The Condenser - Dampers in Ducts

Looking to add dampers to your ducts? You will need to consider a few things first. Learn what to consider when installing dampers in ducts with this Condenser article.

Commercial duct systems need dampers. Dampers perform a variety of important duties in your system, from volume control and pressure balancing to one-way flow and emergency shut off. You will need several types of dampers for a complete HVAC system.

In this Condenser, we will look at what to consider when installing your dampers inside the duct.

Proper Sizing

In-duct mounting involves placing the full damper - frame and all - inside the duct. For the best fit, you will need to measure the damper’s dimensions along the outer edges of the frame.

These are referred to as “outer dimensions” or “O.D.”. Outer dimensions typically receive a nominal deduction of ¼ inches. This accounts for minor changes in the damper’s size.

The metal of the damper's frame will expand when heated. If you don’t think this will be an issue, then you can choose to order the damper with exact sizing. The damper should fit snuggly inside the duct with the nominal deduction made to its dimensions.

For in-duct installations, you will use the outer dimensions to measure the damper's height and width.

Attaching Accessories

Actuators will be the most common accessory for dampers. These useful devices allow you to remotely control the damper’s blade action. Actuators can be mounted on the face of the damper or along the damper’s jambs.

On-face mounting requires a mounting bracket and other equipment to fasten the actuator to the damper’s driving blade. All these parts will be in the air stream when the damper is open, which obstructs the air stream.

On-jamb actuators reduce the number of parts in the air stream, using an extended drive shaft that passes through the duct wall. You will need adequate clearance for the actuator and the extended shaft. 

The actuator will attach to the drive shaft to control blade rotation. This means that the actuator will need to be mounted onto the duct wall at the extended shaft. This installation method can aid with testing the actuator.

Considering the Air Stream

Remember that in-duct dampers will be in the air stream. The damper’s frame may have a negligible effect on air performance. Consider on-face mounting – where the damper’s face is mounted to the end of the duct – for a more efficient air flow solution.

Dampers keep air moving through your system. By understanding your options, you can choose the best possible dampers for your HVAC system.

Looking to add some HVAC dampers to your ducts? Arrow United Industries can build the perfect solution for your system. Choose from our wide selection of control dampers and customize them to fit your designs. Contact Arrow United today and let's work together on your next project.

Having trouble with your HVAC dampers? Tell us in the Comments section. We want to hear from you!

For more on dampers, check out these Newsstand articles:

• Five Types of Dampers in HVAC and When To Use Them
• The Condenser - Blade Design for Dampers
• Four Ways to Make Efficient Airflow Dampers
• Understanding Your Dampers - Important Factors for Damper Installation