Mounting Options for Control Dampers

How you mount the damper will affect how you design it. Learn the four common ways to mount a damper with the MCDLG Newsstand.

You have the right dampers selected. Everything lines up: the damper type, the operating limits, the performance data. The next question should be about installation.

Where will these dampers go? Will they go inside ductwork, or will they fill an opening in a wall? Installation will help determine how you size the damper, among other important details.

There are four ways to mount, or install, a damper in a building. You can technically divide it into two ways. There is the typical “in-duct” installation, the “on-face” installation, the “in-opening” installation, and the “cantilevered” installation.

To simplify that, you can mount a damper “inside” or “on top” of a duct or wall. We are going to take a closer look at each mount type and what it means for your dampers.

In-Duct Mount

The full damper is in the duct. This is a common installation method for control dampers.

Installers place the damper inside the duct and fasten it to the walls of the duct. A hole is made in the duct wall to accommodate the extended shaft kits for attaching an on-jamb actuator. Once the damper is fastened in place, installers will apply caulk to the outer perimeter of the damper’s frame to minimize air leakage.

Pros:

1. The damper is secured to the duct. There is no need for additional supports like a flange frame.
   1. You may need additional support for the duct, depending on the size and weight of the damper.
2. The damper’s actuator is easy to access on the outside of the duct. This allows operators to easily test the actuator and replace it if necessary.

Cons:

1. The damper’s frame will be in the air stream. This will cause additional pressure drop when air is moving through the duct.
2. You will need to disassemble the duct to access the damper. This makes it more difficult to perform maintenance.

Control dampers are commonly installed in duct to control airflow. For in-duct installations, you will size the damper along its outer dimensions. This means you will measure the damper along the outside of its frame.

Outer dimensions ensure the damper’s frame will fit inside the duct. Manufacturers will undercut these dimensions by a quarter inch to account for thermal expansion.

On-face Mount

The face of the damper meets the face of the duct. This mounting method can also make duct-to-duct connections.

Installers mount the damper so that its face meets up with the duct opening. Once in place, the installers will fasten the damper to exterior supports. Then, they will connect the damper to the duct opening. This method provides plenty of free space around the jambs for actuators and other accessory parts. Installers can also fasten the damper to a duct on the other side, so that both sides are connected.

Pros:

1. Easy access to actuators and jambs. Operators can quickly test actuators and replace them as needed.
2. Excellent airflow. Only the damper’s blades are in the airstream.
3. Easy access to the damper. That means easier maintenance. Detach the ductwork on one side of the damper to quickly clean and test it.

Cons:

1. Needs additional support when installed. You will need extra hardware to support the damper’s weight.
2. Potential risk for unseating. The damper could potentially fall or break away from the duct. Checking and replacing fasteners should be a part of your maintenance routine.

Maintenance is a breeze with on-face installation. Operators can easily clean the damper, test its components, and ensure it is in full working order. On-face installation also provides the best airflow option, since the damper’s blades are the only part of the damper in the airstream.

However, you will need to consider your options for support. When sizing this damper, measure the dimensions along the inside of the damper’s frame. These inner dimensions will closely match the size of the duct opening.

In-Opening Mount

The full damper is in the opening. This is a good installation method for ductwork that passes through walls.

Installers will mount the damper inside of the opening of a wall. Then, they will fasten the frame to the substrate of the wall. Substrate refers to the underlying material that makes up the wall, such as concrete or wood. From here, they can attach and fasten ducts to either side of the damper. Installers will apply caulk to the perimeter of the damper to improve the seal between the damper and the wall.

Pros:

1. The damper is fully supported and secure. There is no need for additional support, other than what is provided by the wall itself.
2. Easy access to the damper. Like on-face duct connections, operators can detach the duct to access the damper. This makes it easy to clean and test the damper.

Cons:

1. No jamb accessories. There will be no room along the jambs for actuators or other jamb accessories, like the extended shaft kit. Actuators must be installed “on-face” when installed inside a wall opening.
2. The damper is fixed to the wall. If you need to repair or replace the damper, then you will need to detach it from the substrate of the opening. You may need to repair the substrate or find new fastener points when replacing the damper.

In-opening installation gives you the benefits of on-face installation with the support necessary to hold the damper in place. You won’t have to worry about added support, assuming the wall can hold the damper. The jambs are inaccessible with this option.

That means you will need an actuator mounting kit to install the actuator onto the damper’s face. This option will place the actuator and its mounting kit in the air stream, which will impact airflow. You will size the damper along its outer dimensions, minus manufacturer’s reduction, to make sure it fits inside the opening.

Cantilevered, or “Out of Barrier” Mount

On-face installation for wall openings. Provides easy access to the damper and on-jamb actuator.

Installers position the damper over the opening, then fasten the frame to the opening substrate. This leaves plenty of space around the jambs for an extended shaft kit and the actuator. A flange frame can provide additional support for the damper.

Pros:

1. Easy access to the actuator and the damper. Operators can easily service both. It also makes it easier to replace either component, should they be damaged.
2. Only the blades are in the airstream. This provides relatively unobstructed airflow through the open damper.

Cons:

1. Requires more support than an in-opening install. A flange frame can provide additional points for fasteners, but you will need to add the flanges as a separate part. Not all dampers will have this option.
2. The damper is fixed to the wall. If the wall is made from concrete or masonry, then you may need to repair it before installing the replacement damper.

Like the on-face installation, the cantilevered mount will require adequate support. Use a flange frame where possible, so the damper stays fastened to the wall. Measure the damper’s inner dimensions when sizing, to ensure they match the dimensions of the opening.

Your mounting options will determine the size of the damper and how you will attach the actuator. Your choice will also determine the required support for keeping the damper in place. Manufacturers may not provide all the necessary fasteners.

Be sure to check their installation instructions for details on hardware. Your project will likely use different installation methods for each application. Review what you need, select the dampers that fit those airflow requirements, then review your options for support. Make sure each damper fits in with your project.