In a constant air volume (CAV) system, the air conditioning system supplies a fixed volume of conditioned air to the space regardless of the actual cooling load. When the sensible load decreases to 50%, several things can happen:
Oversupply of conditioned air: Since a CAV system delivers a fixed volume of air, the supply air volume will remain the same even if the cooling load decreases. This can lead to an oversupply of conditioned air in the space. The excess air may result in a colder and potentially uncomfortable environment as the temperature drops below the desired setpoint.
Short cycling: With a reduced cooling load, the CAV system may reach the desired temperature quickly. As a result, the system may cycle on and off more frequently to maintain the setpoint, which can lead to inefficiencies and increased wear and tear on the system.
Limited temperature and humidity control: CAV systems may struggle to provide precise temperature and humidity control when the cooling load decreases. The fixed supply airflow may not be able to adapt effectively to the reduced load, resulting in temperature fluctuations or elevated humidity levels.
Wasted energy: When the cooling load decreases, but the CAV system continues to supply the same volume of conditioned air, it can lead to wasted energy. The system consumes more energy than necessary to cool the space, resulting in higher energy bills and reduced energy efficiency.
To overcome these issues and improve energy efficiency, variable air volume (VAV) systems are often used. VAV systems adjust the supply airflow based on the cooling load, allowing for better control and energy savings. By modulating the supply airflow, VAV systems can match the cooling demand more closely, providing more precise temperature and humidity control while reducing energy consumption.