In accordance with European standard EN 10130: 2006, the American standard ASTM A 1011 and Russian GOST 16523-97 and GOST 9045-93 we use stainless steel 2mm thick grade DC01in production of Lemax boilers series Premium. The heat exchanger has a cylindrical shape, which allows the boiler to work in closed systems with the operating pressure of 1 atm maximum (for Premium-7,5 - Premium-10) and of 3 atm maximum (for Premium-12,5 - Premium-60). Due anticorrosive coating enamel (exposure temperature 950 ° C) and treatment with inhibitory composition, the heat exchanger is protected from aggressive factors, solutions of salts and mineral oils.