IEC Grounding and Bonding 4 — Questions and Answers
Question 1: Which of the following is NOT listed as a grounding electrode in NEC 250.52(A)?
- Concrete-encased electrode
- Ground ring
- Metal underground fuel (gas) piping (Correct answer)
- Metal underground water pipe
Correct answer: Metal underground fuel (gas) piping
Metal underground fuel (gas) piping is explicitly prohibited from use as a grounding electrode per NEC 250.52(B), whereas the others are permitted electrodes.
Question 2: What is the minimum size copper conductor for a ground ring used as a grounding electrode per NEC 250.52(A)(4)?
- #6 AWG
- #4 AWG
- #2 AWG (Correct answer)
- #1/0 AWG
Correct answer: #2 AWG
NEC 250.52(A)(4) requires the ground ring to consist of at least #2 AWG copper conductor encircling the building buried at least 2.5 feet deep.
Question 3: When installing a concrete-encased grounding electrode (Ufer ground), the conductor or rebar must be encased in at least how many inches of concrete?
- 1 inch
- 2 inches (Correct answer)
- 3 inches
- 4 inches
Correct answer: 2 inches
NEC 250.52(A)(3) requires the conductor or rebar to be encased in at least 2 inches of concrete at the bottom of a foundation or footing.
Question 4: Per NEC 250.119, equipment grounding conductors must be identified by which color(s)?
- White or gray
- Green, green with yellow stripes, or bare (Correct answer)
- Orange or yellow
- Black or red
Correct answer: Green, green with yellow stripes, or bare
NEC 250.119 requires insulated equipment grounding conductors to be identified by the color green or green with one or more yellow stripes, or they may be bare.
Question 5: A bonding jumper installed on the load side of the service to connect multiple equipment grounding conductors is called a(n):
- Main bonding jumper
- Equipment bonding jumper (Correct answer)
- System bonding jumper
- Grounding electrode conductor
Correct answer: Equipment bonding jumper
An equipment bonding jumper is used on the load side of the service to ensure electrical continuity between multiple equipment grounding conductors or enclosures.
Question 6: What is the minimum burial depth for a ground ring used as a grounding electrode per NEC 250.52(A)(4)?
- 12 inches
- 18 inches
- 24 inches (2.5 feet) (Correct answer)
- 36 inches
Correct answer: 24 inches (2.5 feet)
NEC 250.52(A)(4) requires the ground ring to be buried at least 2.5 feet (30 inches) below the surface of the earth.
Question 7: Which of the following statements about objectionable current on grounding conductors is TRUE per NEC 250.6?
- Objectionable current is required to ensure proper fault clearing
- Wiring must be arranged to prevent objectionable current from flowing on grounding conductors (Correct answer)
- Objectionable current only occurs in high-voltage systems above 480V
- Grounding conductors are designed to carry continuous objectionable current
Correct answer: Wiring must be arranged to prevent objectionable current from flowing on grounding conductors
NEC 250.6 states that electrical systems must be arranged to prevent objectionable current from flowing on grounding conductors or grounding paths.
IEC Grounding and Bonding 4
Which of the following is NOT listed as a grounding electrode in NEC 250.52(A)?