Vibration isolation keeps fan and motor movement from transferring into duct and structure. If the duct is hard-connected where isolation is required, the duct becomes a vibration path.
Do not make a rigid duct connection to equipment that is on spring or rubber isolation unless the approved detail specifically calls for it.
Check
Look for the isolation system: spring isolators, rubber pads, flexible duct connector, flexible electrical conduit, isolated hanger detail, or notes in the equipment submittal.
Check whether the duct is rigidly bolted to equipment where the approved detail calls for a flex connector. A rigid connection bypasses isolation.
Check whether any duct hanger, brace, strap, or support is attached to the equipment cabinet. Duct supports near equipment should be independent unless the approved detail says otherwise.
If the flex connector is missing, do not make the final duct connection yet. Flag it before sealing or insulating.
If equipment isolators are missing or not set correctly, document it before startup. Running equipment before isolation is corrected can spread vibration complaints through the building.
Steps
Look for the isolation system: spring isolators, rubber pads, flexible duct connector, flexible electrical conduit, isolated hanger detail, or notes in the equipment submittal.
Check whether the duct is rigidly bolted to equipment where the approved detail calls for a flex connector. A rigid connection bypasses isolation.
Check whether any duct hanger, brace, strap, or support is attached to the equipment cabinet. Duct supports near equipment should be independent unless the approved detail says otherwise.
If the flex connector is missing, do not make the final duct connection yet. Flag it before sealing or insulating.
If equipment isolators are missing or not set correctly, document it before startup. Running equipment before isolation is corrected can spread vibration complaints through the building.
Say this to your foreman
The connection at [unit tag/location] looks like it should have vibration isolation, but the duct is currently [rigid / missing the flex connector / supported from the equipment]. Do you want me to hold the final connection until the isolation detail is corrected?