The innovative buffer tank Logalux PNRZ has been perfectly well adapted to the needs of modern heating and fresh water systems. Three optimally layered buffer areas which are separated from each other by separator plates create the maximum of efficiency also for bulk currents; the large-format heat exchanger secures maximum use of solar warmth. Optionally, the PRNZ can be combined with a fresh water station, offering a hygienic and efficient water treatment, because here always the upper buffer area can be used. The energetic efficiency is further improved by different insulations.