What is the role of an economizer cycle in an HVAC system?

The role of an economizer cycle in an HVAC system is to reduce the mechanical cooling load by using outdoor air to cool the building when the outdoor air conditions are suitable. An economizer cycle takes advantage of the fact that in many climates, there are times when the outdoor air is cooler and drier than the return air from the building. Instead of running the mechanical cooling system (chiller or air conditioner), the economizer cycle opens dampers to introduce outdoor air into the system, which can then be used to cool the building directly. There are two main types of economizer cycles: air-side economizers and water-side economizers. Air-side economizers use outdoor air directly to cool the building. Water-side economizers use outdoor air to cool the water in a cooling tower, which is then used to cool the building. The economizer cycle is controlled by sensors that monitor the outdoor air temperature and humidity. When the outdoor air conditions are favorable (i.e., cooler and drier than the return air), the economizer cycle is activated, and the mechanical cooling system is turned off or reduced. This can result in significant energy savings, as the mechanical cooling system is only used when necessary. For example, during the spring and fall, the outdoor air temperature is often cool enough to provide free cooling, reducing the energy consumption of the HVAC system. However, the use of air-side economizers can increase the amount of outside air introduced into a building which may need to be considered in the context of indoor air quality regulations.