Having some issues with newly installed EWC 16x8 ND motorized dampers. I have a 3 zone hot air oil fired furnace. When one of the zone dampers closes is makes a high pitch whistling noise. When its open its fine. This only occurs for one of the 3 dampers. Not sure if there is anything I can do to seal around the damper better prior to placing it within the duct or if I need to adjust it so that it remains slightly opened when its called to be fully closed. Any help would be appreciated.
Thx