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Apprentice answer

Why do sharp offsets right at a VAV inlet cause bad CFM readings

3rd YearAirflow, TAB, Startup & TestingCheck first

Back-to-back offsets at a VAV inlet can spin and disturb the airflow before the sensor. Give the VAV a smoother approved inlet path instead of dumping turbulence into the box.

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Plain-English answer

A VAV inlet sensor needs a stable air profile. Back-to-back sharp offsets, especially flex or hard 90s, can create swirl right before the box and make TAB readings bounce around.

Check the inlet condition, available straight length, obstruction, and submittal requirement. The likely recovery is a revised rigid spool, smoother offset, relocated box, or approved inlet condition so the air settles before the sensor.

Ask Foreman

VAV [tag] has back-to-back offsets right at the inlet and TAB readings are unstable. I checked the obstruction and inlet path. Do you want a smoother rigid spool/offset or box shift?

Verify before acting

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

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