System Design - Duct Sizing

[@Hector-01]

5yr later still an Awesome video, great explanation and example. A+

[@mhagnemae5202]

Beat video on duct sizing I’ve seen to date. Thank you!!!

[@CMN843HVAC]

Yes working my way through as an Hvac Mechanic and this is helping me a lot just got great news from my local sheet Metal Local and they want me to join on next opportunity 👍

[@stefangray692]

Excellent video. Really helped pull of the complicated topics of duct design together! Thank you

[@saiNawKhamOo-o4l]

You Gave Me Very Useful Lectures. Thank You For Engineering Knowledge.

[@afaisal91]

Very informative and very well presented.Thank you

[@tosayd3740]

Excellent explanation

[@wisamrabeea4026]

Sir, I never see anyone explain very good like you. Thank you so much. Is there more classes regarding HVAC?

[@cmolnar65]

There are a ton of videos on this channel that go from the basics and work their way up. Check out my playlists.

[@alexzapata692]

🐐🐐✊🏽🙌🏽👏🏽👏🏽👏🏽👏🏽👏🏽 Thank you so much for this video. Very well explained. Definitely going in my favorites.

[@viniciusbraga5846]

Awesome content! Thanks for sharing it

[@kingofkingstm1]

Thank you You are my hero 🦸‍♂️

[@Reg4JesusChrist]

Greetings Dr. Molnar: Thank you for reviewing my question regarding available static pressure at the 9:40 mark. My reason for the question is because the textbook did not mention what I am about to ask specifically. I wanted to make sure my assumption is correct. When calculating the ASP, I understand we are using the Total Effective Length (TEL). Here is my question. In this example, when we add the supply register, are we ONLY considering the one for the TEL of the supply branch? If so, this clears up my question. Secondly, if the TEL of the return branch has TWO return grills, would I use 0.06 for return grills? My reason for asking these questions is so I can "make peace" with myself that this particular example only considers the TEL of both lines. The textbook never said that, and I always assumed this was true, but I wanted to confirm this if possible. Any guidance you can give will he much appreciated. Thank you SO much for all of your videos.

[@mintukhan4883]

Thank u sir for giving us good video which I need..

[@centrumsolutions4744]

Excellent video Christopher. This is indeed the best video Ive ever seen about duct sizing. Could you please do a video on duct layout too? Sincerely

[@jamesrobertfellabaum1665]

Effective length round is 20:50 but Rectangle is 20:75. Does this mean Rectangular ductwork is better? Or is the higher the number mean its worse?

[@qeesher]

Thank you for the informative video. The only thing... Could you also make a video, how to choose a blower based on the duct/trunk sizes? I see a lot of oversized (compared to trunk sizes) furnaces tripping on hi limit, failing motors etc. A lot of installers change furnaces but dont match it to the duct sizes. Thank you 👍

[@cmolnar65]

Working on something that may help. This is not the ideal way to size equipment, but I may have a solution that won't tell people how to do it the wrong way. If you haven't already, please subscribe so you get notified of the new releases: kzbin.info

[@libertus8924]

I have a 420 square foot building with a furnace and a 19"x12" x 4 foot plenum. I bought 16"x8" rectangular ducts that run 24 foot long with six 6" vents. Are the ducts too big? Should I go with a 14"x8" or a 12"x8" duct size? I haven't installed the 16"x8" yet so I could exchange it. Thanks.

[@andy3590]

Why would you count the take offs of a straight run when you are figuring out the tel?

[@HVACTutorial]

Nice video

[@yamazaheer6966]

Can you please make a video on how much cfm we need for each room ? Like cfm for this much of room size, thank you very much.

[@SamarKakakhel]

This is not how it works. You are actually talking about load calculations and there are many factors you have to take in consideration.

[@theusername07]

6:20. On system design pressure. How do you know to select .1 or .5 wc?

[@cmolnar65]

Equipment specifications are the primary decision. What can the blower and air handler handle?

[@jt3366]

Why wouldn’t you rather design for .1 and run your fan on low speed and the cfm would be pretty close to 1250. Seems like you might have less fan noise, and more efficient.

[@theusername07]

@@jt3366 Right. I've been designing for .1 wc since I started the trade. Now I hear guys saying "designing to blower specs". Some air handlers have a design pressure from .1 all the way to 1.0..

[@craigestelle9553]

Great information. I am currently working on adding air conditioning to my house. Do you design HVAC systems as your profession? I would like to hire you to design my system if possible.

[@ProfCharltonAcademy]

excellent video , thanks alot

[@deekshithns8491]

Dear Sir, I have one query, When designing the HVAC supply duct system, After calculation of ASP from the manufacturer blower data and Device pressure losses. That ASP will become the pressure drop budget for the duct system. Now if we are designing the duct system with equal friction method based on FR calcualted...and CFD analysis of designed duct fetches static pressure and total pressure data w.r.t our design. Now w.r.t ASP which is our pressure drop budget, say some 0.4 inches of water gauge. Now to check whether duct design is within limit in CFD analysis tools. which pressure drop should I consider ( it's a total pressure in the volume or it's difference in Total pressure at inlet to outlets, or it's a max static pressure developed in the air volume inside duct) kindly clarify Dear Sir, I have one query, When designing the HVAC supply duct system, After calculation of ASP from the manufacturer blower data and Device pressure losses. That ASP will become the pressure drop budget for the duct system. Now if we are designing the duct system with equal friction method based on FR calcualted...and CFD analysis of designed duct fetches static pressure and total pressure data w.r.t our design. Now w.r.t ASP which is our pressure drop budget, say some 0.4 inches of water gauge. Now to check whether duct design is within limit in CFD analysis tools. which pressure drop should I consider ( it's a total pressure in the volume or it's difference in Total pressure at inlet to outlets, or it's a max static pressure developed in the air volume inside duct) kindly clarify

[@roanpham9417]

Hi Christopher, It's great! Thank you very much for your showing. If there are multiple levels, 1st, 2nd, 3rd level, how do I calculate ESP? If there is a VD after transition on straight duct on 3rd level and a VD on a take off duct drop down 2nd level, all two VD are calculated in ESP system? Thanks

[@cmolnar65]

Roan, remember static pressure has nothing to do with "movement" or velocity pressure. So once you use the longest length method the static pressure will not change. Just make sure you are using the correct longest length and size all risers from 1st - 3rd floors appropriately. I will sat that if you are doing multiple floors and have the opportunity to zone them with a 3 zone damper system (thermostat on each floor) I would consider doing that.

[@stickystick105]

thank you helped a lot!

[@tin-knockerindustry4868]

Where do you recommend me going to find more information on duct design ...looking to study a further on my own .

[@cmolnar65]

SMACNA manual first, and then also ACCA has some good material. I can't put specific material names here, but both of those organizations have good stuff.

[@somkiattjmanmark49]

👏👏👏👍👍👍 thank you 🙏

[@wyleaziz5050]

Why only 354 likes for this free treasure?

[@shawnfleming4511]

Excellent lesson! How do I enroll and become one of your highly educated students.

[@cmolnar65]

Hi Shawn, I am no longer teaching at a school, I decided that I wanted less stress and returned to the field. If you want the best education I would recommend contacting your local HVACR union or a community college. If none of those are around take a look around at the for-profit sectors, but ask a ton of questions, preferably from a teacher not an administrator. My videos hopefully will get you in the right direction but you need the hands-on found in a formal program.

[@shawnfleming4511]

@@cmolnar65 Thank you!

[@brutoof_ai]

FR=asp x 100 / tel