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Thread: Duct Branching

  1. #1
    Join Date
    Jan 2005
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    Round Rock
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    7
    I'm a home inspector and I'm seeing this more often. Essentially, there's a distribution branch run off of the main plenum of a forced air unit. This branch is then split into two (a "Y") without the use of a "triangle" junction box, AND the split is NOT equal in size (one large branch, and one small). Then further down the larger branch, there's another split without a junction box (again one large, and one even smaller branch). Many of my customers who complain of poor airflow have this configuration. Is this type of thing proper, and if not, what is a better configuration. I would think that no branching would be best. Any help appreciated.

    Peter.

  2. #2
    Join Date
    Nov 2000
    Location
    Waco, Texas, USA
    Posts
    6,153

    This has to be a joke......

    Dude you are freakin cracking me up......hahaha

    The junction boxes you speak of are the worst way to run a duct system. The wyes you see are the best.
    "And remember my sentimental friend......that a heart is not judged by how much you love, but by how much you are loved by others" - Wizard of Oz.

  3. #3
    Join Date
    Dec 2004
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    Derby City
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    3,964
    Peter: don't know if you are referring to a new or old home, where you come across this. Where I am located (Ohio Valley) it is not at all uncommon to come across duct systems in older homes (vintage 50s and 60s) that I refer to as "graduated duct systems." On these galvanized duct systems each time a branch comes off the main trunk, there is a reduction. The transition at this point resembles a "y" in its configuration, but is really a reducer. At each branch the reducer transition is in place. These are actually excellent systems for air distribution as each time a branch lead comes off, the trunk size is reduced accordingly maintaining good pressure within the system. The only reason these systems are not used today is cost. With the number and type of fittings required, the new construction market makes it prohibitive. I couldn't tell if you were referring to round or rectangular duct, but all this duct in these systems is rectangular, even the branches. One thing to note. In these systems I am referring to, there is a volume damper at each one of the transitions to help balance the airflow throughout the system. I am curious. Is it normal procedure for inspectors in your area, or are you just that much more thorough in getting into the air distribution systems of the hvac system? Around here, the home inspectors some of whom have more background in mechanical systems than others usually look at the equipment and note, "yep, that there's a furnace all right."

  4. #4
    Join Date
    Jan 2005
    Location
    Round Rock
    Posts
    7

    A picture is worth ...

    Dear Mr. Wiggins:
    I'm glad I made your day. BTW, I'm just down the road from you in Round Rock. Perhaps I'll have the pleasure of inspecting your work some day ... then we'll see who has the last laugh. Anyway ... here's a picture. You tell me ... is this kind of thing proper?



  5. #5
    Join Date
    Nov 2000
    Location
    Waco, Texas, USA
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    6,153
    Yes that is proper and thanks for the pic. Some cities want to see mastic on the vapor barrier but I wouldn't ever recommend that.

    As for inspecting my work let me let you in on a little secret. I am a design professional and you are not. Challenge me and you will lose.
    "And remember my sentimental friend......that a heart is not judged by how much you love, but by how much you are loved by others" - Wizard of Oz.

  6. #6
    Join Date
    Feb 2003
    Location
    South Carolina
    Posts
    1,333
    Mr Wiggins,
    I to am amused by you. Keep it up.We all know inspecters suck. If he was any good at his job he wouldn't have to ask a thing like that.lol lol lol lol

  7. #7
    Join Date
    Dec 2004
    Location
    Derby City
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    3,964
    those pants seem to be a little short in the "rise."

  8. #8
    Join Date
    Aug 2003
    Location
    Central Kentucky
    Posts
    6,248
    Peter a lot of times that type of duct design has so much pressure drop over the various fittings it just can not properly deliver airflow.
    We have gone in on jobs before & renovated duct systems where we had to remove this type of design.
    It may be ugly but if it delivers airflow & BTU's in the proper quantity to where it is supposed to then no issues.
    Problem is most of them don't even come close.
    Irish,if you are ever in Frankfort look me up.

  9. #9
    Join Date
    Feb 2004
    Location
    chicago suburbs
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    4,422

    Re: A picture is worth ...

    [QUOTE]Originally posted by pjsullivan
    Dear Mr. Wiggins:
    I'm glad I made your day. BTW, I'm just down the road from you in Round Rock. Perhaps I'll have the pleasure of inspecting your work some day ... then we'll see who has the last laugh. Anyway ... here's a picture. You tell me ... is this kind of thing proper?


    [/QUOT

    now that's quality. i bet they can rough in the whole house in 5 hrs.

    irish i completely agree with you. we have alot of the old graduated trunklines around here too.
    FILL OUT YOUR PROFILE!!

  10. #10
    Join Date
    Nov 2004
    Posts
    125
    Irishmist

    That method is called the "static regain method" and I can tell you from experience that it is still used by people that want value rather than price (many still around, you just have to sell TO them). I only use rectangular, wrapped.

    PJ

    that system in the pic is junk. You are gonna have insulation failure where that lawn chair webbing and pan-ties choke that flex. Also if you instal flex systems you should at least stretch out the flex. I guess nowadays that type of install passes for cookie cutter homes.

  11. #11
    Join Date
    Nov 2004
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    125
    Challenge me and you will lose
    lmao

  12. #12
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    Nov 2000
    Location
    Waco, Texas, USA
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    6,153

    Inferior duct design



    "And remember my sentimental friend......that a heart is not judged by how much you love, but by how much you are loved by others" - Wizard of Oz.

  13. #13
    Join Date
    Nov 2000
    Location
    Waco, Texas, USA
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    6,153
    Originally posted by tin_fab

    I only use rectangular, wrapped.

    Hahaha .....what kind of dream world are you living in?
    "And remember my sentimental friend......that a heart is not judged by how much you love, but by how much you are loved by others" - Wizard of Oz.

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