Damper Control System for Preventing Reverse Airflow Through the Exhaust Air Damper of Variable-Air-Volume Air-Handling Units.
Damper Control System for Preventing Reverse Airflow
Through the Exhaust Air Damper of Variable-Air-Volume
Seem, J. E.; House, J. M.; Kelly, G. E.; Klaassen, C. J.
HVAC&R Research, Vol. 6, No. 2, 135-148, April 2000.
dampers; air conditioning; exhaust systems; pressure;
air flow; equations; simulation
Traditional air-handling unit (AHC) control systems link
the position of the exhaust, recirculation, and outdoor
air dampers. Laboratory tests of a varible-air-volume
AHC using the traditional damper control approach
revealed that outdoor air could enter the AHU through
the exhaust air damper. This can negatively impact
indoor air quality. This paper examines the conditions
that lead to this phenomenon and presents a new control
system that can help alleviate the problem. The new
control system links only the position of the exhaust
and recirculation air dampers. During occupied times,
the outdoor air damper is fully open. Simulation
results are presented that demonstrate that the new
damper control system prevents air from entering the AHU
through the exhaust air outlet for all but extreme
conditions that are described in the paper. Laboratory
and field test results are presented that demonstrate
that the new control system prevents air from entering
the AHU through the exhaust air outlet for the same
conditions that cause significant reverse airflow for
the traditional control system. Furthermore, reverse
airflow was not observed for any of the conditions
examined in the laboratory and field tests when the new
control system was used.