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  1. #1
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    New Furnace - Noise from return is more annoying than before

    I recently had my two systems replaced with S8X1C080M5PSAA model American Standard units. Each unit is fed solely by a 20x50 inch ceiling grill with a 20" flex pipe coming from it, in the upstairs hallway. Those are the only supplies:

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    The noise that comes from the returns now is much more annoying than it used to be - it is maybe about the same volume, but it's much more bassy/low toned and it is kind of bothering me. I'm not sure why it's different, since the duct work is all the same as before and if anything these units are moving less air (since they are set to taps 5/6/7 instead of just being full speed like my old units).

    Here are some more pictures from the attic.

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    Does anyone have any ideas to improve the noise situation? My HVAC installer thought the only thing to do would be to add more returns in different locations, but I wasn't sure what the easiest and best way to do that would be. What is the simplest/cleanest way to address the noise issue? I am hoping to avoid having a bunch more ceiling filters to change, and it's also very tight in the attic so I'm not sure what the best approach is.

  2. #2
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    You say it’s 20” flex for the return, what’s the size on those furnaces?
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

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  3. #3
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    Quote Originally Posted by rider77 View Post
    You say it’s 20” flex for the return, what’s the size on those furnaces?
    Each unit is a 5 ton A/C system, the furnace itself is a single stage American Standard S8X1 with an 80,000 BTU gas heater. The A/C units are American Standard Silver 14 seer units.

  4. #4
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    Returns are undersized.
    This should have been caught during commissioning. My guess would be the units were not properly commissioned.
    This must be a substantial home, requiring 10 tons of cooling and 160,000 BTUs of heat. Perhaps in excess of 4,000-5,000 square feet?
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

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  5. #5
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    Quote Originally Posted by rider77 View Post
    Returns are undersized.
    This should have been caught during commissioning. My guess would be the units were not properly commissioned.
    This must be a substantial home, requiring 10 tons of cooling and 160,000 BTUs of heat. Perhaps in excess of 4,000-5,000 square feet?
    It's a 3500 square foot home but in Las Vegas, so it gets to 115+ degrees here. All the installers said 9 or 10 tons of cooling was the right amount, I opted for 10 just so all the units would be the same. I kind of regret not going for 4 ton units instead, but I wasn't sure and I didn't want some home inspector to say I didn't have enough cooling when I go to sell the house, if 9+ was the right amount according to people here.

    One thing I was thinking, those air supply boxes basically sit right over my master bedroom closet which wouldn't be the worst place to add a noisy return (I don't really want to put one right by where anyone sleeps, in case the sound is really annoying by a new return). Would one really easy improvement be to just add duct straight up into the bottom of each box from the upstairs closet? Would it be bad design to supply some of the downstairs air from the upstairs closet (even though it's all supplied from the upstairs hallway right now anyway).

  6. #6
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    .
    Last edited by Bazooka Joey; 11-30-2019 at 10:15 PM.

  7. #7
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    I believe it’s against code to add a return to a closet without a louvered door.
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486 Instructor & Service Technician

  8. Likes Tekjunkie liked this post
  9. #8
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    Quote Originally Posted by Bazooka Joey View Post
    You got auxiliary drain pans under those A/C, doesnt seem like you do?
    I think so, here is the best picture I have of the underside. I know each unit has a secondary overflow drain that goes outside, with some kind of alarm on it and a metal pan

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  10. #9
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    Quote Originally Posted by rider77 View Post
    I believe it’s against code to add a return to a closet without a louvered door.
    That would be annoying - it's a pretty big walk in closet, it's probably about 10'x12'

  11. #10
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    You’d have a rather large negative pressure problem in the closet then, the door would be sucked shut when the unit was running and the air would likely howl around the door.
    You’ll want the return in a more common area.
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486 Instructor & Service Technician

  12. #11
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    Quote Originally Posted by rider77 View Post
    You’d have a rather large negative pressure problem in the closet then, the door would be sucked shut when the unit was running and the air would likely howl around the door.
    You’ll want the return in a more common area.
    Would adding a third ceiling register in the hallway make sense, or redoing the two existing ones to have more than a single 20" pipe coming out of them? It looks really tight up there to me so I can't visualize how they would get another huge duct over to the input of the furnace

  13. #12
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    Whichever way it’s done, it needs more return.
    A bigger single, multiple, your unit needs more air.
    A longer duct helps muffle blower noise.
    I havent failed. Ive just found 10,000 ways that wont work. - Thomas Edison

    Its not whether you get knocked down, its whether you get up. - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486 Instructor & Service Technician

  14. #13
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    Quote Originally Posted by Droo View Post
    I think so, here is the best picture I have of the underside. I know each unit has a secondary overflow drain that goes outside, with some kind of alarm on it and a metal pan

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    There looks to be one under the A/C coil part, in your last photo looks like something black is under the coil? Hopefully your systems got registered as manufacturers warranty decreases significantly if never registered. California need not to register to receive the manufacturers maximum warranty.

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