Dial in the cfm and a friction rate, such as 0.08 or 0.1 inches of water per 100 feet, and the wheel shows the round duct size, the equivalent rectangular sizes and the air velocity. The name is a trademark, but techs use it for any such calculator, card or app. Designers and installers use it for quick sizing in the field and to check whether a run is choking the system.
Ran it on the ductulator, 400 cfm at point one wants a 10 inch, they put in an 8, no wonder it whistles.
Also heard as
- duct calculator
- duct wheel
Related terms
CFM
Cubic feet per minute: the standard unit of airflow through equipment, ducts and outlets.
Static pressure
The pressure air exerts outward on duct walls, the resistance a fan works against, measured in inches of water column.
Tin knocker
Jobsite nickname for a sheet metal worker who fabricates and installs ductwork.