The Condenser - Hat and Channel Damper Frames

There are two common types of damper frame: the hat frame and the channel frame. We discuss their similarities and differences in this Condenser article.

Damper Frames

Dampers consist of one or more rotating blades contained in a frame. We often focus on the blades when talking about dampers, but there are also a few things to think about when considering the damper’s frame. There are two primary types of frames: channels and hats. Both are designed to accommodate in-jamb linkage.

Channel Frames

Channel frames are shaped like the letter “U”. The legs of the “U” form the edges of the frame while the curve makes the interior walls of the damper. Dampers with channel frames will typically sit flat on top of the opening, so that only the blades are in the airstream. Channel frames can also be undersized to fit inside of the duct or opening, depending on what you want to do.

Sizing a channel frame damper will depend on how the damper is installed. Dampers that are mounted on top of the opening will be measured from the inside of the frame, while dampers installed inside the opening will be measured along the perimeter of frame. Want to know more? Read our article on sizing dampers here. 

Hat Frames

Hat frames form the shape of a hat. In fact, the shape closely resembles a boater hat: a hat with a small rigid brim and a shallow crown. The brim of the hat will sit in the opening while the crown of the hat provides space for in-jamb linkage.

Hat-shaped frames are typically installed inside the opening or duct. The entire damper will be inside the airstream. These dampers are typically measured along the perimeter of the frame, minus a nominal deduction from the width and height (¼ inch) to account for changes in the duct’s dimensions.

Notice the similarities? Hat-shaped frames are designed to sit inside the opening and provide room for linkage.

Most dampers will have a predetermined frame style. Hat frames are the most common type of frame for control dampers. If you can choose the frame style, consider the way you will be installing the damper. Do you want to install it inside the opening or have the damper sit flat on top of the opening? The installation type will typically determine the frame style.

For more on control dampers, check out these Newsstand articles:

• The Condenser - A Closer Look at Linkage
• Five Things to Know When Selecting Dampers
• Anatomy of a Damper

MCDLG & Continuing Education

Want to know more? MCDLG offers a free self-paced course on control dampers.  

Learn the basics of control dampers with "An Introduction to Air Control Dampers", including their components, what they do, where they go in an HVAC system, and guidelines for installing and maintaining your control dampers.  

This course provides continuing education credits for a variety of institutions, including ASHRAE's PDUs. Learn and earn at your own pace. Visit the MCDLG Campus Portal today!

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