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  1. #1
    Join Date
    Mar 2006
    Posts
    254

    Knowledgeable HVAC contractors a dying breed?

    This company installed my Carrier HDR38 2 Ton and Perfomance 80 in my small
    887 sq.ft condominum. They are an authorized Carrier installer.

    Physically, they did a good job installing everything. However, when it comes
    to the final part, like assesing loud noise due to possibly undersized flex ducting,
    they are kinda "blow my mind" clueless and just don't want to deal with it.

    I spent the weekend researching ducting sizes and have pretty much determined that my 8" ducting (one takes ony a 12" long elbow directly to my living room vent) is most likely causing what I consider to be noise that can be lessened. I'm no expert, but even rule of thumb says that's why the inordinate amount of air pushing out and the ocean roar (up close to vent you have to squint your eyes the rush of air is so strong).

    I had them come out and got basically no help, no assement of my ducting, just some advice to use Dynomat to help absorb sound on the closet unit.
    They simply weren't interested with what I thought was excessive air flow and ocean roar sound. "Turn up the TV" is about what they care.
    They know I am pleased with the physical installation, I didn't lose my cool.

    I'm going to call other AC companies, with techs that are willing to do technical assesments and give me trained advice, not just "look and listen."

    Those other companies will probably charge too. I'll be paying untill I come upon an HVAC contractor who takes pride in the profession. Wish me luck.

  2. #2
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,962
    Good luck. Ya feel better now?

    Ya wanna friggin hug too?
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  3. #3
    Join Date
    Mar 2006
    Posts
    254
    No hug. Get me another beer.

    Jeesh, the entire duct work is such a short run and could be changed out fairly easy.

    Having just a 18" run with 8" ducting directly from the plenum in the attic right to
    my living room vent....gee, ya wonder why it might be a little noisy and windy?

  4. #4
    Join Date
    Nov 2007
    Location
    Tucson AZ
    Posts
    166

    Rough calculation

    2 tons of air needs 800 cubic feet/minute airflow.

    Air velocity at vent needs to be around 500 feet/minute to avoid noise, so your vent needs an area of just under 2 square feet.

    8 inch round ducting has a cross sectional area of about one third square foot, so the velocity in the duct (if you have the airflow you need) would be 2400 feet/minute. Its going to be noisy!

    Professionals - are these numbers about right?

  5. #5
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,371
    Good luck and hope it turns out okay. You may be in for some substantial ductwork modifications.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,308
    Quote Originally Posted by jeff520 View Post
    2 tons of air needs 800 cubic feet/minute airflow.
    In his other thread, he has pics of his duct system.
    He does have more then just 1, 8" supply.
    This one is just the one that annoys him the most.

    Other wise 800 CFM through a single 8" would be about 2293FPM.
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  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,308
    Good luck.
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  8. #8
    Join Date
    Mar 2006
    Posts
    254
    Quote Originally Posted by RyanHughes View Post
    Good luck and hope it turns out okay. You may be in for some substantial ductwork modifications.
    That's sort of my point, I was willing to pay for it got and very little from them.
    Also, the plenum is a really really short distance to each run to vents. Not a big install.

    My main noise concern is my living room and dining room vents. I have ceiling fan in my bedroom and have been able to sleep fine with no AC and 80F at night.

    Has anyone heard of acoustically modified ducting? I may opt for that.
    I may even go for wrapping it as seen in the pic at that short run to living room.

    http://www.cclveloduct.co.uk/Default...&CategoryID=10

  9. #9
    Join Date
    Mar 2006
    Posts
    254
    Quote Originally Posted by RyanHughes View Post
    Good luck and hope it turns out okay. You may be in for some substantial ductwork modifications.
    That's sort of my point, I was willing to pay for it got and very little from them.
    Also, the plenum is a really really short distance to each run to vents. Not a big install.

    My main noise concern is my living room and dining room vents. I have ceiling fan in my bedroom and have been able to sleep fine with no AC and 80F at night.

    Has anyone heard of acoustically modified ducting? I may opt for that.
    I may even go for wrapping it as seen in the pic at that short run to living room.

    Does this type of acoustically modified duct only keep noise from nearby outside areas or can it reduce inborn air sound rushing thru it to vent?


    http://www.cclveloduct.co.uk/uploads...c_Flexible.pdf

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,308
    Before you spend money on accustical ducts.
    You might want to check if its the duct, or your register.
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  11. #11
    Join Date
    Mar 2006
    Posts
    254
    As much as I appreciate your help BeenThere...hehe, do you really think I would let that possibility slip by? I may still go with the bar type register to help things.

    Anyone know if Tecsonic is just to block noise that goes to outside of the duct?
    Or does it have the capability to absorb noise traveling thru the duct to the register.

    QuietFlex and SilentFlex are two other brand names of this type of flex ducting.

    Sorry for the double post above. The post with the pdf explains the most about
    acoustically modified flex ducts.

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,308
    If you read it. It doesn't stop noise going outside of it.
    It tells you to install it in areas that the noise penetration won't matter.
    Its more restrictive then regular flex duct.
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  13. #13
    Join Date
    Mar 2006
    Posts
    254
    Thanks. "Noise attenuation" and other such terms I'm not that familiar with.

    As far as flexibility (for my purposes) the pic sure shows it's rather flexible.

    Not quite sure what you mean by "restrictive." Oh..air flow because of all
    the little perforations? All them tiny holes grab the air a little bit?

    If so, with my small area to cover and 2 ton AC and a strong blower motor, I might want to look
    into getting this type of ductwork.

    BTW Beenthere, taking off the louvered register seemed to help with the sound a little.
    No doubt..with such a strong flow of air.

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