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NEC Article 240 — Overcurrent Protection

Updated Mar 26, 2026
Circuit breaker and fuse sizing: conductor protection, coordination, available fault current marking.

NEC Article 240: 240.4 protection of conductors: overcurrent device rating not to exceed conductor ampacity per Table 310.16. 240.4(D) small conductors: 14 AWG = 15A, 12 AWG = 20A, 10 AWG = 30A. 240.6 standard ampere ratings: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600. 240.21 feeder overcurrent protection at supply end (exceptions for tap rules: 10ft tap, 25ft tap). 240.67 arc energy reduction required for services and feeders >1,200A (maintenance switch or zone-selective interlocking). 240.87 arc energy reduction for breakers rated 1,200A+ (instantaneous trip, zone-selective, energy-reducing).

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NECovercurrentbreakerfuseconductor-protectionarc-energy
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code year
2023
code system
NEC
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Article 240
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