The purpose of this Code is to establish procedures for the conduct and report of tests of heat recovery steam generators (HRSG) employed in combined cycle installations. Combined cycle, as used herein, shall be interpreted as a gas turbine exhausting into an HRSG, which may or may not be arranged for supplemental firing. This Code provides standard test procedures which will yield results having the highest level of accuracy consistent with current engineering knowledge and practice. The purposes of testing under this Code are the determination of (a) efficiency, or effectiveness, at specified operating conditions; (b) capacity at specified operating conditions; (c) other related operating characteristics such as steam temperature and control range, inlet gas flow and temperature; pressure drops in combustion air, gas, steam and water circuits; quality and/or purity of steam; and air and bypass stack gas leakage. The rules and instructions given in this Code apply to HRSG units employed in combined cycle installations. Units operating with more than approximately 40 percent excess air shall be tested in accordance with the requirements of this Code. Units operating with less than approximately 20 percent excess air shall be tested in accordance with Performance Test Code PTC-4.1, Steam Generating Units. For units operating between 20 percent and 40 percent excess air, guidance as to the preferred test method can be obtained in Appendix 7.1. Orsat analysis is not required for tests performed under this Code. Testing of auxiliary equipment shall be governed by the Performance Test Code applying specifically to the auxiliary in question. This Code is not applicable to solid fuel fired units. The HRSG covered by this Code is encompassed by the envelope boundary shown in Fig. 1.1.