NEC - National Electrical Code Grounding and Bonding Questions and Answers

Question 1

According to NEC Article 250, which of the following is a primary purpose of bonding?

Accepted Answer

To provide a low-impedance path for fault current to facilitate the operation of overcurrent devices.

Answer

To limit voltage imposed by lightning.

Answer

To stabilize voltage to earth during normal operation.

Answer

To connect the electrical system to the earth itself.

Question 2

A feeder is run to a detached garage from a main building. Per NEC 250.32, which of the following is generally required at the detached structure?

Accepted Answer

An equipment grounding conductor run with the feeder and a separate grounding electrode system.

Answer

A connection between the neutral conductor and the grounding electrode.

Answer

Reliance solely on the main building's grounding electrode system.

Answer

A ground fault circuit interrupter for the entire feeder.

Question 3

When installing a single ground rod electrode, it must be supplemented by an additional electrode unless the single rod has a resistance to earth of:

Accepted Answer

25 ohms or less

Answer

10 ohms or less

Answer

50 ohms or less

Answer

100 ohms or less

Question 4

In a separately derived system, such as a transformer, where must the system bonding jumper be connected?

Accepted Answer

At the same point where the grounding electrode conductor is connected.

Answer

At the first outlet supplied by the system.

Answer

Between the primary and secondary windings.

Answer

Only within the main service panel for the building.

Question 5

An electrician is installing a 200-amp feeder using 3/0 AWG copper ungrounded conductors. Due to voltage drop concerns over a long distance, they decide to increase the ungrounded conductors to 250 kcmil copper. According to NEC 250.122(B), what must be done with the wire-type equipment grounding conductor (EGC)?

Accepted Answer

It must be increased in size proportionately to the circular mil area increase of the phase conductors.

Answer

It can remain the size specified in Table 250.122 for a 200A device.

Answer

It must be one standard trade size larger than the original EGC.

Answer

It is no longer required if the raceway is metal.

Question 6

Which of the following is required for the equipotential bonding of a permanently installed swimming pool?

Accepted Answer

A solid copper conductor, not smaller than #8 AWG, bonding specified metal parts.

Answer

Bonding only the pump motor housing with a #12 AWG copper wire.

Answer

Connecting all metal parts to the neutral conductor of the pump circuit.

Answer

Insulating all metal components within 10 feet of the pool.