CEI Grounding & Bonding Requirements 2 — Questions and Answers
Question 1: What is the minimum size copper equipment grounding conductor required for a 60-ampere circuit per NEC Table 250.122?
- 10 AWG
- 8 AWG (Correct answer)
- 6 AWG
- 4 AWG
Correct answer: 8 AWG
NEC Table 250.122 requires a minimum 10 AWG copper EGC for circuits up to 60A, but 8 AWG is required when the overcurrent device rating is 60A.
Question 2: Which NEC section governs bonding of metal water piping systems in a building?
- 250.50
- 250.52
- 250.104 (Correct answer)
- 250.106
Correct answer: 250.104
NEC 250.104 specifically covers bonding requirements for piping systems and exposed structural steel.
Question 3: A separately derived system's grounding electrode conductor must be connected at which point?
- At the first overcurrent device
- At the source of the separately derived system (Correct answer)
- At the main service panel
- At any convenient grounding electrode
Correct answer: At the source of the separately derived system
Per NEC 250.30, the grounding electrode conductor for a separately derived system must be connected at the source (e.g., transformer secondary).
Question 4: What is the maximum resistance permitted for a made electrode (ground rod) before an additional electrode must be installed?
- 5 ohms
- 10 ohms
- 25 ohms (Correct answer)
- 50 ohms
Correct answer: 25 ohms
NEC 250.56 requires an additional electrode if a single rod, pipe, or plate electrode has a resistance to ground exceeding 25 ohms.
Question 5: Which of the following is NOT an acceptable grounding electrode per NEC 250.52?
- Metal underground water pipe
- Concrete-encased electrode
- PVC conduit buried 8 feet (Correct answer)
- Ground ring
Correct answer: PVC conduit buried 8 feet
PVC conduit is non-conductive and cannot serve as a grounding electrode; NEC 250.52 lists only metal or conductive materials.
Question 6: The main bonding jumper connects which two components at the service?
- Grounded conductor and equipment grounding conductor (Correct answer)
- Neutral bus and grounding electrode
- Service entrance cable and meter base
- Grounding electrode conductor and load-side neutral
Correct answer: Grounded conductor and equipment grounding conductor
Per NEC 250.28, the main bonding jumper connects the grounded (neutral) conductor to the equipment grounding conductor and enclosure at the service.
Question 7: When installing a concrete-encased electrode, what is the minimum length of reinforcing steel required?
- 10 feet
- 15 feet
- 20 feet (Correct answer)
- 25 feet
Correct answer: 20 feet
NEC 250.52(A)(3) requires at least 20 feet of one or more steel reinforcing bars of at least ½-inch diameter encased in concrete.
CEI Grounding & Bonding Requirements 2
What is the minimum size copper equipment grounding conductor required for a 60-ampere circuit per NEC Table 250.122?