CEA CEA Grounding, Bonding, and Electrical Service Equipment Questions and Answers 2 — Questions and Answers
Question 1: What is the minimum size copper grounding electrode conductor required for a service with a 350 kcmil copper service entrance conductor?
- #6 AWG
- #4 AWG
- #2 AWG (Correct answer)
- #1/0 AWG
Correct answer: #2 AWG
Per NEC Table 250.66, a 350 kcmil copper service conductor requires a minimum #2 AWG copper grounding electrode conductor.
Question 2: What is the minimum burial depth for a ground rod electrode per the NEC?
- 6 feet
- 8 feet (Correct answer)
- 10 feet
- 12 feet
Correct answer: 8 feet
NEC 250.53(G) requires ground rods to be driven to a minimum depth of 8 feet into the earth.
Question 3: In a separately derived system (such as a transformer secondary), where is the system bonding jumper installed?
- At the main service panel only
- At the source of the separately derived system (Correct answer)
- At the furthest panel from the transformer
- At the first disconnecting means only
Correct answer: At the source of the separately derived system
The system bonding jumper for a separately derived system is installed at the source (the transformer secondary) to bond the grounded conductor to the transformer enclosure and EGC.
Question 4: What is the maximum resistance permitted for a single ground rod electrode before a supplemental electrode is required per the NEC?
- 5 ohms
- 10 ohms
- 25 ohms (Correct answer)
- 50 ohms
Correct answer: 25 ohms
Per NEC 250.53(A)(2), if a single ground rod has a resistance to earth exceeding 25 ohms, a supplemental grounding electrode must be added.
Question 5: Which conductor is NOT permitted to be used as a grounding electrode conductor?
- Bare copper
- Green-insulated copper
- Aluminum in direct contact with masonry or earth (Correct answer)
- Stranded copper with green insulation
Correct answer: Aluminum in direct contact with masonry or earth
NEC 250.64(A) prohibits aluminum or copper-clad aluminum grounding electrode conductors where they are in direct contact with masonry or the earth, or subject to corrosive conditions.
Question 6: What is the purpose of bonding metallic water piping systems in a building?
- To use the piping as the primary grounding electrode
- To ensure all metallic piping is at the same electrical potential, preventing shock hazards (Correct answer)
- To reduce water pressure fluctuations
- To comply with plumbing codes only
Correct answer: To ensure all metallic piping is at the same electrical potential, preventing shock hazards
Bonding the metallic water piping equalizes electrical potential throughout the system, eliminating the risk of shock from voltage differences between piping and other grounded metal.
CEA CEA Grounding, Bonding, and Electrical Service Equipment Questions and Answers 2
What is the minimum size copper grounding electrode conductor required for a service with a 350 kcmil copper service entrance conductor?