- The sub main distribution board is designed for residential and industrial applications suitable for both outdoor and indoor applicationsRFPB type - NRated insulation voltage (Ui) 13.8KV, 33KV / 400/231V, 60HzRated voltage (Un) up to 440V 60HzRated current (in) up to 630 A.Rated short time withstand current (Icw) of 25 kA for 1 secondDegree of pr..