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Thread: Replacement American Standard Furnace is extremely loud

  1. #1
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    Replacement American Standard Furnace is extremely loud

    We had a flood, and our relatively new (~5 year old) furnace was replaced by the insurance company with the exact same model.

    It is an American Standard updraft, 60 mbtu/h 1.5-3ton (400CFM/ton) variable speed furnace (AUH2B060A9V3VBA).

    When we bought the house 1 year ago, we found the furnace to be quite powerful (don't need screws to hold the air intake grills in place...) and a bit loud (fan noise).

    The replacement furnace is even more loud.

    After restoration, we have had the installer back several times to address how much more loud the replacement furnace is.

    - There was harmonic noise over the old metal grill on the air return beside the furnace. The grill has been removed.
    - The original furnace had the filter inside the blower housing, the new furnace has a slot beside the housing. (you can change filters without removing the cover).
    - When the filter is removed, everything is very quiet. With filter, the fan works much harder and causes fan noise.
    - Even a new filter causes the fan to work very hard. A 3M or used filter causes a lot of straining by the fan and a lot of noise.
    - There is a rubbing sound when the blower starts up and stops (overriding door interlock with door open to test).
    - The fan is set for summer mode (low speed always on).
    - The tech changed dip switches to lower the summer mode speed, and it is now much more quiet. Heating mode fan noise is unchanged.
    - Heating mode fan noise is loud enough to wake up the family. A decent comparison would be 2 24" box fans on high...
    - Air return ducting is rectangular 24" x 8", 25x16x1" filter.
    - Some restoration construction dust (drywall, etc.) was probably pulled through new furnace during restoration.
    - Fan was louder after restoration but got *even louder* after furnace/ducts were cleaned after restoration completed.

    Any ideas?

    I am worried blower / blower motor is defective and will wear out and fail, and want to leave the TV volume alone when the heat comes on...

    - Iain -

  2. #2
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    most likely the ductwork is too small and maybe the furnace as well. did the tech look at the ductwork?

  3. #3
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    You're probably just short of RA (return air). That's a very common occurrence.

  4. #4
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    Thread Starter
    Quote Originally Posted by snupytcb View Post
    most likely the ductwork is too small and maybe the furnace as well. did the tech look at the ductwork?
    He didn't mention it - likely because they replaced the furnace with the exact same model.

    So too small, and it would work too hard? Or is it that it would be fine if the ducts were larger and the filter was larger?

    Sigh. If the new furnace was different, it would make sense that sizing could be a problem, but the old one just wasn't loud...

    - Iain -

  5. #5
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    Variable speed furnace - have them set the dip switches properly.
    You still may have duct problems. Most people do.
    "Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler

  6. #6
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    Quote Originally Posted by imcvey View Post
    He didn't mention it - likely because they replaced the furnace with the exact same model.

    So too small, and it would work too hard? Or is it that it would be fine if the ducts were larger and the filter was larger?

    Sigh. If the new furnace was different, it would make sense that sizing could be a problem, but the old one just wasn't loud...

    - Iain -
    it may be able to be corrected simply, or not. the only way to know for sure is to first have a manual j load calculation performed and then have then see how close the furnace size is. then size the ductwork accordingly. who knows, maybe a simple adjustment could work but it doesn't sound that way.

  7. #7
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    Though the manual may say a 25X16X1 is okay, as it is the usual size; I would want a lot more filter area for a 3-Ton system & 60,000-Btu/hr furnace especially when using restrictive filters. Two filter drops or a filter cabinet could make a big difference.

    Make sure the Return air duct system is sized large enough...

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