Under what condition does an economizer typically bring in outdoor air for cooling?

Under what condition does an economizer typically bring in outdoor air for cooling?

• A. When humidity is high
• B. Only during heating mode
• C. Only during nighttime
• D. When outdoor conditions are favorable (cool and dry)

Answer: (D)

Economizers bring in outdoor air for cooling when outdoor conditions are favorable, meaning the outside air is cooler and drier than the indoor air. In that situation, the damper opens to admit outside air, letting the building be cooled with free cooling and reducing the need for mechanical cooling. If the outside air is humid or hot, or if the system isn’t in cooling mode, the economizer stays closed or partially closed to avoid increasing indoor humidity or temperature. So the best condition is cool and dry outdoor air.

Economizers bring in outdoor air for cooling when outdoor conditions are favorable, meaning the outside air is cooler and drier than the indoor air. In that situation, the damper opens to admit outside air, letting the building be cooled with free cooling and reducing the need for mechanical cooling. If the outside air is humid or hot, or if the system isn’t in cooling mode, the economizer stays closed or partially closed to avoid increasing indoor humidity or temperature. So the best condition is cool and dry outdoor air.