A gravity damper is a passive, motorless damper that uses weighted blades to control airflow through ducts based on air pressure differences. These dampers open when positive pressure pushes against them and close when pressure reverses or decreases. Gravity dampers require no electricity, making them ideal for applications where power reliability is uncertain.
Operation and Design
Gravity dampers rely on counterbalanced blades weighted to open at specific pressure thresholds, typically 0.02 to 0.1 inches of water column. The blade design allows unrestricted airflow in the intended direction while preventing backflow. These devices are commonly used in exhaust ducts, fresh air intakes, and one-way ventilation systems.
Applications and Limitations
Gravity dampers work well for preventing unwanted air leakage in exhaust systems and backdrafting in combustion appliance vents. However, they provide no active control and cannot respond to thermostat signals or zone requirements. They are often paired with motorized dampers in modern HVAC systems for enhanced efficiency.