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  1. #1
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    Duct Size Calculations


    I need help in calculation of duct size
    For equal friction method using friction loss of 0.1in/100ft for supply and 0.05/100 ft for return, do we need to calculate friction loss for the actual length of duct after taking in to consideration loss added by fittings. Where do we get information about loss added by fitting. till now I am simply aligning 0.1 in against cfm and finding the duct size in the window disregarding duct length.
    Best regards
    Hamidpia



  2. #2
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    Re: Duct Size Calculations

    Hi,

    Based on equal friction method, you are following correct procedure.

    With reference to length of ducts, it needs to be measured so that static pressure of blowers can be calculated.

    Pressure loss across duct fittings can be obtain from chapter on duct fittings from ASHRAE handbook.

    Regards
    Vijay Kumar
    HVAC Design Engineer

    BMCPL

    "The more you sweat in peace less you bleed in war"

  3. #3
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    Re: Duct Size Calculations

    This is a small software (vietnamese) for Duct Size Calculations.
    You can try using it . Simply, you click start button-enter unit for air volume and.......
    If you have any better software , could you give it to me ?
    Thanks for using my soft and pls give me some comments.
    Bye !
    I forget to give user and password to you
    here
    u : vee
    p: tienvy
    Attached Files Attached Files
    Last edited by lam vy; 25-08-2007 at 03:48 AM. Reason: additional

  4. #4
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    Re: Duct Size Calculations

    Quote Originally Posted by lam vy View Post
    This is a small software (vietnamese) for Duct Size Calculations.
    You can try using it . Simply, you click start button-enter unit for air volume and.......
    If you have any better software , could you give it to me ?
    Thanks for using my soft and pls give me some comments.
    Bye !
    I forget to give user and password to you
    here
    u : vee
    p: tienvy
    lam vy,

    I am Danh new to here. Would you give me more information of how to calculation the duct size please? Send me email at Danny.huu.tran@gmail.com.

    Thanks

  5. #5
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    Re: Duct Size Calculations

    Quote Originally Posted by ddvinothkumar View Post
    I need help in calculation of duct size
    For equal friction method using friction loss of 0.1in/100ft for supply and 0.05/100 ft for return, do we need to calculate friction loss for the actual length of duct after taking in to consideration loss added by fittings. Where do we get information about loss added by fitting. till now I am simply aligning 0.1 in against cfm and finding the duct size in the window disregarding duct length.
    Best regards
    D.Vinothkumar
    HVAC
    Please explain why you have repeated the first post ?
    Brian - Torquay, Devon, UK
    I have to stop saying "how stupid can you be?" to my co-workers.
    They're starting to take it as a challenge...

    BASIC MAINTENANCE. If it doesn't move and it should then use WD40. If it moves but it shouldn't then use Duct Tape.

  6. #6
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    Re: Duct Size Calculations

    there's no english software for calculating the duct size???

  7. #7
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    Re: Duct Size Calculations

    Hi, vee

    Quote Originally Posted by vee View Post
    there's no english software for calculating the duct size???
    for sure there it is ... even searching RE forums is possible to find many links or formulas how to calculate ducts...

    for some reason (or maybe by default) this way is easier ... otherwise our poster/s must spent some time for searching

    ... and maybe learn something what is not so popular nowadays, no time .... only instant answers ...

    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

  8. #8
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    Re: Duct Size Calculations

    Quote Originally Posted by vee View Post
    there's no english software for calculating the duct size???
    An article in the May 2009 ASHRAE journal describes an Excel spreadsheet that sizes ducts by the equal friction method, and computes fan external static. I would attach the article, but it's too big. You may be able to access it at the ASHRAE journal web site. It is possible also that you can still download the spreadsheet from the web site. I have a copy and could attach it, but this forum does not support .xls attachments.

  9. #9
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    Re: Duct Size Calculations

    Quote Originally Posted by dougheret0 View Post
    An article in the May 2009 ASHRAE journal describes an Excel spreadsheet that sizes ducts by the equal friction method, and computes fan external static. I would attach the article, but it's too big. You may be able to access it at the ASHRAE journal web site. It is possible also that you can still download the spreadsheet from the web site. I have a copy and could attach it, but this forum does not support .xls attachments.
    Hi Doug,
    PLease send the spreadsheet to me at subcooleng@gmail.com

  10. #10
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    Re: Duct Size Calculations

    Hi Doug, Pl send me also this spreassheet on gaurav_s55@yahoo.co.in

    regards

    GBRD

  11. #11
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    Re: Duct Size Calculations

    Hello Doug,

    It is great to be able to share our knowledge and experience on this nice forum. I appreciate if you can forward that excel sheet of duct sizing on my email herebelow:
    hamatif@live.com

    Thanks a lot.
    FADI

  12. #12
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    Re: Duct Size Calculations

    I Doug can you can forward that excel sheet of duct sizing on my email herebelow:

    pignatelli.eng@gmail.com

    Thanks

  13. #13
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    Re: Duct Size Calculations

    Quote Originally Posted by dougheret0 View Post
    An article in the May 2009 ASHRAE journal describes an Excel spreadsheet that sizes ducts by the equal friction method, and computes fan external static. I would attach the article, but it's too big. You may be able to access it at the ASHRAE journal web site. It is possible also that you can still download the spreadsheet from the web site. I have a copy and could attach it, but this forum does not support .xls attachments.
    hi doug plz can u forward me execel sheet for duct sizing i wil be very thankful to u mohdmohsin_j32@yahoo.co.in

  14. #14
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    Re: Duct Size Calculations

    Quote Originally Posted by lam vy View Post
    This is a small software (vietnamese) for Duct Size Calculations.
    You can try using it . Simply, you click start button-enter unit for air volume and.......
    If you have any better software , could you give it to me ?
    Thanks for using my soft and pls give me some comments.
    Bye !
    I forget to give user and password to you
    here
    u : vee
    p: tienvy
    hi plz can u send the software for duct sizing in english to mohdmohsin_j32@yahoo.co.in

  15. #15
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    Re: Duct Size Calculations

    hi friends here i attached duct calculator....

  16. #16
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    Re: Duct Size Calculations

    Quote Originally Posted by pramothmech View Post
    hi friends here i attached duct calculator....


    4shared.com/file/FXCjAReY/ductsizer.html use this link to download

  17. #17
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    Re: Duct Size Calculations

    Quote Originally Posted by vee View Post
    hi doug plz can u forward me execel sheet for duct sizing i wil be very thankful to u mohdmohsin_j32@yahoo.co.in
    All you will ever need for duct size calcs and fan engineering go to the link below
    www.flaktwoods.com/34bd869d-e1da-4f17-9209-8bb33b2ffa8a

  18. #18
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    Re: Duct Size Calculations

    At my web site www.nettally.com/doughert you will find an excel spread sheet that calculates duct size, air flow velocity, and external static pressure for a duct system. You can input the friction loss/100 ft that you want to use, the air flow rate, the duct height if rectangular, and the length of each leg. If the duct is round, you just enter 0 for duct height, and the program computes round duct diameter. Instructions for running the macros are on sheet 1.

    This spread sheet was featured in the ASHRAE Journal in May, 2009.

    You may contact me if you have questions.
    Last edited by dougheret0; 21-06-2010 at 01:57 PM. Reason: Add the sentence about the Journal

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