Breaker limits for small wires: 14, 12 and 10 AWG
Small wires have firm breaker limits: 14 AWG copper at 15 A, 12 AWG copper at 20 A and 10 AWG copper at 30 A, with lower limits for aluminum and copper-clad aluminum, unless a specific code permission applies.
What the code requires
After any corrections for ambient temperature and the number of conductors, the overcurrent protection for small conductors may not exceed the limits below, unless 240.4(E) or 240.4(G) permits otherwise.
Copper: 14 AWG at 15 A, 12 AWG at 20 A and 10 AWG at 30 A. Aluminum or copper-clad aluminum: 12 AWG at 15 A and 10 AWG at 25 A.
Smaller conductors: 18 AWG copper at 7 A (continuous load 5.6 A or less, with specific listed devices) and 16 AWG copper at 10 A (continuous load 8 A or less). New in 2023, 14 AWG copper-clad aluminum is limited to 10 A, with continuous load of 8 A or less and breakers or fuses listed and marked for it.
On the job
- 12 AWG copper on a 25 A or 30 A breaker, or 14 AWG copper on a 20 A breaker, is a common correction where no 240.4(E) or (G) permission applies.
- Older references number this list differently. In the 2023 NEC, 14 AWG copper is 240.4(D)(4) and 10 AWG copper is 240.4(D)(8).
Exceptions that matter
- Tap conductors under 240.4(E) and the specific conductor applications in 240.4(G) follow their own rules.
What changed in 2023
The 2023 code added 14 AWG copper-clad aluminum as new item (D)(3), which renumbered the list so 14 AWG copper is now (D)(4) and 10 AWG copper is (D)(8), and added Class CF fuses as an option for 18 and 16 AWG.
Related sections
- NEC 240.4(B)
- NEC 240.4(E)
- NEC 240.4(G)
- NEC 240.4(H)
- NEC 240.6: Standard breaker and fuse sizes
- NEC 210.23(A)
- NEC 310.12: Sizing service wires for a house: the 83% rule
- NEC 310.16: Wire ampacity table and the 60/75 °C terminal rule
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