What is the primary purpose of an outside air economizer?

• A. To increase outdoor air to max during all hours.
• B. To stabilize indoor humidity.
• C. To control outside air to decrease mechanical cooling requirements.
• D. To regulate indoor air quality by filtering outdoor air only.

Answer: (C)

The key idea is that an outside air economizer is used to lower the energy needed for cooling by bringing in outdoor air when conditions are favorable. By sensing outdoor conditions and modulating a damper to mix outdoor air with return air, the system can meet part of the cooling load without running the mechanical cooling coil as hard. This saves energy because conditioning outdoor air (when it's cool and not too humid) is cheaper than cooling indoor air with the equipment.

It isn’t about maximizing outdoor air every hour; the economizer only opens when outdoor conditions help reduce cooling energy, and it closes or reduces outdoor air when conditions would not provide energy savings or would harm comfort. Humidity stabilization and indoor air quality are important, but the primary purpose of the economizer is energy reduction through efficient use of outdoor air, not solely filtration or IAQ control.