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Wire Ampacity and Maximum Lengths

Table C-1 lists the maximum number of amps allowed in various gauges of different copper wire types installed in conduit or supplied in cable. Note that these are independent of the length of the conductor. No matter how short the wire is, do not exceed these current rating. The NEC requires No.12 American Wire Gage (AWG) or larger conductor to be used with Systems under 50 volts.

Tables C-2 through C-7 list the maximum one way wire distance for various wire gauge, voltage, and current combinations. The term "one way" means the distance from one connection point to another, not the round trip distance the electricity makes. Put another way, these distances represent the length of the conduit.

NOTE

Most of the tables in this chapter are for copper wire. Table C-B lists the maximum ampacities for aluminum wire, and is the only reference to aluminum conductors in this Appendix. Refer to the National Electrical Code, Sections 310-16 to 310-19, for more information on both copper and aluminum wiring and the temperature corrections necessary for operating various types of wires in high ambient temperatures.


Table C-1: Maximum Ampacities of Copper Wire in Conduit or Cable

Table C-2: Maximum One-way Copper Wire Distance for 2% Voltage Drop

Table C-3: Maximum One-way Copper Wire Distance for 2% Voltage Drop

Table C-4: Maximum One-way Copper Wire Distance for 2% Voltage Drop

Table C-5: Maximum One-way Copper Wire Distance for 5% Voltage Drop

Table C-6: Maximum One-way Copper Wire Distance for 5% Voltage Drop

Table C-7: Maximum One-way Copper Wire Distance for 5% Voltage Drop

Table C-8: Maximum Ampacities of Aluminum Wire in Conduit or Cable



Table C-1: Maximum Ampacities of Copper Wire in Conduit or Cable

Acceptable Locations and Wire Type


Wire
Size,
Dry,
Indoor
Wet Indoor
or Outdoor
Moist or
Underground
Battery
Cables
AWG T, NM, NMC TW  THW, THWN UF   USE THHN
14
12
10
8

6
4
3
2

1
1/0
2/0
3/0

4/0

15
20
30
40

55
70
85
95

110
125
145
165

195

15
20
30
40

55
70
85
95

110
125
145
165

195

15
20
30
40

65
85
100
115

130
150
175
200

230

15
20
30
40

55
70
85
95

110
125
145
165

195

15
20
30
40

65
85
100
115

130
150
175
200

230

15
20
30
55

75
95
110
130

150
170
195
225

260



Table C-2: Maximum One-way Copper Wire Distance for 2% Voltage Drop

12 Volt Systems

AWG

Amps Watts #14   #12 #10 #8 #6 #4 #2 1/0 2/0 3/0
Distance in Feet
1
2
4
6
8
10
15
20
25
30
40
50
100
150
200
12
24
48
72
96
120
180
240
300
360
480
600

 

45.0
22.5
10.0
7.5
5.5
4.5
3.0
2.0
1.8
1.5
-
-
-
-
-
70.0
35.0
17.5
2.0
8.5
7.0
4.5
3.5
2.8
2.4
-
-
-
-
-
115
57.5
27.5
17.5
14.5
11.5
7.0
5.5
4.5
3.5
2.8
2.3
-
-
-
180
90.0
45.0
30.0
22.5
18.0
12.0
9.0
7.0
6.0
4.5
3.6
-
-
-
290
145
72.5
47.5
35.5
28.5
19.0
14.5
11.5
9.5
7.0
5.5
2.9
-
-
456
228
114
75.0
57.0
45.5
30.0
22.5
18.0
15.0
11.5
9.0
4.6
-
-
720
360
180
120
90.0
72.5
48.0
36.0
29.0
24.0
18.0
14.5
7.2
4.8
3.6
=
580
290
193
145
115
76.5
57.5
46.0
38.5
29.0
23.0
11.5
7.7
5.8
=
720
360
243
180
145
96.0
72.5
58.0
48.5
36.0
29.0
14.5
9.7
7.3
=
912
456
305
228
183
122
91.5
73.0
61.0
45.5
36.5
18.3
12.2
9.2

-Exceeds Ampacity = Over 1,000 Feet       Below steppen line
(red text) -  check ampacity


Table C-3: Maximum One-way Copper Wire Distance for 2% Voltage Drop

24 Volt Systems

AWG

Amps Watts #14  #12 #10 #8 #6 #4 #2 1/0 2/0 3/0
Distance in Feet
1
2
4
6
8
10
15
20
25
30
40
50
100
150
200
24
48
96
144
192
240
360
480
600
720
960
1200
2400
3600
4800
90
45
22
15
11
9
6
-
-
-
-
-
-
-
-
142
71
36
24
18
14
10
7
-
-
-
-
-
-
-
226
113
57
38
28
23
15
11
9
8
2.8
2.3
-
-
-
360
180
90
60
45
36
24
18
14
12
9
-
-
-
-
573
286
143
95
72
57
38
29
23
19
14
11
5.7
-
-
911
455
228
152
114
91
61
46
36
30
23
18
9.1
-
-
=
724
362
241
181
145
97
72
58
48
36
29
14.5
9.7
7.2
=
=
576
384
288
230
154
115
92
77
58
46
23
15.4
11.5
=
=
726
484
363
290
194
145
116
97
73
58
29
19.4
14.5
=
=
915
610
458
366
244
183
146
122
92
73
36.6
24.4
18.3

-Exceeds Ampacity = Over 1,000 Feet       Below steppen line
(red text) -  check ampacity


Table C-4: Maximum One-way Copper Wire Distance for 2% Voltage Drop

120 Volt Systems

AWG

Amps Watts #14  #12 #10 #8 #6 #4 #2 1/0 2/0 3/0
Distance in Feet
1
2
4
6
8
10
15
20
25
30
40
50
120
240
480
720
690
1,200
1,800
2,400
3,000
3,600
4,800
6,000
450
225
100
75
55
45
30
20
18
15
-
-
700
350
175
120
85
70
45
35
28
24
-
-
=
575
275
175
145
120
70
55
45
35
28
23
=
900
450
275
225
190
120
90
70
60
45
36
=
=
725
450
355
300
190
145
115
95
70
55
=
=
=
725
570
480
300
225
180
150
115
90
=
=
=
=
=
765
480
360
290
240
189
145
=
=
=
=
=
960
765
575
460
385
290
230
=
=
=
=
=
=
960
725
580
485
360
290
=
=
=
=
=
=
=
915
730
610
455
365

-Exceeds Ampacity = Over 1,000 Feet       Below steppen line
(red text) -  check ampacity


Table C-5: Maximum One-way Copper Wire Distance for 5% Voltage Drop

12 Volt Systems

AWG

Amps Watts #14   #12 #10 #8 #6 #4 #2 1/0 2/0 3/0
Distance in Feet
1
2
4
6
8
10
15
20
25
30
40
50
100
150
200
12
24
48
72
96
120
180
240
300
360
480
600

 

113
56.3
25.0
18.8
13.8
11.3
7.7
05.0
04.5
03.8
-
-
-
-
-
175
87.5
43.8
30.0
21.3
17.5
11.3
08.8
07.0
06.0
-
-
-
-
-
275
138
68.8
43.8
36.3
28.8
17.5
13.8
11.3
08.8
07.0
05.8
-
-
-
450
225
113
75.0
56.3
45.0
30.0
22.5
17.5
15.0
11.3
09.0
-
-
-
710
355
178
119
88.8
71.3
47.5
36.3
28.8
23.8
17.5
13.8
7.2
-
-
=
567
288
188
144
113
75.0
56.3
45.0
37.5
28.8
22.8
11.4
-
-
=
900
450
300
225
180
120
90.0
72.5
60.0
45.0
36.3
18.1
12.1
9.1
=
=
725
481
363
290
193
145
115
96.3
72.5
57.5
28.8
19.2
14.4
=
=
900
600
450
360
240
180
145
120
90.0
72.5
36.3
24.2
18.2
=
=
=
760
570
457
304
229
183
152
114
91.3
45.7
30.5
22.9

-Exceeds Ampacity = Over 1,000 Feet       Below steppen line
(red text) -  check ampacity


Table C-6: Maximum One-way Copper Wire Distance for 5% Voltage Drop

24 Volt Systems

AWG

Amps Watts #14   #12 #10 #8 #6 #4 #2 1/0 2/0 3/0
Distance in Feet
1
2
4
6
8
10
15
20
25
30
40
50
100
150
200
24
48
96
144
192
240
360
480
600
720
960
1200
2400
3600
4800
224
112
56
37
28
22
15
-
-
-
-
-
-
-
-
356
178
89
59
45
36
24
18
-
-
-
-
-
-
-
566
283
142
94
71
57
38
28
23
19
-
-
-
-
-
900
450
225
150
113
90
60
45
36
30
23
-
-
-
-
=
716
358
238
178
143
95
73
57
47
35
27
14.3
-
-
=
=
569
379
285
228
152
113
91
75
57
45
22.8
-
-
=
=
905
603
452
362
241
181
145
120
90
73
36.2
24.1
18.1
=
=
=
960
720
576
384
288
230
192
145
115
57.6
19.2
14.4
=
=
=
=
908
726
484
363
290
242
182
145
72.6
48.4
36.3
=
=
=
=
=
915
610
458
366
305
289
183
91.5
61.0
45.8

-Exceeds Ampacity = Over 1,000 Feet       Below steppen line
(red text) -  check ampacity


Table C-7: Maximum One-way Copper Wire Distance for 5% Voltage Drop

120 Volt Systems

AWG

Amps Watts #14   #12 #10 #8 #6 #4 #2 1/0 2/0 3/0
Distance in Feet
1
2
4
6
8
10
15
20
25
30
40
50
120
240
480
720
690
1,200
1,800
2,400
3,000
3,600
4,800
6,000
=
563
250
188
138
113
75.0
50.0
45.0
37.5
-
-
=
875
438
300
213
175
113
87.5
70.0
60.0
-
-
=
=
688
438
363
288
175
138
113
87.5
70.0
57.5
=
=
=
750
563
450
300
225
175
150
113
90.0
=
=
=
=
888
713
475
364
288
238
175
138
=
=
=
=
=
=
750
563
450
375
288
228
=
=
=
=
=
=
=
900
725
600
450
363
=
=
=
=
=
=
=
=
=
963
725
575
=
=
=
=
=
=
=
=
=
=
900
725
=
=
=
=
=
=
=
=
=
=
=
913

-Exceeds Ampacity = Over 1,000 Feet       Below steppen line
(red text) -  check ampacity


Table C-8: Maximum Ampacities of Aluminum Wire in Conduit or Cable

Acceptable Locations and Wire Type


Wire
Size,
Dry,
Indoor
Wet Indoor
or Outdoor
Moist or
Underground
Battery
Cables
AWG T, NM, NMC TW  THW, THWN UF   USE THHN
12
10
8

6
4
3
2

1
1/0
2/0
3/0

4/0

15
25
30

40
55
65
75

85
100
116
130

150

15
25
30

40
55
65
75

85
100
115
130

150

15
25
40

50
65
75
90

100
120
135
155

180

15
25
30

40
55
65
75

85
100
115
130

150

15
25
40

50
65
75
90

100
120
135
155

180

15
25
45

60
75
85
100

115
135
150
175

205