Reverse Airflow Through the Exhaust Air Damper of Variable-Air-Volume Air-Handling Units: Part II - Control Solution

Author(s)

J House, J E. Seem, C J. Klaassen

Abstract

Traditional air-handling unit (AHU) control systems link the position of the exhaust air damper, recirculation air damper, and outdoor air damper. Laboratory and field tests on variable-air-volume (VAV) AHU's that use a volume matching to control the return fan have shown that air can enter the AHU through the exhaust air damper. This can negatively impact indoor air quality. The paper presents a new control system for VAV AHU's that use volume matching to control the return fan. The new control system links only the position of the exhaust air damper and recirculation air damper. During occupied times, the outdoor air damper is in the fully open position. Simulation results are presented that demonstrate that the new control system prevents air from entering the AHU through the exhaust air outlet for all but extreme conditions that are described in the body of 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 through the exhaust air outlet was not observed for any of the conditions examined in the laboratory and field tests.
Citation: Hvac&R Research
Pub Type: Journals

Keywords

air flow, air handling, air quality, dampers, variable volume
Created May 07, 2017, Updated February 19, 2017