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Five Types of Dampers and When To Use Them

So many dampers to choose from, but what do they do? Read more about the five types of dampers, now available on the MCDLG Newsstand.

HVAC systems can be large and complicated in buildings with many rooms, such as office buildings or schools. You will need more than duct work to get air to each of these areas. That’s where dampers come in. A damper is a device comprised of blades contained in a square or rectangular frame. This design can vary based on the type and model of the damper. For instance, some dampers can have a round frame to fit into circular ductwork.

Even though they are similar in design, there are several different types of dampers and type of damper will perform a specific task. The following are five types of dampers commonly found in HVAC system.

#1 Control Dampers

AFD20 - Control DamperControl dampers are installed at various points in the duct work to regulate the flow of air through the system. These dampers can also be adjusted for use in air mixing zones for heating and cooling air. Control dampers will fully open or fully close their blades many times a day to perform their given task.

You can choose to install a variety of different actuators to control the movement of the blades. For more on these accessories, read our Newsstand article on actuators.

#2 Balancing Dampers

Balancing dampers are installed to regulate air pressure in rooms connected to the duct work. Air pressure imbalances can cause minor annoyances for occupants, like slamming doors or random gusts of air, but they can cause larger problems for the entire system. An imbalanced room can be more difficult to heat or cool, putting excess strain on the air handling units.

1661 - Balancing DamperBalancing dampers are adjusted by technicians, who will measure the air pressure in a room as they adjust the angle of the damper’s blades. Once the correct air pressure is found, the balancing damper’s blades are locked in place to maintain the necessary air pressure. They can be unlocked in the future for adjustments.

#3 Backdraft Dampers

366 - Backdraft DampersBackdraft dampers are installed in specific areas in the duct work to restrict air flow to one direction only. These dampers have shafts installed on one end of each blade. This design turns the blade into a flap that only opens when air is flowing in right direction.

Backdraft damper blades will close if no air is passing through or if air begins flowing in the opposite direction. Backdraft dampers can have a counterbalance installed to assist or resist the opening action. These dampers do not receive actuators.

#4 Multi-Zone Dampers

Multi-zone dampers are used in buildings with a single air handling unit, such as single-building schools or small-scale office buildings. These dampers are large assemblies comprised of multiple dampers, each tied to a specific zone. Multi-zone dampers connect to multiple ducts and control the flow of air for entire system. Multi-zone dampers will have multiple actuators, each controlling a specific zone. These dampers are often bundled with the air handling unit as a complete package.354 - Multi-Zone Damper

530-531 - Industrial Damper#5 Industrial Dampers

Industrial dampers are designed to withstand massive air pressures and constant temperatures above 250°F. They are built from thick gauge materials, mainly steel, to withstand extreme conditions. All components are welded in place to ensure maximum durability.

These dampers are typically used in factories and power plants; places that require serious air flow. Industrial dampers are the heaviest dampers around.

BONUS - UL Life Safety Dampers

FS1 - Combination Fire-Smoke DamperIndustrial dampers may be able to withstand 250°F, but they cannot be used in lieu of UL-rated fire dampers. UL Life Safety Dampers are specifically designed and rated by UL for use in passive fire protection systems. These dampers have special accessories that close off the damper at the first signs of fire and smoke. This action prevents the passage of fire and smoke through duct work, giving occupants time to vacate the building during a fire event. The following are different types of UL Life Safety dampers:

  • Fire Dampers for Static and Dynamic Airflow
  • Smoke Dampers
  • Combination Fire-Smoke Dampers
  • Ceiling Radiation Dampers
Dampers for Many Applications

There are several types of dampers available and each type serves a purpose. Your HVAC system may require all these dampers working together, except for the single multi-zone damper which is installed with a single air handling unit. Although you will likely use all these dampers, it’s important to know what each damper does and where it will fit into your HVAC system.

MCDLG & Continuing Education

Want to know more about UL Life Safety dampers? MCDLG offers free self-paced courses online through AEC Daily. 

Our UL Damper course, Fire & Smoke Protection with Life Safety Dampers, goes over all of the basic stats, terms, principles and requirements involved in choosing UL-rated dampers for your passive fire protection system.  

Visit AEC Daily to see MCDLG Online Courses

This course provides continuing education credits for a variety of institutions, including ASHRAE's PDUs. Learn the basics of UL dampers and earn credit, at your own pace. Visit the MCDLG course page on AECDaily.com today!

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