NEC 2023 · Article 240
NEC Article 240 — Overcurrent Protection Basics
The rules that pair breakers and fuses with conductors: standard device ratings, when you can round up, the hard caps on small conductors, and where the devices must live.
240.4(D) — The Small-Conductor Rule
Regardless of table ampacity, general-use branch circuits with these conductors are capped at the following overcurrent ratings (equipment-specific articles like motors and HVAC have their own rules):
| Conductor | Max OCPD |
|---|---|
| 14 AWG copper | 15A |
| 12 AWG copper | 20A |
| 10 AWG copper | 30A |
| 12 AWG aluminum / copper-clad | 15A |
| 10 AWG aluminum / copper-clad | 25A |
240.6(A) — Standard Ampere Ratings
Standard ratings for fuses and inverse-time circuit breakers (the list continues to 6000A; 1, 3, 6, and 10A are additional standard fuse ratings):
15A20A25A30A35A40A45A50A60A70A80A90A100A110A125A150A175A200A225A250A300A350A400A… 6000A
240.4(B) & (C) — When You Can Round Up
- • 800A or less — 240.4(B): if conductor ampacity doesn't line up with a standard rating, the next-higher standard device is permitted — provided the circuit isn't a multi-outlet receptacle branch circuit and no other rule caps it lower.
- • Over 800A — 240.4(C): no rounding up. The conductor ampacity must be at least the device rating.
- • Example: 500 kcmil Cu at 75°C carries 380A. On a feeder, 240.4(B) allows a 400A breaker. A parallel run totaling 760A protected at 800A is fine; at 1000A it is not.
240.24 — Where Overcurrent Devices Can Live
- • Readily accessible, with the center of the operating handle no more than 6 ft 7 in. above the floor or working platform.
- • Not exposed to physical damage, and not near easily ignitible material — clothes closets are specifically out.
- • In dwellings and guest rooms: not in bathrooms, and not over the steps of a stairway.
- • Occupants must have access to the devices protecting their unit (with limited exceptions for managed buildings).
Sizing a feeder and the ampacity lands between breaker sizes?
Give ElectricAI the conductor, termination temperature, and load — get a cited Article 240 answer in under a minute.
Ask ElectricAI Free →