PROBLEM: Find the size of the over current protection device required for this motor with full-voltage starting and code letter G.
STEP 1: NECTable 430-150
A 20-horsepower, 460-volt motor has a 27 amp full-load current rating.
STEP 2: NEC 430-52(a), Ex. 1; Table 430-152
The maximum allowed is 175%.
27 amps x 175% = 47 amps.
STEP 3: NEC 240-3(f); 240-6.
ANSWER: The nearest standard size larger fuse is 50 amps. The minimum size is 45 amps.
NOTE: If the motor will not start, a 60-amp fuse may be used per 430-52(a), Ex. 2b.
