Where exactly should I drill the test holes for the balancer in the main trunk line?

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.

['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.']

Stop if

• Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

Steps

• 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...

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