Overview
The Duct leakage test plays main role in the installation of the HVAC systems. Duct leakage is when conditioned air gets distributed from AC unit leaks through holes/cracks/seams in the ductwork (a.k.a. air ducts) before it reaches the desired rooms/spaces in a home or building. According to ASHRAE (industry authority for HVAC stuff), 75% of buildings have duct leakage.
Duct leakage reduces the air quantities at terminal points unless the total air quantity is adjusted to compensate. Leakage should be considered a transmission loss in duct systems. The certain leakage limits for ducts and outlines procedures for testing ducts for conformity with air leakage limits that are set forth in a designer’s project specification. Duct leakage test performed under pressure in accordance with SMACNA duct leakage testing manual. SMACNA Standards applied only if any parts of the duct installation Standards are not covered by DW/ 143 or DW/ 144.
Industry-wide methods of assessing duct leakage are based on duct pressurization tests and focus on “high pressure” ducts. Even though “low pressure” ducts can be a large fraction of the system and tend to be leaky, few guidelines or construction specifications require testing these ducts. We report here on the measured leakage flows from ten large commercial duct systems at operating conditions: three had low leakage (less than 5% of duct inlet flow), and seven had substantial leakage (9 to 26%). By comparing these flows with leakage flows estimated using the industry method, we show that the latter method by itself is not a reliable indicator of whole system leakage flow, and that leakage flows need to be measured.