Where exactly should I drill the test holes for the balancer in the main trunk line?
4th YearTAB / Startup PrepYELLOW · Check First
Locate a flat, straight section of the primary supply or return air trunk line that sits at least 7 to 10 straight duct diameters downstream from any primary fan discharge or major elbow fitting. * Drill a neat row of test ports (sized to accept a standard 3/8-inch or 1/2-inch pitot tube probe) spaced uniformly across the face width of the metal to allow the balancer to perform an accurate cross-sectional traverse reading.