The MasterSol Tank in Tank unit combines a boiler room boiler with a buffer tank and connects to the boiler or solar collectors. The tank-in-tank installation provides better performance with simultaneous fuel savings and production of domestic hot water.

It allows for the use of up to three different heat sources and, optionally, an electric resistance. Its purpose is to produce hot water either from the boiler or the solar collector, store it, and allow its supply when the operation of one or the other ceases.

This results in the burner operating even fewer hours, minimizing the energy requirement for space heating. The insulating material surrounding the buffer tank retains the water temperature for a long time because it is not necessary for the boiler or heat pump to operate when the circulation of hot water is done by the water stored in the buffer tank.