Cable Tray Fill API
Cable-tray fill engineering maths as an API, computed locally and deterministically from NEC Article 392 — the allowable-fill, single-layer and tray-width numbers an electrician, estimator or designer runs for a tray run. The fill endpoint applies NEC 392.22(A)(1) Column 1 for multiconductor power and lighting cables no larger than 4/0 in a ladder or ventilated-bottom tray: the total cable cross-sectional area is capped at the tray width × 7/6, so a 12-inch tray allows 14 in² — sum every cable's csa, get the percentage fill and whether it is within code, with the spare area left. The large-cable endpoint covers cables 4/0 and larger, which must lie in a single layer with the sum of their diameters not exceeding the tray width — no stacking — so it returns the spare width and the code check. The min-width endpoint inverts the rule to size the tray: minimum width = cable area × 6/7, rounded up to a standard 6/9/12/18/24/30/36-inch width, leaving room for spare capacity and future cables. Everything is computed locally and deterministically, so it is instant and private. Ideal for electrical-design and estimating tools, industrial and OSP utilities, and code-check calculators. Pure local computation — no key, no third-party service, instant. Ladder/ventilated trays; solid-bottom and mixed fills use the other NEC columns, and ampacity must be derated for fill. 3 compute endpoints. For conduit and box fill use a conduit API.
api.oanor.com/cabletray-api
