In economizer operation, what is the effect when outdoor air conditions are favorable?

• A. Open OA damper and reduce cooling energy.
• B. Close OA damper.
• C. No effect.
• D. Open the OA damper when outdoor air conditions satisfy cooling needs, reducing cooling energy.

Answer: (D)

Economizer operation uses outdoor air to meet part of the cooling load when conditions outside are cool and acceptable for occupancy. Opening the outside-air damper under those favorable conditions lets outdoor air do the cooling instead of running the mechanical cooling, which lowers the energy required for cooling. If outdoor conditions aren’t suitable, the damper stays closed to avoid bringing in hot or humid air. So opening the OA damper when outdoor air satisfies cooling needs, thereby reducing cooling energy, is the correct behavior.