Page 2 of 2 FirstFirst 12
Results 14 to 16 of 16
  1. #14
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,062
    about a week

  2. #15
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,198

    Newest Man D takes a different approach

    Quote Originally Posted by Gross View Post
    hm. right outta manual d and on the back of the ductulator :recommended velocty for residential main ducts 700-900 fpm.,...maybe we've all been doing it wrong and didnt know it.
    You're right, the old velocity guidelines of 900 FPM max for supply and 700 FPM for return were mostly for noise concerns with bare sheet metal. The latest edition removes those guidelines because if you were to use ductboard or trunk with flex branches then noise is not as much of a concern.

    BUT it has always been the intent of MAN D to CALCULATE how much static pressure is left after you deduct the coil, filter (sometimes) and registers and grill so you can get the ASP ( available static pressure) which you then divide by the measured length and fitting equivalent lengths to CALCULATE A FRICTION RATE. the friction rate you use is a calculation NOT a Guess!

    Oh if you go above the 900/700 then you need to adjust the fitting length values in the appendix.
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  3. #16
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,423
    Thanks genduct, as always a great explanation!
    Make your expertise uniquely valuable.

    Make your influence uniquely far-reaching.

Page 2 of 2 FirstFirst 12

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