PC Wiring Methods and Protection 2

Question 1

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

Accepted Answer

6 inches

Answer

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

Question 2

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

Accepted Answer

EMT with THHN conductors

Answer

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

Question 3

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

Accepted Answer

6 inches

Answer

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

Question 4

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

Accepted Answer

6 feet

Answer

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.

Question 5

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

Accepted Answer

6 inches

Answer

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

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