NEC Table 310.19 — High-Temperature Ampacity in Free Air
Single conductors rated 150°C, 200°C and 250°C in free air, 40°C (104°F) ambient.
12 AWG copper in free air carries 60 A at 150°C, 68 A at 200°C and 78 A as 250°C nickel-coated conductor, at 40°C ambient.
| Size | 150°C — Type Z (Cu) | 200°C — FEP, FEPB, PFA, SA (Cu) | 250°C — PFAH, TFE (nickel / nickel-coated Cu) | 150°C — Type Z (Al) |
|---|---|---|---|---|
| 14 AWG | 46 | 54 | 59 | — |
| 12 AWG | 60 | 68 | 78 | 47 |
| 10 AWG | 80 | 90 | 107 | 63 |
| 8 AWG | 106 | 124 | 142 | 83 |
| 6 AWG | 155 | 165 | 205 | 112 |
| 4 AWG | 190 | 220 | 278 | 148 |
| 3 AWG | 214 | 252 | 327 | 170 |
| 2 AWG | 255 | 293 | 381 | 198 |
| 1 AWG | 293 | 344 | 440 | 228 |
| 1/0 AWG | 339 | 399 | 532 | 263 |
| 2/0 AWG | 390 | 467 | 591 | 305 |
| 3/0 AWG | 451 | 546 | 708 | 351 |
| 4/0 AWG | 529 | 629 | 830 | 411 |
These tables cover special high-temperature conductors — fixture and appliance wiring, furnaces, kilns and industrial process equipment. They are based on a 40°C ambient, not 30°C, and the terminations must also be rated for the temperature; ordinary breakers and lugs are not. The 250°C column applies to nickel or nickel-coated copper conductors.
Frequently asked questions
What is the difference between Table 310.18 and 310.19?
Both cover 150–250°C conductors at a 40°C ambient. Table 310.18 is for up to three conductors in a raceway or cable; Table 310.19 is for single conductors in free air and gives higher values.
What is 14 AWG high-temperature wire rated for in free air?
46 A at 150°C, 54 A at 200°C and 59 A for 250°C nickel-coated conductors.
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