CEI CEI Service Entrance & Metering Inspection 2 — Questions and Answers
Question 1: During a meter socket inspection, an inspector finds the meter enclosure is not bonded to the service-entrance neutral. What NEC section requires this bonding?
- NEC 250.24(A)
- NEC 250.28
- NEC 230.94
- NEC 250.92 (Correct answer)
Correct answer: NEC 250.92
NEC 250.92 requires that the service enclosures, including meter enclosures, be bonded to the service neutral (grounded conductor) at the service entrance.
Question 2: What is the purpose of the main bonding jumper at the service equipment?
- To connect the neutral conductor to the equipment grounding conductor (Correct answer)
- To bond the service panel to the building steel
- To connect the grounding electrode to the service equipment
- To bond the meter socket to the utility transformer
Correct answer: To connect the neutral conductor to the equipment grounding conductor
Per NEC 250.24(B), the main bonding jumper connects the grounded (neutral) conductor to the equipment grounding conductor and service equipment enclosure at the service disconnect.
Question 3: An inspector finds a service rated at 200A with a service-entrance conductor of 2/0 AWG copper. Under NEC 310.15, is this conductor adequately sized?
- No, 200A service requires a minimum 3/0 AWG copper
- Yes, 2/0 AWG copper is adequate for 200A under the 83% rule (Correct answer)
- No, 200A service requires a minimum 4/0 AWG copper
- Yes, but only if the conductors are in free air
Correct answer: Yes, 2/0 AWG copper is adequate for 200A under the 83% rule
NEC 310.15(B)(7) permits 2/0 AWG copper (rated 175A) to serve as a 200A service conductor when it supplies a dwelling unit service.
Question 4: Which of the following is NOT a permitted grounding electrode per NEC 250.52?
- Metal underground water pipe in direct contact with earth for 10 feet or more
- Concrete-encased electrode (Ufer ground) with 20 feet of rebar
- A driven ground rod 5/8 inch diameter and 8 feet long
- A steel well casing that is not bonded to water supply piping (Correct answer)
Correct answer: A steel well casing that is not bonded to water supply piping
NEC 250.52(A) lists acceptable grounding electrodes; a steel well casing alone, without meeting specific criteria for other electrode types, is not a listed grounding electrode.
Question 5: During a service entrance inspection, what is the required minimum burial depth for a service lateral installed in rigid metal conduit (RMC)?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 24 inches
Correct answer: 12 inches
Per NEC Table 300.5, RMC and IMC installed as direct-buried service laterals require a minimum cover of 6 inches, but when under a building slab or in RMC, 6 inches is the minimum; general direct burial of RMC requires only 6 inches — however standard NEC Table 300.5 specifies 6 inches for RMC.
Question 6: What is the minimum ampere rating of a service disconnecting means for a one-family dwelling, per NEC 230.79?
- 60 amperes
- 100 amperes (Correct answer)
- 150 amperes
- 200 amperes
Correct answer: 100 amperes
NEC 230.79(C) requires the service disconnecting means for a one-family dwelling to have a rating of not less than 100 amperes, 3-wire.
CEI CEI Service Entrance & Metering Inspection 2
During a meter socket inspection, an inspector finds the meter enclosure is not bonded to the service-entrance neutral.
What NEC section requires this bonding?