184.108.40.206 Ductwork and Plenum Leakage
Ductwork and all plenums with pressure class ratings shall be constructed to Seal Class A. Openings for rotating shafts shall be sealed with bushings or other devices that seal off air leakage. Pressure-sensitive tape shall not be used as the primary sealant unless it has been certified to comply with UL-181A or UL-181B by an independent testing laboratory, and the tape is used in accordance with that certification. All connections shall be sealed, including but not limited to spin-ins, taps, other branch connections, access doors, access panels, and duct connections to equipment. Sealing that would void product listings is not required. Spiral lock seams need not be sealed. All duct pressure class ratings shall be designated in the design documents.
Ductwork that is designed to operate at static pressures in excess of 3 in. of water and all ductwork located outdoors shall be leak-tested according to industry-accepted test procedures (see Informative Appendix E). Representative sections totaling no less than 25% of the total installed duct area for the designated pressure class shall be tested. All sections shall be selected by the building owner or the designated representative of the building owner. Positive pressure leakage testing is acceptable for negative pressure ductwork. The maximum permitted duct leakage shall be
Lmax = CLP0.65
|Lmax||=||maximum permitted leakage, cfm per 100 ft2 of duct surface area|
|CL||=||4, duct leakage class, cfm per 100 ft2 of duct surface area per in. of water0.65|
|P||=||test pressure, which shall be equal to the design duct pressure class rating, in. of water|