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Thread: Adding a return

  1. #1

    Adding a return

    Hi all:

    A couple of years ago my contractor replaced my old A/C only 2 ton 10 SEER York with a 14/15 SEER 2.5T Goodman with variable Air Handler (16x20). Each of 4 bedrooms has it's own 8x8 return, except the master BR which is 12x12. Since that time, the return 12x12 in the master bedroom howls as if the unit is starved for air or velocity is too high. None of the returns in the smaller bedrooms make any noise or are blocked. None of the duct work was changed when the unit was changed. I understand you can't have to much return and I'd like to add another 12x12. My question: I'd like to avoid cutting sheet metal to tap into the return plenum. Can I put a metal T into the 12" line coming from the 12x12 and put another 12x12 in the MBR? IOW will the 12" flexduct handle 2 12x12 returns and cut down the noise? So I'd have 2 12x12 returns joined through 12" flex. It would be about 8' between returns in the MBR. From what I can see 12" will pass 600CFM.

    The other idea was to cut into the metal return duct and run a separate 12" return. It's just that the space is difficult to work in and cutting in the T would be a piece of cake.

    I hope I'm making this clear. My thanks to anyone responding.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,048
    Another return, another run back to the plenum.
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  3. #3
    Join Date
    Jun 2011
    Location
    Houston area
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    Quote Originally Posted by beenthere View Post
    Another return, another run back to the plenum.
    Ditto x 200%
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  4. #4
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    5,520
    The ductwork should have been evaluated when the size of the system was increased. Actually it should have been evaluated regardless... especialyl going to vairable speed. A system that was previously short of airflow, migh have underperformed, but not been too moisy. A VS will run at much higher RPMs attmepting to reach the correct CFM. This can make the system very noisy and actually consime more power than a standard blower.

    Just curious, why did they upsize? IF the old sysetm was marginal, it's rpobably because it had issues or a dirty indoor or outdoor coil, or was shrot on airflow.

  5. #5
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    1,391
    You should hire someone that understands airflow to evaluate the duct system. 600 cfm through 12" flex even if installed perfectly will be noisy.
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  6. #6
    Added a 10x10 to the system and it's much quieter now.

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