Ampacity by temperature rating
| Temperature rating | Ampacity | Typical insulation |
|---|---|---|
| 60°C | 285 A | — |
| 75°C | 340 A | THW |
| 90°C | 385 A | THHN / THWN-2, XHHW-2 |
Reference tables · Aluminum ampacity
2023 NEC · Table 310.16
600 kcmil aluminum wire ampacity
At a 75°C termination rating, 600 kcmil aluminum carries 340 A under the published table's basis conditions — 30°C ambient, no more than three current-carrying conductors.
What 600 kcmil aluminum is used for
600 kcmil aluminum carries 340 A at 75°C. Conductors in the kcmil range are service, feeder, and distribution conductors, frequently run as paralleled sets under rules this reference does not model. It pairs with a 300 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 340 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 | 377.4 A | 301.9 A | 264.2 A | 188.7 A | 169.8 A |
| 30°C | 340 A | 272 A | 238 A | 170 A | 153 A |
| 40°C | 299.2 A | 239.4 A | 209.4 A | 149.6 A | 134.6 A |
| 50°C | 255 A | 204 A | 178.5 A | 127.5 A | 114.8 A |
Properties
| Circular mils | 600,000 |
|---|---|
| DC resistance | 0.0353 Ω per 1000 ft |
| Ampacity at 75°C | 340 A |
| Overcurrent ceiling | Set by ampacity |
| Largest standard breaker | 300 A |
| Area, THHN / THWN-2 | 0.8676 in² |
| Area, XHHW-2 | 0.8709 in² |
| Area, THW | 0.9729 in² |
Voltage drop over distance
Single-phase 240 V, carrying 340 A on 600 kcmil aluminum.
| One-way distance | Drop | Within 3%? |
|---|---|---|
| 25 ft | 0.25% | Yes |
| 50 ft | 0.50% | Yes |
| 100 ft | 1.00% | Yes |
| 150 ft | 1.50% | Yes |
| 200 ft | 2.00% | Yes |
| 300 ft | 3.00% | 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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