AHRI 550/590 (I-P) and 551/591 (SI): Performance Rating of Water-Chilling and Heat Pump Water-Heating Packages Using the Vapor Compression Cycle

Standard Scope

This standard applies to factory-made water-chilling and water-heating packages utilizing the vapor compression cycle as defined in Section 3. These water-chilling and water-heating packages include:

  • Water-cooled, air-cooled, or evaporatively-cooled condensers

  • Water-cooled heat recovery condensers

  • Air-to-water heat pumps

  • Water-to-water heat pumps with a capacity greater or equal to 135,000 Btu/h


  • Water-to-water heat pumps with a capacity less than 135,000 Btu/h are covered by the latest edition of ASHRAE/ANSI/AHRI/ISO Standard 13256-2.

  • Air-to-water units designed exclusively to heat potable water as covered by the latest edition of AHRI Standard 1300.

  • Water-chilling packages are excluded when the condenser is actively adiabatically-cooled. An adiabatically-cooled condenser is an air-cooled condenser that uses evaporative cooling to pre-cool air before that air reaches the dry heat transfer surface.

  • Water-chilling or water-heating packages with both an air-cooled condenser and a water-cooled condenser are outside the scope of this standard when operating in any mode (cooling, heating, heat recovery, or simultaneous heating and cooling) with the heat rejection split between the air-cooled condenser and water-cooled condenser.

  • Units with evaporators or condensers that use any liquid other than water are outside the scope of this standard.

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