ISO 5151:2017 specifies performance testing, the standard conditions and the test methods for determining the capacity and efficiency ratings of air-cooled air conditioners and air-to-air heat pumps. ISO 5151:2017 is applicable to the following equipment: - non-ducted air-cooled air conditioners and non-ducted air-to-air heat pumps; or - ducted air conditioners and/or ducted heat pumps rated at less than 8 kW and intended to operate at an external static pressure of less than 25 Pa. ISO 5151:2017 is limited to: - residential, commercial and industrial single-package and split-system air conditioners and heat pumps; - factory-made, electrically driven and use mechanical compression; - utilizing single, multiple and variable capacity components; - multiple split-system utilizing one or more refrigeration systems, one outdoor unit and one or more indoor units, controlled by a single thermostat/controller. The requirements of testing and rating contained in this document are based on the use of matched assemblies. ISO 5151:2017 is not applicable to the rating and testing of the following: a) water-source heat pumps or water cooled air conditioners; b) multi-split-system air conditioners and air-to-air heat pumps (follow ISO 15042 for the testing of such equipment); c) mobile (windowless) units having a condenser exhaust duct; d) individual assemblies not constituting a complete refrigeration system; e) equipment using the absorption refrigeration cycle; f) ducted equipment except for those specified in this clause (follow ISO 13253 for the testing of such equipment). ISO 5151:2017 does not cover the determination of seasonal efficiencies, which can be required in some countries because they provide a better indication of efficiency under actual operating conditions. NOTE Throughout this document, the terms "equipment" and "systems" mean "air conditioners" and/or "heat pumps".