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Thread: cfm

  1. #1
    Join Date
    Jan 2005
    Posts
    3

    Question

    HOW MANY CFM FLEX DUCT WILL CARRY 4" THRU 20"

    I KNOW 6"FLEX IS ABOUT 100
    AND I THINK 7" IS ABOUT 150


  2. #2
    Join Date
    Nov 2001
    Posts
    1,874
    I show a 6" flex being less then 85 cfm, a 7" @ 120 cfm.

    I'm not going to list from 4" to 20"

    They make charts and tools for that.
    My listings were for .10 static

    Thats why if your not sure what your doing you can really mess up an install.

    A 6" flex is not a 6" metal, and shouldn't be thought of or sized as one.

    [Edited by Toolpusher on 06-22-2005 at 03:26 PM]
    If you try to fail, and succeed.
    Which have you done ?



  3. #3
    Senior Tech Guest
    Try writing your question another way....honestly it makes no since at all to me....

  4. #4
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,248

    Exclamation LOts

    OHaH, about 700 F P M
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  5. #5
    Join Date
    Apr 2004
    Posts
    7,680
    Agree with Toolpusher and others. Get a flex calculator and then realize that it is only accurate with the flex pulled tight and straight. IMHO in most applications 85 CFM for a 6" Flex is on the high side of reality.

    I suggest looking for rules of thumb be eliminated from your list of things to do.

  6. #6
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    The ductolator for flex or metal ,shows what the cfms will be at a "selected" Friction Rate(FR is static per 100 equivalent feet of duct),so without knowing the FR of the duct system,it's really useless.

    Order Manual D for ACCA,along with J and S,and never have a duct or sizing problem with your installs again,plus fix all the bad ones you will find.

  7. #7
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,248

    Thumbs up Fit ulator Needed

    Duct ulator is only ~ 1/3 of the total dP concern.

    The MAJORITY of pressure losses are in the
    fittings: elbows, transitions, tees, junction boxes, entry, exit, ...

    I guess I need to
    Invent the FitUlator
    for obtaining the toal System Losses.

    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

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