In a mixed air system, if the outdoor air is substantially warmer than the return air, what would happen to the mixed air temperature?

In a mixed air system, outdoor air and return air are combined to achieve a desired temperature for the conditioned space. When the outdoor air is significantly warmer than the return air, the resulting mixed air temperature increases. This is due to the fact that a larger proportion of the warmer outdoor air is now being blended with the cooler return air, raising the overall mixed air temperature.

The mixed air temperature depends on the ratio of the return and outdoor air as well as their respective temperatures. Since the incoming outdoor air is at a higher temperature, its influence will dominate, leading to an increase in the final mixed air temperature. This principle is fundamental in understanding how HVAC systems regulate temperatures and why proper air mixing is crucial for maintaining comfort in a controlled environment.