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Article 392 (Part 3 of 3)
Cable Trays — Fill Limits, Support, Splices, Grounding & Construction!

SLIDE 1 — Number of Conductors/Cables — Fill Rules (392.22)
📊 MULTICONDUCTOR CABLES ≤2000V (392.22(A))
🔹 Ladder/ventilated trough, mixed cable sizes: all 4/0 AWG+ → sum of diameters ≤ tray width, single layer. All smaller than 4/0 → fill area limited per Table 392.22(A)(1) Column 1. Mixed sizes → smaller cables limited per Column 2, with 4/0+ cables in their own single layer.
🔹 Control/signal-only cables in shallow trays (≤6 in. usable depth) → fill ≤50% of interior cross-section (ladder/trough) or ≤40% (solid bottom)
🔹 Solid bottom trays → similar rules using Columns 3 & 4 of the table, with 4/0+ cable diameters limited to 90% of tray width
🔹 Ventilated channel & solid channel trays → single-cable and multi-cable fill limits per their own dedicated tables
📊 SINGLE-CONDUCTOR CABLES ≤2000V (392.22(B))
Fill rules depend on conductor size (1000 kcmil+ vs 250–900 kcmil vs 1/0–4/0 AWG), each with its own diameter-sum or fill-area formula from Table 392.22(B)(1).
📊 MV/MC CABLES OVER 2000V (392.22(C))
Sum of diameters (single conductors AND multiconductor combined) ≤ tray width, single layer — triplexed/quadruplexed groups follow the same diameter-sum rule.
💡 Bottom line: fill math changes based on cable type, size, and tray style — always check the specific table for your configuration.

SLIDE 2 — Securing & Supporting (392.30)
📏 CABLE TRAYS THEMSELVES (392.30(A))
Supported per the manufacturer's installation instructions.
🔗 CABLES & CONDUCTORS (392.30(B))
🔹 Non-horizontal runs → cables fastened securely to transverse tray members
🔹 Supports required to prevent cable stress where cables enter raceways from the tray
🔹 Transitions between trays, or tray-to-raceway/equipment → distance can't exceed 1.8m (6 ft); conductors must be secured at the transition and protected from physical damage
🔹 Cable ties must be listed and identified for securement/support use

SLIDE 3 — Expansion, Bushed Conduit & Splices (392.44, 392.46, 392.56)
🌡️ EXPANSION SPLICE PLATES (392.44)
Provided where needed to compensate for thermal expansion/contraction.
🔌 BUSHED CONDUIT/TUBING (392.46)
No box required where cables transition from tray to a raceway through bushed conduit/tubing — nonmetallic-sheathed cables can enter enclosures this way (secured at the transition, conduit sealed at the outer end) OR through a flanged connection mounted directly to equipment (opening sealed/covered, cables protected from abrasion).
🔗 SPLICES & TYPE MV JOINTS (392.56)
Permitted within the tray if accessible — approved methods only. Splices/joints CAN project above the side rails if not subject to physical damage.

SLIDE 4 — Grounding, Ampacity & Construction + Final Exam (392.60, 392.80, 392.100)
🌎 GROUNDING & BONDING (392.60)
🔹 Metal trays CAN serve as the EGC where qualified persons maintain the system, per 250.96 & Article 250 Part IV
🔹 Steel/aluminum trays used as EGC need: identified sections/fittings, minimum cross-sectional area per Table 392.60(B), legible marking of that area, and bonded connections per 250.96/250.102
🔹 Steel trays: EGC use capped at 600A ground-fault protection. Aluminum trays: capped at 2000A
🔹 Discontinuous sections need a bonding jumper sized per 250.102 to maintain continuity
🌡️ AMPACITY (392.80)
Ampacity depends heavily on cable type, voltage, tray coverage (covered vs. uncovered), and spacing — pulls from Table 310.16/310.18 (≤2000V) or Table 315.60(C) series (2001V+), with specific percentage derates for covered trays and various single-conductor configurations.
🏗️ CONSTRUCTION (392.100)
🔹 Strength/rigidity to support all wiring
🔹 No sharp edges/burrs that could damage insulation
🔹 Corrosion-resistant (ferrous material per 300.8)
🔹 Side rails or equivalent structural members
🔹 Fittings for direction/elevation changes
🔹 Nonmetallic trays must be flame-retardant

🧠 FINAL EXAM QUESTION FOR ARTICLE 392 (Part 3)
Q: Per 392.60(B), steel cable trays used as an equipment grounding conductor shall NOT be used for circuits with ground-fault protection above what amperage?
A) 400A
B) 600A
C) 1000A
D) 2000A
(Drop your final answer 👇)

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