For a 7.5 horsepower induction-type squirrel cage motor with nameplate current rating of 23 amperes operating at 3-phase, 208 volts, what is the full-load current used in calculations for motor branch-circuit conductor ampacity, short-circuit and ground-fault protective device ampere rating, and motor branch-circuit switch ampere rating?

For a 7.5 horsepower induction-type squirrel cage motor with nameplate current rating of 23 amperes operating at 3-phase, 208 volts, what is the full-load current used in calculations for motor branch-circuit conductor ampacity, short-circuit and ground-fault protective device ampere rating, and motor branch-circuit switch ampere rating?

• A. 24.2
• B. 23
• C. 28
• D. 25.6

Answer: (A)

In motor calculations, the value used to size conductors, protective devices, and motor switches comes from the motor’s full-load current (FLC) as specified in the NEC motor tables for the given horsepower and voltage, not simply the nameplate current. Those tables provide standardized FLC values that reflect typical operating conditions and rounding used for design. For this motor—7.5 horsepower, 208 volts, three-phase—the NEC table lists a full-load current of 24.2 amperes. That is the current used in calculations for conductor ampacity, short-circuit/ground-fault protective device ratings, and the motor branch-circuit switch rating. The nameplate current of 23 A is the actual rated current, but the code requires using the table value, which is why 24.2 A is the correct choice. The other figures (like 23 A or numbers like 28 or 25.6) don’t align with the NEC’s designated full-load current value for this exact motor rating.

In motor calculations, the value used to size conductors, protective devices, and motor switches comes from the motor’s full-load current (FLC) as specified in the NEC motor tables for the given horsepower and voltage, not simply the nameplate current. Those tables provide standardized FLC values that reflect typical operating conditions and rounding used for design.

For this motor—7.5 horsepower, 208 volts, three-phase—the NEC table lists a full-load current of 24.2 amperes. That is the current used in calculations for conductor ampacity, short-circuit/ground-fault protective device ratings, and the motor branch-circuit switch rating. The nameplate current of 23 A is the actual rated current, but the code requires using the table value, which is why 24.2 A is the correct choice. The other figures (like 23 A or numbers like 28 or 25.6) don’t align with the NEC’s designated full-load current value for this exact motor rating.