Rectangular Duct: Stick to Even Dims?

[CuriouslyGeorge]

As I understand it, rectangular duct is commonly stocked and/or fabricated in even dimensions. Therefore, when sizing ducts, select only even dimensions for wxd. Is this correct? Do you avoid odd dim's, even if you have to go up to the next equivalent duct diameter to find even dim's on your chart or table? (I am using the ASHRAE Fundamentals 2001 - F34.10 table)

Thanks!

 

[DUMechEng]

i use odds all the time. whether mr contractor actually installs it is another story.

 

[DRWeig]

Even, odd, nowadays no duct is "in stock" for many contractors, they fab it with a machine unless it's round. The guy who spec'd the building I'm in right now somehow liked to mix 'em up. Not an issue anymore I don't think.

Let us know how your project goes!

Old Dave

 

[CuriouslyGeorge]

Circa 2001, I worked for a mid-sized engineering firm in Baltimore that did some big HVAC jobs. The rule of thumb was to avoid odd dimensions. Do you think it was an old stigma that failed to die? Was it once a problem getting odd sized rectangular duct?

 

[cme]

CG,
Most everything is even sized (diffuser necks, vav boxes, etc) .... now and then you'l get a bastard size