Revision content of AHRI 551/591-2011(SI)

Briefly looks back the origin and course of the AHRI Standard 550/590. Based on the comparison with its 2003 version, presents the revision content in AHRI 551/591-2011(SI), including expansion of performance rating scope and certification scope, rating of part load conditions, four normative appendixes and new specifications of the IPLV index.