What happens to the outdoor air dampers on an economiser system if the outdoor air is above the temperature set-point?

In an economiser system used for HVAC applications, outdoor air dampers play a crucial role in regulating the amount of outdoor air that is mixed with return air from the building. When the outdoor air temperature exceeds the set-point, the system needs to prioritize energy efficiency and maintain indoor comfort.

The correct choice indicates that both the outdoor air dampers and the exhaust dampers will close. When the outdoor air temperature is too high, bringing in additional outdoor air may actually result in increased cooling loads, making it counterproductive. Closing the outdoor air dampers prevents excessive warm air from entering the system, allowing for more efficient operation. Simultaneously, closing the exhaust dampers helps retain cooler indoor air, thus improving the overall efficiency of the system and helping to maintain the desired indoor temperature without overworking the HVAC equipment.

In this scenario, the system effectively shifts from economising mode, which aims to leverage cooler outdoor air for cooling purposes, to a mode where it limits outdoor air intake to optimize performance based on current conditions.