Duct Pressure Classification?

[russmech]

Can anyone tell me where I would find the definition of "medium pressure" ducting? I've looked in my SMACNA manuals and can't find it. Is this, perhaps, an outdated definition. Everyone uses the term, but I can't find a definition written down anywhere.

 

[CRG]

Static Pressure

Low Pressure 0 to 2 inch wg
Med Pressure 2 to 6 inch wg
High Pressure 6 to 10 inch wg

Hope this will help. It came from a design manual I put together a long time ago. I don't know the reference. It is most likly ASHRAE.

 

[russmech]

Thanks for the reply. What you've listed is what I remember, but I've looked in SMACNA, ASHRAE and my INDUSTRIAL VENTILATION BOOK to no avail. Can anyone else out there help?

 

[ChasBean1]

This is not as cut and dry as we engineers would hope. The SMACNA Duct Construction Standards manual does contain the answers, although many of us interpret simple alternatives. Have you reviewed the charts in the back of the standard?

I think that some of the common philosophy is that the vertical risers and mains are high, the ducts leading to terminal boxes are medium, and the duct work downstream of terminal boxes are low...

This all depends on the sheet metal gauge and how the ducts are put together, and the sealant used. I'm not the authority on this, but have had some experience...