How does an enthalpy economizer differ from a dry-bulb economizer?

How does an enthalpy economizer differ from a dry-bulb economizer?

• A. Enthalpy considers both temperature and humidity; dry-bulb uses temperature alone, affecting humidity control.
• B. Enthalpy only uses humidity; dry-bulb uses temperature and humidity.
• C. Enthalpy is an older term for temperature; dry-bulb is the modern metric.
• D. Enthalpy and dry-bulb are identical in how they control economizers.

Answer: (A)

Enthalpy is the total heat content of air, combining both sensible heat (temperature) and latent heat (moisture). An enthalpy economizer uses this total to decide whether outdoor air will actually reduce the building’s cooling and humidity load. If outdoor air has a lower enthalpy than the return air, it can be brought in to save energy and help control humidity. A dry-bulb economizer, by contrast, looks only at dry-bulb temperature and ignores humidity, so it might bring in cool-but-humid air that ends up increasing moisture problems and dehumidification needs. So the key difference is that enthalpy accounts for humidity as well as temperature, while dry-bulb uses temperature alone. The other statements misstate what enthalpy measures or claim the methods are identical.

Enthalpy is the total heat content of air, combining both sensible heat (temperature) and latent heat (moisture). An enthalpy economizer uses this total to decide whether outdoor air will actually reduce the building’s cooling and humidity load. If outdoor air has a lower enthalpy than the return air, it can be brought in to save energy and help control humidity. A dry-bulb economizer, by contrast, looks only at dry-bulb temperature and ignores humidity, so it might bring in cool-but-humid air that ends up increasing moisture problems and dehumidification needs. So the key difference is that enthalpy accounts for humidity as well as temperature, while dry-bulb uses temperature alone. The other statements misstate what enthalpy measures or claim the methods are identical.