IEC - Independent Electrical Contractors Overcurrent Protection Questions and Answers

Question 1

According to NEC® 240.21, where must an overcurrent protective device (OCPD) be located in a circuit?

Accepted Answer

At the point where the conductor to be protected receives its supply.

Answer

At the midpoint of the branch circuit.

Answer

Within 3 feet of the load.

Answer

Only within the main service panel.

Question 2

A feeder is protected by a 300A circuit breaker. Under the '25-foot tap rule,' what is the minimum required ampacity of a tap conductor connected to this feeder?

Accepted Answer

100A

Answer

75A

Answer

150A

Answer

30A

Question 3

Which of the following is NOT a standard ampere rating for a fuse or inverse time circuit breaker according to NEC® 240.6(A)?

Accepted Answer

120A

Answer

90A

Answer

110A

Answer

150A

Question 4

In a motor branch circuit, the short-circuit and ground-fault protective device is sized larger than the conductor's ampacity. What is the primary reason for this allowance?

Accepted Answer

To allow for the high inrush current when the motor starts.

Answer

To account for voltage drop over the length of the circuit.

Answer

To simplify the selection of overcurrent devices.

Answer

To provide overload protection for the motor.

Question 5

An electrician is installing a new branch circuit for a continuous load of 18A using THHN copper conductors. What is the minimum required rating for the overcurrent protection device?

Accepted Answer

25A

Answer

20A

Answer

18A

Answer

30A

Question 6

Which of the following BEST describes the function of 'supplementary overcurrent protection' as defined by the NEC®?

Accepted Answer

It is used in addition to a branch-circuit OCPD for specific equipment protection.

Answer

It is the primary protection for an entire branch circuit.

Answer

It must always be readily accessible.

Answer

It can be used in place of feeder protection.