What characteristic defines economizers in HVAC systems?

The characteristic that defines economizers in HVAC systems is that they recover both sensible and latent energy. Economizers are designed to improve energy efficiency by using outside air for cooling whenever conditions permit. This process involves managing both the temperature (sensible heat) and humidity (latent heat) of the outdoor air.

When an HVAC system includes an economizer, it can take advantage of cooler, drier outdoor air, thus minimizing the need for mechanical cooling. This is especially beneficial in transitional weather conditions when the temperature and humidity levels outside are favorable for indoor climate control. By recovering both types of energy, economizers significantly lower energy costs and enhance indoor air quality.

In contrast, options that suggest recovering only sensible energy do not capture the full benefits of economizers, as they overlook the importance of humidity control. Similarly, generating energy through combustion does not align with the energy-saving purpose of economizers, and the use of fans to circulate outside air, while related, does not define the economizer's primary function of energy recovery.