Differentiate between VAV and CAV systems.

Differentiate between VAV and CAV systems.

• A. VAV modulates airflow to zones; CAV supplies constant airflow with varying temperature to meet loads.
• B. VAV is fixed flow; CAV modulates.
• C. VAV modulates temperature; CAV modulates humidity.
• D. VAV uses constant supply; CAV uses variable supply.

Answer: (A)

VAV systems control how much air each zone receives, while keeping the supply air temperature relatively steady. A zone damper continually adjusts its position to match the cooling or heating demand of that space, so the airflow to each zone varies as needed. In contrast, CAV keeps the total supply air flow constant and meets changing loads by changing the temperature of that air—cooler air for more cooling, warmer air for less—rather than sending more or less air to different zones. That’s why the statement describing VAV as modulating airflow to zones and CAV as providing constant airflow with varying temperature to meet loads is the best fit.

VAV systems control how much air each zone receives, while keeping the supply air temperature relatively steady. A zone damper continually adjusts its position to match the cooling or heating demand of that space, so the airflow to each zone varies as needed. In contrast, CAV keeps the total supply air flow constant and meets changing loads by changing the temperature of that air—cooler air for more cooling, warmer air for less—rather than sending more or less air to different zones.

That’s why the statement describing VAV as modulating airflow to zones and CAV as providing constant airflow with varying temperature to meet loads is the best fit.