This episode of the HVAC school podcast is made possible by testo and carrier, and i have been testing out a lot of different test ou products. Recently I've been using the test of smart probes. App I've been using. The 605 is quite a bit, which is the thermo hygrometer.

They do a really great job of measuring temperature and relative humidity. Dew point wet bulb, dry bulb all that, but I've really been enjoying the test. Oh 550, which is their simple kind of base manifold set, and what I really like about it is the combination of its functionality plus its price point, and it's also bluetooth connected it's truly the manifold set that I'm suggesting to my own technicians when they buy tools. That's the one that I'm recommending to them to buy.

Also thank you to carrier for supporting this podcast. I've worked with carrier now for 12 years. In my own business and through the ups and downs carrier has taken really good care of us and I'm really excited to see what carrier has been up to lately. We deal with carrier enterprises here in Florida and they've really treated us well, we actually are getting a new carrier Enterprise right behind our office here in Clermont, I'm glad to see them continuing to expand.

The one thing I really do like about carrier is how strong its distribution network is. So I was talking to one of the other distributors from the south up in Georgia and in the panhandle of Florida, and some of the other states called mingled Orff's and I've. Just always impressed by the quality of distribution that carrier brings on carrier turn to the experts. Also, this episode is sponsored by the danfoss family of apps, so danfous has created some really great free apps for iPhone and Android, with the technician in mind, apps like the refrigerant slider app, which is a really great PT, chart type app.

But it's a lot better than the chart, it's very easy to use and the troubleshooter app and many more you can find all the free danfoss apps. By going to Danfoss com4, slash cool apps, that's danfoss com4, slash cool apps. I don't know who you are. I don't know what you want, but I will find you and I will Gary with the moral superiority of proper equipment sizing.

Okay, I need to make a confession confession time, as they say, I haven't always been the best about doing proper manual, d-duck sizing, okay and when I say always like okay, maybe a week ago, duck sizing has not been my thing and the reason that that is Is because I've never done new construction, especially not residential, new construction? Since I started in business and in commercial, you always have a designer who tells you what to put in right, so you'd rely on them. They tell you what size ducts to put in and all that kind of thing, many of a test and balance contractor who comes in after you. So the reality of designing a residential duct system is not something we do often and when we do it, it's in a retrofit application and we do our due diligence to the best of our best of our limited knowledge. I picked up a book recently and this book is called understanding manual D for residential duct systems, a companion guide to manually - and it's like it's really good, I'm flipping the pages right now.

That's just not a flip to the page is flipping. You know why, because it's a real page-turner, that's why no really is a good. It's a really really good book and it's got. It's got great pictures in it too, like it's actually just really good.

It's well-written. It's got nice illustrations and it's actually published by akka. It's got the big akka stamp right on top, so I figured I figure when I first look at it's going to be a dry read not at all, and the writer is mr. Jack rise.

So, if you've, if you've kind of followed the manual J manual D world for a while, you I'm sure, you've heard Jack's name, if you look up on YouTube, you'll see some of his videos there and he's done a lot of training for akka. I kind of put him on par with Dan Holohan as far as the way that he speaks in the way that he writes. It's very matter-of-fact, there's a lot of story in it. A lot of experience Jack's been doing this a really long time and I found out he's a Floridian, so he doesn't actually live too far from me or flirting, and now I guess I should say, he's a transplanted Floridian, and so I asked him to come on The podcast and he agreed, which is weird like it's weird - that people actually agree to come on this thing, but I guess I guess, there's the power of radio as they say so here we go, we've got a jack rise and actually I pointed out to him It that we are both in Florida - and I said you know Jack, why do you think people are so critical of people who live in Florida? Don't they know that we are in? We are in the cyber pocket of greatness.

How do you get to be jack rise, Wow? Well, I was born into the industry. You know my dad was a contractor and he was a great teacher, although, like all teachers, he was limited in what he knew. He can only teach me what he did know. Nobody can teach you what they don't know, but that was a great beginning because I would run around as a kid.

You know you've love to run around in trucks with your father when you're young and handing tools and learning all that stuff early on it just got me into a mode where I realized that the more I knew the better I was at what I didn't. I think most people want to be good at what they do and I went into oh god, mine. I was 18 years on my own as a contractor 13 years in wholesale distribution of HVAC products, and then I worked for York International for five years. So I pretty much followed the chain of distribution from manufacturer to middleman wholesaler to contractor to end-users, so I've been very fortunate.

I've had opportunities that a lot of people just don't get in the industry. I can envision many people coming in at the helper level. If you will and then they learn to be, you know, installation, technicians and eventually service technicians, and they still don't have the opportunities that I had. I worked for very large companies at one time or another that gave me total freedom carte blanche to do whatever.

I wanted if I wanted to go to the little red schoolhouse at being G's campuses, I'd just get in a plane and go and be gone for a week. You know I just had extraordinary opportunities, most people don't get, and it's not like I sorted out. It's just presented itself and I guess the only thing I was really smart about is. I took advantage of it when it did present itself, I'm not the typical person and when I talk to groups like a vocational school group or something like that, I try to remind them that there's something other than just doing service in this industry.

There's a whole lot. Wholesaling, I mean training goes on and on, but I've been very fortunate. Was there anywhere along the line that was sort of an epiphany? You know something that came up that made. You realize that you really wanted to be a trainer yeah early on by the way I totally rejected this.

I did not want to be in this industry thing. I have to recall cause it's my brain right now. I have to say it. I was moving from one house to another and my uncle's.

We have very tight family, my uncle's were helping me out and I'm in the back of the truck with bed sheets, and you know couch and all this stuff when we're driving in my uncle Walter said to me, he said: what are you going to do for The rest of your life - and I was about maybe 20 years old time - 22 - something like that and I said gee. I never thought about it. I'd just been kind of handling things as they came along. You know he said you know Jackie, I think you're doing it right now.

You just don't realize it yet, and I came to realize later on it. What I really enjoyed about the industry was training was teaching, because I thought it did the most good and when I was a wholesaler, I did a lot of training because I was the middle man. It was my job to add value to the product that I took from the manufacturer and passed on to the contractor, so I got heavy involved with it. Then we would have training courses every week literally every week there was a sign-up sheet at the counter.

Big big company in South Jersey, a lot of money, a lot of opportunity again for me to do whatever I wanted to do. I had a newsletter we sent out. We had 9,000 people subscribed to it. It went out monthly.

It was just a great place to work and no matter what I was doing when I was contracting, I wanted to be a wholesaler and when I was working for York International, I felt more like because I was running the New Jersey branch or running the operations Manager and the technical service manager at that facility, and at that time we were the only York distributor in the state. So that gave me a lot of opportunity to do training and you know improve the knowledge. You know you go in the field and your tool bag is empty. How much work? Can you really do if you can fill that tool bag with this kind of training? This kind of information knowledge is power in our industry.

It really is. I got to stop myself from talking I'll go on all day. No I enjoy I enjoy, because I think a lot of people want to know the person behind the training. You know who you know.

I remember when I was early on in the trade. I would go to these training classes and I would listen to trainers, and I was so in awe by all the things that these guys knew and for me the epiphany was. I really want to be the person who understands the trade deeply, because my experience was most of the guys who I rode with though they were really great guys, and they taught me a lot about how to physically execute the work. They really didn't understand the.

Why of what they were doing so when I listened to you and I read what you write, you have a really clear understanding of the whys behind what we do and so for me, it's nice to kind of know where that comes from yeah. That's very important! You know I've been with a lot of people in industry, as you can imagine, trainers and whatnot, and nobody knows everything for one thing. You know, I think it was Abraham Lincoln, and it said at one time that knowledge is not knowing everything it's knowing where to find out everything it's more about reference than it is about rote memory, knowledge and I've been with the and been in classes with a Lot of trainers that really don't understand the industry they're, essentially reading out of a textbook in fact, reminded me funny story, our SES refrigeration service engineer Society is where I went. Thank God early on to learn about this industry.

The very first teacher I had I walked in my very first classes. At night it was at a wholesalers second floor classroom put that in quotes. I walked in there and sat down, didn't know anybody in the room. There were maybe 15 20 guys here.

The instructor stands up at the podium in the front of the room and he starts reading out of the man and if you asked him a question, he would reread the last paragraph. That was my first instructor so immediately. I knew I could do better. Ah, but I I have to tell you that it came into my head: well, you see that even nowadays you walk into a presentation without a trainers, giving anybody who's in the field and goes to these presentations a lot of times it's with manufacturers or different associations.

You walk into this presentation and if the presenter starts reading the slides to you, you immediately know it's going to be a long day and talk about that right I mean what do you expect? Our industry has somehow made this McDonald's fast-food when somebody says they're going to have a class in something if it lasts more than 90 minutes jeez. I got to get to my kids soccer game. You know we've somehow and I think it's the manufacturers that have done it. It's all product, specific information, it's very hard to find generalized information about refrigeration, air conditioning.

You know whatever it's almost like we're hiding it. The good organizations like our SES and that used to do all that kind of work. I looked at your podcasts that are available. You get a lot of good information in there, but that stuff's hard to find if you're dealing from a carrier outlet somewhere in North Jersey or something like that and they're going to have a class.

It's going to be on a specific product and exactly how to install it and how to repair it when it goes bad they'll just say: well: pull a 500 micron vacuum. What the hell is a 500 micron vacuum yeah. Nobody ever explains that part to you. So what are the guys? Do they go in the field they put their service gauges on and they see that they have 30 inches of mercury and they figure that's 500.

The width of the needle is 3,000 microns wide that they're looking at we're doing it all wrong and I'm sure that's not true exclusively everywhere, but as a rule, wherever I go, we're not doing it right. I go up to Denver where they should be using 500. 540 CFM cubic feet of air per minute for every ton of cooling capacity there. I asked him what they use and they tell me 400 and I try to explain it to them and it's like looking into the eyes of a deer in the headlights.

You know there's not enough good information out there, at least that's my opinion, so I want to introduce the manual D training that you do because that's sort of the meat and potatoes that I want to talk about today. But what I really like about your guide, you know the official companion guide to the manual D that you wrote is that it's written in a style that I akin to the way the day and Holohan writes. I don't know if you're familiar with Dan and his role on hydraulics yeah, I know damn well, he is my hero. We had very similar paths.

He was working for Wallace Ennis back in the days when I was in Bricktown working for lmh plumbing and heating supplies. I was running the HVAC division and dan and I we spent a lot of time talking. He gave me a lot of advice when I first went out of my own teaching full-time, I think the welded animal and, in fact, if you look up hydraulics in the dictionary, it says, see Dan holla hands page on the opposite page. You know all right.

The way you write is so similar to the way that Dan writes in that when you get something, that's the essentially the official companion guide from akka. You sit down and you open it up, and you expect it's going to be a lot of really super boring, just mathematical equations with very little real-life examples. But that's not how you write at all. You write very practically very openly and even in some cases, critically of things that go on in the industry, which isn't what you would expect and that's the same way that Dan writes it's super engaging, which is why I knew you would be good on the podcast.

Your book is one that I could probably just sit down and read into the mic and would be entertaining and interesting to the people who listen, not that I would do that. Of course you know patent pending copyright, akka and jack rice industries, but so thank you. Yeah, it's really good stuff, so I want to just kind of jump into that then and start with asking the general broad question: what inspired you to write that in the first place, what was it that caused you to actually sit down and put fingers to keyboard And write that out absolutely exhausting frustration active sends me to a lot of places. I have a lot of people all over the country to call me in from time to do training and what is contained within the pages of the I'm gon na call.

The unabridged edition of manual d is absolutely wonderful. Engineering, Hank, Roth Kowski is the single most brilliant man I have ever met in my life. I will sit at his feet and learn until the day I die. His perspective of this industry is so refreshing every time.

I'm in a class with him, he blows my mind, you'll say something or do something that'll cause me to look at a subject matter that is so different from any other way. I ever looked at that subject. What caused me to write it. Akka came to me and they said we want you to write a couple of books.

They said three books JD and s, and I said well, why do you want a book and they said well, people are studying for exams, and you know, although the CDs are good and all that, but they have to keep backing up a CD to get ready For an exam, that's hard to do, that's not comfortable! So if you write a book and they can open up to a page and study a certain area or whatever then that'll be beneficial, so I get it reluctantly and once they gave me the charge to do that, it just took on a whole new dimension. That's where I got into remembering everything while I was in Denver when I was in Phoenix and I'll go to a dry portion of Arizona, and somebody will start talking to me about having moisture in their pants. You know it just is so much information out there and people insisting when I pick my equipment. I go right to a HRI and pick 70/30 combinations.

They publish you're in the desert, man you're 4,000 feet in the air. You don't have moisture in air. If you do turn the sprinklers off on your lawn because it shouldn't be - and you know I just got so frustrated with every time when I give a manual D class. The first thing I have to do is D program, the thinking of everyone in the class.

If they've been in the industry for any amount of time, they know point, one is how you design a duck system. That's the friction rate. They know there's 400 CFM and a ton. They know.

There's 12,000 BTUs per ton, that's ingrained into their memory and that's about the extent of their knowledge. So it's a lot of undoing, but the true reason I wrote it I was asked to, and once I got that charge you know that you go do this man, it just turned a lot of stuff loose in my brain. So if the book seems a little erratic or something that's on purpose, I'm told I explain things well and that to me is baffling because I really don't think I'm doing I'm constantly trying to find words in my head, but if I did that well, if I Explained how Manuel D works well, then, I'm very happy with what I produce, whether people like it or not. It's a good explanation.

I think what you did really well. Is you thought like a technician Thanks and you intentionally deprogrammed, you didn't just build up in the way that an engineer would build up. You knows from the simple building blocks all the way up. You first were intentional about actually battling the false thinking that a technician is going to come to the table with in the first place I mean you start right off at the beginning.

You know just debunking some myths. So, let's start there because the first thing you brought up was the point one static: that's how you design a duct system by point one static. So let's talk about when a technician says that what are they saying first off and why is it totally wrong? Okay, they're saying it because that's what they were taught that's what I was taught my dad was more in the hydronic side of heating. He also had a plumbing license, so he favored the plumbing and heating end of the HVAC business.

So I can remember, I don't know 16 17 years old and I said pop: why do we use 24 bay duck in it mrs. Smith's job the other day? How come we didn't use a different size? You know you get to an age where you start to question things. You know and he said well here you went to high school, you can read, look it says right here. Somebody unfortunately wrote right on the duck: calculator set, your volume, CFM opposite point one and a duck calculator, and that's all you have to do.

Oh hell, man, I was empowered by the way you know how he taught me to like pop. Why do we use an 80,000 BTU furnace and mrs. Jones yesterday got the hundred thousand hundred and twenty in stock? How come we used a t, OE z here, length times, width times ceiling. I he didn't know that was a volume.

God bless my father. He quit school in the eleventh grade. Joining Navy went off to fight World War two, so he had limited education, so he would always say length times, width times, ceiling height times, eight wow. It's all you got to do sure.

Okay, how can we use the two and a half ton cooling unit ah length times, width, I'm ceiling height times three? Well, I took that form of low calculation and good old point one into the field took on homes. My father would never take on and almost lost my shorts until, thank God, I had other mentors that push me in the right direction. There is so much misinformation out there, and what do we do is recipients of that information. We take it and run with it because it's easy, we want the path of least resistance.

Friction rate is a pain in the neck. First of all, it's not static pressure. Static pressure is simply taking a Magna hillock or a manometer inclined, manometer drill, a hole in the duct system, put a static pressure tip in there and read pressure static pressure in the case of a static pressure tip. If you put a regular probe in there, you're just going to read total pressure, but that's all it is it's a point in time.

It would be no different than me taking a water gauge, putting it on a water pipe and saying. Oh, I got fifty five pounds pressure, that's good! I don't need to increase the pressure. I don't need something to reduce the pressure. I have a good, steady, fifty five pounds, but that's all it tells you and it's no different, no system when we put a static pressure tip in the system, and we see that we have 0.25 or something on the supply side.

It's only telling us what the pressure is in that system at that point in time. If you want to know what the friction rate, the pressure drop per hundred feet of equivalent duct is, then you have to do the calculation and the friction rate is equal to the available static that you have left over after you've discounted your coil. You know the pressure drop across coil, your air filter, UV lights, whatever you have the available static times, a hundred, because it's pressure drop per hundred feet of equivalent duct divided by the total effective length of the system. That's a little more difficult than just putting twelve hundred CFM opposite point, one on a duct calculator, but the friction rate you're going to use to enter a duct calculator.

I can tell you from forty five fifty years of experience at doing it by hand is never going to be 0.1, I think twice in my life, I ended up in point one: it's going to be somewhere between point zero, six and point one: eight, that's the Akka wedge, which is, I believe, the cause of the misunderstanding: the myth involved with point one when you teach manual D at some point in time, you have to discuss available static pressure versus total, effective length, and that is a graph that akka created and they say On the graph that, if you have a friction rate between oh six and one eight point, zero six and point one eight, then you have a good duct system. If your friction rate is less than point: zero, six you're not going to have good air flow. It's going to be very light. You're going to have to increase the speed of the fan, get a bigger speed.

You got to do something different if it's greater than point one: eight you're going to have noise so full nicely somewhere between point zero, six and point one, eight! What's right in the middle point, one two rounded up point one that and the fact that, for instance, when I teach manual Q, commercial duct system design, you tell the students assign point one to supply ducts, assign point zero, eight to return ducts and none. Because you treated so differently the way you do the calculations in commercial compared to residential, for instance, when I'm doing a commercial load, the assumption is I'm using manual Q. The assumption is, I can go out by any blower. I want any air handler whatever okay, so I'm not restricted to seven Isis.

When I'm in the commercial sighs, I got seven choices, one and a half to two and a half three three and a half four and five pick one and by the way, they're all rated at high-speed half inch external static pressure right and by the way, if You've got a blower in a coil. You ain't never ever going to have Oh point: 5-inch external static pressure. Unless you have two feet of total duct length, all right, it's just simply not possible. The coils today are running point three and higher the W coils the egg coils.

They start at point four or five and go up there's just no way you're going to end up in the point five column. So that's a whole other issue. When I'm doing commercial work, I'll assign point one to the duct system and a supply side - Oh weighted and a return side, but now I'm going to treat it differently. I'm going to calculate every elbow every fitting in my duct run and I'm going to assign it a pressure drop in inches of water column and then, at the end of the day, I'm going to add up all those pressure drops and go out and buy a Commercial blower that can overcome that and still deliver my volume of air so get on the phone to a manufacturer.

Hey, I need a twenty thousand cubic foot. Blower fan, throw in a two and a half million BTUs steam coil. I need a six by six foot print and it has to overcome five inches of external static pressure. How much are you shop it around? You get the best price and then you order the product.

It's very simple, all right! It's not hard residential can't do that. You only got seven sizes and they're all rated at half-inch, so you can't just look at an elbow and say all right. That has a point. Oh, oh six, seven pressure drop across it.

You have to determine what the equivalent length of that is and then you're going to add those equivalent lengths for each fitting into the total measured length and, at the end of the day, you're going to have a certain distance you're going to use called total effective Length that you're going to divide into the available static from that blower. You chose times 100 and that will give you the friction rate that you're going to use to the duck calculator with or friction charts in the back of manual date. Whatever. However, you do it duck.

Calculators, are much easier to use. You'll, go blind and start developing facial pimple complex, trying to read the closed lines on a friction chart in the back of manual date, but that's the procedure. Okay, you can cheat all you want. Most of the jobs I go on in the real world somebody's cheated.

If I go up to an existing system - and I measure the duck and it's 24 by 8 - and I put that on my duck calculator - and I see that opposite point. One is the volume of air that they're trying to handle there. I know, without ever doing anything else, that somebody just used point one, there's nothing wrong with duck calculators, providing you apply them as you should, but there's a whole lot wrong with people that write things on very good duck, calculators that destroy them right. Things like this is your setting recommended residential setting.

That kind of thing I'm actually processing some of this as you're talking and I'm thinking about ways to think about this. For somebody who has never thought about this before first off, I guess the total effective length. That's the total length to the furthest point, including all of the fittings that are in that particular length, correct yeah, it's not necessarily the furthest. It's the supply outlet with the greatest resistance to air flow and the return Inlet with the greatest resistance, the airflow.

It's not always the furthest, but it most cases most balance systems. If you have equity in a system, the branches are all within 10 feet of each other. It's probably going to be one of the longest, but it's the one with the greatest resistance to air flow and that's called by the way, the critical path, because what Manuel D teaches is an equal friction method. That's why you're only looking for the worst case scenario, the assumption is, if you can get air from the inlet with the highest resistance, the air flow to the outlet with the highest resistance air flow, then you can easily get air to the ones in between.

So what Manuel D teaches is to calculate that run. Take that friction rate and apply it to all the runs in the system, got it, and then that still is relying on in that type of setup. You do still need to use balance and dampers absolutely correct. In a properly designed system is only going to be one damper, that's wide open and that's going to be the one that was the one with the greatest of resistance, the air flow, all the others will have to be controlled by the way you can take the Equal friction method and modify it to what they call a modified equal friction method, and that's where you calculate a separate friction rate for every single branch run out.

The disadvantage of that is that it's time-consuming. I mean it takes a couple hours to do a simple system, because you have to do what you did for the longest run for every single branch run and that can get very time-consuming and boring and you're going to start making mistakes. The great thing today is the tools we have computers. They work at the speed of light, and you know you can make a computer giggle by giving it that much math to do you know it's a wonderful tool and shame on you.

If you're not using the tools, I use right soft, I think it's a best program out there. It's easy to use. It follows manuel jay manuel d to the letter, the definitions, the pictures, everything our word for word, the same so there's no loss in accuracy, no loss in the technology, the science we're using to calculate loads and lay duck systems up. So they give you an option for a modified, equal friction method and that way, your duck sizing becomes more and more precise.

You'll see four and five and six inch 7 inch branch lines on the same job, you're doing ok, so the technician out there who's listening to this and saying but jack. How do I control the face velocity on my actual diffusers that if I have this type of setup, isn't they gon na be all over the place? What do you say to that? Oh sure it is, and that is absolutely critical if you don't control the face. Velocity on a register, you have no control over whether the air in the room is going to mix and remember, returns, don't do anything in a room. They have zero effect on air movement in a room.

It's the supply outlets that cause the air in a room to move. If I have a hundred CFM coming out of a sidewall register, it will cause a thousand to 2,000 cubic feet of air in that room. Second area - and you know the primary air - is the air stream coming out of the register. It will cause ten to twenty times the amount of that primary er to move into the secondary air stream.

It's an induction thing. The primary air coming out of the register is at such high velocity. It creates a hole in the air in the air that surrounds that primary air stream is sucked in literally to that primary air stream. Okay, that's what causes air to move in a room? The returned grills only have an effective area of maybe 30 to 36 inches.

From the face of the register. Hold a candle go, find ugliest, noisiest, greasiest, suckiness return. You can find get three feet away from it: hold a candle straight up and the light on that candle won't move unless there's primary air blowing on it. The closer you get to that, the more that light on that candle will be forced into the return grill.

If a high return, grill could suck cold air off of a floor or if a low grill could suck heat off of the ceiling, it would literally have to be strong enough to pull your clothing off as you walk by it, and we simply don't have blowers In a residential industry that can do that, knowing some of my technician, friends, they might want to use that clothes sucking technology in certain applications, but I guess we'll leave that for another huh yeah, and so when technicians talk about is the way that they tend to Talk about it would be, you know, they'll talk about, throw but they're, not thinking so much about the fact that secondary air is being drawn in and one interesting thing that I've heard for years, but it is never really clicked with me, is when you see supply Air vents that have the dirt that accumulates around them a lot of what's going on there is that secondary air is being drawn in against that ceiling surface and and in turn, causing those dirty streaks on the ceiling, which is just sort of visual evidence. Of what we're talking about that's exactly right, I'll, calm, the uninitiated we'll go into a building like that and say all you need. Your ducts cleaned has nothing to do with the ducts needing cleaning if the ducts needed cleaning and it had that kind of dust. Inside of it, it would be attaching to your furniture somewhere, that's called streaking and the only thing it causes that is, the secondary air being pulled into the primary air stream.

It's no different than being in a shower, and the water stream comes out. The shower curtains want to pull in it's the exact same effect. Mother Nature doesn't like imbalance. Mother nature wants balance.

So if you have a high positive pressure, negative pressure is going to seek it out or it will seek the negative pressure out. I should say all right: high pressure goes to low pressure. High temperature goes to low temperature. Hot goes to cold, because hot has more energy than coldest.

The greater will always go to the lesser until they are both equal, which brings up the next thing that I wanted to talk about. Is you address this specifically in your book? Is the differences in trunk and branch design, velocities yeah? So can you talk about that? For a second yeah, first of all, if you don't have a difference, you have no control over where the air is going to go. The way I mean it could stay in the trunk duct it could go to the branch outlet. You have no idea, you have to create a difference and essentially, when you create a velocity pressure, difference, you're, creating a reason for the air to go from the high pressure area, the low pressure area.

So your high pressure is inside the trunk. You want to keep the trunk somewhere between 700 and 900 feet per minute and by the way, if you want air to move out of a duct, you have to create a difference for that and you do that by creating the duct a given size for a Given volume and remember this is all about control, you can have the same velocity in the trunk and in the branch, but again you lost control. Now you really don't know where the air is going to go, it's an uncontrolled airflow and that can lead to huge problems. Remember when people say they don't have enough heating or enough cooling they're saying they don't have enough airflow, alright, because the only way the BTUs there is.

It rides on the back of the volume, the cubic feet of air. If you need more BTUs in the given area, you need more CFM in a given area. The sensible heat equation says it all. Cfm is equal to the sensible BTUs divided by 1.1 times the temperature difference times the altitude correction factor, if you have one, but he gets there with more air cooling, gets there with more cooling air, more cooling CFM.

I forgot the question: what the heck were. We talking we were talking something about air conditioning. It was something related to HVAC akka manually, no we're talking about controlling the duck velocity in the trunk and yeah yeah, ideally 700 to 900 feet per minute in the trunk duck truck duck. Velocity is very important.

You can scroll around a lot with the branch velocities by changing the registers and grills, but trunk velocity is very important if you drop below 700 feet per minute in a trunk, then you're approaching branch velocity, which ideally again, would be somewhere between 400 and 600 feet Per minute and again, if you have the same velocity air is not going to be controlled, all right, it's going to go where it wants to go, take the path of least resistance. Always if you go above 900 feet per minute in the trunk duct then you're going to have noise. Noise is going to be transferred to the branch duct and that will be transferred to the environment and when we design duct systems, the whole idea is to make people as comfortable as possible, and nobody wants a noisy duct system, but that main trunk duct. I don't care whether it's the first of a three or four reducing trunk ducts, or it's just a splicer box, the junction box for a flex, duct system.

It has to be sized properly and you talk about nightmares. That's where a lot of that dirty word. I just mentioned flex: duct gets involved, I've seen absolute abortions and attics. If I go to an attic anywhere in Florida, I can expect to see what looks like an explosion in a flexible duct factory.

It's so poorly installed, crimping binding compression, it's a nightmare but yeah seven to nine hundred feet per minute in the trunk four to six in the branchline. Ideally, but you have a lot of latitude in a branch line. Faq Hank does it, and I think I repeated it in my book. I can bring a 12 inch round duck to a four by ten floor register 4 by 10 to 12 inch round 90 degree.

Boot is not in every one shelf. You're gon na have to make that, but that can work if I properly control the volume in that 12 inch round duct to be whatever it should be. 100 110 CFM and I picked the right register because remember I have to have good face velocity doesn't matter. What's in the branch line, doesn't matter what's in a trunk line, I have to have good face velocity at the register to cause the air in the room to move, and I create that face velocity by choosing the right size register and locating it where it can Do the best work, and so just very simply when it comes to register selection, you're wanting to keep your velocity to the point that you're inducing in secondary air.

But you want to keep the velocity low enough that you're not creating a bunch of noise and discomfort from having extremely high velocity exactly right. That would be the extremes on one end: make sure you can cause air to mix in the room on the other end. Make sure you don't create a disturbance and when you think about commercial, very, very large spaces, you'll have tremendous face velocities. In some cases you know you'll be sitting in a church or something and you'll be sitting there and you'll get hit in the face with this stream of air and that's coming from.

You know 30 feet away and it makes sense that you would do that because you have so much more air that you need to mix. So it makes sense that the velocity you know could be greater yeah. Absolutely right, but remember rule number. One is don't blow air on people, it makes them angry.

Seventy degree air, you know blowing your hand very lightly. It's warm. You know same 98.6 that time who gave me a chill and I'm sitting in a 70 degree room. So you know don't blow air on people.

Rule number one rule number, two, two more I'll. Let you have the more comfortable the occupants are. If somebody is blowing are on you in a church, they didn't understand distribution. True, I'm just imagining myself like teaching my 4 or 5 year old sons, the life lessons and I sit down - and I say, son rule number one Jack rice taught me this don't blow our on people.

He's gon na give me a weird look but you're terrible. What do you son teach teach them the ways that I've learned from Jackie? Do you River greats just so long as I'm teaching him something? That's the important part all right, so we're going to take a quick, quick break for our tool, tip corner here. The one thing that you may have noticed, if you measure air flow, is the measuring CFM, it's kind of hard to do accurately. I mean you can do it is some fairly accurate ways.

A lot. A lot of guys have talked about the heat rise, calculation for the entire equipment and that's a tricky thing to get really accurate. And then sometimes you can use the fan tables for a particular blower. But then that's especially tricky if the unit's older, because if the blower is dirty at all, then that's going to affect your fan tables.

If your coils dirty, if you have a fan coil, then that's going to affect it so they're. Just it's just tricky. It's tricky to get actual CFM I mean you can use a pitot tube and then you can take the area of a duct and measure the CFM, but that's tricky, and so what a lot of people rely on is using an anemometer, an actual vane anemometer, and You know using the timed average method and kind of painting the vent in order to measure the airflow output. You know either shouldn't say just output, but either the air coming out of the air going in to return in CFM and that can work.

But the challenge there is is, you have to know the K factor, a K factor the area factor for the vent in order to know how many CFM are actually being produced with the open area of that vent is, and that can be tricky at times. But the one thing that's not tricky to do with a vane anemometer is to measure the velocity, and so when Jack's talking about you know having the proper velocity the actual face velocity of event, you can do that fairly easy with the vane anemometer and you can Do that, with the time to average method, it's actually really easy to do with the test. Oh for 10, I you can paint the entire the entire outlet vent and register whatever you want to call it. I always I've always traditionally called them fence, but Jack calls and registers.

So I'm gon na go with Jack and call them a register, paint the entire register and see what the average feet per minute output is and then that will tell you whether or not you are going to be in training the right amount of air mixing. The air in the space or not, and so when Jack talks about that, that concept of getting the proper face velocity, that's an easy thing for you to measure in the field. Even if you don't know exactly what the CFM is going to be, because you don't know the a k-factor on the vent, you can darn well darn sure know, as they say, darn sure know what the feet-per-minute is coming out of that vent. So testo makes the 4:10 eye, which is part of the smart probes kit, and that makes it really easy to do the time average method, but even a better product.

As far as accuracy is a large vein. Anemometer. The testo 417, which i've used quite a bit and you can do the time to average method right and within the actual device itself on the test of 4:17. So if you do not have a vein anemometer on your truck, I would consider getting it because it's a really good way to to make sure that you have the proper face velocity on your registers.

So one other thing that I wanted to mention that I haven't mentioned in a couple episodes is that you can get the best quality tools, all the different tools that I mentioned here on the podcast from true tech tools. Comm, that's t ru tech tools, comm use the offer code gets cooled all one word at check out to get a great discount and I recommend true tech tools with absolutely no reservations. There are great people, and I think, you'll be really really happy with the products that you get and then, if you ever need support they're there to help you both bill and Eric I've met both of them. I've worked with both of them.

If you do end up with true tech tools, mind some tools, just let them know that I sent you all right back to Jack Rhys alright. So I want to ask this question because I think this probably is coming up in some people's minds. Is that when you talk about available static, so you know the static that you have left over for what the system can handle, essentially that you've arbitrarily decided, because, like you already stated, if it's designed for 0.5, you pretty much out of the box are already kind Of screwed, you know you're not going to have 0.5. So now you say: ok! Well, 0.7! You know so I have point two of available static but in certain circumstances, couldn't you have situations based on the filter? That's chosen and some other design elements that you don't have control over, at which you have such low available static, that your duck velocities are now going to be below the desired range how's.

That question makes sense, absolutely does and that's typically, what you find in existing systems that weren't properly designed you got to have a place to go. This all goes back to picking the right size. Blower remember what the available static is. You've picked a blower, let's say I'll use the example in a book.

I need 1,200 cubic feet of air and I'm picking the blower out of the point. Eight column, not the point five column, because I'm never going to be there. I'm never going to be in six. I'm just trying out point eight to see how it works.

I might have to go to 0.9. I might have to go to 1.0 and not all manufacturers allow their furnace blowers to do that. Most of them cut off. At point eight, it's a liability issue.

You know a fire liability issue, so if I pick it at point, eight and I've got a coil that wet is 0.3 pressure drop across it. I subtract point three from point. A time left with point. Five is my available.

Oh wait a minute. I got a media filter in there, a five-inch filter with a point two five drop now. I subtract that, from my point, five I'm left with 0.25. That may be my available static pressure, multiply that by 100 divided by the total equivalent length, and if I'm not between point O six and 0.18, I got a problem and I won't be if my available static is below point four.

This is something I've learned and I don't have a rule for it. It's just doing thousands and thousands of jobs by hand in the old days and with computers. Laying around that. I noticed that if my available static is not at point four, I'm not going to end up in the oh six to 1/8 AK a wedge that I need to be.

So what do you do at this point? Well, I've picked a blower. That was point eight. I could get a blower that would give me twelve hundred CFM against one point O and that would bring me back up to 0.45. Now I'd be in good shape, or I can take the media filter out that had two five and I could put in a disposable filter for 0.05, something like that and get back in the ballpark.

That's the process of choosing a blower and ending up with a friction rate, that's acceptable. I think this is exactly what we're pointing at and just so you're aware. I don't know if you know this, but I'm in Orlando, oh you're. In the Tampa area right I am mommy Tampa yeah, okay, so I've essentially spent my entire career working with a fan, coils yup, very few furnaces and then be flexing board systems.

And so you can imagine how screwed up my brain is because, when you say selecting a blower, I'm like well, how do you select a blower in a fan coil, you know you have what you have. You know when you're pretty much stuck you're exactly right. You have a whole different set of circumstances when you're talking about fan coil one piece units, you don't get to pick the blower. What you have to make sure in the environment you're working in is that you are in fact in 2.5 column, and you should well be in at 0.5 column, I mean external static pressure when you've already included the pressure drop of the evaporator in the tables they Give you for airflow there's no reason to ever be outside of that point five column.

You might find yourself in two point, four point: three: in some cases you know a simple spider system. It's done well, you're, going to end up somewhere around point three right. That is true on the systems that we install where we're actually designing it. You know with some thoughtfulness, probably not with the level that you prescribe and well at least not right now tomorrow.

It will be, of course, because I'm going to listen to every piece of advice you give and that type of compliance Jack. I'm sure you can tell that already: oh yeah, oh yeah! Absolutely so, when we install systems with properly designed duct systems with fan, coils you're right in general, we're going to have point forward to deal with so really is no excuse, but in many cases we're coming up to systems that already kind of have issues. You know that we're already dealing with and the retrofit side of things, which is a different consideration all together. So let me ask that question, because you know you having all this knowledge and having designed all these systems, you now live in Florida.

You move into your first house in Florida and you look at this duct system. What do you do to a system? That's already existing, that has these issues in place. What would your approach be if you were a contractor in this market, where there are all these flex and board systems that haven't been designed with anything other than point one in mind? What's the approach? Well, the easy thing to do is what I did when I moved down here and got in this house and by the way I want a reason I bought this house. It was next door to my daughter who was starting to have babies and my wife.

Just she didn't care what we had it that we were going to live next door to her. So unfortunately, we were both near retirement, but what I did was just rip everything out and start all over again. It was so convoluted in such a terrible mess. I mean it was really poor.

It's a track development. Every house was done exactly the same way, regardless of what direction the wind is faced a typical day here in Florida, you know in the summertime is 91 92 93 where we live. Where you are it's a lot hotter and the unit would run all day and not satisfy the load somewhere to three o'clock in the morning. It would shut off for the first time it was charged properly.

Air flow was as good as it could be under the circumstances you know, with the fiberglass duct board box and 50 feet of Flex thrown in every other direction. It was undersized. That's the other problem you're going to find now what I find generally in the field, regardless of the climate I mean, if I'm in New Jersey or in Florida, it doesn't matter. What I'm finding is that, if it's an overhead, the duct system is usually larger than it needs to be, because they use point one and when it's a furnace, coil combination basement crawlspace, whatever it's way too small the ductwork, because they use point one.

So you have a lot of latitude, especially existing systems. I would look very carefully at the Flex. Duct make sure you understand what is it appendix three? I think in manual D, about compression and sag, and things like that that can really when it comes to flex that dramatically affect the airflow. I had a little routine.

I used to do when I worked at air group in New Jersey. I was hired to train everybody in the company and I would be with the installation technician on a job, a new guy, that I want to see how he was doing and we would have say a three ton air handler in a box with a big, maybe 30 by 30, 30 by 24 return grill. We would have a 16 18 inch flex duct coming off of that box, where the grill is in the ceiling, I'm in an attic and that would be attached to the return plume and, of course it would sag. Even if it was six or eight feet long because of the weight of that mass that flexed up, so I would hook up a magnet hillock put.

You know the negative probe into return facing the direction of airflow the supply. The positive probe in this supply facing the airflow I would start to unit up and then I would hold the bottom of the flex duct and I would push it up so that it made a nice 90-degree angle, nice, smooth turn and the drop-off of pressure. It would go from like point five point: six down to 0.02 0.03, something like that. It was extraordinary, but it burnt into the brain of that new guy.

How important it was to have everything at right angles, everything's straight and plumb and vertical, and I would just move it up and down and we use the Magna helix, the dial gauge and an analogue scale would just go back and forth and back and forth. As I moved it up and down it's a great teacher but flex duct look for compression look for sag. I can tell you just from memory. I've taught it so many times that if you take a piece of 25 foot flex, duct uncut and you put it into a 20-foot span - that's 25 % compression and the maximum compression allowed by the air diffusion cancel the ADC.

The people that write the Bible for installing flex duct the maximum is 4 %, and I know everybody, including myself, won't cut five feet off of a 25 foot piece of flex, you're just going to put it in here and that slight amount of compression you're creating.