The duct run vibrates or rattles when the air handler starts
Treat startup vibration as a support/connection/TAB symptom. Check hangers, flex connector, joint tightness, equipment connection, isolation, and whether duct weight is being carried by the wrong part.
Do not grab vibrating duct, wedge random material into supports, or silence the symptom without finding the cause.
Check
Stand clear of moving/vibrating components.
Check if vibration starts at equipment or a loose duct section.
Look for missing support, long unsupported span, loose joint, flex connector stretched tight, or metal rubbing structure.
Photograph/video the symptom and location.
Ask before adding random screws/bracing.
Steps
Stand clear of moving/vibrating components.
Check if vibration starts at equipment or a loose duct section.
Look for missing support, long unsupported span, loose joint, flex connector stretched tight, or metal rubbing structure.
Photograph/video the symptom and location.
Ask before adding random screws/bracing.
Say this to your foreman
When the AHU starts, this duct vibrates/rattles at [location]. I checked supports and equipment connection. Do you want me to inspect hangers, joint fit-up, or flex connector first?