Fantech RSK8 Backdraft Damper

8 inch diameter

Galvanized steel, back draft dampers are used to prevent thermosyphoning of cold air at night in air heating systems. These dampers are spring-loaded, allowing air flow in one direction only. When mounted directly downstream of the blower output, they offer virtually no resistance to air flow when open. The damper automatically closes when the blower is off, thereby preventing thermosyphoning.

ref. 5C525