The FUSION-TEC has been designed specifically to optimize Free Direct Ambient Cooling (DAC) opportunities. By implementing a reverse-airflow design, productive outdoor air for free cooling is brought into the system from the lower portion of the chassis. The heat in the shelter is exhausted out of the top of the chassis which completely eliminates any possibility of recirculating hot exhaust into the cool air entryway. When outdoor air is not productive for free cooling, the FUSION-TEC system has a fully flexible mechanical cooling operation that operates at an IPLV of up to 17.0, and also satisfies the D.O.E.'s future 11.0 EER efficiency requirements.