Attaining long life and reliable performance of compressors for air conditioners and heat pumps requires a combination of well-designed equipment, proper installation procedures and systematic maintenance by the owner. This paper reviews the importance of the stability of critical materials and components in these systems, how stability limits can be determined and how they interrelate with compressor operating parameters. The contributions of well-designed, cost-effective manufacturing processes to production of reliable hermetic compressors is reviewed. The compressor designer must specify the thermal capability of the hermetic motor and determine that the motor thermal protection system provides an adequate margin of safety for the selected motor insulation materials. The inadequacy of conventional thermal rating systems as a means of selecting hermetic motor insulation systems is noted. The refrigerant-oil working fluid must meet specified requirements of lubricity and stability. The paper describes procedures for selecting lubricant or lubricant additive combinations and provides examples of the range of properties that can be expected. Emphasis is placed on systems using Refrigerant 22 as working fluid and a comparison with other refrigerants is sometimes provided. The paper concludes with observations concerning the interpretation and utility of field tests for acid in hermetic units. A critical review of system performance and operating history is highly recommended before an oil change is endorsed.
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