Tables › Overcurrent Protection
Overcurrent Protection NEC 240.4
Maximum overcurrent protection for conductors per NEC 240.4(D) and standard overcurrent device sizes per 240.6(A).
Small Conductor Protection — NEC 240.4(D)
| Conductor Size (AWG) | Max Overcurrent Device (Amps) | Notes |
|---|---|---|
| 14 AWG Copper | 15A | Most general lighting and receptacle circuits |
| 12 AWG Copper | 20A | Kitchen, bath, laundry, garage receptacles |
| 10 AWG Copper | 30A | Dryers, water heaters, A/C circuits |
Standard Overcurrent Device Sizes — NEC 240.6(A)
| 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, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, 6000 |
Conductor Overcurrent Protection Summary
| Conductor Size | 75°C Ampacity (Cu) | Max Standard OCPD | Next Size Up Allowed? |
|---|---|---|---|
| 14 AWG | 20A | 15A | No — 240.4(D) limits to 15A |
| 12 AWG | 25A | 20A | No — 240.4(D) limits to 20A |
| 10 AWG | 35A | 30A | No — 240.4(D) limits to 30A |
| 8 AWG | 50A | 50A | Yes — 240.4(B) allows next size up |
| 6 AWG | 65A | 70A | Yes — next standard size up from 65A |
| 4 AWG | 85A | 90A | Yes |
| 3 AWG | 100A | 100A | Exact match |
| 2 AWG | 115A | 125A | Yes |
| 1 AWG | 130A | 150A | Yes |
| 1/0 AWG | 150A | 150A | Exact match |
| 2/0 AWG | 175A | 175A | Exact match |
| 3/0 AWG | 200A | 200A | Exact match |
| 4/0 AWG | 230A | 250A | Yes |
| 250 kcmil | 255A | 300A | Yes |
| 300 kcmil | 285A | 300A | Yes |
| 350 kcmil | 310A | 350A | Yes |
| 400 kcmil | 335A | 350A | Yes |
| 500 kcmil | 380A | 400A | Yes |
Exam Tip
14 AWG = 15A max. 12 AWG = 20A max. 10 AWG = 30A max. These three are locked by 240.4(D) regardless of the ampacity table. This is one of the most commonly tested NEC rules.
14 AWG = 15A max. 12 AWG = 20A max. 10 AWG = 30A max. These three are locked by 240.4(D) regardless of the ampacity table. This is one of the most commonly tested NEC rules.
Next Size Up Rule — 240.4(B)
For conductors 8 AWG and larger (where 240.4(D) doesn't apply), if the ampacity doesn't match a standard OCPD size, you may use the next standard size up — but only if the circuit doesn't supply multiple outlets or receptacles.
For conductors 8 AWG and larger (where 240.4(D) doesn't apply), if the ampacity doesn't match a standard OCPD size, you may use the next standard size up — but only if the circuit doesn't supply multiple outlets or receptacles.
For reference only. Verify all results with the current NEC and local amendments. See Terms of Use.