How is an economizer best described in a cooling system?

• A. a controllable damper
• B. a compressor cylinder bypass
• C. a return air system
• D. an indoor air recirculating system

Answer: (A)

The key idea is that an economizer is a controllable damper that modulates how much outdoor air enters the air-handling system. When outdoor conditions are favorable—cooler than indoors—the economizer opens to bring in outside air, providing free cooling and reducing the need for mechanical cooling. When outdoor conditions are not favorable, the damper closes or limits outdoor air and the system relies more on recirculated indoor air to maintain comfort, still aiming to save energy.

The other options don’t describe this function. A bypass around a compressor relates to refrigerant flow in the cooling cycle, not to outside air admission. A return-air system or an indoor air recirculating system describes circulating indoor air rather than bringing in outside air for cooling.