NEC 1999: Table 310-17
Allowable Ampacities of Single-Insulated Conductors in Free Air, based on Ambient Air Temperature of 30C. | |||||||
Size | Temperature Rating of Conductor | Size | |||||
AWG or kcmil | 60ºC | 75ºC | 90ºC | 60ºC | 75ºC | 90ºC | AWG or kcmil |
(140ºF) | (167ºF) | (194ºF) | (140ºF) | (167ºF) | (194ºF) | ||
Types | Types | Types | Types | Types | Types | ||
TW UF |
RHW THHW THW XHHW |
RHH THHN XHH XHHW |
TW UF |
RHW THHW THW XHHW |
RHH THHN XHH XHHW |
||
Copper | Aluminum | ||||||
18 | — | — | 18 | — | — | — | ---- |
16 | — | — | 24 | — | — | — | ---- |
14 | 25 | 30 | 35 | — | — | — | ---- |
12 | 30 | 35 | 40 | 25 | 30 | 35 | 12 |
10 | 40 | 50 | 55 | 35 | 40 | 40 | 10 |
8 | 60 | 70 | 80 | 45 | 55 | 60 | 8 |
6 | 80 | 95 | 105 | 60 | 75 | 80 | 6 |
4 | 105 | 125 | 140 | 80 | 100 | 110 | 4 |
3 | 120 | 145 | 165 | 95 | 115 | 130 | 3 |
2 | 140 | 170 | 190 | 110 | 135 | 150 | 2 |
1 | 165 | 195 | 220 | 130 | 155 | 175 | 1 |
1/0 | 195 | 230 | 260 | 150 | 180 | 205 | 1/0 |
2/0 | 225 | 265 | 300 | 175 | 210 | 235 | 2/0 |
3/0 | 260 | 310 | 350 | 200 | 240 | 275 | 3/0 |
4/0 | 300 | 360 | 405 | 235 | 280 | 315 | 4/0 |
250 | 340 | 405 | 455 | 265 | 315 | 355 | 250 |
300 | 375 | 445 | 505 | 290 | 350 | 395 | 300 |
350 | 420 | 505 | 570 | 330 | 395 | 445 | 350 |
400 | 455 | 545 | 615 | 355 | 425 | 480 | 400 |
500 | 515 | 620 | 700 | 405 | 485 | 545 | 500 |
600 | 575 | 690 | 780 | 455 | 540 | 615 | 600 |
700 | 630 | 755 | 855 | 500 | 595 | 675 | 700 |
750 | 655 | 785 | 885 | 515 | 620 | 700 | 750 |
800 | 680 | 815 | 920 | 535 | 645 | 725 | 800 |
900 | 730 | 870 | 985 | 580 | 700 | 785 | 900 |
1000 | 780 | 935 | 1055 | 625 | 750 | 845 | 1000 |
1250 | 890 | 1065 | 1200 | 710 | 855 | 960 | 1250 |
1500 | 980 | 1175 | 1325 | 795 | 950 | 1075 | 1500 |
1750 | 1070 | 1280 | 1445 | 875 | 1050 | 1185 | 1750 |
2000 | 1155 | 1385 | 1560 | 960 | 1150 | 1335 | 2000 |
CORRECTION FACTORS | |||||||
Ambient Temp (C) | For ambient temps of other than 30C (86F), multiply allowable ampacities shown above by the appropriate factor shown below | Ambient Temp (F) | |||||
21–25 | 1.08 | 1.05 | 1.04 | 1.08 | 1.05 | 1.04 | 70–77 |
26–30 | 1 | 1 | 1 | 1 | 1 | 1 | 78–86 |
31–35 | 0.91 | 0.94 | 0.96 | 0.91 | 0.94 | 0.96 | 87–95 |
36–40 | 0.82 | 0.88 | 0.91 | 0.82 | 0.88 | 0.91 | 96–104 |
41–45 | 0.71 | 0.82 | 0.87 | 0.71 | 0.82 | 0.87 | 105–113 |
46–50 | 0.58 | 0.75 | 0.82 | 0.58 | 0.75 | 0.82 | 114–122 |
51–55 | 0.41 | 0.67 | 0.76 | 0.41 | 0.67 | 0.76 | 123–131 |
56–60 | — | 0.58 | 0.71 | — | 0.58 | 0.71 | 132–140 |
61–70 | — | 0.33 | 0.58 | — | 0.33 | 0.58 | 141–158 |
71–80 | — | — | 0.41 | — | — | 0.41 | 159–176 |
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