The invention relates to a compressor which operates within a system having a cooling capacity below 60 tons. The compressor includes a hermetically sealed housing and a drive module and aero module within the housing. The drive module includes a motor, a rotor, and oil free bearings. The aero module has a centrifugal impeller driven by the drive module to compress a working fluid. The compressoris arranged such that the working fluid flows through the drive module before reaching the aero module.