The M50 Downflow air conditioning unit is designed for easy installation on commercial roof curbs. The a/c unit delivers an EER above 40 when used as a stand-alone unit, and above 21 when working in concert with direct expansion (DX) rooftop units (RTUs). The M50 Downflow can meet the cooling demands of a building by itself or can be installed to help RTUs during the first stage of cooling and bringing fresh air into the building while reducing the energy consumption and keeping the building cool. The unit comes with a factory-installed insulated plenum and a galvanized stainless steel skirt for a convenient connection to the roof curb. The unit offers simple access to the air filters, motor assembly, and controls for easy preventive maintenance. The units are modular in design, so they can be installed flush next to each other.