HVAC Duct Design: Manual D, Fittings, Friction Rate, Pressure Loss, & Static Pressure w/ Alex Meaney
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- Опубліковано 23 лис 2024
- We're back again with my HVAC design calculations trainer Alex Meaney (MeanHVAC.com), to talk about duct design calculations, the Manual D and ASHRAE ways. Thanks to Southwark Metal (www.southwarkm...) for the sweet training posters:
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Different Room & Outdoor Design Temperatures: • Different Room Tempera...
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All HVAC people and DIY Homeowners should watch this video.
I started on the journey of adding a central system to an old cabin with several small expansions. Up until that point we had a small oil furnace from the 70's (still works).
Every quote has been 18-20k. Here's the kicker, the three contractors, all top rated in the area, provided a quota in that range. Selling carrier rebranded Gree. (yes the same thing as the DIY systems).
Not one of them arrived with a laptop, an ipad, a notepad, a PHONE, or a measuring tape.
I finally asked the 2nd to last guy, what their plan was for the duct. One big plenum box the size of the air handler, going out 36-48", and a spider. The return, in the center of all the rooms in a hall, one giant one ...14" duct.
So I set on the journey to learn more about ductwork, design, friction, system sizing, return, and of course how to get ductwork through this crazy system.
Sadly I either must put the air handler in the attic or in a smaller bedroom but all the duct would be routed through the attic sans one 12"
That contractor list would be a game changer. Even the Mitsubishi Diamond dealers in Chicago have no idea how to design a ducted heat pump systems. Most are upfront and say they will not attempt to do it but a few just ghosted me. I as a homeowner took this on myself and am happy I did since I know any contractor I have spoken with would have not taken the time to properly size, route, and seal the ducts to the degree that I have doing it myself.
GOOD WORK buddy. I’ll have it up asap.
@@HomePerformance Where can we find this list when it is ready or maybe it is already posted somewhere? Planning a build now and would love to get ahead of the game.
Check our latest vid, Mr. Beans
@@HomePerformance Thanks!
Many HVAC pros want to do most jobs as quickly and with least costs involved, yet still charge premium rates, at least thats how it is here in central valley ca!
Central Florida beach town. We’re a Diamond Dealer. I have to redesign almost every system that Engineers design. If they actually installed Residential HVAC, that might not be the case. Most Homes are Icynene foam encapsulated Attics that are treated as conditioned spaces. Bottom line…the CFM in each room is what I grab onto. Field conditions dictate duct design on these Monster custom Homes. Everything looks great on paper. We basically somewhat oversize all ducts compared to old school flex sizes. The new ECM motors need the extra breathing space. Prolific motor failure rates when slapping a high SEER system on an old school duct system. Just some thoughts from the peanut gallery!
9:10 To add some context about filter pleats: on our Helicopters we have pleated intake filters. These are about the size of a large residential furnace filter, 2 inches thick and oiled (washable and reoiled) there are so many pleats you can barely fit anything larger than tongue depressor between them. This filter passes 17,000 CFM with a pressure differential of less than 8 in-H2O of pressure drop as thats where the Low Pressure switch illustrates for emergency bypass door activation.
And we fly these filters on fighting wildfires with water buckets on fires lines with heavy ash in the air (reduced cleaning hours though). We can operate them in normal operation for 300hrs between cleanings, for a total service life of 4500hrs.
(Edited because I converted 2.5kg/s air to CFM wrong initially)
Haha geez man. Awesome details.
Once again great presentation that made sense to us Non technical folks out here. Again, after watch all your vids (along with Risinger & other quality building science folks) I'm a bit saddened that I'll have to custom build my next home, just to get it built right on a building science perspective, & not because I want high end finishes. (it would be nice to have both, but not made of money and would rather have the money spent in the right places, as opposed to cosmetic ones)
Spot on. Same here. I'm planning a 2024 build and will be forced to use expensive contractors just to get a quality, efficient envelope to start with. We will be sacrificing many other things to get the comfort and air quality right, which *should* be the most basic things.
My dad worked for "Skidmore Owings & Merrill". He was telling me about one building he did where they only supplied heat. I think it was a concert hall of some sort. They needed it to be very quiet. He designed it similar to a data center with a structural floor, then 4 feet above that, a false floor. The plenum space between the two was used as the air supply (instead of duct work). The seating was bolted to the floor, and the registers were located beneath the seats. The air return was located on the far side of the performance stage. By having such a massive surface area for both the registers and the air flow, the ventilation was effectively silent.
Gotta love Alex Meaney! I just tiok a 2 day class from him. My design consulting business is stronger because of it!
This is the side of HVAC I really enjoy. Thank you for the information guys.
This is why I'm scouring UA-cam, so I can can make smarter decisions as we get started designing our future home. We won't be able to afford all of the best/better options, but info like this will go a long way in being long term smart setting the priorities of where to spend the money. Can't wait to see that list of contractors & desperately hope that one or more is in my area.
Strong recommendation: Do not use central forced air.
A mini-split heat pump system will do much better in heat balancing areas. You can also control rooms individually.
Small pipes carrying cooling fluid (like water, glycol, or R type fluids) around are much lower loss due to dramatically less surface area, and easier to insulate to get even better efficiency. Smaller pipes are also much easier to route and run on install.
You can get mini-splits with in-cavity design so you don't need the ugly surface mount units.
@@quentintodd5856 even for a smaller house, that's almost certainly going to be dramatically more expensive & I'm already having to make cost/benefit decisions & delaying some features to future upgrades.
Great video! Also, great idea to have a database of contractors that pledge to adhere to the science of system design!
I'm working on designing my house around my hvac system not vice versa like 99% out there. Found this video doing my research.
Good work
lol insulate it just as good
I love this! I need to know more. I’ve been doing this since 1995, I need to update some of my practices. Some things I do as a constant are the things he said we should be doing.
This is something i hope we learn downunder as ducted systems get more popular.
But getting them to design a house with heating and ventilation built in is major problem at the moment.
Update: I just inspected the run of flex line that runs to my room and found 3 inch by 2 inch hole in the side of it next to the trunk line. I spray foamed the hole and the duct works much better now. Unfortunately I am a big guy at 6 foot 6 and don’t fit well in the attic. After summer, I will get someone out to do a proper repair.
The effective length of fittings can have a significant effect. Every room in the house was 69 degrees when it was 104 outside. My bedroom at 10PM was 84 degrees(hotter during the day). By removing the grill from the duct, by 10PM my bedroom dropped to 71 degrees, and was 78 during the day.
Also all of the other rooms are fed by 8 inch ducts, and my bedroom is a 4 inch or 6 inch duct. It was quicker and easier to remove the grill than it will be to replace the duct line. I also don't want to be cruel to whomever the worker is. It was 109 today at 60% humidity. It is probably 140-160 in the attic. I can wait till the fall when it cools down.
Let’s go! Looking forward to learning more about this
@Alex Meaney I do the same thing! Once you educate the contractor that their oversized/ under ducted netting the lower tonnage.
Great video guys!
It’s so so hard to find a competent residential hvac firm that will actually do a manual D at all, let alone correctly. My god, you can even get the vast majority of subs to use hard duct !
You can find one but it's not going to be cheap! I work for a residential HVAC company. For custom projects the Owner and Install Manager will happily do a full custom duct system and design. It can be $20,000 for all metal ductwork installed plus the system (west coast prices).
@@KPHVAC And that's the huge issue with building in general; doing it right is too damn expensive and out of reach for normal people, so we keep building inefficient houses with crappy HVAC. There is very little incentive for your average HVAC company to bother with this stuff when most people can't afford it anyway.
@@DeuceDeuceBravo I totally agree!! The price of everything is insane and we don't have enough skilled labor in this country. We need more young adults to get into the trades. I'm happy to work for an amazing company with fantastic people. They all do fantastic work and they get paid well for doing it!
Yep. Not enough Customers value it. Not enough juice for the squeeze in most cases
It’s literally impossible to find a hvac company but there are 3rd party companies that do load calc and duct design. But still finding. Ahavac company capable of doing it right is next to impossible.
As a homeowner we switched to a ductless multi zone mini split inverter heat pump. We always had cold registers at the far end of the octopus box and drafts. Never going back to ducted heating again.
Thanks Guys...this was Great!! As an Owner/Builder looking for design help, slash, a contractor that likes and understands math, your videos are extremely helpful. Once you put your list together, I need someone in the Charlotte area. 😉
Wow, what a great deep-dive conversation... even for non-HVAC contractor folks like me! 😎
I really hope you and Alex are successful in creating this list of Science-minded contractors because it is extremely hard to find them.
Between your ducting install video and this one... man, do I need a dedicated & thoughtful installation contractors in my area.
Cheers, Eric
I have a big attic with a 12/12 pitch roof. when the second floor was added they created a conditioned utility room in the attic with the HVAC but the duct work goes out from their into unconditioned spaced and then the bedrooms. Could I build an enclosure around the duct work using polyiso panels to make it almost = to conditioned space? All duct work lays on the ceiling joist so I think it would be easy to do. What concerns would I have (mildew)? I have a main 20x20 main duct that goes from the conditioned attic room near all the vents with feeder lines off it to the vents. live in the Chicago area.
Thanks for the video, I learned something and look forward to finding more videos like this.
👍
@39:30 yes.. finally a list. I have started asking if they were familiar with your channel ( or even spray jones), if not.. I recomend it.
And very true.. if they don't agree to this process in the first place, they are pretty much in the old mindset, and don't care.
Because of this.. lack of care I am still having issues with my new system. Unbalanced rooms.
I’m not able to do installs anymore due to health issues and I’ve been in the field 9 years I’m 31. And I want to get into load calc side to use my brain to help design duct systems that will be perfect for all these new systems. Because I’ve seen company’s go with the same tonnage with old duct and man problems arise
Keep in mind that fitting TELs are dependant on the velocity of the air running through them. Manual D shows them at 900 FPM which is the max velocity in residential supply ducts. At a lower velocity (bigger ducts) the TEL of fittings goes down.
Video idea from a Canadian viewer.
I am starting to learn about the CSA F280-12. I am guessing they are similar, but I would be interested in knowing the differences that exist.
Haha already in process my man! Stay tuned.
Great video - I'm fighting HVAC problems in a new construction house, and the General Contractor's HVAC guy looks like he has spent more time in rehab than working on HVAC, so I am trying to work backwards and fix the problem myself, which appears to be a duct/airflow problem. You wouldn't believe the work it too just to get them to re-size the filter on the furnace to the correct size called out in the manual (they had a 16x25 instead of the 20x25, which if you do the math is about 20% smaller than it should have been). It is too bad that it is so hard to find trained professionals who really know their craft in the trades these days. Thanks for the educational video guys!
How big is your unit?
Giggity
Fantastic, and PLEASE say more about make-up air. (I'm in zone 4C) If the duct is at the range hood, is a simple filter box adequate?
Great stuff , ill be happy to understand how we can get more training and information about it !!
I believe I met your trainer in Elizbethton KY for a training event for Wrighsoft.
Ok, I don't do HVAC, but I do things that often require steps that tend to be either hard or annoying and tend to be frequently short-circuited (literally in some cases). I have to say I LOVE the bearded guy (Alex?). His attitude of 'shortcuts are bad' pretty closely matches mine in my own realms (computers, electronics, and radio). There's a lot of stuff you can "get away with" and things will "work". But you'll always get better -overall- performance/quality/whatever's relevant by taking the time to actually do those annoying or difficult steps that everyone tries to ignore or bypass.
I think its easier to think of it like gas pipe sizing. Btu's per room cooling and heating. .that will determine the cfm needed which will determine the take off run size. Making the shortest run possible. That takes you to the trunk and as you work your way back to the furnace you duct size increases till you get to the plenum. rule of thumb is to stay under 16 vents per unit. Now you have2 blowers two choose from . as it turns out . the heating size on a modulating or 2 stage is always right. now make your return to match or exceed the volume the supply needs factoring in the added coil.
Fantastic idea! Would love to see Olympia, WA area on the list. Thanks Corbett!
Can’t wait to watch this! 🎉
I have a very central located furnace in a square house (renovation). Can I come off the plenum like an octopus or Medusa and use a damper on each one in order to fine tune balance?
Would love to get your thoughts on the Rheia duct system and how using many small ducts in parallel might bring benefits and the downsides from a performance standpoint.
It’s on the list Brenton
I’m in Middle TN and my local HVAC contractor absolutely refuses to install a dehumidifier in my encapsulated crawl space and refuses to install an ERV, whole house dehumidifier because of the amount of humidity in TN and the heat that dehumidifiers create. He wants to condition the crawl space by incorporating the crawl into the HVAC system just the same as the conditioned attic. He also recommends a two pipe (in and out) vent hood for the stove/cook top. This is a new construction 3800 sqft build two story home, 2x6 exterior walls, 2” of poly iso rigid foam, open cell under the roof decking to the top plates and 4” of crawl space wall insulation. He’s recommended a 5 ton or a split 2 ton up 3 ton down stairs SEER 20 Mitsubishi or Trane variable speed heat pump.
Any updates on this?
True and True no thought of where duck work goes.Thats why so important homeowners have to get involved
What is a reasonable price for new duct work?
10 runs (10ft - 30ft each).
2000 square feet ranch, single story, AC in attic center of the home.
I had a couple of those manuals, I grabbed from a house cleanout
This video is exactly why I'm spending the money on an engineer to do a Man J/S/D for my new house this year. After watching this video the $3000 quote I got seems like a steal
Is the list up yet? Where can I find the list of contractors that know about this stuff?
Yes, the list is up with about seventy contractors:
homediagnosis.tv/hvac-installers
Also something that was not mentioned that is a wide problem is Flex Duct Compression. 10% - 15% is super easy to have in a mediocre install and will instantly undersize the whole duct system, thus leading to the upset customers.
Just had a Bosch 2.0 IDS installed in our existing ductwork located in the attic. Things are working out ok for now (92 degree days we are maintaining 72 on the bottom floor and 69 on the top) but I really want to reevaluate the setup and ensure the ductwork is optimal (outside of being in an unconditioned attic, which we can't change). Do you offer a service for something like this? What I'm imagining is giving you a layout our of ducts, and you making changes to it/redesigning the whole thing to work better. Would love to hear what options we have. I know for a fact that a there are aspects of this duct design that are not ideal for my system, and I really want to get it right. Bosch has a static pressure charge that's used to basically set the two speeds of the blower, but I'm sure there's more to this as the system was designed in the 80s and there are two balancing dampers (one on the supply/return) which are fully open. The supply ductwork is branched galvanized with parallel flex feeding the top floor, and flex feeding sheet metal ducts in the closets bringing air to the first floor. As it stands, the first floor is always 2 degrees warmer in the winter. I'm sure a lot of the ducts are undersized for the needed CFM of the room. My grills also have dampers that you mention in your video that can be manipulated to get more velocity out of them, but we haven't messed with that. Lastly, the end of our straight supply trunk run is into a massive vaulted part of the house and that room suffers the most and is usually 2 degrees warmer unless I mess with the balancing dampers. Long story short, I just want to make the ducts better and if that means I have to redesign it, I'd be fine with that. Very handy and would love to pay for that kind of service.
We live in south Florida, we need to replace our ac duct work ,should we use flex or a metal aluminum duck? Also what would a general price be to replace a house that is 3,1000 square feet. We have 21 supplies, 2 returns that we need to add. Thank you...
How do you feel about duct sealant sprays that are meant to seal the inside of ducts to prevent loss. Are they safe long term? Any odors?
Get your mechanicals figured out during the building plane phase!! One day I will custom build a single story home with a 5 foot crawlspace or unfinished basement so everything has space!!
Is there a capacity in manualD to measure, test, and evaluate an existing duct system and use that to determine if the existing duct system is sufficient or can be adjusted to better fit the existing equipment (or a new system)? That feels like a missing piece in the whole conversation around retrofitting a pre-building-science house into a BS-aware home.
Interesting Q, Thomas- will put this vid on the list, but short answer is static pressure mapping, duct leakage testing, and velocity/cfm measurements at grilles. All of which we have separate videos on.
I'm doing this exact thing at the moment as a DIYer since I could not find a local company to do this work and the geothermal company I'm working with seems incapable of doing a correct duct design. The approach that I'm taking is following all of the normal things that you might do like figuring out your Max ESP, TEL, ASP, etc. Then, you need to figure out what you can reasonably modify and what will need to stay constant - for example, I have several ducts going to my living room that I would consider "undersized", however they're buried in spray foam and can't easily be accessed or replaced. Similarly, the main trunks are considered constant since due to the construction of the home, it's not reasonable to upsize the vast majority of the trunks. Once those constraints are in place, you can start playing with the numbers for each individual branch to see how close you can come to the ideal design. It may not be possible in a retrofit situation, but you can probably come very close.
@HomePerformance my question to you is do you know of any contractors or professionals that would be willing to consult for an hour of time to double check that work and review the overall design?
homediagnosis.tv/pro
In regards to residential properties, doesnt variable flow cassette style multi zone minispits, make all ducted central hvac tech, obsolete and unnecessarily expensive?
Long shot. Does anyone knows where to begin learning how to design my own incinerator complete with blower and heat management and whatever it is that is needed to that I don't blow up or collapse while in use? Primarily for burning paper products. sized probably about 10ft x 10ft x 10ft? I won't be worried about emissions at this stage as I plan to figure that out after I learn the basics of the incinerator. Also can the HVAC softwares mentioned in the video be used to calculate the ductings for incinerator?
The size of the filter the thickness and filtering depends on how dirty you are..
I use one of those old time mesh spider web looking filters.
Clean blower.
Any info on return plenums? I’ve read somewhere manual d specifies return plenums should be sized based off of blower wheel diameter, can find it though.
What are the names of the software programs a good HVAC designer should be using? I'm working on my dream house design and would like to make sure my GC and his HVAC sub is on the right path.
A HVAC business that is good at these designs are not always good at execution. Duct work is usually an entry level position. A good designer and a good installation technician working together will ensure a good job. I was good designer / salesperson but I had no authority over the installation team or what team was sent on jobs.
where is the link to the digital ductulator?
When do you use fiberglass liner to reduce sound? Is it best to use flex duct runs instead for reducing sounds transmission and duct noise?
need to run 3 more ducts to upper rooms my 2nd story has no heat, would have to get something that can fit in the walls, is this possible on a furnace only supplying heat to the 1st floor, I live in WV and the upstairs is unusable in winter, and it is where my shower is, not fun showering in the cold
@HomePerformance @Alex Meaney, at 13:00 when you say "the outside air should come in, touch the grille, and then leave" how exactly do you recommend setting this up? I've been advised that bringing in air near the hood, especially if using a powered make-up air fan, can introduce turbulence that might push the fumes into the kitchen. What do you think about a grille placed right behind the range pointing up at the hood to essentially capture air up the way up? Or does it have to be pointing down at the cooktop, to then touch and return up out the hood?
Hey Andrew- like this: 3 Rules for Kitchen Make Up Air Systems: HVAC Training for Home Ventilation that Performs
ua-cam.com/video/36eMZNyAlGY/v-deo.html
Greenheck and CaptiveAir no longer recommend this method of introducing MUA(front of the hood). Disappointing because the idea sounds great. Alternatives are a duct going down close to the floor behind the range or just a run in the room to prevent depressurization while not affecting hood flow. With residential systems where the variable speed fan may be utilized the throw of the MUA would be inadequate in low demand conditions as well.
I would love one visual aid for majority of flex, metal, and duct board equivalent feet
Corbett, if I'm ever fortunate enough to build my own house, I'm hiring you as my GC
Aw shucks
Same
Could someone post a link to the Southwark duct fitting poster shown at 18:40. Would be helpful couldn't find it..
buildingperformanceworkshop.com/blog/2023/5/12/manual-d-duct-design-with-alex-meaney
I've never seen someone avoid eye contact this much🤣💙 some fantastic information.
Oh man. It's so depressing how much work, and engineering has gone into proper duct/HVAC design. Yet almost every HVAC contractor will STILL just say "you need 600sqft per ton and a 6" duct to every room".
Hey Corbett, any chance of getting this as a Podcast on your Building Performance Podcast channel? I just don’t have time to sit and watch many 40 min videos.
Hey thx for the q- drowning in my to do list as it is, probably won’t get to that. But I do have a podcast ep coming soon!
@@HomePerformance awesome, looking forward to it!!!
Do you guys help with master exam knowledge? Im studying for the HVACR masters exam I got 6 books and have no idea how to study for it other thwn read through the books hope and pray I can pass it
I don't get how the air inside the duct moving more slowly would chill the outside of the duct more than air that is moving faster. If the air is moving fast, then each unit of air sucks less heat out of the duct skin and surrounding air, but the units of air are moving through and being replaced inside the duct with new units of air fresh from the chiller. They're going to chill the duct skin more than the slower air!
The only solution to the condensation problem is to have the air outside the duct conditioned so that it won't release condensation onto the duct skin just because the duct has cold air inside it.
im using ashrae dw 144 lib to calculat friction loss in strait duct and fitting when im drawing 3D duct run in AutoCAD MEP in real time
Mannnn I spent THOUSANDS on my system. And it is terrible. The ducting is my issue and now I have no money to rectify it. Hard pill to swollen here in the northern Midwest.
Do like to share this interesting video about the HVAC Duct Design, please.
I nominate The Comfort Squad in central Virginia for “The List”.
You will be the first people I ask. Especially considering Jon did my own home’s duct design!
28:22 🤔 interesting I would have thought that is what should happen when you live in a cold northern climate MN
Is there a better (and not prohibitively expensive) way to condition make up air for hot/humid summer and winter seasons?
Thank you so much!
This is why they charge so much to use the wind tunnel friction thing nascar uses
16:00 the fact is that he didnt bring up that the heat is warm air now not hot air. Also we have cool air not cold air.
I cant even get the hvac dealers to offer referrals for design, their answer "go find an engineer"?????😮
Exactly Jeff
Cone Segmental Elbows, Cones and other.
Dude on the right needs to let OG talk.
you should let you guest talk and not cutting him off
Fireplace makes a house a home.
“Not comfortable with math” Sweet low key way to say challenged lol
Finally everyone keeps looking at me like I’m retarded the hvac guy says my unit is not big enough but I think that if I put the ducts in the house instead of outside the conditioned area I feel like it’s adequate
I thought an attic is suppose to be the same temp as it is outside…so putting ductwork or and AHU up there wouldn’t make sense.
Conditioned attic is the opposite- same temp and RH as the living space
@HomePerformance And the reason, Corbett, is that over the long term, it cuts down on operational costs of the hvac system?
Vid coming soon unicorn
@@CajunGreenMan Of course it does. Current duct insulation requirement is R-8, it used to be R-4.
It is very common to find a million dollar house with a terrible HVAC duct design. I would venture to say that 70 per cent of duct systems are not worth the money paid to put them in.
Is ductless better than ducted?
You’ll never guess- we have a video about that:
HVAC Reality Check: Are Duct Systems Dumb or Essential?
ua-cam.com/video/5VPqFSITm0w/v-deo.html
Nothing like a multi million dollar home with atrocious flex monster attic duct and hideous crooked basement duct work. Makes me want to flip out sometimes. HVAC is always the last thought and you’re so right about the stupid 10” range vent hoods that nobody needs unless you’re a professional chef.
If they don't design the distribution system correctly, the seer means nothing...
Use flex all day long on million dollar builds. No issue no wide temperature differential between rooms well within 4' code ususally within 1'. Use Wrightsoft and common sense. It goes a long way. Wish we could use more trunk and branch but builder won't pay for it. All RNC market is nothing but flex and boxes.
But if im growing pot..... i mean lavender i may require a certain area to be 60RH 60°F.... as a former tinknocker this seems all too easy....
Edit i live in an apt building.... be very quiet installing.... shhhhhh
Whoever created that duct design must not like square supply registers.
I’d love to find a manual D explanation that’s aimed at 5th graders. The terminology looses me every time.
Vav boxes replaced by raspberry pies, relays, and solenoids.... pnuemantic controls at your finger tips for dirt cheap.... just got to be commfortable with linux....
Tecchnology is carnivourous.... who needs a siemens controller..... not meeeee
Clearly not building in a cold environment. The building science doesn’t support your OPINION!
👍👍👍👍👍
Thanks for this information.
Corbet = I would love to see you do a collaboration with Incredible Tiny Homes: youtube.com/@IncredibleTinyHomes
You two could offer a super well sealed tiny home that people could buy!! I like what Incredible Tiny Homes is doing but they need a high efficiency option that you could help them with!!