IEC 60519-21:2008 is applicable to indirect resistance heating equipment for the heating and melting of glass, operating in voltage bands 1 and 2. These particular requirements also apply to equipment for direct resistance heating and melting of glass by means of current introduced by electrodes passing through the charge to be heated. This new edition of IEC 60519-21 takes into account the latest editions of IEC 60519-1, of IEC 60519-2 and of IEC 60050-841.