In a VAV system, what is typically adjusted by the VAV box?

• A. The temperature of the supply air.
• B. The system's overall cooling load.
• C. The volume of air supplied to a zone.
• D. The speed of the primary supply fan.

Answer: (C)

The key idea is that a VAV box serves as a terminal device that changes how much air is delivered to a specific zone. It does this by adjusting its damper to vary the volume of supply air, in response to the zone’s temperature needs. The supply air temperature is typically set by the central system, not by the VAV box itself, and the overall cooling load and the primary fan speed are managed at the system or plant level, not by each individual box. Some VAV boxes may include a reheat option to fine-tune the zone temperature, but the primary function is to modulate the volume of air reaching the zone.