Home›Knowledge›NEC 240.4 — Conductor Overcurrent Protection
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NEC 240.4 — Conductor Overcurrent Protection

Updated May 22, 2026
Conductors must be protected at their ampacity. 240.4(D) small-conductor rule: 14 AWG max 15A, 12 AWG max 20A, 10 AWG max 30A.

Critical when sizing breakers in a panel directory. The mep-load-calc wireSizeForBreaker() helper enforces 240.4(D) limits before returning a wire size.

TAGS
NEC240.4overcurrentbreaker-sizingwire-protection
DETAILS
book
NEC 2023
section
240.4
mep calc workflow
q-panel-schedule
SOURCES
🔗https://codes.iccsafe.org/content/NFPA702023/article-240
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