Pressure class, 3 pressure class, Duct pressure classifications – Retrotec Commercial 441 and 451 DucTester User Manual
Page 39: Specified test pressure
Page 39 of 56
©Retrotec Inc. 2015
8.3
Pressure Class
Duct pressure classifications
The duct system designer should designate the Pressure Class or classes for construction of each duct
system and clearly identify these in the contract document.
Where no pressure classes are specified by the designer, the 1 inch Water Column (in WC) Pressure
Class will be the basis of compliance with SMACNA, regardless of velocity in the duct, except variable
volume duct upstream of VAV boxes which must have a 2″ in WC Pressure Class.
Conventional leak testing requires a positive test pressure.
Specified Test Pressure
The ducts should be tested at this pressure if specified but the Test Pressure shall not exceed the
Pressure Class. Normally the designer will specify the Test Pressure.