Cable Trays practice questions

Correct: D — Based on the four current-carrying conductors within this specific cable

Section 392.80(A)(1)(a) limits adjustment factors to the number of current-carrying conductors within the cable itself (here, four), not the number of conductors in the whole tray, and the adjustment applies regardless of cover status once the three-conductor threshold is exceeded.

Correct: D — In industrial establishments where conditions of maintenance and supervision ensure only qualified persons service the cable tray system

392.10(B) restricts single-conductor cable in cable tray to industrial establishments with maintenance and supervision conditions ensuring only qualified persons service the system. It is not a general allowance for commercial buildings, all occupancies, or dwellings.

Correct: C — 75% of the ampacities in Table 315.60(C)(3) and Table 315.60(C)(4)

Per 392.80(B)(2)(1), 1/0 AWG and larger single-conductor cables in uncovered trays with no special spacing are capped at 75% of Table 315.60(C)(3)/(C)(4). The 70% figure only applies once a solid unventilated cover runs longer than 6 ft; the 95% figure is the multiconductor cover derate under 392.80(B)(1); the full Table 315.60(C)(1)/(C)(2) value requires the 2.15×O.D. triangular/square spacing under 392.80(B)(2)(3).

Correct: C — The conductors secured at the cable tray transition point and the conduit sealed at its outer end

392.46(A) permits a boxless transition through bushed conduit only if conductors are secured at the point of transition from the cable tray and the conduit is sealed at the outer end to keep debris out. A junction box is exactly what this section allows you to avoid, and the flanged method belongs to 392.46(B), not (A).

Correct: D — 392.100(C)

392.100(C) is the construction rule requiring cable tray systems to be corrosion resistant, with ferrous material protected per 300.6. 392.60(B) instead covers grounding/bonding continuity for steel or aluminum cable tray systems, not corrosion protection, and 392.100(D)/(A) cover side rails and strength/rigidity respectively.

Correct: B — The Column 1 value in Table 392.22(A)(5)

392.22(A)(5)(a) states that where only one multiconductor cable is installed in a ventilated channel tray, its cross-sectional area must not exceed the Column 1 value of Table 392.22(A)(5). Column 2 of that same table applies only when more than one cable is installed. Table 392.22(A)(6) is for solid channel trays, not ventilated ones, and the 40% figure is not the rule used here.

Correct: C — 392.22(A)(1)

392.22(A)(1) covers ladder or ventilated trough trays with any mixture of multiconductor power, lighting, control, and signal cables, including the mixed 4/0-and-larger-plus-smaller case in 392.22(A)(1)(c) with its Table 392.22(A)(1) fill-area calculation. 392.22(A)(3) is the solid bottom tray counterpart for the same mixed-cable scenario, and 392.22(A)(2) only addresses control/signal-only fill, not mixed power cables.

Correct: C — Sum of cable diameters compared to the tray width, in a single layer

Per 392.22(B)(1)(a), when all single conductors are 1000 kcmil or larger, the sum of their diameters must not exceed the tray width, installed in a single layer. The area-based Table 392.22(B)(1) methods (Column 1 and Column 2) apply to 250–900 kcmil cables and to mixed-size installations, not to all-1000-kcmil-or-larger trays, and there is no generic 40% fill ratio in this section.

Correct: A — The tray is listed and labeled for wet locations

392.60(B) lists four requirements: identification as an EGC, meeting Table 392.60(B) area, durable marking of that area, and bonding per 250.96 with connectors or jumpers sized per 250.102. Wet-location listing is not among them — it's an unrelated tray requirement from elsewhere in Article 392.

Correct: B — "DANGER — HIGH VOLTAGE — KEEP AWAY"

392.18(H) specifies the exact required wording: "DANGER — HIGH VOLTAGE — KEEP AWAY." The other options resemble generic electrical hazard signage but don't match the fixed wording the section requires.

Correct: B — 392.20(C)

392.20(C) specifically addresses paralleled single conductors, requiring groups of not more than one conductor per phase to prevent current imbalance from inductive reactance. 392.22(B)(1) instead covers fill/spacing (how many single-conductor cables fit in a tray), not the grouping arrangement for paralleled sets, and 392.20(A) applies to multiconductor cables, not single conductors in parallel.

Correct: C — 1.8 m (6 ft)

392.30(B)(3) caps the distance between a cable tray and the raceway(s) or equipment where conductors terminate at 1.8 m (6 ft), with the conductors secured at the transition and protected from physical damage. The 3.0 m and 0.9 m figures don't correspond to this rule, and a distance is explicitly limited, not left unlimited.

Correct: D — Only when installed in accordance with 392.10(B)(1)

392.10 permits single insulated cables and single insulated conductors in cable tray only when installed per 392.10(B)(1) — it's a specific carve-out, not a general allowance based on ampacity, tray material, or airfield use.

Correct: A — 392.18(E)

392.18(E) is the rule requiring cable trays to be exposed and accessible except as permitted by 392.18(D); 392.18(F) instead addresses maintaining sufficient working space/clearance around a tray that is already exposed, and 392.18(D) is the exception for routing through partitions/walls, not the general accessibility mandate itself.