I have an old switchboard with a \$16 mm^2\$16 mm2 mains cable and a \$16mm^2\$16mm2 neutral return. At a different date, someone has added another \$16mm^2\$16mm2 single main cable to the board. The two phases are feed from 2 x× 63 amp fuses.
They have rewired the board to balance the two phases. JustI'm just asking if the neutral is capable of carrying the load of the two phases?