NEC 240.6(A) standard breaker & fuse sizes
The NEC 240.6(A) standard ampere ratings for fuses and inverse-time circuit breakers, plus the 240.4(D) small-conductor rule that caps the breaker regardless of ampacity.
Standard OCPD sizes — 240.6(A)
15 A20 A25 A30 A35 A40 A45 A50 A60 A70 A80 A90 A100 A110 A125 A150 A175 A200 A225 A250 A300 A350 A400 A450 A500 A600 A
When a calculated load falls between two standard sizes, 240.4(B) generally allows rounding up to the next standard size for circuits of 800 A or less (with conditions). Solar Scripto uses the next-standard-size rule automatically.
Small-conductor limits — 240.4(D)
Regardless of its ampacity, a small conductor's overcurrent device may not exceed:
| Copper | Max OCPD | Aluminum | Max OCPD | |
|---|---|---|---|---|
| 14 AWG | 15 A | 12 AWG | 15 A | |
| 12 AWG | 20 A | 10 AWG | 25 A | |
| 10 AWG | 30 A | — | — |
Related: 310.16 ampacity · 250.122 EGC by OCPD.
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