Other refrigeration system requirements include appropriate operating pressure, smaller compressor size, and lower compressor-discharge temperature. As far as safety is concerned, toxicity, flammability, and pressure govern the proper use of a refrigerant. However, there are a few Class B refrigerants, such as R-123 and ammonia, that need additional equipment safety. Refrigerants are classified in three groups, according to their flammability. Ammonia is a Class 2 refrigerant.
Some refrigerants exhibit high pressures.
There are many national and international standards that govern the use of high-pressure refrigerants. The reliability of a refrigeration system depends to a large extent on the chemical stability of the refrigerant and its compatibility with the various system components and the compressor lubricant. The refrigerant should not decompose under the temperatures and pressures experienced in the system. It also should not dissolve, swell, or embrittle the elastomers and plastics used in the valve seals and motor components. The refrigerant should be reasonably miscible at all temperatures with the lubricant used.