Wiring methods & materials: Minnesota Class A Journeyworker Electrician Practice Questions

According to the NEC, what is the general rule for the conductors of one circuit, including the grounded conductor and EGC?

Section 300.3(B) keeps all conductors of the same circuit together to limit inductive heating and keep circuit impedance low.

According to the NEC, conductors of 120/240 V and 480Y/277 V systems may share a raceway when:

Section 300.3(C)(1) allows conductors of different systems of 1000 V or less in the same raceway, cable or enclosure if every conductor's insulation is rated at least the maximum voltage applied to any conductor there.

According to the NEC, when NM cable runs through bored holes in wood studs, the edge of the hole must be at least how far from the nearest edge of the stud?

Section 300.4(A)(1) requires bored holes to be at least 1 1/4 in from the nearest edge of the wood member, so drywall screws and nails do not reach the cable.

According to the NEC, if a bored hole cannot be kept far enough from the stud edge, the cable must be protected by a steel plate at least how thick?

Section 300.4(A)(1) requires a steel plate or bushing at least 1/16 in thick (or a listed plate giving equal protection) covering the area of the wiring.

According to the NEC, where NM cable is laid in a notch cut in a wood stud, what is required?

Section 300.4(A)(2) allows cables in notches only where the notch does not weaken the structure, and requires a 1/16-in steel plate over the notch before the finish is applied.

According to the NEC, when NM cable passes through punched holes in metal studs, what is required?

Section 300.4(B)(1) requires NM cable through holes in metal framing to be protected by listed bushings or grommets securely fastened in the opening before the cable is installed.

According to the NEC, a cable run parallel to framing members must be installed so it is at least how far from the nearest edge of the framing?

Section 300.4(D) requires cables and raceways run parallel to framing to be at least 1 1/4 in from the nearest edge, or protected by a 1/16-in steel plate.

According to the NEC, cables and raceways installed under metal-corrugated sheet roof decking must be kept at least how far from the lowest surface of the decking?

Section 300.4(E) requires 1 1/2 in from the lowest surface of metal-corrugated roof decking, so roofing screws do not reach the wiring.

According to the NEC, when 4 AWG or larger insulated conductors enter a cabinet through a raceway, what protects the conductors?

Section 300.4(G) requires an identified fitting with a smoothly rounded insulating surface, such as an insulating bushing, where 4 AWG and larger conductors enter an enclosure from a raceway.

According to the NEC table of minimum cover requirements, what is the minimum cover for direct-buried cable under a lawn (no traffic, not under a building)?

Look it up in Table 300.5: direct-burial cables and conductors need 24 in of cover in the general case.

According to the NEC table of minimum cover requirements, what is the minimum cover for rigid metal conduit in the general case?

Look it up in Table 300.5: rigid metal conduit and IMC need only 6 in of cover in the general case because the steel itself resists damage.

According to the NEC table of minimum cover requirements, PVC conduit listed for direct burial without concrete encasement needs what minimum cover in the general case?

Look it up in Table 300.5: nonmetallic raceways listed for direct burial without concrete encasement need 18 in of cover in the general case.

According to the NEC table of minimum cover requirements, a residential 120 V, 20 A GFCI-protected branch circuit buried in a yard may have a minimum cover of:

Table 300.5 has a column for residential branch circuits of 120 V or less with GFCI protection and overcurrent protection of 20 A or less, allowing 12 in of cover in the general case.

According to the NEC table of minimum cover requirements, what is the minimum cover for any wiring method under a public street, road or alley?

Table 300.5 requires 24 in of cover for all wiring methods under streets, highways, roads, alleys, driveways and parking lots.

According to the NEC, direct-buried conductors that emerge from grade must be protected by enclosures or raceways up to what height above finished grade?

Section 300.5(D)(1) requires protection from the minimum cover depth up to at least 8 ft above finished grade (it need not exceed 18 in below grade).