I just got a new central air conditioning for my 2100 square feet houes with one 14"x30" and 14"x14" air return. The air returns make very loud noise. My contractor said that is normal, but I don't think so. The inspector from township said they used R-6.0 ducts instead of R-8.0 ducts. Is the duct size influence the noise? How to solve this problem

If you have a whistling or allot of wind noise it may be due to the small 6" ducts that you have. I would have your contractor back to replace your 6" ducts with 8" ducts, and just explain that you can't stand the noise.

If the noise is coming from the return air duct you may can change to a different return air grill, one with more unrestricted area and heavier vanes. The thinner vanes vibrate and hum making noise and they set a harmonic wave that is very big nuisance.
Another thing you can do is to lind the inside of your return area with a stiff sheet of insulation glued to the inside walls of the area.

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Originally Posted by thommyschnak

If you have a whistling or allot of wind noise it may be due to the small 6" ducts that you have. I would have your contractor back to replace your 6" ducts with 8" ducts, and just explain that you can't stand the noise.

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My contractor refuse to change the ducts for me. He said that is normal because the unit on the attic and close to the air return, so 6" same as 8". Should I believe him? What can I do? This is a big headache to me. Anyone can help me, I really appreciate!

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Originally Posted by letmetellu

If the noise is coming from the return air duct you may can change to a different return air grill, one with more unrestricted area and heavier vanes. The thinner vanes vibrate and hum making noise and they set a harmonic wave that is very big nuisance.
Another thing you can do is to lind the inside of your return area with a stiff sheet of insulation glued to the inside walls of the area.

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Where can I find the heavier vanes? I want to try it.

Thank You!

You may have to go to a Heating and Air Conditioning company, these were always used more for comericial work.

If you have one return air duct at 6 inch. What size is the other. I hope not 6 or 8 inch. What size unit do you have.

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Originally Posted by T-Top

If you have one return air duct at 6 inch. what size is the other. I hope not 6 or 8 inch. What size unit do you have.

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I have Rheem 14 seer air-cooled condensing unit and 4 Ton 15 seer high efficiency Air Handler(R-410A). I don't know if the 6" duct match the unit. How can I find out?

Your going to need a lot more return air duct than 6". Your going to need a 18" or larger to go along with that 6" duct.