Daily review: Part 1 – Motor Load Circuits: NEC Terms and Terminologies | Part 11 – Sizing Disconnecting Means for Motor & Controller | Part 10 – Overcurrent Protection for Motor Control Circuits Quiz

Q: According to the NEC, what is the required ampere rating for a motor disconnecting means that is disconnecting a motor with a full-load current (FLC) of 20A?

25A — Per NEC 430.110(A), the disconnecting means must have an ampere rating of at least 115% of the motor full-load current rating (20A * 1.15 = 23A; standard rating 25A).

Q: Which term describes a motor control circuit that is tapped from the load side of the motor branch-circuit short-circuit and ground-fault protective device?

Control circuit — A motor control circuit carries the electric signals directing the performance of the controller but does not carry the main power current.

Q: For a stationary motor of 2 horsepower or less, what is permitted to serve as the disconnecting means?

All of the above — NEC 430.109(A)(1) allows a branch-circuit breaker, general-use snap switch, or a plug-and-receptacle as a disconnecting means for motors 2 HP or less.

Q: When must a motor control circuit be provided with overcurrent protection?

Only if the circuit extends beyond the motor control equipment enclosure — Per NEC 430.72, overcurrent protection is required if the control circuit extends beyond the enclosure of the motor controller.

Q: What is the primary function of a motor 'controller' as defined in Article 100?

To govern the starting, stopping, and speed of a motor — A controller is a switch or device that is normally used to start and stop a motor by making and breaking the motor circuit current.

Q: What is the maximum rating of an overcurrent protective device for a control circuit conductor with an ampacity of 15A that is protected by a 20A branch circuit breaker?

15A — The overcurrent protection must not exceed the ampacity of the control circuit conductors (NEC 430.72(B)).

Q: Where must the disconnecting means for a motor be located relative to the controller?

Within sight from the controller — NEC 430.102(A) requires the disconnecting means to be in sight from the controller location.

Q: The 'Full-Load Current' (FLC) rating of a motor is used for which of the following calculations?

All of the above — The FLC (NEC Tables) is the standard value used for sizing conductors, disconnects, and protective devices.

Q: If a motor controller is 10 HP, which type of disconnecting means is required?

A motor-circuit switch or circuit breaker rated in horsepower — Motors over 2 HP require a disconnecting means that is horsepower-rated (NEC 430.109).

Q: What happens if a control circuit is tapped from the line side of the motor branch-circuit protective device?

It must have its own separate overcurrent protection — If tapped from the line side, it is not protected by the motor branch-circuit OCPD and must have dedicated protection (NEC 430.72(A)).

medium 10 Questions

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Question 1 of 10

According to the NEC, what is the required ampere rating for a motor disconnecting means that is disconnecting a motor with a full-load current (FLC) of 20A?

Per NEC 430.110(A), the disconnecting means must have an ampere rating of at least 115% of the motor full-load current rating (20A * 1.15 = 23A; standard rating 25A).

Question 2 of 10

Which term describes a motor control circuit that is tapped from the load side of the motor branch-circuit short-circuit and ground-fault protective device?

A motor control circuit carries the electric signals directing the performance of the controller but does not carry the main power current.

Question 3 of 10

For a stationary motor of 2 horsepower or less, what is permitted to serve as the disconnecting means?

NEC 430.109(A)(1) allows a branch-circuit breaker, general-use snap switch, or a plug-and-receptacle as a disconnecting means for motors 2 HP or less.

Question 4 of 10

When must a motor control circuit be provided with overcurrent protection?

Per NEC 430.72, overcurrent protection is required if the control circuit extends beyond the enclosure of the motor controller.

Question 5 of 10

What is the primary function of a motor 'controller' as defined in Article 100?

A controller is a switch or device that is normally used to start and stop a motor by making and breaking the motor circuit current.

Question 6 of 10

What is the maximum rating of an overcurrent protective device for a control circuit conductor with an ampacity of 15A that is protected by a 20A branch circuit breaker?

The overcurrent protection must not exceed the ampacity of the control circuit conductors (NEC 430.72(B)).

Question 7 of 10

Where must the disconnecting means for a motor be located relative to the controller?

NEC 430.102(A) requires the disconnecting means to be in sight from the controller location.

Question 8 of 10

The 'Full-Load Current' (FLC) rating of a motor is used for which of the following calculations?

The FLC (NEC Tables) is the standard value used for sizing conductors, disconnects, and protective devices.

Question 9 of 10

If a motor controller is 10 HP, which type of disconnecting means is required?

Motors over 2 HP require a disconnecting means that is horsepower-rated (NEC 430.109).

Question 10 of 10

What happens if a control circuit is tapped from the line side of the motor branch-circuit protective device?

If tapped from the line side, it is not protected by the motor branch-circuit OCPD and must have dedicated protection (NEC 430.72(A)).

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