This paper studies the current practice of manufacturers' data in unitary HVAC equipment in terms of data structure, simplification, and approximation. Both an improved DX cooling coil modeling in split systems and a self-validation validation by manufacturers' data are used in this study. It shows that the current approximations of dependent variables with their independent variables in manufacturers' data cause an unacceptable level of error, while all dependent variable estimation functions have valid partial derivatives with respect to outside air temperature (OAT). Therefore, a generic equation about the total cooling capacity difference between the base OAT (35 degrees C) and any other OAT is developed to accurately simplify a manufacturer's data, and accordingly a simplified table of this manufacturer's data is also presented here. However, the non-additivity of sensible heat ratio (SHR) requires another method to accurately simplify SHR with its independent variables. These accurate simplifications and approximations allow manufacturers to post less performance data, facilitate calculations for manufacturer's data-based models, and validate data from field or laboratory experiments. (C) 2014 Elsevier B.V. All rights reserved.