HEWALEX SWT VF2 heater is equipped with two coils to heat usable water. Bottom coil uses the energy coming from the solar collectors and top coil the heat energy from the heater. In addition the heater has a stub pipe which enables building in an electric heater. The heater is made of standard steel with a ceramic coating, protecting from corrosion, on the inside. It is thermally insulated with polyutherane layer (50mm thick). On the outside a skay cover is used. Additional protection against corrosion is provided by a magnesium anode.