F80 Code Requirements 3 — Questions and Answers
Question 1: According to the NEC, what is the minimum burial depth for a rigid metal conduit (RMC) installed under a residential driveway?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 24 inches
Correct answer: 12 inches
NEC Table 300.5 requires RMC to be buried at least 6 inches under a residential driveway, but under a one- or two-family dwelling driveway the requirement is 12 inches.
Question 2: Under the NEC, which of the following locations requires GFCI protection for 15- and 20-ampere, 125-volt receptacles?
- Finished basement living areas (Correct answer)
- All bedroom outlets
- All dining room outlets
- All outlets within 20 feet of a pool
Correct answer: Finished basement living areas
NEC 210.8(A) requires GFCI protection for receptacles in unfinished and finished basement areas of dwelling units.
Question 3: What is the maximum length of a flexible cord that may be used as a fixed wiring method for a stationary appliance under the NEC?
- 2 feet
- 3 feet
- 6 feet
- Flexible cords cannot be used as fixed wiring (Correct answer)
Correct answer: Flexible cords cannot be used as fixed wiring
NEC 400.12 prohibits flexible cords from being used as a substitute for fixed wiring, regardless of length.
Question 4: According to NEC 310.15, which conductor ampacity correction factor applies when conductors are installed in an ambient temperature of 40°C (104°F)?
- 0.91
- 0.82 (Correct answer)
- 0.71
- 0.58
Correct answer: 0.82
For 75°C-rated conductors at 40°C ambient, NEC Table 310.15(B)(1) specifies a correction factor of 0.82.
Question 5: The NEC requires service-entrance conductors to be protected from physical damage. Which of the following is NOT an acceptable wiring method for service-entrance conductors above a roof?
- Service entrance cable (SE cable)
- Rigid metal conduit (RMC)
- Intermediate metal conduit (IMC)
- Type NM cable (Correct answer)
Correct answer: Type NM cable
NEC 230.43 lists acceptable wiring methods for service-entrance conductors, and Type NM (non-metallic sheathed) cable is not among them.
Question 6: Under NEC 250.52, which electrode is NOT considered a grounding electrode?
- A concrete-encased electrode (Ufer ground)
- Metal underground water pipe
- A driven ground rod with 25 ohms resistance (Correct answer)
- Metal frame of a building connected to earth
Correct answer: A driven ground rod with 25 ohms resistance
A single ground rod that measures more than 25 ohms resistance must be supplemented with an additional electrode per NEC 250.56, but it is still considered a grounding electrode.
Question 7: According to NEC 230.24, what is the minimum clearance required for service-drop conductors over a public road when traffic could include trucks?
- 10 feet
- 12 feet
- 15 feet
- 18 feet (Correct answer)
Correct answer: 18 feet
NEC 230.24(B) requires service-drop conductors over roads subject to truck traffic to maintain a minimum clearance of 18 feet.
F80 Code Requirements 3
According to the NEC, what is the minimum burial depth for a rigid metal conduit (RMC) installed under a residential driveway?