Constant air volume (CAV) is a method for climate control systems in buildings to provide a constant level of air. flow at two different temperatures and maintains a standard air pressure throughout the system. Because it is one way to build a standard HVAC system, the actual function of the equipment can vary depending on the needs of the building. An alternative to a constant airflow system is a variable air volume (VAV) system. Although both are used in building design, each has several unique advantages over the other.
The main problem with a constant airflow system is that it typically requires two sets of ductwork throughout the building – one for heated air and one for cooled air. These air supplies are provided either by individual air handling units or by one central unit, known as a CAV unit, which can switch between heating and cooling the air it forces into the ductwork. Individual rooms or businesses in an office building then control the temperature in the room by adjusting the mix of hot and cold air entering the space. This gives a constant air volume system an advantage over its alternative in that room temperatures can change more rapidly than in a VAV system.
Variable air volume systems tend to be much more complex than their CAV counterparts because they must utilize temperature control and manage the actual volume of air blown into each room. To facilitate this, variable speed dampers and fans are built into the ductwork, and the control system automatically opens and closes them and turns them on and off as needed. Although more difficult to design and implement, a VAV system is more energy efficient than a CAV system because the components of a variable airflow design operate only as needed.
The basis of any CAV regulator is the self-balancing mechanism. It is the design of this mechanism that determines the accuracy of maintaining the set flow rate, the noise level, the minimum resistance of the regulator, the flow range and other parameters. There are various designs of the self-balancing mechanism on the market, which largely determine the cost and technical characteristics of CAV regulators.