Why does a fan coil need a flexible connector at the duct connection

Plain-English answer

Rotating equipment can send vibration straight into rigid ductwork if there is no break between the unit and the metal duct. That hum can travel into the ceiling grid and occupied space.

The fix is to install the project-approved flexible connector/canvas/isolation detail at the equipment connection, with enough slack and proper clamping/fastening. The duct still needs its own support; the flex connector should not carry weight or be stretched tight.

Field checklist

• Confirm the vibration source is the unit, not loose ceiling, hangers, or duct rubbing.
• Check whether a flexible connector/isolation detail is shown on the submittal/drawings.
• Make sure ductwork is independently supported and not hanging from the unit collar.
• Check connector material, slack, alignment, and access.
• Recheck vibration/noise after startup.

Ask Foreman

Verify before acting

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

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