Conductor ampacity and wire-sizing reference data, published as language-neutral JSON. No code — just the tables every implementation needs, one file per standard, each carrying its own provenance.
data/e11.json— ABYC E-11 wire sizing and derating for DC wiring on boats and RVs.data/nec.json— NEC (NFPA 70) ampacity, ambient and conductor-count derating for land installations.data/uscg-33cfr183.json— 33 CFR 183.425 amperage and derating for US recreational boats.fixtures/— spot-check cases per standard; an implementation should reproduce them exactly.
The standards are not interchangeable and the package does not pretend they are. E-11 derates for engine spaces and bundling; the NEC derates for ambient and for conductor count in a raceway. Their shapes differ because the tables differ, and a consumer picks the one its jurisdiction adopted.
Every value's source is recorded in the JSON itself under provenance, with a
URL. Summarised:
- ABYC E-11 values are transcribed from Table 6A as republished with ABYC's permission at https://boathowto.com/wiresize/wiresize_tables_abyc.pdf.
- NEC values are transcribed from attributed third-party technical reproductions — manufacturer and distributor ampacity publications, and a US state fire marshal's reproduction of an adopted amendment — cross-checked so that every cell agrees across at least two independent sources. Nothing was taken from NFPA's own free-access portal, whose terms forbid redistribution. The 2011, 2017 and 2023 editions carry identical values (the table numbers moved between editions, and the dwelling table was prose-only in 2017); pre-2008 reprints differ, and are still in circulation.
NFPA asserts copyright in the NEC and ABYC in E-11. What is published here is the numeric content, attributed, not the standards themselves. Size to the edition your jurisdiction has adopted.
- wire-wright — JavaScript library + CLI, and a browser demo that bundles these tables straight in, no re-transcription.
This package is data-only so ports (Python, Kotlin, anything) can share one source of truth and one fixture set instead of re-transcribing tables.
MIT, covering this compilation and the fixtures. Standards bodies retain whatever rights they hold in their own tables; neither ABYC nor NFPA is affiliated with this project or has endorsed it.