Wiring Methods and Protection Flashcards

What is the minimum cover requirement for direct-buried conductors rated 0–600V in a residential driveway under a concrete slab?

Answer: 6 inches

NEC Table 300.5 allows a 6-inch minimum cover for conductors under a concrete encasement at least 2 inches thick.

Which wiring method is specifically listed for use in ducts, plenums, or other air-handling spaces without restriction?

Answer: EMT with THHN conductors

EMT with THHN conductors is permitted in environmental air spaces; Type MC, AC, and ENT have restrictions under NEC 300.22.

Per NEC 300.14, at least how much free conductor length must be left at each outlet, junction, or switch point?

Answer: 6 inches

NEC 300.14 requires at least 6 inches of free conductor at every outlet, switch, or junction point for splicing or connecting.

Flexible metal conduit (FMC) used as a grounding path must not exceed what maximum length?

Answer: 6 feet

Per NEC 350.60, FMC is permitted as an equipment grounding conductor only when the total length in the ground return path does not exceed 6 feet.

What is the maximum size of rigid metallic conduit (RMC) recognized by the NEC?

Answer: 6 inches

NEC 344.20 lists RMC in trade sizes from ½ inch through 6 inches.

When installing conductors in a raceway exposed to different temperatures, what NEC rule applies to prevent moisture condensation?

Answer: Seal the raceway at the point of temperature transition

NEC 300.7(A) requires raceways to be sealed where they pass between areas of different temperatures to prevent condensation from traveling to warmer areas.

Type NM cable is NOT permitted in which of the following applications?

Answer: Exposed industrial occupancies

NEC 334.10 prohibits Type NM cable in commercial or industrial occupancies where exposed wiring is required to be in conduit.