Why would hot air whistle out of the reheat coil frame on a VAV box?

A coil frame or casing gap can dump conditioned air into the ceiling and whistle. Shut down, clean the seam, fasten the frame, and seal with the approved temperature-rated sealant/detail.

['A VAV reheat coil area can leak if the coil frame, slip track, or casing seam is not tight. That leak may be loud and can dump hot or conditioned air into the plenum instead of the zone.', 'Confirm power/fan status, clean the metal, close the mechanical gap with fasteners where allowed, and seal with the approved temperature-rated sealant or gasket detail. If the coil or heater section is damaged, hold for equipment/vendor direction.']

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