Duct Branching - Page 3
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Thread: Duct Branching

  1. #27
    Join Date
    Oct 2004
    Location
    Texas
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    1,172
    PJ, how did you get in my attic? Seriously, That method used in the picture in my opinion is an abhorent way to install flex duct work. The Y branching method is fine if installed correctly. Is that amalgamation of ducts that I see installed correctly? NO! there is your answer. Is it going to be a problem? That is not a question anyone can answer except the technician who does an airflow analysis on that duct system. So tell your client to hire an HVAC professional to perform an airflow analysis. If that is not acceptable then you or anyone else cannot honestly answer if "It will be a problem".
    Saddle Up!

  2. #28
    Join Date
    Nov 2000
    Location
    Waco, Texas, USA
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    6,153
    Originally posted by pjsullivan


    "The HVAC ductwork in the photo, although branched correctly, may not provide adequate airflow to the smaller diameter sections of the branches. Recommend a qualified HVAC professional evaluate and determine a course of corrective action."

    PJ, that statement is horribly inaccurate. You are going to have an a/c contractor dead in the middle of your xxxx.

    Part of the problem here is there is no design requirement on the blueprints. You will find all sorts of other trades design but no hvac. The builders refuse to pay a design professional to draw out good design. Therefore all the decisions are left up to the installing contractor or his subs.

    This notion you have of the smaller branches not getting enough air is weak. How do you know how much air should be coming out of the supply register? Even if you measured it with a balometer you still won't know because there is no requirement for that to be listed on the blueprints.

    "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. #29
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
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    14,914
    What it comes down to is whether the duct system was designed and sized properly for the fittings and materials used. I'll bet any of you a weeks pay that it is not, and the installer just tied all that together as the most convenient place to do it, using the least materials.

    Ductwork run like that is very typical here in north Texas, and in my experience, is the cause of a lot of airflow issues.
    Any time I see multiple wyes that close together in flex duct like that, I find badly uneven airflow.

    At least they used metal wyes, those ductboard triangle things are total crap, and should be outlawed, lol.
    If more government is the answer, then it's a really stupid question.

  4. #30
    Join Date
    Jan 2005
    Location
    Round Rock
    Posts
    7
    Thanks so much -80guru. I followed your advice, and informed my client that if he still has a concern regarding the ductwork, then he should contact an HVAC pro to perform an airflow analysis.

    And thanks sincerely to all who replied. I will definitely be coming back here whenever I have HVAC questions.

  5. #31
    Join Date
    Oct 2001
    Location
    Waterford Michigan
    Posts
    2,668
    Originally posted by pjsullivan
    Thanks so much -80guru. I followed your advice, and informed my client that if he still has a concern regarding the ductwork, then he should contact an HVAC pro to perform an airflow analysis.

    And thanks sincerely to all who replied. I will definitely be coming back here whenever I have HVAC questions.
    Now your acting like a true professional, good job.

  6. #32
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
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    3,304

    What can you see

    A question I hope one of the more expert people will answer: Is the problem with this picture, partly that the Wyes are so close together? Can anyone explain why triangle boxes degrade airflow?

    What can you see that will degrade airflow? Can you describe in a few words how it would be built better?

    If there were a clear and simple answer, and the price were not thru the roof, I would probably pay to have it corrected in my own house.

    Thank you -- P.Student

  7. #33
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    There is nothing wrong with the wyes,or even tri-boxes,IF they are accounted for in the Man. D ,duct design.

    In this case we have no information,to make a decision,as to what the airflow will be.

    If you want to redo your duct system,it's Man. J,room by room,then a redesign using Man D.This will allow you to bring the ESP down to whatever you select,and provide even temperatures throughout the home.

  8. #34
    Join Date
    Feb 2004
    Location
    chicago suburbs
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    4,422
    flex duct degrades the airflow. it is not smooth like the metal pipe. the smoother and squarer the duct, the better. the part here that gets me is even if you went with CHEAP round "stove" pipe it would be way better than this. it would be fairly close in price and you wouldn't need a
    tin-shop. this way saves on labor mainly and what's more important than their bottom line anyway. i'm happy they don't do this around Chicago.
    FILL OUT YOUR PROFILE!!

  9. #35
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
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    3,304

    Pre-planning vs. follow-up

    Dash, I have always consistently heard that message from you, "Manual D is the only way to be sure". Thanks for reassuring me that the universe is governed by natural laws and not by whims.

    Although after the system has already been built, would not a flow hood test of each supply register (and maybe the returns too) give a valid after-the-fact answer?

    Best wishes -- P.Student

  10. #36
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    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    Re: Pre-planning vs. follow-up

    Originally posted by perpetual_student
    Dash, I have always consistently heard that message from you, "Manual D is the only way to be sure". Thanks for reassuring me that the universe is governed by natural laws and not by whims.

    Although after the system has already been built, would not a flow hood test of each supply register (and maybe the returns too) give a valid after-the-fact answer?

    Best wishes -- P.Student
    Testing would give you the total airflow delivered,thru the supply and return ducts,less any duct leakage.

    This is valuable information,but you need to know what each rooms cfm should be(Man J),and what is the airflow thru the equipment(ie. without leakage).



  11. #37
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    Aug 2002
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    Office and warehouse in both Crystal River & New Port Richey ,FL
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    Originally posted by tinner73
    flex duct degrades the airflow. it is not smooth like the metal pipe. the smoother and squarer the duct, the better. the part here that gets me is even if you went with CHEAP round "stove" pipe it would be way better than this. it would be fairly close in price and you wouldn't need a
    tin-shop. this way saves on labor mainly and what's more important than their bottom line anyway. i'm happy they don't do this around Chicago.

    Flex is not a problem,IF the Man.D design is for flex.Flex does not degrade airflow,poor design and install does.

  12. #38
    Join Date
    Apr 2004
    Location
    Lubbock, Texas
    Posts
    267

    PJ

    You are on the right path /do have an HVAC company check the design airflow airflow airflow 2nd only to unit size in importance the pic you showed actually looks better than most but that does not mean it is sized correctly to the unit or that the unit is sized correctly to the bldg. location have a manul j and manual d calc done

    sorry dash I had not read the 3rd page before I posted you already settled it apologies for the redundancy

    [Edited by conrad1 on 01-09-2005 at 11:59 AM]
    Learning never ends and everyone has something to teach. Some people teach me what to be like others teach me what not to be like!

  13. #39
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    Aug 2002
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    Looking at the photo,I'd check to make sure the wyes are insulated properly.

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