, like 0.08 and 0.1, we're like yeah that filter but we're if we're using the 25 By 16, opening on the side of that furnace, with a three ton drive that opening mathematically converts to 500 feet per minute. Now i got a 0.4 drop across the filter that i wanted to use. Would you ever use a 0.4 drop in a filter? No that's! Why, if you fill out the friction rate worksheet, it's i like using the phrase. You know that predictability or the keys of the kingdom velocity through return trunks max 700 feet per minute.

I like to keep him at 600., then i know i'm never going to have noise and everything's going to be good if i'm putting them in the unconditioned space. I want to run my velocities at the max, but if they're in the condition space i try and keep them under you're going to see a chart, it'll all make sense. The pressure drop has to be a real pressure, drop, not assumed. We got to look it up depending on how time goes.

We might be able to look that up today, pressure drops across the coil. It is not uncommon to see 0.3 drops across evaporator coils if we have a 0.3 drop across here and a 0.2 drop across here. We better have a whole lot of oomph coming out of that blower. That's why seeing numbers of 0.7 and 0.8 and 0.9 aren't out of the realm of possibilities and you'll have people that are fixated on 0.5 from a furnace, and i can't emphasize enough that that's that's just a load of crap and finally furnace manufacturers have started to Publish you can run this thing between .15 and a full inch, because that's realistically, where it's going to happen, i've literally stood in technical committee meetings yelling at people that i like and saying you know, you're wrong and they're telling me i'm wrong, and you know on The ground headlocks knees to the groin.

Well, i'm exaggerating, maybe a little. Maybe it was a need of the midsection, but people have very strong opinions of this stuff and it's all been solved just by a manufacturer. Finally publishing stuff. That is the way it should be.

So it makes me feel better. So if you want to use a coil with a big pressure drop, you can because it's legit. Yes, sir, you have a little extra that you can use later. One of my big things and the question was: if you have a design for a wet coil, but then you check it with a dry coil you're, going to see different numbers and that's that's a fact.

If it's going to be dry and heating - and you want to slow your fan down a little bit not to meet your numbers good but leave it where your original design was because when and i don't want to say that it's always more airflow required for cooling. Because it's not true, but we want to keep that wet coil in our design and our setup when it runs in cooling because it's going to be wet, then there's there's a bunch of fluff in the friction rate worksheet that i'm okay with and ultimately, if we Test it at the end we can adjust, and if we have that that extra, the extra, let's just call it extra, it's never going to hurt us because we can always slow the fan down. It hurts us when we don't have enough and we can't always speed the fan up, because that usually entails reducing effective length, and you can't always do that. If we're already on high speed, we can't make it go any faster and then it gets into changing the blower and you don't change a blower.

You change the whole air handler fan, coil or furnace, so it depends if your blower, the question is: where do you take this reading? Is for i'm doing it after the filter here, because this furnace does not. This manufacturer does not publish its data, including a filter. It's pretty rare that they publish with a filter anymore. I saw a youtube video and not to pick on youtube, but i'm gon na pick on youtube where a guy said something about yeah.

You got ta. Take the pressure drops across the secondary heat exchanger into account and as much as it hurt my wrist. I reach right through that computer and grab them by the throat, because that's not true, but he also was saying that if you set your duck slide at point, one you'll have a 0.1 static pressure in the uh, the supply duct. And then i went to staples and bought a new monitor because i took my phone and i smashed my computer screen.

So i stopped gouging my eyes because that was doing permanent damage. I'm going to call him in a few weeks and tell him what's what it's a true story, though i am going to call him. Yes, manuel d gives us guidance max velocity in the supply and that's going to be 900 feet per minute 700 feet per minute. 900 feet per minute branch runs.

I like six to seven hundred feet per minute. I can get the proper amount of throw. I don't think i'm going to get into much manual t stuff, but there's as much importance in grill selection or supply grill selection. To the point where, if we're not looking at throw and terminal velocity and all that kind of stuff we're hitting the tall guy in the head with the air and he's complaining and he's not, you know, gon na have us come back to do any more work.

So it's just not aesthetics, you know it's just not those the heart. Cooley 411s, the brown or off white floor registers. If you're running them at six or seven hundred feet per minute, they got six and a half feet of throw how many houses are you working in that six and a half foot ceilings right, there's only so many people that are, you know shorter than me that Live in them houses that walk around like this all right, you got to hit the. If for air conditioning, we got to hit the ceilings right, you need eight feet of throw, so you got to be designing at velocities.

That include that, and that's one of those little snippets in this class that, if you're right with me on what i just said, you're, probably already designing pretty good duck systems if you're going well, we we pick them by how they look. You can make significant impr. 80 percent of our industry is that's one thing. I definitely want to make clear if i'm saying stuff that you're like ooh, i'm not doing that.

Nobody else is either so don't beat yourself up about it, but make some corrections whenever you're looking at the duct your unit system - and you say you get a point - seventy a thousand cfm so you're doing total static of the unit, no matter what size filter that You put on yes, the comment was with placement of the return static, tip, we're measuring external static pressure. I don't use the word total in front of it, because i can't find a legitimate source that uses it other than bergman and we went through some stuff with some stuff that recently got published. I don't know where total comes from, i just say external static pressure. It's not wrong, but it's just the way.

It's expressed, hey, go ahead. It's the same thing. It's in our definitions is the most adequate way to check that is, pull the filter out. Read it read what the filter is for the design and just add it to it, or is there a way to check it? I'm not going to answer you because i'm going to go step by step at the end after we do our design and measure it all right.

We got to get back to our topic. It was almost like. I did that on purpose right. That was pretty good.

All right never start on high speed when you're doing a design. In case i don't say this six times, i'm gon na do my best to do it six times, don't start on high speed. When we look at our blower tables start on something other than high speed, you guys are paying attention medium, speed or lower, or a tap if you're, using a constant, torque ecm and by the way, everything that we're talking about today basically addresses a psc motor or A constant torque ecm if you're putting it in the constant airflow just put 0.3 for your available static pressure and don't exceed the velocities. Do it essentially, whatever you want that's kind of tongue-in-cheek, but it's kind of true too.

Don't start off in high speed. We're going to populate that number we look at our chart. Our chart tells us for a thousand cfm we're going to do a little interpolation between 0.7 and 0.8 lies 1000 cfm. Everybody cool with that, so we have 0.75 is where we're starting.

It's not 0.5. Just to be clear, it's 0.75 you're going to put a air conditioning system in your design. I am that one right. There e29a, i went with the e29a in lieu of b or c, because i have height restrictions.

What's my pressure drop when it's wet right there? It's 0.2, nothing difficult about that agreed right. How to read sharp boom point. Two is populated, there's the coil that we used next in line electric resistance heat. Do we have that in our fossil fuel furnace? No, do we have a hot water coil nope? Do we have a heat exchanger? Yes, in fact, in that furnace that i showed we have two, those pressure drops are included in our blower table right already taken into account.

It's probably been, oh, i don't know 68 or 69 years since heat exchangers were separate, but i think that really is left in there, because it can count as other right, there's, there's no other in there yep. So these come into play in other designs, not in the design that we're currently doing filters are next. This is my favorite slide because it shows her or him. I don't know which it is.

I love that when i become king someday, i will require every filter manufacturer to publish that right on the filter. No looking it up! No math they're telling us that if i'm moving a thousand cfm, i'm going to have a 0.21 drop, so i'm going to do one of two things. I'm going to make sure i have enough fan to overcome that pressure drop. If i don't have enough fan to overcome the pressure drop, i'm going to put two of them in and it's going to equal something closer to 0.08 or 0.09.

When i say two filters: no, yes, all right, everybody's with me on that! I'm sorry! I stole it from somebody's thing on the internet, eric what's his last name. That's i stole that picture from him or i stole that picture from steve, because steve had the same picture and steve brags about that company. I'm talking about captain america out there. He he brags that that, if they're a really smart company, because they're from uh minneapolis that make that it's three a 3m product, what and that's what i believe - that's where that picture came on a five from system in most cases.

Realistically, that's the way it works out, so we're going to have air flow in excess of that or around that and who would purposely put a filter with a 0.45 drop in it. Now i could start off with you know over an inch up here and be very, very strict about keeping these numbers down and make it work, but that's not how it works. Somebody started off with a three ton drive in their furnace on a three-ton ac and they end up with no available static pressure, which means they're going to run a real external static pressure of 0.7 or 0.8, which is well out of the desired air flow. It kind of goes back to and i'm not going to spend any more time than just this quick thought, because if i don't get it out i'll keep thinking about it and i can't speak, but a big external static pressure is not bad, it's relative, so you Can have a big number and things are good.

You can have a small number and things are bad. You have to take a static pressure reading and compare it to something that makes a difference right. So i love this. No other way to put it that we just made it easy.

This is hard you have to interpret and decipher, and all that and it's why people just damn i'm just going to put any filter in, but at a thousand cfm. This particular filter has a 0.19 drop, nothing wrong with that, but i got to make sure i have enough or pressure to overcome that drop. Next, we got the uv light because everybody likes putting them in. Are you taking them into account? As pressure drops, i watched john i'm forgetting his last name alice and he didn't put one in.

I think he put nine in buy eight get one free, there's a good strategy right, it creates a pressure drop and if you want to do that, do it make sure you got enough fan to make it happen, then we get into a supply outlet and what We see here is a standard number that is populated very frequently on the friction rate worksheet, you see 0.03.03 and 0.03, a supply covering a return covering and a branch damper, that's the guidance of manual d, and there is one of them. The idea behind manual d is to calculate what is referred to as the critical path. The critical path is the longest circulation path that takes place in the system. We find the problem run.

It has the longest tel. If we can supply the critical path with the proper volume at an acceptable velocity, then we can do the rest of them worst thing. That's going to happen is the air is going to take the path of least resistance. We're going to have some guys that are like me on a saturday right, trying to get away with not path of least resistance, and we just block them off and it ends up being what they refer to as equal friction.

So everybody's getting the same or the design error by slowing down the ones that have an easier path. That's all and the whole friction rate thing is per 100 feet. Essentially, what you're doing is calculating the pressure drop per 100 feet, whether your duct system is two or three or four or five or where's house 750 feet long right, we're we're breaking it down into our pressure drop or friction per 100 feet. So we know we have enough to deliver the proper volume at an acceptable velocity to each supply outlet that last 90 seconds was the heaviest that we're going to do for the rest of the day.

If you want a friction rate worksheet or you want to do it on a computer, this is free from acca. You can download the speed sheet and you have to fill everything in because, if you don't it curses at you, it's a bunch of hashtags and exclamation points like the cartoon. So that's how they would curse. That's what it does.

If you don't fill it out right. I do it like that, all right, no computers, i i draw it on my little dry, erase board it's the way. I do things all right back on track to specifically what we're talking about and that's filling out the friction rate worksheet one grill one register because they're in our critical path. We got to add that guy.

So we got 0.03 and 0.03 when i'm doing a duct design. I just write point one and take care of all them. Don't even bother do you think, and i am going to back up. Do you think that guy right there has a .03 drop that hart and cooley 411 has a bigger drop than this at five or six hundred feet per minute? The royal air 531 doesn't see a pressure drop that high until you're almost pushing a thousand feet per minute.

That guy right there at uh, six or seven hundred feet per minute is half of that .03. So that's why i'll take another one. Thank you very much. Oh i'll take both of them souvenirs from florida baby.

I don't get out much so when i get to take stuff home, i take it home, so they're all populated and that guy's populated so we're golden we're going to add them up. You don't need a calculator, but that's just my segue into the next slide. Everything's populated, we add them up. We come up with 0.54, they are our total component losses.

Our available static pressure is equal to our external static pressure, less our device losses and i get to slip that device in there because that's what the old sheet says do a little bit of math our available static pressure is 0.21. Did we do anything difficult yet? Have you been forced to do something so far? Yeah, it's the path right. First, couple time you do it right. You know that plate plate might meet wall.

We talked about the keys on the floor. Hopefully not, but sometimes you know, vent that frustration if you need to all right. I got .75. Minus 0.54 gives me that 0.21, so that part of my task has been completed.

We can use the friction rate worksheet and at the bottom of it it has a friction chart to solve for our friction rate, or we can do it with math before we can use this chart or this chart. We have to finish step four.

28 thoughts on “Duct design for great results w/ ed janowiak (acca)”
  1. Avataaar/Circle Created with python_avatars ReThink HVAC says:

    You said ductulator Are you in Barrhaven ?

  2. Avataaar/Circle Created with python_avatars David Williams says:

    If I got an online now can I upgrade it to a symposium before Feb.

  3. Avataaar/Circle Created with python_avatars Tabitha Franklin says:

    What is this? A Joke? The dude takes FOREVER to get to the point!

  4. Avataaar/Circle Created with python_avatars Gregarious Antithesis says:

    I simply use 1 cfm per sq foot and size my room duct size based on that simple math and it works out golden. Did the static tests and right on the money. Granted it was all metal duct no flex. Reality is doing all the calculations makes more sense on complex larger systems to get everything well balanced but fact is it is your usually rounding up because calculations usually are between sizes often so there is no perfection in design no matter how complex the calculations. Willing to bet there is a common factor that could be used based on a few typical conditions that you use as a multiplier that will get you every bit as close. Most of the frictional loss factors are just that anyway.

  5. Avataaar/Circle Created with python_avatars Matthew Arndt says:

    Man a lot of good info very thankful!

  6. Avataaar/Circle Created with python_avatars Brian Porter says:

    When I lived in NJ, I attended a class that Ed taught in Mt Laurel. It was an air flow class. The first thing he said was "guys it's all about air flow" If the air flow is not right, then your charge will not be either. Very true, especially with the crappy duct systems we see in new construction.

  7. Avataaar/Circle Created with python_avatars Albert Lowes says:

    Thank goodness for ductless ac.

  8. Avataaar/Circle Created with python_avatars MJ says:

    Nice video. Always a quality show.

  9. Avataaar/Circle Created with python_avatars Ty Branaman says:

    I was in that class! Great job Ed

  10. Avataaar/Circle Created with python_avatars P F says:

    how do two stage system affect your minimum velocity requirement? Are you in Ottawa ?

  11. Avataaar/Circle Created with python_avatars garbo says:

    Wish I had a dollar for houses and commercial sites that contractor cut corners installing undersized duct. Went round & round after installing a VFD for a 100 HP air handler. Could not run motor over 88 to 90% of full speed or motor would draw too much current. Problem went away when door on both sides of fan were tied open. Worst part the undersized duct ran up 6 floors to mechanical room. Just great on cold days when they only run 100' of duct in a 300" long room.

  12. Avataaar/Circle Created with python_avatars Balint133 says:

    This could have been an hour shorter if the guy would've stopped talking about irrelevant staff all the time.

  13. Avataaar/Circle Created with python_avatars asdasda z says:

    Some of the fittings on manual D are really hard to tell what they are based on the pictures.

  14. Avataaar/Circle Created with python_avatars Kyle Ricciardi says:

    Judging from the comments we got quite a few that fit in the "80% don't do this".

  15. Avataaar/Circle Created with python_avatars Bill Cowhig says:

    Thank you for the review of ACCA Manual D, and for exposing the hard to find fact that TESP = ESP. If contractors actually use Manual D to design residential duct systems and retrofits, why do studies find that the majority of them are deficient? Do inspectors require acceptance tests of any kind designed to protect ignorant homeowners? Are you in Orleans ?

  16. Avataaar/Circle Created with python_avatars Tom Griebe says:

    Too loud, annoying personality.

  17. Avataaar/Circle Created with python_avatars Anthony Brown says:

    Bryan thanks for the vid,but please learn how to edit these types of videos. This guy is hard to listen to,full of nothing stories that we all have in the field.

  18. Avataaar/Circle Created with python_avatars smacleod69 says:

    Doing ductwork systems and change outs for over 20 years. Not many companies do this. When you only have a certain amount of time given to get the job done. You can go by the .1 static pressure to design your system. Go with .5 total esp from the furnace specs. you will be just fine.

  19. Avataaar/Circle Created with python_avatars 77kthomas says:

    Straight up simple math and installed a system in my moms house and it works beautifully if you need a lesson on duct install contact me it’s not that hard. Service area Kanata??

  20. Avataaar/Circle Created with python_avatars A. T. says:

    Bryan, I appreciate the effort to provide us with duct design training but I"m certain there's a much simpler way of doing it. Some years ago I took a duct design course at the local college for two semesters, it was properly presented and easier to absorb which I appreciated. I appreciate all you do for us and hope you take this as constructive criticism. Thank you….

  21. Avataaar/Circle Created with python_avatars home serve says:

    why is it that some instructors have to give you their life history and make up jokes. Glad I didn’t have to pay for this class. If I go to learn something I want to be taught we all have our own stories.

  22. Avataaar/Circle Created with python_avatars pepeshopping says:

    Condense the knowledge. I don’t need jokes.

  23. Avataaar/Circle Created with python_avatars A/C SuperCool says:

    Come on Bruh… Talk about killing guys with data… This is great on paper, totally not realistic in the really real world. Give these guys a good KISS method to do in the field & don't require an engineering degree with 2 weeks of calculations to achieve a duct design that WILL CHANGE once on the job….

  24. Avataaar/Circle Created with python_avatars gary smith says:

    Well that was about as clear as mud Service area Nepean??

  25. Avataaar/Circle Created with python_avatars Ivan Hall says:

    Thanks. Dropbox info?

  26. Avataaar/Circle Created with python_avatars SuperVstech says:

    I love the ACCA ductulator app for iPad.

  27. Avataaar/Circle Created with python_avatars Ed Lauren says:

    It’s difficult to listen to the screaming voice.

  28. Avataaar/Circle Created with python_avatars Neil Comparetto says:

    HVAC School and chill tonight.

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