Which statement about economizers is true?

Which statement about economizers is true?

• A. An economizer increases mechanical cooling energy use.
• B. An economizer uses outdoor air exclusively when outdoor conditions are poor.
• C. Outdoor air is never used for cooling.
• D. An economizer uses outdoor air to assist with cooling when conditions are favorable, reducing mechanical cooling energy use.

Answer: (D)

An economizer is designed to use outdoor air to help cooling whenever outdoor conditions are favorable. When the outside air is cooler (and acceptable in humidity), the economizer opens dampers to bring in outdoor air to mix with return air, reducing the load on mechanical cooling and cutting energy use. The idea is to take advantage of mild weather to “free cool” the space, rather than relying solely on the chiller or compressor. The other statements don’t fit because they imply increasing mechanical energy use, using outdoor air only when conditions are poor, or never using outdoor air, all of which contradict how economizers operate.

An economizer is designed to use outdoor air to help cooling whenever outdoor conditions are favorable. When the outside air is cooler (and acceptable in humidity), the economizer opens dampers to bring in outdoor air to mix with return air, reducing the load on mechanical cooling and cutting energy use. The idea is to take advantage of mild weather to “free cool” the space, rather than relying solely on the chiller or compressor. The other statements don’t fit because they imply increasing mechanical energy use, using outdoor air only when conditions are poor, or never using outdoor air, all of which contradict how economizers operate.