Boxes and Conduit Bodies practice questions

Correct: D — 22.50 in³

314.16(B)(1): the 4 conductors add 9.00 in³. 314.16(B)(2): internal clamps add one allowance = 2.25 in³. 314.16(B)(4): each of the two device yokes gets a double allowance = 9.00 in³. 314.16(B)(5): the grounding conductors together add 2.25 in³. Total 22.50 in³ is the correct minimum; the other options drop the clamp allowance, count a yoke only once instead of double, or count each ground separately instead of as a single allowance.

Correct: B — A double volume allowance based on the largest conductor connected to that yoke

Per 314.16(B)(4), each yoke or strap containing one or more devices gets a double volume allowance based on the largest conductor connected to that yoke. This is in addition to conductor fill counted under 314.16(B)(1) — it's a distinct, separate allowance, not a substitute for it, and it's double rather than single.

Correct: A — No, because the box must be listed for at least 60 lb or the fixture supported independently

Per 314.27(A)(2), a standard ceiling box is only required to support 23 kg (50 lb). A luminaire over 50 lb must be supported independently unless the box is listed for at least that weight and marked accordingly. The 70 lb figure is the paddle fan limit under 314.27(C), not a luminaire threshold, so that reasoning doesn't apply here.

Correct: A — 24 inches, using the 8x straight-pull multiplier

Per 314.28(A)(1), straight pulls require box length of at least 8 times the largest raceway's trade size: 8 x 3 = 24 inches. The 6x multiplier applies to angle or U pulls and splices under 314.28(A)(2), not straight pulls, and the Table 312.6(A) substitution only applies to a raceway entry opposite a removable cover.

Correct: D — The box must be durably and legibly marked with its volume by the manufacturer

314.16(A)(2) requires nonmetallic boxes to be durably and legibly marked with their volume by the manufacturer — Table 314.16(A) applies only to standard boxes covered under 314.16(A)(1), not nonmetallic boxes, and installers can't substitute their own external-dimension measurement.

Correct: C — No, the securing exception only applies to single-gang nonmetallic boxes no larger than 57 mm x 100 mm

314.17(B)(2) limits the no-securing exception to single-gang nonmetallic boxes not larger than nominal 57 mm x 100 mm (2-1/4 in. x 4 in.), with the cable fastened within 200 mm of the box and the sheath extending 6 mm through the knockout. A 2-gang box doesn't meet the single-gang size limit, so general securing rules still apply — it's not that nonmetallic boxes are always exempt or never exempt.

Correct: D — Only if the conduit body is durably and legibly marked by the manufacturer with its volume

Per 314.16(C)(2), only conduit bodies durably and legibly marked by the manufacturer with their volume may contain splices, taps, or devices. The doubled cross-sectional area rule from 314.16(C)(1) governs plain pass-through sizing, not splicing rights, and short-radius bodies like capped elbows are explicitly barred from splices under 314.16(C)(3).

Correct: C — 30.2 mm (1-3/16 in.)

314.24(B)(4) sets 30.2 mm as the minimum depth for boxes enclosing devices supplied by 12 or 10 AWG conductors. The 12.7 mm figure is for empty boxes with no device under 314.24(A), 23.8 mm applies to 14 AWG or smaller under 314.24(B)(5), and 52.4 mm applies to 8, 6, or 4 AWG under 314.24(B)(3).

Correct: B — The box has a volume over 1650 cm3 (100 in.3) and the installation meets 314.28(E)(1) through (E)(5)

314.28(E) permits power distribution blocks in pull and junction boxes over 1650 cm3 (100 in.3) for connections of conductors, provided the installation complies with 314.28(E)(1) through (E)(5). Equipment grounding terminal bars, not distribution blocks, are the item permitted in smaller enclosures. Conductor size and cover accessibility aren't the qualifying condition here.

Correct: D — 450 mm (18 in.)

314.23(F) applies once a device is present, and it sets a flat 450 mm (18 in.) securing requirement with no same-side/different-side distinction. The 3 ft option and the side-dependent rule belong to 314.23(E), which only governs enclosures without devices, luminaires, or lampholders.

Correct: C — 314.23(A)

314.23(A) is the general rule requiring an enclosure mounted directly on a building surface to be rigidly and securely fastened, adding support if the surface alone isn't adequate. 314.23(B) instead covers boxes supported from a structural member using a separate brace, and 314.23(B)(1) only addresses the specifics of nail/screw fastening methods, not the general surface-mounting duty.

Correct: B — The location must be effectively described and accessible for excavation, with that description available to authorized personnel

314.29(B) permits listed boxes and handhole enclosures to be covered by gravel, light aggregate, or noncohesive granulated soil if the location is effectively described and accessible for excavation, and that description is available to those authorized to access, maintain, or inspect the wiring. It does not ban coverings outright, require flush mounting, or mandate a permit process.

Correct: D — 13 mm (1/2 in.)

314.72(E) requires block-type letters at least 13 mm (1/2 in.) in height for the "DANGER — HIGH VOLTAGE — KEEP OUT" marking. The smaller 6 mm option is too small to meet the rule, and 25 mm/50 mm overstate the minimum.

Correct: B — It must be made flush with the box interior

Per 314.5(6), fasteners penetrating the wall of a box not exceeding 1650 cm3 (100 in.3) must be made flush with the box interior. The 6 mm and 11 mm allowances apply only to boxes exceeding 100 in.3, and the 8 mm limit applies to fasteners penetrating a cover, not a box wall — this box is well under the 100 in.3 threshold.

Correct: A — 314.25(A)

314.25(A) specifically requires metal covers and plates to be connected to the equipment grounding conductor per 250.110. 314.25(B) addresses combustible finishes around canopies, 314.25(C) addresses cord pendant bushings, and 314.24(B)(5) is a box-fill depth rule, none of which govern metal cover grounding.

Correct: D — It must be listed for use in wet locations

314.15 requires boxes, conduit bodies, outlet box hoods, and fittings installed in wet locations to be listed specifically for wet locations. A damp-location listing isn't sufficient for a wet location, and a drainage opening alone doesn't satisfy the listing requirement. Hazardous-location listing is a separate, unrelated requirement.

Correct: B — 314.30(A)

314.30(A) is the handhole-specific sizing rule, which points to 314.28(A) for conductors at 1000 volts or below and to 314.71 for over 1000 volts — but for a handhole enclosure itself, 314.30(A) is the section to open first, not 314.28(A), which governs pull and junction boxes generally.

Correct: C — 314.100(C)

314.100(C) sets the 1.35 mm (0.053 in.) minimum uncoated thickness specifically for sheet steel boxes over 1650 cm3 (100 in.3). 314.100(B) covers the thinner 1.59 mm requirement but only applies to boxes not over 100 in.3, so it doesn't govern this oversized box.

Correct: C — 36 times the outside diameter, over sheath, of the largest cable or conductor entering

Per 314.71(B)(1), the distance to the opposite wall must be at least 36 times the outside diameter, over sheath, of the largest cable or conductor entering. The 24x figure only applies when cables are nonshielded and not lead covered, and the internal-conduit-diameter and fixed-inches options aren't part of this rule.

Correct: D — 314.28(B)

314.28(B) specifically requires conductors to be cabled or racked in pull/junction boxes with any dimension over 6 ft. 314.28(A)(1) instead sets minimum box sizing for straight pulls, not conductor arrangement, and 314.28(C)/(D) cover covers and barriers, not conductor support.

Correct: A — A specific set of Part I and Part II general provisions listed in 314.70(A)

314.70(A) requires compliance with Part III plus a named subset of Part I (314.2, 314.3, 314.4, 314.5) and Part II (314.15, 314.17, 314.20, 314.23(A)/(B)/(G), 314.28(B), 314.29) sections — not the entirety of Part I/II, and not a wholesale substitution with Article 300.

Correct: D — The luminaire is at least 2.5 m (8 ft) above grade and 900 mm (3 ft) horizontally from doors and windows at that elevation

314.23(H)(2) allows unlocked single-conduit threaded joints only if the luminaire is at least 2.5 m (8 ft) above grade or a standing area and at least 900 mm (3 ft) horizontally clear of windows, doors, porches, or fire escapes at that elevation. Stem length under 18 in. only affects whether a swivel hanger is required, IMC vs. rigid conduit doesn't change the thread-locking requirement, and cord grip fittings apply to flexible-cord support under 314.23(H)(1), not conduit stems.