Anatomy of a Damper

Anatomy of a Damper

In this Condenser article, we review the parts of a control damper. Each part is important. Learn how these parts work together on the Newsstand.

The Parts of a Damper

Dampers typically consist of several adjustable blades contained in a frame. This basic design can differ from damper to damper, but the general principle is the same: the damper will open and close to regulate air flow. To understand dampers, you should understand their parts and how they all come together.


The damper frame encompasses the damper blades

The frame is the metal perimeter of the damper. Square and rectangular dampers will have frame with four sides. The left and right side of the frame are referred to as the jambs. Jambs will have holes at set points for the damper’s blade axles. They can also contain the linkage assembly for the damper. Frame members can have one of three shapes: channel, hat, and round.

The profile of the channel frame forms a flat U-shape. Channel frames can sit flat against the surface of the opening, inside the opening, or inside duct with no special considerations. Hat-shaped frames have two flat pieces along the outside that form the “brim” of the hat. The area within the “hat” provides space for in-jamb linkage. Hat-shaped frames will sit inside the opening or duct. You will need to account for this when installing the damper. Check out this Condenser article for more on hat and channel frames. Round damper frames are a single piece of metal that form a cylinder. Round frames have a bracket piece to secure the blade axle to the frame. Other than this piece, the round frame will be smooth and featureless.


Damper blades rotate to open and close the damper

Blades are the long metal pieces inside the frame. Blades come in different shapes to serve different purposes. Read our primer article on damper blades for a full explanation on the different types of blades and their purposes. The blade’s main function is to regulate airflow through the damper. Damper blades will rotate along their axles, also known as shafts, to close off the damper or open it up.

Modulating dampers can set their blades to any angle between full-open and full-closed, while typical dampers will be full-open or full-closed only. By rotating the blades, dampers can direct airflow through the system, balance air pressure, or fulfill other important roles in your HVAC system. Blade design will play a significant role in the damper's performance.


Blades will rotate around their axles. One axle will be the driving axle.

Axles are lengths of metal used to rotate the blade. Axles can run through the center of the blade or along one edge of the blade for backdraft blades. Wherever it is located, the axle is fixed within the blade so that the blade will rotate with the axle. Blade axles run through the jambs of the damper and are secured to the jambs with bearings. The ends of the axles will be capped or tied to an in-jamb linkage assembly.

Driving axles can receive an extended shaft kit to increase its reach to other dampers in a multi-panel assembly, so that a single actuator can control multiple dampers. For more information on these options, read our article on extended versus extendable shafts.


Linkage translates the rotation of the driving axle to all connected damper blades

Linkage refers to the series of connectors that translate the rotation of a driving axle to every axle on the damper. Linkage can be installed on the face of the damper’s blades or within the damper’s jambs. On-face linkage will remain in the airstream when the damper is open. In-jamb linkage will not block the airstream but requires adequate space for the linkage assembly to move. Once installed, the linkage translates the rotation of the driving blade to all connected blades in the damper.

When the driving axle rotates, the linkage will rotate the axles of the other blades so that all blades move at the same time. Linkage can be configured to rotate all blades together or to rotate every blade in the opposite direction of their neighbors. This is known as parallel and opposed blade orientation. Read more about these configurations in our Newsstand article Parallel or Opposed?


Actuators are connected to the blade axle and govern the rotation of the driving blade

Actuators are not a standard part of a damper, but they are commonly added to dampers to facilitate blade rotation. There are three types of actuators: electric actuators that employ an electric motor, pneumatic actuators that use pressurized bladders, and manual actuators that must be operated by hand. Actuators are installed on the axle of the damper’s driving blade. When the actuator rotates the axle, the linkage translates that rotation to all connected blades.

Electric actuators and pneumatic actuators can remotely perform blade rotation, while a manual actuator requires an operator present to manually adjust the blades. Electric actuators can be tied to a central control system to automate blade action across multiple dampers. Each actuator type will have a variety of options to consider. For a full discussion of actuators, check out our Newsstand article: Actuators, Making Adjustments.


Transitions allow for the damper connections to ducts of different shapes

Transition collars allow dampers to be installed in ductwork of different shapes. These accessories are important when you find a damper that fits your requirements, but not the shape of your ductwork. For instance, a round transition will allow a square damper to be installed in a circular duct.

Transition collars are installed over the face and rear of the damper and caulk is applied to the seams. This ensures a tight seal between the transition collar and the damper. Once in place, the transition collar is connected to the ductwork to join damper with duct. Transitions are available in round, oval, square, and rectangular shapes. Check out this Newsstand article for more on round dampers.

Dampers are the sum of their parts. Each part comes together to play a role, whether the damper directs airflow or balances pressure, or prevents fire from passing through a fire barrier. It’s important to understand the anatomy of a damper and how its parts work together. 

For more on dampers, check out these Newsstand articles:

Want to talk about control dampers? Share your thoughts in the Comments section. MCDLG wants to talk!

Dampers are the sum of their parts. Every part plays an important role.


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