NEC Grounding and Bonding 2 — Questions and Answers
Question 1: What is the minimum size copper grounding electrode conductor required for a 200-ampere service with a single ground rod electrode per NEC Article 250?
- 6 AWG copper (Correct answer)
- 4 AWG copper
- 8 AWG copper
- 2 AWG copper
Correct answer: 6 AWG copper
NEC 250.66 limits the grounding electrode conductor to a single rod, pipe, or plate electrode to 6 AWG copper regardless of service size.
Question 2: According to NEC 250.53, when a single ground rod does not achieve 25 ohms or less to earth, what must be done?
- Install one additional electrode (Correct answer)
- Install three additional electrodes
- Use a larger diameter rod
- Replace it with a concrete-encased electrode
Correct answer: Install one additional electrode
NEC 250.53(A)(2) requires one additional electrode when resistance of a single rod exceeds 25 ohms.
Question 3: Which NEC article specifically covers grounding and bonding requirements?
- Article 250 (Correct answer)
- Article 230
- Article 310
- Article 220
Correct answer: Article 250
NEC Article 250 exclusively covers all grounding and bonding requirements for electrical systems.
Question 4: What is the purpose of an equipment bonding jumper (EBJ) per NEC 250.102?
- Connect metal parts to ensure electrical continuity (Correct answer)
- Increase fault current capacity
- Reduce voltage drop on branch circuits
- Connect grounding electrodes together
Correct answer: Connect metal parts to ensure electrical continuity
An EBJ connects metal enclosures, raceways, or equipment to ensure a low-impedance fault current path.
Question 5: Per NEC 250.24(A), where must the grounding electrode conductor connection be made on a service entrance?
- At the service entrance equipment (Correct answer)
- At the first overcurrent device
- At the meter base only
- At the load center only
Correct answer: At the service entrance equipment
NEC 250.24(A) requires the grounding electrode conductor to be connected to the service entrance equipment.
Question 6: What is the maximum spacing allowed between two ground rods when used as a grounding electrode system per NEC 250.53?
- 6 feet (Correct answer)
- 4 feet
- 8 feet
- 10 feet
Correct answer: 6 feet
NEC 250.53(B) requires ground rods to be spaced no less than 6 feet apart from each other.
Question 7: Under NEC 250.119, which color or marking is required for equipment grounding conductors (EGCs) larger than 6 AWG?
- Green or green with yellow stripe, or identified at terminations (Correct answer)
- Bare copper only
- White or gray
- No color requirement exists for large conductors
Correct answer: Green or green with yellow stripe, or identified at terminations
EGCs larger than 6 AWG may be any color but must be identified with green marking or green tape at terminations.
NEC Grounding and Bonding 2
What is the minimum size copper grounding electrode conductor required for a 200-ampere service with a single ground rod electrode per NEC Article 250?