Per NEC 450.3, when a transformer has primary overcurrent protection set at no more than 125% of rated current, secondary overcurrent protection:
-
A
Must always be provided at 125% of secondary rated current
-
B
Is not required for transformers with a 2-wire secondary
-
C
May be omitted if primary protection does not exceed 125% of primary rated current
-
D
Must be rated at 250% of secondary rated current