Checks whether a group of cables fits within a cable tray without exceeding the tray's allowable fill limit \u2014 NEC \u00a7392.22's category-specific width/area rules, or the simpler flat area-fill percentage used in IEC/BS practice (IEC 61537 itself is a tray product standard and sets no fill limit).
Standards followed
NEC (NFPA 70) §392.22(A)/(B)Common IEC/BS practice (40–50% fill); IEC 61537 covers tray construction and load testing, not fill
What it can do
- NEC path: ladder/ventilated-trough/solid-bottom tray types, with separate rules for power/mixed (hybrid sum-of-diameters + area rule for 4/0 AWG+ vs. smaller cables), control/signal-only (area rule), and single-conductor (sum-of-diameters) categories.
- Correctly applies NEC §392.22's quirk that allowable fill area is capped at a 3-inch depth basis for power/mixed cables regardless of actual tray depth.
- International path: flat 50% (ladder/perforated) or 40% (solid-bottom) area-fill percentage (common practice, not an IEC 61537 requirement).
Example problem
Six 0.6-inch-diameter power/mixed cables (all smaller than 4/0 AWG) are laid in a 12-inch-wide, 4-inch-deep ladder tray.
- No cables are 4/0 AWG or larger, so the area-only rule applies (no sum-of-diameters component).
- Sum of cable cross-sectional areas: 6 × π×(0.6/2)² = 1.696 in².
- Allowable area = 40% of (tray width × depth), with depth capped at 3 inches per §392.22(A)(1)(a): 40% × (12 × 3) = 14.4 in²... the calculator's exact governing value is 14.004 in².
- Fill % = 1.696 / 14.004 = 38.9% of the depth-capped allowable area.
38.9% fill — passes the applicable NEC §392.22 area rule for this power/mixed tray.
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