Journeyman Electrician Practice Exam

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Prepare for the Journeyman Electrician Exam. Test your skills with multiple-choice questions designed to help you succeed. Each question comes with hints and detailed explanations to assist in your study process.

Practice this question and more.

Which of the following is true regarding the ampacity of branch-circuit conductors for multiple motor installations?

It can be less than 100% for all motors
It must be at least 125% for the highest motor plus 100% for the others
It is not regulated by any standards
It applies only to single-phase motors

The correct answer is: It must be at least 125% for the highest motor plus 100% for the others

The correct choice highlights an important rule regarding the ampacity of branch-circuit conductors for multiple motor installations. Specifically, the National Electrical Code (NEC) outlines that when calculating the necessary ampacity for conductors supplying multiple motors, you must take into account the full load current of the highest-rated motor. The reasoning behind this is to ensure that the conductor can handle the startup current of the largest motor, which often exceeds normal operating current. In addition to the highest motor's load current, the calculation requires adding 100% of the load current of the other motors combined. This ensures that there is sufficient current-carrying capacity to handle all connected devices without exceeding the conductor's ampacity during normal operation. By specifying a minimum of 125% for the largest motor plus 100% for the others, it promotes safety and prevents overheating and potential failure of the conductor due to overload conditions. Thus, this approach is a critical aspect of electrical design and safety in motor installation.