Psychrometric testing of a Room Air Conditioner (RAC) has been undertaken using variable inlet conditions, rather than fixed inlet conditions common to current rating methods. The goals of the experiment are fourfold: (1) to develop a means of testing cooling capacity and efficiency with minimal time, effort and equipment, (2) to determine the experimental uncertainties inherent in such an approach, (3) to derive prediction equations for performance attributes of the test unit under ranges of inlet conditions, and (4) to apply the results of tests to a means of rating RAC's for specific localities based on local climate data.

The test method combines features of existing accepted tests for HVAC products, but differs by allowing indoor and outdoor inlet conditions of temperature and humidity to vary, and by influencing those conditions throughout ranges of interest using both output airflows from the test unit. Instead of collecting data at a few set points, as with current test standards, data has been collected to enable statistical analysis of the unit's performance over a continuum of conditions within a test time comparable to existing methods. Uncertainty analysis has been performed in accordance with ANSI/ASHRAE standard guidelines. Prediction equations for total and sensible cooling capacities and for energy efficiency ratio, based on outdoor and indoor dry-bulb temperatures and relative humidities, have been developed for the test unit. These performance models are used to compute ratings for the test unit for comparison to the manufacturer's ratings at standard conditions, and to synthesize ratings for varying climatic conditions for several cities in the United States.

The estimated rating of the test unit for standard test conditions agrees with the labeled rating within the range of error of the experiment. Further development of the distributed multi-point testing and rating technique can aid HVAC equipment designers in meeting growing challenges posed by expanding markets and evolving legislation regarding energy efficiency and refrigerant replacement. Improved ratings can enable product customization based on location of use, and consumers can make more informed choices when purchasing these appliances.