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Calculator 18 / NEC 392 & 376

Cable tray & wireway fill

Check conductor and cable fill against the NEC 392.22 cable tray tables and the 20% wireway rule of 376.22.

Installation

Rule is chosen per conductor size: 4/0 and larger use Table 392.22(A)(1) cross-sectional area; smaller than 4/0 use the 392.22(A)(1)(b) sum-of-diameters check against tray width.

QtyGaugeInsulationCh. 9 Table 5 area

0.1906 in²

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Cable Tray & Wireway Fill Report

Project / job name: —

Date: —

Site: voltforgelab.com

Inputs

InstallationCable tray, single conductors, ladder tray, 12 in

Results

4/0+ cross-section

0 in²

Allowed in a 12 in ladder tray: 8 in².

NEC 392.22(A)(1)(a) · Table 392.22(A)(1)

Sum of diameters (< 4/0)

5.91 in

Shall not exceed the 12 in tray width.

NEC 392.22(A)(1)(b)

Fill verdict

PASS

All applicable single-conductor checks pass.

NEC 392.22(A)

Engineering disclaimer: This design aid is not a substitute for engineering judgment. Confirm final design with a licensed professional engineer and the authority having jurisdiction.

How this was calculated

  1. Conductor areas come from NEC Chapter 9 Table 5 (as stored in the rule table) and diameters from area: d = 2√(A/π).
  2. Conductors 4/0 and larger: sum of areas 0 in² vs 8 in² (Table 392.22(A)(1)).
  3. Conductors smaller than 4/0: sum of diameters 5.91 in vs 12 in tray width (392.22(A)(1)(b)).
  4. Both checks must pass: PASS.
Engineering disclaimer: Cable tray sizing also involves support spacing, loading, and clearance rules (NEC 392); verify tray manufacturer usable area and cable OD data. Confirm final design with a licensed professional engineer.