Ampacity is the maximum current that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. Current is measured in amps. You must use the correct size wire for the current (load) requirement of the circuit to prevent the wire from overheating.
|
Wire Gauge Size
|
|
Copper
|
Aluminum
|
60˚ C
(140˚) F
|
75˚ C
(167˚) F
|
90˚ C
(194˚) F
|
75˚ C
(167˚) F
|
90˚ C
(194˚) F
|
|
NM-B
|
THW
|
THWN-2
|
THW
|
XHHW-2
|
|
UF-B
|
THWN
|
THHN
|
THWN
|
THHN
|
|
—
|
SE
|
XHHW-2
|
SE
|
TWHN-2
|
|
—
|
USE
|
—
|
USE
|
—
|
|
—
|
XHHW
|
—
|
XHHW
|
—
|
|
| 14 |
15 |
20 |
25 |
— |
— |
| 12 |
20 |
25 |
30 |
20 |
25 |
| 10 |
30 |
35 |
40 |
30 |
35 |
| 8 |
40 |
50 |
55 |
40 |
45 |
| 6 |
55 |
65 |
75 |
50 |
55 |
| 4 |
70 |
85 |
95 |
65 |
75 |
| 3 |
85 |
100 |
115 |
75 |
85 |
| 2 |
95 |
115 |
130 |
90 |
100 |
| 1 |
— |
130 |
145 |
100 |
115 |
| 1/0 |
— |
150 |
170 |
120 |
135 |
| 2/0 |
— |
175 |
195 |
135 |
150 |
| 3/0 |
— |
200 |
225 |
155 |
175 |
| 4/0 |
— |
230 |
260 |
180 |
205 |
| 250 |
— |
255 |
290 |
205 |
230 |
| 300 |
— |
285 |
320 |
230 |
260 |
| 350 |
— |
310 |
350 |
250 |
280 |
| 500 |
— |
380 |
430 |
310 |
350 |
| 600 |
— |
420 |
475 |
340 |
385 |
| 750 |
— |
475 |
535 |
385 |
435 |
| 1000 |
— |
545 |
615 |
445 |
500 |