E2 Grounding and Bonding 2 — Questions and Answers
Question 1: What is the minimum size equipment grounding conductor required for a 200-ampere circuit per NEC Table 250.122?
- 6 AWG copper
- 4 AWG copper (Correct answer)
- 2 AWG copper
- 8 AWG copper
Correct answer: 4 AWG copper
NEC Table 250.122 requires a 4 AWG copper equipment grounding conductor for circuits rated up to 200 amperes.
Question 2: Which NEC article specifically addresses grounding and bonding requirements?
- Article 230
- Article 250 (Correct answer)
- Article 300
- Article 310
Correct answer: Article 250
NEC Article 250 covers all general requirements for grounding and bonding of electrical installations.
Question 3: What is the purpose of bonding jumpers in a commercial electrical system?
- Increase circuit capacity
- Ensure electrical continuity and reduce impedance (Correct answer)
- Replace ground fault circuit interrupters
- Limit fault current magnitude
Correct answer: Ensure electrical continuity and reduce impedance
Bonding jumpers ensure electrical continuity and create a low-impedance path to facilitate overcurrent device operation during a fault.
Question 4: A separately derived system must have its grounding electrode conductor connected at which point?
- First disconnect means
- Source of the separately derived system (Correct answer)
- Main service panel
- Any convenient metallic structure
Correct answer: Source of the separately derived system
Per NEC 250.30(A), the grounding electrode conductor for a separately derived system must connect at the source (e.g., transformer secondary).
Question 5: What is the maximum resistance allowed between a grounding electrode and the earth per NEC 250.53(A)(2)?
- 5 ohms
- 25 ohms (Correct answer)
- 50 ohms
- 100 ohms
Correct answer: 25 ohms
NEC 250.53(A)(2) requires supplemental electrodes when a single rod, pipe, or plate electrode has resistance exceeding 25 ohms.
Question 6: In a commercial building with multiple services, bonding between services is required to prevent what condition?
- Overloading
- Voltage differences that can cause hazardous current flow (Correct answer)
- Phase imbalance
- Harmonic distortion
Correct answer: Voltage differences that can cause hazardous current flow
Bonding between multiple services prevents dangerous voltage potential differences that could cause hazardous current flow between systems.
Question 7: Which conductor connects the grounded service conductor to the grounding electrode at the service?
- Equipment grounding conductor
- Main bonding jumper
- Grounding electrode conductor (Correct answer)
- System bonding jumper
Correct answer: Grounding electrode conductor
The grounding electrode conductor (GEC) connects the grounded service conductor (neutral) to the grounding electrode system.
E2 Grounding and Bonding 2
What is the minimum size equipment grounding conductor required for a 200-ampere circuit per NEC Table 250.122?