Table 310.20 Ampacities of Not More Than Three Single Insulated Conductors, Rated 0 Through 2000 Volts, Supported on a Messenger, Based on Ambient Air Temperature of 40°C (104°F)
| Temperature Rating of Conductor | |||||||
| Size AWG or kcmil | 75°C (167°F) | 90°C (194°F) | 75°C (167°F) | 90°C (194°F) | Size AWG or kcmil | ||
| Types RHW, THHW, THW, THWN, XHHW, ZW | Types MI, THHN, THHW, THW-2, THWN-2, RHH, RHW-2, USE-2, XHHW, XHHW-2, ZW-2 | Types RHW, THW, THWN, THHW, XHHW | Types THHN, THHW, RHH, XHHW, RHW-2, XHHW-2, THW-2, THWN-2, USE-2, ZW-2 | ||||
| COPPER | ALUMINUM OR COPPER-CLAD ALUMINUM | ||||||
| 8 | 57 | 66 | 44 | 51 | 8 | ||
| 6 | 76 | 89 | 59 | 69 | 6 | ||
| 4 | 101 | 117 | 78 | 91 | 4 | ||
| 3 | 118 | 138 | 92 | 107 | 3 | ||
| 2 | 135 | 158 | 106 | 123 | 2 | ||
| 1 | 158 | 185 | 123 | 144 | 1 | ||
| 1/0 | 183 | 214 | 143 | 167 | 1/0 | ||
| 2/0 | 212 | 247 | 165 | 193 | 2/0 | ||
| 3/0 | 245 | 287 | 192 | 224 | 3/0 | ||
| 4/0 | 287 | 335 | 224 | 262 | 4/0 | ||
| 250 | 320 | 374 | 251 | 292 | 250 | ||
| 300 | 359 | 419 | 282 | 328 | 300 | ||
| 350 | 397 | 464 | 312 | 364 | 350 | ||
| 400 | 430 | 503 | 339 | 395 | 400 | ||
| 500 | 496 | 580 | 392 | 458 | 500 | ||
| 600 | 553 | 647 | 440 | 514 | 600 | ||
| 700 | 610 | 714 | 488 | 570 | 700 | ||
| 750 | 638 | 747 | 512 | 598 | 750 | ||
| 800 | 660 | 773 | 532 | 622 | 800 | ||
| 900 | 704 | 826 | 572 | 669 | 900 | ||
| 1000 | 748 | 879 | 612 | 716 | 1000 | ||
| CORRECTION FACTORS | |||||||
| Ambient Temp. (°C) | For ambient temperatures other than 40°C (104°F), multiply the allowable ampacities shown above by the appropriate factor shown below. | Ambient Temp. (°F) | |||||
| 21-25 | 1.20 | 1.14 | 1.20 | 1.14 | 70-77 | ||
| 26-30 | 1.13 | 1.10 | 1.13 | 1.10 | 79-86 | ||
| 31-35 | 1.07 | 1.05 | 1.07 | 1.05 | 88-95 | ||
| 36-40 | 1.00 | 1.00 | 1.00 | 1.00 | 97-104 | ||
| 41-45 | 0.93 | 0.95 | 0.93 | 0.95 | 106-113 | ||
| 46-50 | 0.85 | 0.89 | 0.85 | 0.89 | 115-122 | ||
| 51-55 | 0.76 | 0.84 | 0.76 | 0.84 | 124-131 | ||
| 56-60 | 0.65 | 0.77 | 0.65 | 0.77 | 133-140 | ||
| 61-70 | 0.38 | 0.63 | 0.38 | 0.63 | 142-158 | ||
| 71-80 | – | 0.45 | – | 0.45 | 160-176 | ||