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  1. #1
    Join Date
    Sep 2011
    Location
    Cotuit Ma
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    18

    Small ducks , wrong size furnace

    I would like an opinion what would make sence.
    I had furnace replaced 3 yeas ago by Hvac guy "ex friend" who got me new bryant 100k btus, 1570 cfm. My house 1450 sqf according to software calculation needs 55k-60k furnace. Do i upgrade duck to proper size OR get new proper furnace and still need to upgrade ducks?
    House is 25 years old , ducks uninsulated, a/c is 2.5 tons.

    Thanks

  2. #2
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,593
    Will you forgive me if I have a little fun, at your expense?

    These are small ducks.



    I think you mean ducts.

    Similarly, when people say "duck tape," they mean "duct tape."

    Okay, fun's over.

    Call someone to perform a "Manual J " load computation and a "Manual D" analysis, and that will tell you if your ducts are sufficient for your needs.
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  3. #3
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,562
    Quote Originally Posted by timebuilder View Post
    Will you forgive me if I have a little fun, at your expense?

    These are small ducks.



    I think you mean ducts.

    Similarly, when people say "duck tape," they mean "duct tape."

    Okay, fun's over.

    Call someone to perform a "Manual J " load computation and a "Manual D" analysis, and that will tell you if your ducts are sufficient for your needs.
    I've actually seen "duck tape" at hardware stores and the like. It even had a picture of a duck on it. Never at an a/c supply house though.
    I like DIY'ers. They pay better to fix.

  4. #4
    Join Date
    Jun 2011
    Location
    Wake Forest, NC
    Posts
    352
    Your furnace is WAY oversized unless you live in Antarctica. I would guess that a 60K would do the trick for you, but a load calc needs to be done to determine proper sizing. Im suprised you havent had problems with the furnace going out on high limit... Replace the furnace first, smack your friend second, then see if you need addition duck work (haha) once the proper furnace is in place.
    It's not rocket-science...

    It's electromechanical thermodynamic engineering

  5. #5
    Join Date
    Jul 2010
    Location
    georgia
    Posts
    562
    If I remember correctly, the fabric tape commonly referred to these days as "duct tape" was created for the military, primarily to seal ammo boxes. I think the grunts nicknamed it "duck tape" since it shed water like a duck. No idea what the "official" name of the tape was.

    After the war it became known as "duct tape" as its primary post war use was in the HVAC field.

  6. #6
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361

    Talking Just for fun:

    Quote Originally Posted by timebuilder View Post
    ....Similarly, when people say "duck tape," they mean "duct tape." ...
    I guess it is official:

    Did You Know?
    Duct tape actually emerged from the trenches of World War II. GI's used the government issue sticky stuff to keep boots and ammo boxes dry, calling it "duck" tape for its ability to repel moisture. When soldiers brought the tape home after the war, the housing boom provided them with many uses for it, including holding together heating and cooling ducts. Thats when it became "duct" tape, though Duck Tape survives as a trademarked brand.

    This Old House, January/February, 2003, page 20.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

  7. #7
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,004
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  8. #8
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,989

    Talking

    I needed that humor...

    Those little ducks will get bigger, the other ducts won't...
    --------------
    I'd get a new furnace & then optimize the duct system for it & any A/C or heat pump...
    Last edited by udarrell; 09-05-2011 at 10:32 AM. Reason: little ducks...

  9. #9
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    5,047
    Your furnace is grossly oversized for you house.
    Resizing the duct to the furnace isn't going to fix the problem. Now you've just got an oversized furnace attached to correct ductwork.

    Replace the furnace. Who knows, maybe the duct is correct for the correct furnace?
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  10. #10
    Join Date
    Sep 2011
    Location
    Cotuit Ma
    Posts
    18
    Most Of my ducts are definetly wrong size. Example: supply main 8x20 , return 8x16. No return to Second Floor. I had no issue with my heat system ,but noice is unbareble. No zoning for two story house.
    Does btu's per room and fan cfm dictates size of ducts (don't mind friction and length of ducts) ???
    Last edited by Armis; 09-05-2011 at 11:47 AM. Reason: None

  11. #11
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,196
    Do both. Get the ductwork taken care of. Return to upstairs for better cooling. And right sized furnace. Shove that 100K up your friend's ...

  12. #12
    Join Date
    Nov 2006
    Location
    Southeastern Pa
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    18,593
    Quote Originally Posted by BaldLoonie View Post
    Do both. Get the ductwork taken care of. Return to upstairs for better cooling. And right sized furnace. Shove that 100K up your friend's ...
    ...exhaust duct?
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







  13. #13
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361

    Seems like the #1 problem here is noise.

    Quote Originally Posted by Armis View Post
    .... I had no issue with my heat system, but noise is unbearble. No zoning for two story house.
    • A pro might be able to select a lower fan speed and check heat rise to be within design limits.
    • It is possible that the noise is whistling caused by air moving across cheap grilles.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

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