TAB found zero airflow or no air at a diffuser

Trace the diffuser backward before blaming the unit. Zero airflow usually starts with a closed damper, disconnected branch/flex, blocked boot, wrong device, or sealed/covered opening.

Stop if

• TAB is getting zero/no air at [device]. Can I trace the branch back and verify boot, flex, damper, and VAV/main connection before we blame the unit?

Watch out

• Do not randomly open/reset unknown dampers or blame the unit without tracing the branch.

Check

• Confirm the room/device tag.
• Check diffuser/boot connection.
• Trace flex/branch back to damper/main/VAV.
• Check damper position and access.
• Report the first restriction/mismatch before changing controls/equipment.

Steps

• Confirm the room/device tag.
• Check diffuser/boot connection.
• Trace flex/branch back to damper/main/VAV.
• Check damper position and access.
• Report the first restriction/mismatch before changing controls/equipment.

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