Standard breaker and fuse sizes
The NEC lists 38 standard ampere ratings for fuses and inverse-time breakers, from 10 A to 6,000 A, plus additional standard fuse ratings of 1, 3, 6 and 601 A. In 2023, 10 A became a standard breaker rating.
What the code requires
Table 240.6(A) lists the standard ratings for fuses and inverse-time circuit breakers: 10, 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, 700, 800, 1,000, 1,200, 1,600, 2,000, 2,500, 3,000, 4,000, 5,000 and 6,000 A. Fuses also have standard ratings of 1, 3, 6 and 601 A, and nonstandard ratings are permitted.
For an adjustable-trip breaker, the rating is its maximum possible setting. If access to the adjustment is restricted by a sealable cover, bolted doors, locked doors for qualified persons only, or a password, the breaker may be rated at its long-time pickup setting instead.
New in 2023, 240.6(D) lets remotely adjustable breakers be rated at their adjusted setting when adjusted through a local non-networked interface, or through a networked interface with cybersecurity-evaluated equipment or a documented cybersecurity assessment.
On the job
- The next-size-up allowance in 240.4(B) only reaches ratings in this table. Using it to land on a size that is not listed is a correction.
- Since the 2023 code, a 10 A circuit breaker is a standard size, not only a 10 A fuse.
What changed in 2023
The 2023 code made 10 A a standard breaker rating by moving it from the fuse-only list into the table, and added 240.6(D) for remotely adjustable breakers.
Related sections
- NEC 240.4(B)
- NEC 240.4(D): Breaker limits for small wires: 14, 12 and 10 AWG
- NEC 210.23(A)
- NEC 240.87: Arc energy reduction for breakers of 1,200 A and up
Where this comes from
Send a photo. Get a real answer.
Text is fastest, and a photo quote is free. Call if it is urgent, if you smell something burning, or if a breaker will not reset.
CSLB #354550 · C-10 Electrical · Licensed since 1978 · $25,000 contractor's bond