Variable Air Volume systems respond to changing thermal loads by doing what?

• A. Varying The Flow Of Supply Air
• B. Varying The Temperature Of Supply Air
• C. Maintaining Constant Pressure
• D. Increasing Outdoor Air Fraction To 100%

Answer: (A)

VAV systems manage changing thermal loads by varying the flow of supply air to each zone. The air temperature supplied to the space is kept near a constant setpoint by the coil, so the system adjusts how much air is delivered rather than changing its temperature to meet the heating or cooling needs. When a zone requires more cooling, the VAV box opens more to push in more cool air; when the load decreases, it closes to reduce airflow. This approach is what allows a single system to efficiently handle varying occupancy and heat gains without constantly shifting the air temperature.

The other options aren’t the primary mechanism: the supply air temperature is typically not the main variable controlled to meet load in VAV; maintaining constant pressure is a goal of the fan system but not how the zone load is addressed; and increasing outdoor air to 100% is not how VAV responds to a changing load, though economizer logic may adjust outdoor air for ventilation reasons.