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Thread: Sound Dampening

  1. #14
    Join Date
    Mar 2008
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    14
     They try to make them as quiet as they can, but efficiency and cost are the deciding factors.

    I’m not sure I entirely agree with this point. Clearly the materials needed to dampen the noise output exists. I’m thinking that none of the manufacturers will promote an extra quiet product that isn’t in their premium model. It is probably a so-called “value engineering” decision. Sure price competition has something to do with this decision, but marketing decisions, that is, the decisions by those who promote the product to a likely group of buyers at price point over-ride engineering for efficiency or quiet. In this case, it appears that the degree of “quiet” is a pawn in a bigger scheme. So the deciding factors becomes what the manufacturers think they can price certain features at. Certainly nothing new! I do agree that due to recent advances in bearing and magnet technologies used in modern fan motors are far more efficient.

    Also I thought that a roughly 80% efficient gas furnace has been a standard for about the last 40 years or so? If not what was the standards from the ‘60s to the ‘80s?

  2. #15
    Join Date
    Dec 2007
    Location
    Ohio
    Posts
    2,876
    Quote Originally Posted by Justan View Post
    Also I thought that a roughly 80% efficient gas furnace has been a standard for about the last 40 years or so? If not what was the standards from the ‘60s to the ‘80s?

    There was none...LOL
    I need a new signature.....

  3. #16
    Join Date
    Mar 2008
    Posts
    14
    The getting rid of the throat clearing is the only goal. They are not trying to sell me a different furnace. They’ve been out 3x trying to remedy the problem. They used a cork and plastic composite to help isolate the furnace from the hanging frame.

    They turned down the volume of gas that reaches the burners so that the furnace would heat more slowly and i guess not be as loud. That change made the furnace run for an hour where it ran for 15 minutes prior to the change. And it was no quieter. I asked them to reverse it.

    Last trip out I asked about decoupling the furnace from the ducting. I had the idea of putting in about a foot of flex ducting between the furnace and the rigid ducting. They did mention after the fact that the 90% efficient one was quieter. Same as folks here say. I whish they would have made this distinction at the outset. I didn’t expect that a modern furnace would be significantly louder than the one it replaced.

    The person I spoke with, who said he’d been a furnaces tech for 27 years said he had doubts that decoupling the furnace would solve the noise problem.

  4. #17
    Join Date
    Dec 2007
    Location
    Ohio
    Posts
    2,876
    Quote Originally Posted by Justan View Post
    The person I spoke with, who said he’d been a furnaces tech for 27 years said he had doubts that decoupling the furnace would solve the noise problem.

    10 to 1...he just didn't want to have to do it! LOL
    I need a new signature.....

  5. #18
    Join Date
    May 2006
    Location
    watertown ct
    Posts
    134

    Confused noise

    as far as them coming right out do you still owe them a final payment did they do a accurate heat load on youre house or they just replaced it with the same btu rating as far as adjusting gas presure i hope they are using a combustion tester when they turn down the gas presure the air would need to be adjusted as far as under firring the unit you may condesate in the flue wich is acidic and will ruin the chimney insulate the cieling above the furnace if it isnt already make sure to keep youre distance as per recomended by appliance manufacturer and dont used faced insulation you can also install some sheet rock above but watch youre clearances furnace is probably oversized you could try to insulated the inside of the plenum with duct liner it might help a little bit I would have sold you a 90 plus or nothing price isnt that much more and you could have had multi stage comfort fuel savings quiet and happines instead of low cost and no comfort

  6. #19
    Join Date
    Mar 2008
    Posts
    14
    They said there is sound insulation in the plenum. I can hear the dragon, even about 25 feet away. The sound is coming through the vent.

    I actually did ask for an over-sized (if that’s the right term) fan. The thought was that the greater air flow will heat the house quicker, which it does - takes literally half the time to bring the house up to temperature than it did with the former furnace - and down the line when we add A/C it will help to more readily circulate cooling. The house has a west exposure with lots of windows. When it’s 70 outside the house will be near 80 inside.

  7. #20
    Join Date
    Nov 2006
    Posts
    523
    If your old furnace was 30yo then most likely it was a 60% efficient model which likely had long quiet ribbon or slotted burners and a large (possibly belt driven) blower. All new 80% furnaces are going to be somewhat louder regardless because they use inshot jet burners and direct drive blowers plus an inducer blower. However the loudness does vary from manufacturer to manufacturer, so brand does indeed matter.

    Also some manufacturers go to great lengths to make quiet 80% furnaces, and they do indeed promote them. Carrier has quiettech and lennox has SilentComfort. Some brands use more insulation in their cabinets or heavier gauge metal.


    90% furnaces on the other hand are a different animal. Part of what gives them their higher efficiency is sealed combustion, so as a result all the 90% furnaces ive worked on regardless of brand have been really quiet. Some are almost completely silent, others have a little hum, but all are generally quiet, even the value brands.


    As for oversizing the fan, if you have the fan at too high of a speed it will take longer to heat the house because your temperature rise will be reduced.

  8. #21
    Join Date
    Mar 2008
    Posts
    14
    Great feedback. Didn’t know that older furnaces were generally in the 60% efficient range. I’m guessing that is a hip shot estimate. Our house has always cost little to heat (less than $70 per month during the winter months) so I just guessed it was pretty efficient. This is for a roughly 3,000 sq foot house.

    Based on your comment, they probably put in a slightly larger furnace and not just a bigger fan. The time it takes to heat between the night temp and the day temp is half of what it was with the old furnace.

    It still strikes me as completely unacceptable that a furnace which by all accounts is built for a very wide range of customers by a national brand makes this throat clearing noise. It amounts to a manufacturer who doesn’t much care about customer satisfaction.

    I’ll find out next week what the cost will be to be shed of this noisy but quick furnace and replace it with one that is, hopefully not noisy.

  9. #22
    Join Date
    Jun 2007
    Location
    sullivan, mo
    Posts
    36
    I get alot of homeowners after an install who complain f these similar noises. When you go from a natural draft ribbin burner(old style) to a induce draft inshot burner they are alot louder. I'm not saying that there isnt a problem, sounds like they have verified everything is working properly.

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