Ampacity by temperature rating
| Temperature rating | Ampacity | Typical insulation |
|---|---|---|
| 60°C | 400 A | — |
| 75°C | 475 A | THW |
| 90°C | 535 A | THHN / THWN-2, XHHW-2 |
Reference tables · Copper ampacity
2023 NEC · Table 310.16
750 kcmil copper wire ampacity
At a 75°C termination rating, 750 kcmil copper carries 475 A under the published table's basis conditions — 30°C ambient, no more than three current-carrying conductors.
What 750 kcmil copper is used for
750 kcmil copper carries 475 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 450 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 475 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 | 527.3 A | 421.8 A | 369.1 A | 263.6 A | 237.3 A |
| 30°C | 475 A | 380 A | 332.5 A | 237.5 A | 213.8 A |
| 40°C | 418 A | 334.4 A | 292.6 A | 209 A | 188.1 A |
| 50°C | 356.3 A | 285 A | 249.4 A | 178.1 A | 160.3 A |
Properties
| Circular mils | 750,000 |
|---|---|
| DC resistance | 0.0171 Ω per 1000 ft |
| Ampacity at 75°C | 475 A |
| Overcurrent ceiling | Set by ampacity |
| Largest standard breaker | 450 A |
| Area, THHN / THWN-2 | 1.0496 in² |
| Area, XHHW-2 | 1.0532 in² |
| Area, THW | 1.1652 in² |
Voltage drop over distance
Single-phase 240 V, carrying 475 A on 750 kcmil copper.
| One-way distance | Drop | Within 3%? |
|---|---|---|
| 25 ft | 0.17% | Yes |
| 50 ft | 0.34% | Yes |
| 100 ft | 0.68% | Yes |
| 150 ft | 1.02% | Yes |
| 200 ft | 1.36% | Yes |
| 300 ft | 2.04% | Yes |
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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