Cable Tray Fill
Cable-tray fill against the NEC 392.22 sum-of-diameters or cross-sectional-area allowance, with a pass/fail.
Example
You enter
- Tray type ladder
- Tray inside width (in) 12
- Cables: count,diameter(in),large|small per line count 6, diameter (in) 1.5, large true
You get
- Fill value 9
- Allowable 12
Checked against published worked examples from: NEC Article 392.22(A) (by name).
Details, formula, and sources
Formula or tableNEC 392.22(A): cables 4/0 and larger, sum of diameters <= tray inside width (90% of it on solid bottom, 392.22(A)(3)(a)); smaller cables, sum of cross-sectional areas <= the column allowable (~1.167 * width ladder/ventilated, ~0.917 * width solid bottom); mixed loads reduce that area by 1.2 * the sum of the 4/0-and-larger diameters on ladder/ventilated (392.22(A)(1)(c)) and by the sum itself on solid bottom (Column 4).
Source and editionCable-tray fill per NEC Article 392.22 (the sum-of-diameters rule for cables 4/0 and larger and the cross-sectional-area allowance for smaller cables), by name.
Free accessNEC is free to read at nfpa.org/freeaccess. Ampacity derating for tray fill (392.80) is a separate check.
What governsEstimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.
API field namestray_type, tray_width_in, cables, fill_value, allowable
- Column-1 / Column-3 allowance the linear Column 1 (ladder) / Column 3 (solid bottom) area the NEC Table 392.22(A) encodes; verify against the adopted tableNEC Table 392.22(A)