What Does a Damper Do?

...
How Does an HVAC Zone Control Damper Work?
...
A motorized damper

Dampers are like the traffic cops of any sort of pipe or tube. In plumbing, they control the amount of water that may pass through a pipe. In ventilation systems, they define how much heated or cooled air can go that segment of pipe at that time.

What Are the Benefits of a Damper?

A damper gives the user control over how much air is distributed to a particular zone. A zone can be a room or floor of a house or an office or section of offices.The damper system works differently than just closing a vent on a floor or wall. When you shut the vent, the heated or cooled air still must travel the length of the pipe to reach the outlet. When it is denied an exit, the air usually sits in the pipe and becomes room temperature. A damper is usually setup at the mouth of a distribution pipe and allows or denies air at that point. This maintains the pressure in the pipe and redistributes the airflow to the rest of the structure.

How Is It Operated?

There are two types of dampers--manual and motorized. Manual dampers work exactly as they sound. The user twists a screw, which governs the flow of air to a section of pipe. The motorized damper works similarly except that the twisting of the screw is done by a machine. The sophistication level of motorized dampers varies. They can be as simple as an attachment to the screw or as advanced as the system pictured at the top of the page. This uses a computerized screen to determine how far open the damper should be, based on a percentage--0 percent would be closed, 100 percent would be completely unobstructed.