Natural circulation solar system for the production of domestic hot water Reduced Heating Time Self-supporting Frame for Flat Roof Simplify Installation Indirect Exchange to Avoid Freezing Risk Fast and Easy Installation Reduced Time to Reach Comfort Temperature Limited Risk Of Over Heating Efficient Stratification System Wide Range to Cover Different Domestic-hot Water Needs Fast Connector on Hydraulic Pipes Easy Installation by Self-supporting Frame for On-roof And Flat Roof Installation Structural Strength of Cylinder and Collector Possibility to Integrate Solar By Electrical Resistance inside Cylinder 200 lt, 1 or 2 collectors, on-roof and flat roof 300 lt, 2 collectors, on-roof and flat roof