Air Duct Calculators: How To Size A Duct System For A House

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In this video I explain how I have used a ductulator to design a duct system for a house. This video is filmed to help fellow HVAC technicians learn industry standards for supply and how to size duct systems for homes. This is particularly helpful for the NATE Review Exam.
In this design we are working with a three ton system with 400 CFMs per ton which is the industry standard for supply. We'll also walk through the process of determining when and how to add more than one return to your system.
It's important to use the correct duct sizing in your design so that your unit is not over taxed, does not experience high amp draws and does not experience various issues with your air handler or compressor.
Thanks for watching!
- David
David@DavidJonesAC.com
Follow me on Facebook: / david-jones-ac-1010702...
** Please do not attempt this at home. Only a Licensed HVAC technician or Licensed Electrician Should Attempt what is shown in our videos. They are just for reference only.

Опубликовано:

4 июл 2024

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Комментарии : 31

@rodrigorodriguez7410 2 года назад

200cfm for free??. You are a such a nice guy Mr Jones.

@CarlosMartinez-gd9ux 2 года назад

I really appreciate you helping the H-VACR community 🙏 Thank you !!!!!

@shawnroddick7523 3 года назад

i like the videos i did a/c service for about 3 yrs and was tired of the hours so i went into another career but i still like learning about this stuff i have no idea on the static pressures and didn't have an idea on my return grill size either so this has definetly helped alot! thank you so much for helping further my knowledge of the field i will be using this for better efficiency

@kwiz8848 3 года назад

I learn something new each time I watch one of your videos

@mohammedalobaidi9981 Год назад

Thanks Mr. David for these videos.

@eliazarsanchez9495 4 года назад

Good videos sr. David Jones thanks for your help everytime you make at videos.

@zaidalithawi6773 2 года назад

Thank you very much Very useful and helpful information I’m a new hvac contractor and the info in your videos helped me out a lot

@jimmyjean6663 4 года назад

Nice video, I love it. May God bless for sharing your knowledge to me as a new apprentice to the field..

@jonesacnaples 3 года назад

Thanks and welcome

@quengaskhan7171 2 года назад

Thank you sir 🤙🏽🇬🇺very good info

@JulesODwyer 4 года назад

Great Video but lots of guys in the Trade may know the refrigerant side of the equation but have No Clue on the Airside and how it affects the system.This is the reason all A/C guys just starting in the Trade should Install for a Couple of yrs before learning the Refrigerant side makes a well Balanced Mechanic.Yrs ago I was subbing an Install the guy was a Refrigeration Mechanic,Coolers. Freezers etc .I asked him what size for each room he said just put 9inch in every room then I asked him you ever sized an A/C system and he said No ,I shook my head and took out my Ductulator and sized in for him ,Lol

@jasonLeno 2 месяца назад

Everyone talks about the branches, how about sizing a plenum????

@marvinweinberg1715 3 года назад

How can you calculate the duct work size without consideration for the component friction loss including register AK factor and the total equivalent length of the duct runs after you have that info then you could use the duct calculator

@RichardT123456789 2 года назад

Hello David, How would you calculate a mobile home split system with an inside down flow air handler 3 ton . No return . The Mobile home is 16X80 single wide with 8 vents total. The original duct is the rectangular sheet metal, and it is degrading.The mobile home is 1999 model . The local supply shops do not have the sheet metal available & I am considering using Flex duct & I am not sure what size or may I even use flex duct in replacing the sheet metal . Thank you

@ascensionpm1742 3 года назад

Hello David, I enjoyed your video. I have a large upstairs room that I am trying to cool that has existing AC/ heat. We recently took out a tree at the front of the house and noticed that the room is not cooling like it use to. Would it be wise to add another return air vent in the ceiling in this room? The room is 9 ft tall by 20 ft x 15 ft and has three vents that are feed by one 12 inch flex supply duct (split three ways). The nearest return air vent is about 20 ft away from the room entryway. Any advice would be helpful, I am going to do this myself if possible.

@larryzdanis5377 Год назад

If you keep the room door closed, then a separate return in the room should increase the cooling airflow to that room; if problem exists even with upstairs room door open then an extra return wouldn't make much difference - in that case, you may need to balance the supply flows to increase the flow to this room relative to the other due the added heat load due the absence of tree shade.

@shawnroddick7523 3 года назад

ok a little confused here if the duct size is to low its causing an airflow restriction on the low side the high side is breathing freely unless installed without enough room. So why would head and suction be high I would assume it would be lower due to the airflow restriction and cause the system to ice up he says this at 7:25. Maybe he is talking about a heat pump in heating season but cooling it would be opposite

@larryzdanis5377 Год назад

He was a little confusing here, I agree.. He started talking about the refrigerant line pressures.. I believe he is suggesting that decreased airflow diminishes the proper superheating (or even prevents evaporation) of refrigerant (in the evaporator coil) which reduces system performance and can even damage a compressor if its being fed liquid.

@jerzzzeyful 3 года назад

My ac guy use a single 14" flex for a return on a 2.5 ton ac/heating gas unit.. 2 story home.. no return upstairs and its hot upstairs with ac on.. I need another return upstairs cause a 14" flex is only 700 cfm and I need to return 1000 cfm of air.. am I correct.. not enough return

@bigozzy710 3 года назад

14” inch flex is 1000 cfms, but the more return air drops the better.

@blackishpariah 3 года назад

Return should be upstairs as well. Good luck making that happen

@richardvisco6370 2 года назад

I thought duct system were designed for half inch ststic

@brandondartez3483 3 года назад

Hey Mr David do u have a new email

@sohailali2190 3 года назад

wonderful video i like now i understand how to use duct size calculator thanks

@wayneschneyer8699 3 года назад

As an instructor of manual J and manual D, and a follower of ACCAs guides including their excellent duct calculator that includes FLEX Duct! Your video is so full of errors and totally lacking proper procedures for a duct design it’s pathetic. Guys don’t follow this nonsense. Duct design STARTS with a room by room load calculation. CFMs are based on BTUs needed!! One must know what the equivalent length of the duct system will be for the longest supply run and return run. Next you need to know what the blowers total external static pressure per ton is rated for. Ductalators are calibrated per 100 equivalent feet of duct run. If any of the above is foreign to you then take a ACCA duct design course. This video is what’s WRONG with our industry!!

@Millionaireheatingairplumbing 2 года назад

please post a video that uses the duct calculator correctly

@jeanpaulg1037 3 года назад

Is that 400 cfm the same for Miami , FL where it might be hotter?

@larryzdanis5377 Год назад

Yes, he mentioned 400cfm/ton of cooling capacity. As your system tonnage goes up, so do the airflow. If its hotter, you'll need more tonnage and more airflow, but the same airflow-per-tonnage (cfm/ton).