Zone minimum airflow set point in a single-duct VA V terminal unit with reheat has a great impact on zone reheat requirement and ventilation efficiency. Lowering the set point reduces the zone reheat requirements but drops the ventilation efficiency and thereby increases the ventilation load. When the economizer is enabled, a large amount of fresh air is introduced into the system, and then the set point can be lowered to reduce reheat requirements without any effect on ventilation load. Thus, this paper introduces a control strategy to reset the minimum airflow set point during partial or full free cooling mode and measure its performance under various conditions through simulations and experiments done in fully instrumented VA V systems located in the HVAC lab at the University of Cincinnati. The experiments were conducted on chilled-water VAV system that serves three controlled zones with hot-water reheat VAV boxes controlled by a typical commercial BACnet web-based building automation system BAS. The simulation studies were conducted using the building energy simulation software EnergyPlus to evaluate the strategy in different locations. The results show that, depending on locations, the minimum airflow rate resetting strategy can reduce the reheat requirement by 12 -32, fan energy use by 1.5 -6, and the cooling load by 0.5 to 1.
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