All installed power supplies must blow air in the same direction (front-to-back or back-to-front) and must match the airflow direction of the installed fan modules.
If the power supply has a red tab, the airflow is front-to-back. Use a power supply labeled Air Out.
If the power supply has a blue tab, the airflow is back-to-front. Use a power supply labeled Air In.
Note
The operating-system software cannot display the airflow direction.
