How to Size my Return Air Conditioning Grills Correctly?
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- Опубліковано 28 кві 2013
- David explains return grills, return grill whistling. Generally: 200 sq. inches per ton.
Thanks for watching!
- David
David@DavidJonesAC.com
Follow me on Facebook: / david-jones-ac-1010702...
You have the best videos for learning the proper techniques for HVAC repair and troubleshooting. Thank you for sharing.
I hope you find this video helpful...thanks for watching from Jones Air Conditioning & Electric in Naples, FL!
Great video, just changed out my louvered door for full 6-panel door, & installed a 24x24 in the wall & 8x30 grill above the door to give 816 for my new 4-ton unit. My contractor tried to tell me that the 24x24 would be fine, but it was easy to add the grill above my new door. Looks much better. Sounds quite now Thanks!
Great video! Easy to understand, quick and to the point. Thanks for posting!
Been doing this 15 years ...best explanation ive ever heard.
thanks for schooling us with this quick, easy to understand, fun to watch tutorial. You're awesome.
David you are the greatest.... Thanks for sharing your knowledge.......
thank you man. i wish my contractors knew it when the did the job
Thanks for making this video.
It's great that you've pointed out the problem that many customer's and even many contractor's don't seem to realize,. I was on a job recently that the return was so small that when the customer installed (pleated)1inch "High efficiency"filtersthey were pulled out of the R/A grill and up into the ductwork.
The question I have is when you talk about 200 sq.in per ton, Are you taking into account the free area or "K" factor, because each one of those louvers is a restriction, and if you were to slide them all to one side and add up the area they take up, it's significant, one third or better of the grill's area, which is why the manufacturer's have to calculate the amount of free area for each Supply and Return Grille and register
I had a 2.5 Ton Unit Residential A/C. I went to a 3 Ton Unit. Does this mean My grill is too small? I noticed an opening at the front side of grill. It doesn't close totally like before.
Thank You!
Thanks for the video. I've been having issues with my old system and not 1 person mentioned to me that the size of the return needs to be increased. I have a 24"x16" 384 sq.inches when I need 600 for my 3 ton unit. This is half my problem
Great video David !! Take care, Brett
Building a home on my own.
This will help.
Thanks!
great job.thanks for all your wisdom.you are planting seeds into million dollar business!!!
Good job David ...!!!.
We always need to have a laugh I.am always joking around. Thanks for watching.
thanks, outstanding lesson.
You are the best thanks Mr jones
thanks i have a test over this on Thursday and my teachers are horrible at explaining that. u just taught me more than my teacher did all class period
thanks for the comment
I will, keep in touch. Thanks
well job sir.. proud of your skills..
I hope it's a 2 million dollars a year. I will be here for support.
Thanks for explaining that.
I will work on it.. Thanks
Thanks for nice advice.
Great video. Thanks
Great video thank you!
Nice video David👍👍
thanks
Excellent Tortola. I never had to replace an Air Conditioner Air Handler. Àlways a first!
great video you help me alot
Thanks, Brett
Thanks David
really like your video s.. appreciate the knowledge.. How would u size the proper flex return for that grill?
very good video thank's!!!
You Rock! Thanks.
Thank u sir very helpful video
Thank you very much for a such valuable information. I have an open concept home and my living room is 16 feet tall. I have two ac units. One downstairs and one upstairs. If I need to add an extra return does it matter if it's at floor level or ceiling level?
Thank you.
Thanks for this video, but need another help please tell me how to calculate supply air grill size to consider supply cfm?
Great series of videos, Dave! I have a quick question. I would like to finish my basement but I have one room where the return duct, leading to the furnace, is hanging down 9" and would make for a very unattractive bulkhead and low overhead. If this basement duct is 9" X 20" can I change that to 5" X 36" ? It's the same amount of square inches and those extra 4" of overhead room would really make a big difference to the look of the finished room.
Yes you can, it will be ok
I wanted to apologize about the Monkees and the pirate comment. I have been watching HVAC videos and started watching yours, good stuff, God bless.
Hi David jones, thanks for the video, what I'd like to know is what type of duct are you using in your design, is it flex, metal or fabricated board?
Amazing guy
Thank you so much
Someone capped a floor return for a 3 ton unit. It has been pulling crawl space air into a open flash pan under house, then out to the packaged unit. I believe I will have to have a 20 x 30" filter grille installed in the floor
Thanks for the video Its really helpful, I just want to as that you told Thumb rule for sizing Return Grill that 200 sq inch = I TR Is it standard of ASHRAE Or SMACNA??? Secondly is it valid for all type Units for example VRF Indoor , AHU etc??
Correct!!
Good info.
Thank you
Awesome Dave, but could you also address R/A duct size.
Residential is sometime harder. Going behind some one else can be tough. But you can make your money faster. I would try that less starting
Capital. Good luck.
Hi David, my AC is 3.5 ton unit while the furnace is 4 ton unit. The house is about 2,500 sq. ft divided into 3 zones and I have only 2 returns with the total of 744 sq. inches. Do you think having another return will help the air flow since one of the zone now has much lower flow? Thanks in advance.
hey. i have a question .recently i had installed 2.5 tonn rheem unit for heat and AC
and there is only 1 return duct which is 12 by 14 and followed by 16 by24 main return built in unit filter. can it provide enough air volume for this unit? so it can work properly
David, what size of duct should I put for on those return grills?
My heating system is in a mechanical room. I have a large return grate in the wall outside of room next to the heater. There is a filter on the unit but no duct connecting the grate to the unit. Is it important to have this short run from grate to unit ran through duct? Probably 2 feet from the grate to the unit inside the mechanical room.
Can you make a video on how to size diffusers? Do you size grills with return ducts in the same way you size grills with no return ducts
what would be the effects of having an undersized return? I've only got a 24×18 return so obviously that needs to be enlarged, tech never mentioned it, learning on my own at this point. I've had major sweating issues with my air handler, I've done everything to treat the attic and it stays under 90°f up there. Could the small return be contributing to the sweating issues?
Mr David, I currently have a 2.5 ton unit. I'm stepping up to a 3 ton. My return air is 274 sq inches. Should u install another 275 sq inch return grill? Does my ductwork have to be taken into account? Thanks
The house we bought has three returns with filters at each return. The air handler itself has a place to put a filter. Is it better to have the filters at the returns, is it better to just have a single filter at the air handler or does it not really matter? I question if all the filters add restriction, making the return more inefficient (they appear sized right for 3 ton system, 2 - 12x24 and 1 - 12x12). Thanks.
Does the 200 sq inch rule work for just a heating system as well? I don't have ac (tons) just heat. Not sure what the BTUs are but the unit puts out quite a bit. Thanks
very good infomation , When you say generally 200 sq. in. , could or would there be any reason for a change
The right way
What if am using media filters? Calculations will be different. And if is for commercial installation also will be different. Had to consider the fresh air, so less static will be at the return grill.
thank you, in hawaii and my ac is 3 ton , gettin gonly about 324sq in" return thats squealing, my poor ac is starving of air so im going to go install another grill,,,, does it matter how long the duct is ? thank you so much for you video ,helped me alot, i got quoted 710. to run a new return and a 12" duct about 20 feet. is that accurate? thank you again ! Sarah
Thanks, I hope it helps.
What about converting to a 4 inch deep filter does that change the math...4x the filtration area or is the math just about the opening? Thanks
I live in a mobile home that has a 3.5 ton heat pump on it. My furnace sits in the hallway, and the door/grill is the only return I have because it free pulls from there. The opening of the grill only measures 17” x 23”, which is way too small for a 3.5 ton system. My calculations using this method bring me to the conclusion that I could just cover up that door somehow, and install a 24” x 30” filter grill. Would that work in this situation?
I have 4 ton roof packaged unit with 20x30 intake. Seems to be working fine with 600 inches. What do you think?
Thanks for the great information. Could an AC start forming ice on the coils if it is starving for air? My 4 ton unit has 1 return duct register of 13x21.5 sq inches (280 sq inches) approx I've had the HVAC tech stop by and check for refrigerant leaks, or issues with the TXV and they all look good. He is recommending to add additional return air registers in the house to help with reducing the ice buildup.
If you get this reply, ice on the indoor coil is EXACTLY what you should expect from a unit that is starving for air. If more warm air was flowing over the coils, they would be kept above freezing. The engineers who design these units assume that the indoor coil will soak up as much heat as the outdoor coil can dissipate.
Niyati Abhi Gupta Hope you didn't have that done. All you needed was to increase the size of the existing return duct. Literally splice it, and add to it. Having just a couple extra feet that the air has to travel can make the difference, especially a couple degrees in which 33°F at the coil would not create ice. Either that or he was actually talking about a dump or bypass... oh well.
So if i have a 2 ton a/c unit would i need 400 square inches of return a/c grille space? If i am suppose to have 400 square inches for a 2 ton a/c unit will a 25 x 16 return a/c grille work since it comes out to 400 square inches?
Is cutting the register necessary if I have wood studs where the register needs to go?
I have a 16x20 grill on 3 ton. Iam trying to put my own unit in and all the runns. My house is only less than 2000 square feet house one story with 2 bathrooms 3 bedroom s. All my rooms are about 14 x14 except my bathrooms and laundry room their 7x8. Whats the best size duck's do i need 6 in or bigger
My house has a 5 ton unit and the return grill is 20x25 , so I need to add one more grill correct?
Sir can u pls explain about slots calculation of linear plenum
QUESTION: What if you have a 2 or 4in filter? Does that “take away” square inches? Doesnt a bigger filter create more static pressure and affect the return numbers?
I got a new return grille 20x20 and it's alittle smaller than my current old one and the filter is snug also I've searched for wider dimensions but none that goes to 23 on the outside, It's not in yet I need help on what to do
Do all air returns have to be that size.. ie adding a return in a bedroom?
thank you
Question, does the design of the air return flex matter? Square versus round? Also, if a return is closer to the air handler does that mitigate the need for the rule of thumb 200" per ton? :-)
Hello! Great video one question how would you translate this into cfm's? Example I have a 4 ton unit with only an 8x12 grill it's freezing up and flowing ice into the ducts. I know I need more air but honestly I would like to understand the difference between cfm's and free air. Thanks in advance
OK here is a back of the envelope swag:) :
(1) Old rule of thumb is 400 cfm per ton thus 4*400 =1600 cfm. ( cubic feet of air per minute)
(2) Grille area minimum = 4 tons *200 inches squared is 800 sqin . 800/144= 5.56 sqft too.
(3) For fun the air velocity is 1600 cubic feet per minute / 5.56 sqft = 288 ft per minute.
Ok 288/60 = 4.8 ft per second.
Or just use the formula for the cfm each grill will allow. width x length x 2 will also let you know how much cfm is allowed thru that grill.
Ex. 20x25x2= 1,000 cfm which is good for a 2 or 2.5 ton a/c.
I have 228 inches of grill space but it’s using my wall space which is only 3 inches deep. Will increasing the size of the grills actually help any? There’s two. A 14 x6 and a 24 x6.
Edit: I plan on adding jump ducts for the bedrooms and a return vent in the finished basement
@@michellemajako What size is your AC system? The size of your inside walls is only going to carry about 120 cfm in each bay. So, according to caculations. thats barely enough for a 1.5 ton ac. Increasing the size of the grills won't help much. Added in new returns in other rooms will definately help.
@@smacleod69 Three tons!! Added a 14x12 (I think that was the size) return grille and connected the register box with an 8 inch starter collar in the basement. There are two output registers down there. The basement is warmer this winter. Plan is to add returns to the bedrooms because we need more return than just the hallway and the new one downstairs. It has to be hard on the system. Also, the bedrooms just do not stay warm/cool. No idea how the company who put this system in thought that size was a good idea. This house is only a 1K square foot ranch, too. Thank you so much for your answer. Did leave the hallway returns that size.
excellent video I would like to work for your company and learn how to design systems of air-conditioning
, , when putting the air grill back onto the wall doesn't make a difference if the slots are facing down or up?
I have Two( 20 by 20s ) for a 5 ton central unit.
what is difference in R22 vs R410A return inches per ton>?
My system has an appropriately-sized grill but immediately inside it is a much smaller round duct. I'm amazed by the widespread incompetence in the HVAC industry.
how did you come up with 200? basic rule of thumb number just curious
It seems that is " A rule of thumb ".. We have to go back and check manufacturer's specifications. moreover registers/supply air outlets concept will be different because of many constraints Air Velocity, Sound level , etc.. Although the demonstration is very helpful .. Thanks
My house is 1800 sq ft what size unit do I need and what size return
if you have a 3 ton let say you need at least 18 inch, then a 10 in another part of house
make sure your return grills are large enough for the air flow
look at my video on sizing
Good demo and video sir.
I think my return is very undersized, but I don't see any adverse symptons. I have a 3 ton unit with an 18x18 return mounted in an 18x18x20 plenum, connected with a 12in x 3 foot flex to the unit.
According to the calculation that's liike 1/2 the size needed? Yet there is no whistling or even observable wind noise, and airflow seems to be excellent. THe return is in the tongue & groove hallway ceiling so its hard to make it larger.
I should also mention- the air-handler opening itself is about 20x20
that that's only 400 in2 - sized for a 2-ton unit. So even if I went to 24x24 return grille, it reduces to 20x20 at the handler? ALso the 12in flex area is pi x 36 =~ 113in2 ! - sized for a 1/2 ton!
Malabar Spyder Yes, but the air-handler opening and the flex duct do not have filters in them, so the air freely flows through them. To insure adequate air flow through the filter, the area of the filter must be greater than that of the duct and air-handler opening.
I have a question. My return is fed through in between the walls , so the cavity is like 32 x 3.5 inches, Due to the placement of the main floor support beam ( 2x 8) it chokes of the cavity from like 3.5 inches down to about 1.5 to 2 inches . and comes back to 3.5 inches x 32 . The grille size for my air handler is correct but this " choking " does it matter or doesnt it, since because after passing passing the support joist it comes back up to 3.5 inches wide?
Thx in advance
This starts to make things really really complicated.
What duct work would the 600 sq in grille plunem?
How about sizing supply registers?
what about size of the flex in the grill
How do you measure cold air return for filter
What is general rule for supply grill ?? Or any formula
Dave, Im considering starting my own business. Im a journeyman sheet metal mechanic with my local. Work is slow and i mainly worked on commercial projects. Whats the biggest difference between residential and commercial work?
does your general rule of 200 sq inches per ton take into account the k-factor of the grille?
How much can you oversize the supply and return ?
I have a 5 ton unit I know I need a thousand square inches of return grill right now I only have about four hundred square inches and I am whistling I change the blower motor for the guy and that's when it saw that whistle he said it never whistled before if I open up another return give another 600 square inches do you think I'll take care of my problem ty for all your videos
you are on the right track
David r I
Sir,how to design Register per square inch
How about without the filter? How do you calculate that?