Motors & EquipmentQuestion 92 of 120
When sizing motor branch-circuit conductors and short-circuit protection, which current value must be used?
a.The locked-rotor current from the nameplate code letter
b.The motor nameplate full-load amperes
c.The full-load current from Table 430.248 or 430.250
d.The larger of nameplate current or table current
Explanation
Conductor sizing, branch-circuit protection and disconnect rating are all based on the table values, which are conservative and independent of a particular manufacturer's nameplate. Nameplate current is used only for overload protection under 430.32, and locked-rotor current is used for withstand and disconnect horsepower comparisons, not for conductor sizing.
Law Reference: 2023 NEC §430.6(A)(1)Practice all 120 questions free — no signup required.
Related questions on this topic
- A 30-horsepower, 460-volt three-phase motor has a table full-load current of 40 amperes. What is the minimum ampere rating of the disconnecting means?
- A feeder supplies a 25-horsepower motor (34 amperes) and a 10-horsepower motor (14 amperes), both 460 volts three phase. What minimum conductor ampacity is required?
- For that same two-motor feeder, if the largest branch-circuit protective device is 90 amperes, what is the maximum feeder overcurrent device rating?
- A continuous-duty motor over 1 horsepower is marked with a temperature rise of 40 degrees C but no service factor. What percentage of nameplate full-load current sets the maximum overload device?
- A continuous-duty motor over 1 horsepower has no marked service factor and no marked temperature rise. What is the maximum overload device rating as a percentage of nameplate full-load current?
- Where must a motor disconnecting means be located relative to the motor?
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