Results 1 to 8 of 8

Thread: Friction Loss

  1. #1
    Join Date
    Jan 2008
    Posts
    23

    Friction Loss

    For new installs, do you rely on a standard figure or are you using a formula to arrive to a given factor?

  2. #2
    Join Date
    Apr 2008
    Location
    Princeton, NJ
    Posts
    581
    I beleive I read on the Udarrel site (one of the Pro's here) a recomendation of 0.05 or 0.06 water column per hundred ft of duct.

    I'm shooting for lower static pressure so my new duct sytem is being designed closer to 0.04.

    Key1

  3. #3
    Join Date
    Jan 2007
    Location
    Minneapolis, MN
    Posts
    415
    I rely on ACCA manual J, D, S, T, RS, Quality Install, Right Suite Universal, and some others to come up with the correct friction loss and design.

  4. #4
    Join Date
    Jan 2008
    Posts
    23
    I know that manual D provides the formula for sizing and such, however I don't think it addresses the formula to obtain or verify the correct friction loss.

    Aside from a rule of thumb method, how is friction loss verified?

    key1cc: I could be wrong, but using .5/100' as a standard sounds incorrect. I mean I could be wrong, but if that is true you're saying a 6" round will flow around 220CFM. I have always been under the belief that a 6" has a flow closer to 110CFM. Referencing the ductalator, that equates to a friction loss of .1, which is 100% variation from .5

    Now I am not a sheet metal guy, and I am not saying that using .5 as a standard is incorrect, but it dose seem right to me. Frankly this is why I have asked the question to begin with.

    Without knowing how to arrive to the correct FL, you are essentially guessing.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,758
    Key posted .05", NOT .5"

    And Manual D does have the FR formula.

    Reread it.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  6. #6
    Join Date
    Jan 2008
    Posts
    23
    Quote Originally Posted by beenthere View Post
    Key posted .05", NOT .5"

    And Manual D does have the FR formula.

    Reread it.
    Thanks for the correction, I overlooked the extra digit. I suppose that using.05 dose make more sense in that it would yield a more conservative CFM flow, and perhaps build in some redundancy to help prevent A coil freezing on designs that may not have too much restriction.

    One of the reasons I started the post is that I cannot find my book. It has been years since I have seen it. Can you bring me up to speed on the formula?

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,758
    (asp*100)/tel=fr

    Eg: (.18*100)=18,/295=.06"fr
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  8. #8
    Join Date
    Jan 2008
    Posts
    23
    Quote Originally Posted by beenthere View Post
    (asp*100)/tel=fr

    Eg: (.18*100)=18,/295=.06"fr
    Thanks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event