PC Grounding and Bonding 2 — Questions and Answers
Question 1: According to NEC Article 250, what is the minimum size copper equipment grounding conductor required for a 100A circuit protected by a 100A breaker?
- #8 AWG (Correct answer)
- #6 AWG
- #4 AWG
- #10 AWG
Correct answer: #8 AWG
NEC Table 250.122 requires a minimum #8 AWG copper EGC for circuits with overcurrent protection rated at 100A.
Question 2: Which of the following locations requires a grounding electrode system to include a ground ring if no other electrode is available?
- Residential service panels under 200A
- Buildings with concrete-encased electrodes already installed
- Buildings or structures where no other electrode type exists on-site (Correct answer)
- Commercial occupancies over 1000 sq ft
Correct answer: Buildings or structures where no other electrode type exists on-site
NEC 250.52(A)(4) allows a ground ring as a grounding electrode when other electrode types are unavailable at the structure.
Question 3: What is the primary purpose of bonding in an electrical system?
- To provide a return path for fault current to the source
- To establish electrical continuity between conductive parts to eliminate voltage differences (Correct answer)
- To reduce the grounding electrode resistance to earth
- To protect equipment from lightning surges
Correct answer: To establish electrical continuity between conductive parts to eliminate voltage differences
Bonding ensures electrical continuity between conductive parts so no dangerous voltage differences exist between them.
Question 4: A concrete-encased electrode (Ufer ground) must contain at least how many feet of bare or zinc-galvanized steel reinforcing bars or rods?
- 10 feet
- 20 feet (Correct answer)
- 50 feet
- 100 feet
Correct answer: 20 feet
NEC 250.52(A)(3) requires at least 20 feet of steel reinforcing bar or rod encased in concrete for a Ufer ground.
Question 5: When installing a grounding electrode conductor in a metal raceway, what additional requirement applies?
- The raceway must be bonded to the grounding electrode conductor at both ends (Correct answer)
- The raceway must be PVC-coated to prevent corrosion
- The raceway must be at least 1-inch trade size
- The raceway must contain only the grounding conductor, no other wiring
Correct answer: The raceway must be bonded to the grounding electrode conductor at both ends
NEC 250.64(E) requires that when a GEC is installed in metal raceway, the raceway must be bonded to the GEC at both ends to prevent inductive choke.
Question 6: Which NEC article specifically addresses grounding and bonding requirements?
- Article 200
- Article 230
- Article 250 (Correct answer)
- Article 280
Correct answer: Article 250
NEC Article 250 covers all grounding and bonding requirements for electrical installations.
Question 7: In a separately derived system (e.g., a transformer), where must the system bonding jumper be installed?
- At the first overcurrent device downstream
- At the grounding electrode only
- At the source of the separately derived system (Correct answer)
- At the main service entrance
Correct answer: At the source of the separately derived system
NEC 250.30(A)(1) requires the system bonding jumper to be installed at the source of the separately derived system.
PC Grounding and Bonding 2
According to NEC Article 250, what is the minimum size copper equipment grounding conductor required for a 100A circuit protected by a 100A breaker?