FREE Licensed Electrical Contractor Grounding and Bonding Questions and Answers

Question 1

An electrical service is supplied by 4/0 AWG copper service-entrance conductors. According to NEC Table 250.66, what is the minimum size copper Grounding Electrode Conductor (GEC) required to connect to a metal underground water pipe electrode?

Accepted Answer

2 AWG

Answer

According to NEC Table 250.66, when the largest ungrounded service-entrance conductor is over 3/0 AWG through 350 kcmil copper, the minimum size for the copper Grounding Electrode Conductor is 2 AWG.

Question 2

What is the primary purpose of bonding all non-current-carrying metal parts of an electrical installation together?

Accepted Answer

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

Answer

The primary purpose of bonding is safety. It creates a continuous, low-impedance path for ground-fault current to return to the source, ensuring the current is high enough to trip a circuit breaker or blow a fuse, thereby clearing the fault. While grounding helps stabilize voltage and dissipate lightning, bonding specifically deals with creating an effective ground-fault current path.

Question 3

According to NEC 250.52(B), which of the following is expressly NOT permitted to be used as a grounding electrode?

Accepted Answer

A metal underground gas piping system.

Answer

NEC Section 250.52(B)(1) explicitly prohibits the use of metal underground gas piping systems as grounding electrodes due to the inherent safety risks, such as the potential for a fault to ignite the gas. The other options are all permissible types of grounding electrodes described in NEC 250.52(A).

Question 4

A contractor is installing a branch circuit protected by a 60-amp circuit breaker. What is the minimum size copper Equipment Grounding Conductor (EGC) required for this circuit?

Accepted Answer

10 AWG

Answer

The Equipment Grounding Conductor (EGC) is sized based on the rating of the overcurrent protective device, not the load. According to NEC Table 250.122, for a circuit protected by a 60-amp device, the minimum required size for a copper EGC is 10 AWG.

Question 5

When installing a separately derived system, such as a dry-type transformer, which component is required by NEC 250.30 to connect the system's grounded conductor (neutral) to the equipment grounding conductor(s)?

Accepted Answer

A system bonding jumper.

Answer

For a separately derived system, a system bonding jumper is required to be installed at the source. Its purpose is to connect the grounded conductor to the equipment grounding conductor and the normally non-current-carrying metal parts of the system, establishing the necessary low-impedance path for fault current.

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Practice Test

FREE Licensed Electrical Contractor Grounding and Bonding Questions and Answers