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  1. #14
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Quote Originally Posted by regis101 View Post
    Thankx dash.

    I am under the assumption that the length(s) of the ducting is part of, not just the reason, of the Man D to help get the airflow down to the rooms requirement.

    As dash mentioned, a shorter run will get more air. So this means a longer run will slow it down? If so, will having to take a branch line from 20ft as drawn down to 8ft affect the airflow as described for that room.
    Man. D determines he friction rate,which determines the duct size based solely on the longest return and supply air path.So all the shorter runs tend to get more air.Man. D suggests that balancing dampers be installed at each branch take-off,to allow for adjustment due to this.

    We find that the dampers at the supply grilles will take care of any required balancing.

    So yes yes,shortening it will have a minor increase in air flow,likly not an issue with proper design,in all other aspects of Man. D.

  2. #15
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    If you shortened the longest runs,it could increase the total air flow,in which case you would select a lower fan speed,or add restriction to the main ducts to get the correct air flow.

    We add 4 non-existent elbows to new home designs,to account for fild changes,and our installers know it,if the don't add any,we have less static which is easy to deal with,as stated above.

  3. #16
    Join Date
    Nov 2007
    Location
    Livermore, Ca
    Posts
    163
    Some knowledge. Thanks.

    With all the hammering you guys, the powers that be, do, about getting the
    Manuals J,D, and sometimes S, forgive me when I have a question that deviates from what has been stamped out.

    And well, if it takes three or four times to get the point across, so be it.

    When talking with the tin knockers at work, they mention not to make a tap at the end of a run. Instead, have a dummy leg, of sorts, as the last few feet of the (trunk) line. Acts as a buffer or bumper or something. They deal with mostly, if not all, metal trunks as done in the commercial world. Maybe another moot point.

  4. #17
    Join Date
    Nov 2007
    Location
    Livermore, Ca
    Posts
    163
    Thanks for the replies. I'm done

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