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Noisy ductwork

What is going on

Possible causes and checks for: noisy ductwork.

Likely causes

  • Velocity >700 fpm (blower sped up to cover undersized equipment/duct)
  • Sharp edges in grille/duct
  • Vibrating panels (oil-canning)
  • Fan/motor rumble
  • Expansion popping

Check in this order

  1. Remove grille test
  2. Measure velocity
  3. Lower velocity
  4. Vaned/long-radius elbows
  5. Line/wrap duct
  6. Cross-break panels
  7. Fabric joint at furnace
  8. Acoustic chamber

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Source: General HVAC service practice — verify per model. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.