FREE TN-LLE Grounding and Bonding Questions and Answers

Question 1

Which of the following is NOT permitted to be used as a grounding electrode according to NEC 250.52(B)?

Accepted Answer

An underground metal gas piping system

Answer

NEC 250.52(B)(1) explicitly prohibits the use of metal underground gas piping systems as a grounding electrode. This is a critical safety rule to prevent electrical current from flowing on gas pipes, which could create an ignition source.

Question 2

If a single rod electrode is installed and its resistance to ground is greater than 25 ohms, what does NEC 250.53(A)(2) require?

Accepted Answer

A second grounding electrode must be installed.

Answer

When a single rod, pipe, or plate electrode does not have a resistance to ground of 25 ohms or less, it must be augmented by one additional electrode of any of the types specified in 250.52(A)(2) through (A)(8). The second electrode must be installed no closer than 6 feet from the first.

Question 3

What is the minimum size copper grounding electrode conductor (GEC) required for a service with 4/0 AWG copper service-entrance conductors?

Accepted Answer

2 AWG

Answer

NEC Table 250.66 is used to size the grounding electrode conductor based on the size of the service-entrance conductors. For 4/0 AWG copper service conductors, the table requires a minimum of a 2 AWG copper GEC.

Question 4

What is the primary purpose of a main bonding jumper at the service equipment?

Accepted Answer

To connect the equipment grounding conductor to the grounded (neutral) conductor

Answer

The main bonding jumper, as described in NEC 250.28, provides the critical connection between the equipment grounding conductor(s) and the grounded (neutral) conductor at the service. This connection creates a low-impedance path for ground-fault current to flow back to the source, allowing the overcurrent device to operate.

Question 5

A bonding jumper is required to be installed around a water meter on a metallic water piping system when that system is used as a grounding electrode. Why?

Accepted Answer

To ensure continuity of the grounding path if the meter is removed

Answer

According to NEC 250.68(C), bonding jumpers are required around equipment like meters and filters because these devices can be removed for service. Installing a jumper ensures the integrity and continuity of the grounding path is maintained even if the meter is temporarily or permanently replaced with a non-metallic one.

TN LLE - Tennessee Limited Licensed Electrician Practice Test

TN LLE - Tennessee Limited Licensed Electrician Practice Test

FREE TN-LLE Grounding and Bonding Questions and Answers