Ampacity by temperature rating
| Temperature rating | Ampacity | Typical insulation |
|---|---|---|
| 60°C | 130 A | — |
| 75°C | 155 A | THW |
| 90°C | 175 A | THHN / THWN-2, XHHW-2 |
Reference tables · Aluminum ampacity
2023 NEC · Table 310.16
3/0 AWG aluminum wire ampacity
At a 75°C termination rating, 3/0 AWG aluminum carries 155 A under the published table's basis conditions — 30°C ambient, no more than three current-carrying conductors.
What 3/0 AWG aluminum is used for
3/0 AWG aluminum carries 155 A at 75°C. Conductors this size are service entrance and main feeder conductors — the run between a meter and a panel, or between a main panel and a large subpanel. It pairs with a 150 A overcurrent device.
Terminations usually decide the practical answer. Breakers and equipment are typically listed for 60°C or 75°C, so even 90°C-rated insulation on this conductor is normally limited to the 155 A column at the terminals. Check the equipment's listing rather than assuming.
Derating
Ampacity in real conditions
| Ambient | 3 conductors | 4 conductors | 7 conductors | 10 conductors | 21 conductors |
|---|---|---|---|---|---|
| 20°C | 172.1 A | 137.6 A | 120.4 A | 86 A | 77.4 A |
| 30°C | 155 A | 124 A | 108.5 A | 77.5 A | 69.8 A |
| 40°C | 136.4 A | 109.1 A | 95.5 A | 68.2 A | 61.4 A |
| 50°C | 116.3 A | 93 A | 81.4 A | 58.1 A | 52.3 A |
Properties
| Circular mils | 167,800 |
|---|---|
| DC resistance | 0.126 Ω per 1000 ft |
| Ampacity at 75°C | 155 A |
| Overcurrent ceiling | Set by ampacity |
| Largest standard breaker | 150 A |
| Area, THHN / THWN-2 | 0.2679 in² |
| Area, XHHW-2 | 0.2642 in² |
| Area, THW | 0.3117 in² |
Voltage drop over distance
Single-phase 240 V, carrying 155 A on 3/0 AWG aluminum.
| One-way distance | Drop | Within 3%? |
|---|---|---|
| 25 ft | 0.41% | Yes |
| 50 ft | 0.82% | Yes |
| 100 ft | 1.63% | Yes |
| 150 ft | 2.45% | Yes |
| 200 ft | 3.26% | No |
| 300 ft | 4.90% | No |
Source: NFPA 70, National Electrical Code, Table 310.16; NFPA 70, National Electrical Code, Table 310.15(B)(1)(1); NFPA 70, National Electrical Code, Table 310.15(C)(1); NFPA 70, National Electrical Code, Chapter 9, Table 8. Published by NFPA.NEC 2023
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