For simultaneous increase of refrigerating capacity and efficiency of large industrial ammoniac refrigerating machineries it is possible to apply the cooling of coolant before it trolling with the help of external refrigerating machines of small productivity. The general thermodynamic regularities of processes of continuous and discrete cooling are received. The optimum decrease of temperatures on separate sites of the general process of cooling is found. Parameters of various ways for cooling of streams of liquid coolant are determined. It is shown that the most favourable to carry out cooling of coolant with the help of the two-temperature compressor refrigerating machine. The circuit of such machine is resulted in which an ejector is used for manufacture of cold at two temperature levels, and it include between two evaporators.