Refrigerant compressor 

        (a) taking suction from LP side of system.                   

        (b) No coolers (or condenser on the compressor)      

        (c) Safety spring above discharge valve                  

        (e) Single stage compression                                    

         (f)  Mechanical shaft seal  Lip seal

         (g) No breather                                                         

         Operate as a CLOSED system  Operates as a OPEN system

Refrigerant compressor  Air compressor

         (a) Drawing air (atmosphere) via a coarse strainer.

        (b) Intercooler and aftercooler 

        (c)  Pressure relief valve (LP & HP side)

      (d) Unloads by releasing air after inter and after coolers respectively

        (e) Multi-stage compression

         (f)  Lip seal

         (g)   breather from the crankcase

        (h) Operates as a OPEN system