Which component primarily modulates zone cooling in a VAV system?

Which component primarily modulates zone cooling in a VAV system?

• A. Variable air volume box at each zone.
• B. Fixed duct with manual dampers.
• C. Dedicated outdoor air handler.
• D. Single central supply fan.

Answer: (A)

In a VAV system, zone cooling is controlled primarily by the VAV box at each zone. This box is the point where conditioned air is delivered to a specific space and it contains a damper that automatically opens or closes to regulate how much air enters the zone. When the zone thermostat calls for cooling, the VAV box responds by increasing airflow to the space; when less cooling is needed, the damper closes to reduce the delivered air. This per-zone modulation lets each area reach and maintain its setpoint efficiently, without changing the overall supply rate for the entire building. The other components don’t provide the same zone-specific modulation. A dedicated outdoor air handler mainly handles outside air intake, not the precise adjustment of cooling for each zone. A single central supply fan moves air through the system, but it doesn’t tailor airflow to individual zones. A fixed duct with manual dampers requires manual adjustment and can’t automatically respond to changing zone conditions.

In a VAV system, zone cooling is controlled primarily by the VAV box at each zone. This box is the point where conditioned air is delivered to a specific space and it contains a damper that automatically opens or closes to regulate how much air enters the zone. When the zone thermostat calls for cooling, the VAV box responds by increasing airflow to the space; when less cooling is needed, the damper closes to reduce the delivered air. This per-zone modulation lets each area reach and maintain its setpoint efficiently, without changing the overall supply rate for the entire building.

The other components don’t provide the same zone-specific modulation. A dedicated outdoor air handler mainly handles outside air intake, not the precise adjustment of cooling for each zone. A single central supply fan moves air through the system, but it doesn’t tailor airflow to individual zones. A fixed duct with manual dampers requires manual adjustment and can’t automatically respond to changing zone conditions.