CEI Grounding & Bonding Requirements 3 — Questions and Answers
Question 1: At a subpanel (remote distribution panel), the neutral bus and ground bus must be:
- Bonded together
- Separated and not connected (Correct answer)
- Connected via the main bonding jumper
- Tied together only if the panel is metal
Correct answer: Separated and not connected
At a subpanel, the neutral and ground buses must be kept separate to prevent objectionable current from flowing on grounding conductors per NEC 250.142.
Question 2: What minimum burial depth is required for a ground rod electrode?
- 4 feet
- 6 feet
- 8 feet (Correct answer)
- 10 feet
Correct answer: 8 feet
NEC 250.53(G) requires ground rods to be driven to a depth of at least 8 feet in contact with the soil.
Question 3: Which conductor is used to connect the grounding electrode to the grounded service conductor or equipment?
- Equipment grounding conductor
- Main bonding jumper
- Grounding electrode conductor (Correct answer)
- System bonding jumper
Correct answer: Grounding electrode conductor
The grounding electrode conductor (GEC) is the conductor that connects the grounding electrode system to the grounded conductor or equipment per NEC Article 100.
Question 4: Bonding of metal gas piping is required when the piping system could become energized. The bond must be connected to:
- The nearest water pipe
- The grounding electrode directly
- The equipment grounding conductor or grounded service conductor (Correct answer)
- The neutral bus at the subpanel
Correct answer: The equipment grounding conductor or grounded service conductor
Per NEC 250.104(B), metal gas piping must be bonded to the service equipment enclosure, grounded conductor at the service, or grounding electrode conductor.
Question 5: What is the minimum size copper grounding electrode conductor for a service with 3/0 AWG copper service-entrance conductors per NEC Table 250.66?
- 4 AWG
- 2 AWG (Correct answer)
- 1/0 AWG
- 2/0 AWG
Correct answer: 2 AWG
Per NEC Table 250.66, service-entrance conductors of 2/0–3/0 AWG copper require a minimum 2 AWG copper grounding electrode conductor.
Question 6: An equipment grounding conductor run with circuit conductors in a raceway must be:
- Bare copper only
- Insulated green or bare (Correct answer)
- Green insulation only
- Any color except white or gray
Correct answer: Insulated green or bare
NEC 250.119 permits EGCs to be bare, covered, or insulated; if insulated, they must be green or green with yellow stripe.
Question 7: When two ground rods are used to meet the 25-ohm requirement, what minimum separation must be maintained between them?
- 3 feet
- 4 feet
- 6 feet (Correct answer)
- 8 feet
Correct answer: 6 feet
NEC 250.53(B) requires multiple rod electrodes to be at least 6 feet apart to ensure their effective resistance areas do not significantly overlap.
CEI Grounding & Bonding Requirements 3
At a subpanel (remote distribution panel), the neutral bus and ground bus must be: