At what conditions subject to American Standards is an air conditioning unit's capacity rated. In question a water cooled heat pump/ marine air conditioner.
For residential/small commercial air-cooled equipment the rating standard is ASHRAE 37. The standard does not define exact rating conditions, it defines a method of test, and the data that must be provided in the report. I believe this concept is common across all ASHRAE standards for HVAC equipment.
There is no way to set a single set of standard conditions, because operating conditions and design conditions are highly dependent on the application.
So, any proper rating should be in the general form of:
"This unit is rated at so many BTU/hr when tested per ASHRAE standard whatever at the following conditions."
And rating claim that does not contain all of this information is incomplete, and may even be an attempt to decieve you.
You can refer to Water Furnace International Spectra Water Source Heat Pump Catalog.
Water source heat pumps are rated per ARI 320. Cooling capacities are based on 80°F DB, 67°F WB entering air temperatures with 85°F entering water. Heating capacities are based on 70°F entering air temperature and 70°F entering water. COP figures do not include power consumption for water pumping.
Ground water source heat pumps are rated per ARI 325. Entering air conditions for cooling & for heating are the same as per ARI 320 but unit capacity ratings are given at entering water temperatures of 70°F & also at 50°F for cooling and for heating. Thus each unit has (2) cooling capacity figures & (2) heating capacity figures indicated. Also COP figures include power consumption allowance for water pumping.
Ground source closed loop heat pumps are rated per ARI 330. Again entering air conditions for cooling & for heating are same as ARI 320 but unit capacity ratings are given at 77°F entering water for cooling & 32°F entering water for cooling. COP figures include power consumption for water pumping.
