Research — Illustrative (draft, unvalidated)

Breaker vs conductor

Choose a conductor size, material and terminal temperature class, then slide the breaker through the standard ratings. The small-conductor cap in 240.4(D) holds even where Table 310.16 would allow more, and the next-size-up allowance in 240.4(B) only opens when you say the circuit is not a multi-outlet cord-and-plug branch circuit.

Conductor size

Sizes the harness ingests: 14 AWG through 500 kcmil.

Material

Terminal temperature class

You state the column; the check never assumes copper or 75 °C.

Breaker (OCPD) rating

15 Asnaps to NEC 240.6(A) standard ratings600 A

Circuit type · 240.4(B) condition 1

Panel, conductor cross-section and the amps bar

Breaker vs conductor

Breaker

Maximum permitted

Margin

How the check read it

    Client-side port:the logic and table in this page are a TypeScript port of the harness function, checked against values exported from the Python tests. Not a live API call. Module maturity, quoted from the domain page: “Draft, unvalidated. No licensed electrician, electrical PE or inspector has reviewed any of the 13 functions, and output should not be represented as authoritative NEC guidance until a review is logged. Some table values rest on secondary sources rather than a licensed NFPA 70 copy.” The table values here are a TypeScript port of the harness table, checked against values exported from the harness's own function (a full sweep of size, material, temperature class and standard rating, plus the pytest acceptance cases). The conductor cross-section is a relative-size schematic from the AWG / circular-mil definitions, not harness data.Real function this maps to:check_breaker_conductor_ampacity_match.Not modeled: the other 12 of the 13 ubm checks (this page covers only the breaker-versus-conductor match), any load calculation (no Article 220), ambient-temperature and bundling adjustment, 240.4(D)'s own exceptions, and which terminal temperature column should govern (NEC 110.14(C)). You state the column; it does not decide it.See also:Breaker vs conductor — auto