This work showed the design of a refrigeration system by means of water recirculation for a laboratory equipment (distiller). The system of auxiliary refrigeration comes near to one of first order in which design a PI control who is in charge to maintain the temperature of the cooling fluid in a fixed value. The main refrigeration system and the system of auxiliary refrigeration are implemented on a receiving water container with the characteristics of a condenser to evaporate and the level and temperature controller implements itself in a programmable device PIC18F452, the values of the temperatures, date, hour and values of level (renovation of cooling fluid) can be read directly of the device through a screen LCD. The instrument is totally automatic in the filling variables and drained of the tank, control of flights, ignition and extinguished of the refrigeration recirculation, water temperature control,of the water and tube temperature and allows to a saving of the cooling fluid (water) and distillation time.