Which device is typically adjusted by the zone thermostat to meet the zone's cooling or heating demand in a VAV system?

Which device is typically adjusted by the zone thermostat to meet the zone's cooling or heating demand in a VAV system?

• A. Chiller discharge pressure.
• B. VAV damper.
• C. AHU supply filter.
• D. Electrical main switch.

Answer: (B)

In a VAV system, the zone thermostat drives the final control element that adjusts how much air actually reaches the zone. That element is the VAV damper in the zone’s air handling unit or VAV box. By opening or closing the damper, the system changes the volume of supply air delivered to the space, allowing the zone to meet its cooling or heating demand. If more cooling is needed, the damper opens to allow more conditioned air in; if heating is needed and the system supports it, the damper may restrict flow and a reheat stage can be used, but the key action is modulating the damper position. The other components aren’t controlled by the zone thermostat to meet zone load. Chiller discharge pressure is a plant-wide variable managed by the chiller controller, not the zone thermostat. The AHU supply filter is a passive component that doesn’t adjust to demand, and the electrical main switch simply controls power.

In a VAV system, the zone thermostat drives the final control element that adjusts how much air actually reaches the zone. That element is the VAV damper in the zone’s air handling unit or VAV box. By opening or closing the damper, the system changes the volume of supply air delivered to the space, allowing the zone to meet its cooling or heating demand. If more cooling is needed, the damper opens to allow more conditioned air in; if heating is needed and the system supports it, the damper may restrict flow and a reheat stage can be used, but the key action is modulating the damper position.

The other components aren’t controlled by the zone thermostat to meet zone load. Chiller discharge pressure is a plant-wide variable managed by the chiller controller, not the zone thermostat. The AHU supply filter is a passive component that doesn’t adjust to demand, and the electrical main switch simply controls power.