To increase the efficiency in a furnace installation for melting down metallic or metal-containing charge materials, where an electrode system with a roof (6) for operating the melting-down process mainly with secondary energy can be swung into position on a lower shell part (14, 15) of a furnace (A, B), an upper shell part (17) can be swung into position on the lower shell part (14, 15) to form a premelting vessel (16). The upper shell part (17) includes a vessel wall (18) that substantially upwardly extends the vessel wall of the lower shell part (14, 15) in and additionally has a roof (7).