A modular packaged environmental control unit designed specifically to maintain the ambient air temperature and/or humidity of spaces that typically contain data communcations equipment. These products can typically perform all (or a subset) of the following functions: cool, reheat, humidify, dehumidify. They may have multiple steps for some of these functions. CRAC units should be specifically designed for data and communications equipment room applications and meet the requirements of ANSI/ASHRAE Standard 127-2001, Method of Testing for Rating Computer and Data Processing Room Unitary Air Conditioners