NCCER Electrical Grounding & Bonding 3

Question 1

How is a ground fault best defined in the context of electrical installations?

Accepted Answer

An unintentional electrically conductive connection between an energized conductor and a grounded surface or metal enclosure

Answer

An intentional connection made between a neutral conductor and a grounding electrode

Answer

An open circuit caused by a broken grounding conductor

Answer

A circuit that exceeds its rated ampacity under normal load

Question 2

What type of fault does a Ground Fault Circuit Interrupter (GFCI) primarily protect against, and what is its detection threshold?

Accepted Answer

Ground faults by detecting current imbalances of approximately 4–6 milliamperes between hot and neutral

Answer

Overloads exceeding 20 amperes

Answer

Short circuits between phase and neutral conductors

Answer

Voltage transients above 200 volts

Question 3

Per NEC 250.64(B), which wiring method is NOT permitted to protect a grounding electrode conductor from physical damage?

Accepted Answer

Flexible metal conduit

Answer

Rigid Metal Conduit (RMC)

Answer

Intermediate Metal Conduit (IMC)

Answer

Schedule 80 PVC

Question 4

When two ground rods are required, what is the minimum separation distance between them per NEC 250.53(B)?

Accepted Answer

6 feet

Answer

3 feet

Answer

8 feet

Answer

10 feet

Question 5

Per NEC Table 250.66, what is the maximum copper conductor size that may be required as a grounding electrode conductor for a single set of service-entrance conductors, regardless of how large those conductors are?

Accepted Answer

3/0 AWG

Answer

2 AWG

Answer

1/0 AWG

Answer

250 kcmil

Question 6

Which grounding electrode type generally provides the lowest resistance to earth and is recognized by NEC 250.52(A)(3)?

Accepted Answer

A concrete-encased electrode (Ufer ground)

Answer

A single driven ground rod

Answer

A buried ground plate

Answer

A metal underground water pipe

Question 7

If a single driven ground rod is installed and tested, revealing a resistance to earth of 38 ohms, what action is required by NEC 250.56?

Accepted Answer

A supplemental electrode must be added to the grounding electrode system

Answer

The rod must be replaced with a larger diameter rod

Answer

The service must be derated to account for the high ground resistance

Answer

The measurement must be reported to the authority having jurisdiction but no action is required