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  1. #1
    Join Date
    Nov 2009
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    13

    Furnace with ECM Motor Any Quieter than similar regular motors?>

    Anybody installed a natural gas furnace with an ECM (electronically commutated motor)? Are they much quieter than similar units without ECM?
    I have to decide between an Luxaire 95% AFUE Regular Motor and a Luxaire 95% ECM Motor. I am willing to pay the price difference as I am getting back quite a bit in the rebates/tax credit. However, my main requirement is a quieter furnace, as both are similar in efficiency. Is there a decibel level comparison available?

    If there is not much noticeable difference of noise between the two, I will go for rhe NON-ECM standard motor as it will be less hassle and less expensive to repair down the road.

    Any experience good or bad or comments, positive or negative will be appreciated. Thanks.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,712
    About the same sound level.

    Unless your duct is undersized. Then the ECM can be louder.
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  3. #3
    Join Date
    Nov 2009
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    13
    Beenthere,

    Thank you for your reply. Is there a rule of thumb to check the duct sizing for the flow put out by the furnace? Any links to check the duct sizing would be appreciated.

    Thanks again.

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    No good rule of thumb.
    And unfortunately, its rule of thumb that causes many duct systems to be installed undersized.

    When you screen contractors. Ask them if they can check your systems static pressure.
    If they can't. Then they probably can't tell you if your duct is sized right either.
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  5. #5
    Join Date
    Jan 2008
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    1,956
    The Luxaire with PSC motor is 95.5 I believe, and is single stage.
    The one with the ECM motor is 97.7, and is a modulating furnace.
    The modulating furnace is very nice.
    Luxaire might make a mod with a PSC, or a single stage with ECM, but I've never seen those.
    Even if your ductwork is sub-par, you'll probably will never hear a modulating run, untill it bumps up to a higher output. Then it could get noisey.
    Ask your contractor to explain things a little better, and you'll make a wiser choice.
    If he doesn't know the difference, and explain it clearly, find another contractor.
    "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
    Join Date
    Jan 2008
    Posts
    1,956
    You couldn't really have a modulating furnace with a PSC motor. My bad!
    "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

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Yes, they make a Mod with a PSC blower motor. It uses a Baldor ball bearing motor, not a standard sleeve bearing motor. And its speed is varied by the furnaces control board.
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  8. #8
    Join Date
    Aug 2006
    Location
    Wyoming
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    293
    My answer is yes and no. If set up properly and duct work is good for both furnaces, then there should be no difference in sound. What I see all too often is an oversized furnace installed in an old house with way undersized duct work, resulting in tons more air noise, especially with an ecm.

    Now, set up properly and with correct ducts, an ecm furnace can sometimes be quieter or at least less noticeable than the standard blower you're replacing, particularly if the ecm furnace has any type of staging.

    The kicker here is, rarely is the existing system done right so there are always variables.

  9. #9
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
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    4,568
    Quote Originally Posted by high plains View Post
    My answer is yes and no. If set up properly and duct work is good for both furnaces, then there should be no difference in sound. What I see all too often is an oversized furnace installed in an old house with way undersized duct work, resulting in tons more air noise, especially with an ecm.

    Now, set up properly and with correct ducts, an ecm furnace can sometimes be quieter or at least less noticeable than the standard blower you're replacing, particularly if the ecm furnace has any type of staging.

    The kicker here is, rarely is the existing system done right so there are always variables.
    This is correct, but if the furnace quoted with the ECM is a modulating furnace you will notice much quieter operation in general. It takes a mod 20 minutes of continous operation to run at full output. 95% of the time it will be running at 50% or less and be much quieter.
    Aire Serv of SW Connecticut- Gas heat, dual fuel and central a/c systems installed and serviced

  10. #10
    Join Date
    Feb 2005
    Posts
    54
    All the ECM motors I've run across ramp up and down when starting up and stopping, while running noise may very well be the same you don't notice it coming on much at all. Most furnaces with ECM motors also have more speed choices available to more closely match your systems needs.

  11. #11
    Join Date
    Dec 2008
    Location
    Ontario Canada-in the Banana Belt!!
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    211
    I am putting one in right now and will see how it compares to the other one I did a few months ago with the variable speed board in it....The undersized duct thing has me a little concerned now that I read this, but I have never had a customer complain that it was too loud ...But there is always a first time. Hopefully not this time!!

  12. #12
    Join Date
    Aug 2007
    Location
    louisville, ky
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    951
    ECM motors are very much more quiet than PSC motors mechanically, but in a high static duct system the ecm motor will ramp up much higher to deliever the air needed, so the motor itself will be quieter, but it may cause high velocity coming out of supply registers, and whisling coming from return vents. But if this is a modulating furnace as said before then most of the time it will never get close to full speed and it will be much quieter overall. ecm motors also give u much more versatility in the setup, and use less electricity to operate.

  13. #13
    Join Date
    Dec 2008
    Location
    Ontario Canada-in the Banana Belt!!
    Posts
    211
    Nice...Maybe I will bite the bullet and swap in the $ VS board if it is a problem...Knowing this homeowner, he will probably like the fact that there is nice strong warm air coming out of the vents at mach I speed...lol

    Nice C5 btw!!!
    Got to get my C3 on my profile
    Last edited by beenthere; 11-11-2009 at 04:46 AM. Reason: Removed price

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