It is more important than ever for a building’s HVAC system to be adjusted and balanced correctly to achieve the required indoor air quality at the lowest possible operating costs. Pressure imbalances within an HVAC system can make it more difficult to maintain a given condition within a room (i.e., temperature, humidity, percentage of fresh air, etc.). If not balanced correctly, the HVAC system works harder to meet these requirements resulting in higher energy usage and operating costs.

Balancing dampers are a type of control damper that regulates the flow of air. They are not intended for use in positive shut-off or automatic control applications.

Four main types of balancing dampers are:

  • Manual Balancing
  • Cable-Operated
  • Remote Balancing
  • Automatic Balancing

Manual Balancing Dampers

Manual balancing dampers typically use a manual hand quadrant to set the blade position and lock it in place. Usually the lowest cost option, this damper is ideal for locations where you have easy access to adjust the damper. They are available as single blade, multiblade, or round dampers.

Manual Balancing Damper – Greenheck Model MBD-10

Cable-Operated Dampers

Cable-operated dampers are ideal for locations where it is difficult to get access to manually adjust the damper and balance airflow. A cable runs from the damper to an access port in the ceiling or wall plate with adjustment using a nut driver. They are available as single blade, multiblade, or round dampers.


Another style of cable-operated damper is a radial blade damper (also known as a bowtie damper). It is designed for adjustment at an air outlet or plenum neck where it can be adjusted using a nut driver or screwdriver.

Cable-operated radial blade damper (Bowtie damper) – Greenheck Model BTDR-50

Remote Balancing Dampers

Remote balancing dampers use a 9-volt actuator to adjust the blade position. The EZ balance remote controls the damper motor by connecting to the wall, ceiling, or diffuser-mounted RJ11 connector. This damper is for applications where it is difficult to gain access to manually adjust the dampers. They are available as single blade, multiblade, or round dampers. Power comes through the remote, so no additional wiring and no outside power are required.

Remote Balancing Damper – Greenheck Model RBDR-50

Automatic Balancing Dampers

Automatic balancing dampers automatically adjust to changes in the system pressure to maintain a constant airflow and have different CFM set points for precise control. The blade automatically adjusts to changes in pressure to maintain constant airflow. These dampers can balance HVAC systems eliminating or reducing the need for on-site balancing.

Automatic Balancing Damper – Greenheck Model ABD

Common applications for automatic balancing dampers are:

  • Supply and exhaust air in offices
  • Balancing exhaust/return and supply airflow in high-rise building risers, shared areas, and living spaces
  • Regulation of make-up air
  • Bathroom exhaust
  • Clean room air supply balancing for ceiling filter modules. Maintains constant airflow even as filter resistance increases
  • Balancing supply airflow from packaged rooftop air conditioning units
  • Balancing supply and exhaust return of heat recovery ventilation systems
  • Regulating outdoor air injections from the central supply fan into individual room fan coil units or heat pumps

Certain UL-Approved Dampers Can Also Act as Balancing Dampers

Did you know in applications requiring a UL-approved damper product, you can also use that damper for balancing the HVAC system, too? Here are examples of how you can use the following dampers for additional cost savings:

  • Multiblade fire dampers with manual quadrants function as both a fire damper and manual balancing damper by manually adjusting the blades to a set airflow.
  • Ceiling radiation dampers supplied with volume controllers allow you to regulate the airflow through the damper by manually setting the blades to a given angle.
  • Combination fire smoke dampers with a modulating actuator and a Belimo SGA-24 or third-party potentiometer can remotely control the amount of airflow by sending a signal to the actuator to adjust the blades.

Selecting the right type of balancing damper will help you balance your HVAC system correctly to achieve the required indoor air quality at the lowest possible operating costs.

For more information on testing, adjusting, and balancing HVAC systems, reference SMACNA: HVAC Systems – Testing, Adjusting & Balancing.