Heaters are equipped with automatic two-stage power switch activated depending on quantity of flowing water. Thanks to microprocessor control and using adequate knobs it is possible to chose one of five heater's work modę. Comparing to similar heaters this enables morę economical work. In heaters of this series unreliable contact switches have been eliminated and replaced with electronic elements (triac). Significant prolongation of heater's non-de-fective working time was reached in result. Heater is equipped with flexible connect-ing tubes as well as control valve containing water filter. This simplifies assembly and significantly shortens installation time. Heaters of this series are equipped with safety hydraulic switch to increase user's safety.