Dampers are the final control devices for nearly all airflow in HVAC systems, while actuators
serve as the interface between the control system and the mechanical system. Together, they are
critical for accurate and reliable airflow control.
The Importance of Accurate Actuation
In modern HVAC systems, over 80% of DDC outputs are sent to actuators.
If actuators do not position dampers accurately, all other parts of the air system are
affected.
Unfortunately, actuator selection is often based only on torque, ignoring accuracy,
which cannot be corrected by controllers.
TAB (Testing, Adjusting, and Balancing) contractors or commissioning authorities can
only partially compensate for poorly sized or inaccurate dampers.
Focus on Final Control Elements
Many airflow issues arise not from equipment sizing, but from air distribution
problems.
Factory-built mixing boxes often struggle with flow control due to space constraints.
Ignoring these constraints in design can result in systems that work only part-time or
inconsistently.
Larger projects increase complexity and magnify small miscalculations.
Common Sources of Airflow Issues
Airflow in a space can be affected by numerous factors, including:
Wind effects on intakes and exhausts (overflow or underflow)
Damper and duct leakage (supply and return)
Infiltration and exfiltration
Cross flows from air handlers or multi-tenant systems
Internal doors and doors to the outside
Elevator shafts
Exhaust fans and relief systems
Plenum versus ducted returns
Ventilation effectiveness and air quality distribution
Heat-recovery equipment performance
Flows in voids, hidden spaces, and shafts
Fan performance and stack effects
Variable-air-volume (VAV) box supply vs. return inconsistencies
Leakage paths through ceilings, floors, pipes, chases, and penetrations
Potential cross-contamination of exhaust and intake air
Unknown or unpredictable variables
Accurate damper and actuator selection is critical to system performance. Focusing on final
control elements during design—rather than relying on airflow adjustments later—solves most
common HVAC airflow problems and ensures consistent comfort and energy efficiency.