High-performance floor-standing indirect heating boilers with an enameled tank. The helical heat exchanger ensures fast and efficient water heating up to 65°C in 20 minutes. The steel internal tank of the boiler is coated with high-elasticity enamel (Sapphire Flex Technology), which significantly extends the service life of the appliance. Using unique materials allows for uniform expansion/contraction of the enamel and the internal tank walls during water heating or cooling, preventing the formation of microcracks in the enamel and, consequently, corrosion. The GLF model features the ability to connect to a recirculation line, ensuring constant temperature maintenance in the DHW circuit: hot water flows immediately upon opening the tap.