This document defines the general terms and the calculations used to determine the thermohydraulic performance of heat exchangers. It includes the general test procedure and related theories. This document is intended to be used for acceptance-testing heat exchangers in test facilities such as laboratories, manufacturer test facilities and final installation site. This document specifies three acceptance levels: — level 1 for minimum tolerances; — level 2 for nominal tolerances; — level 3 for maximum tolerances; This document constitutes an application-specific standard in line with EN 305 and EN 306.