Voltage Drop Tables
The National Electrical Code limits voltage drop to a maximum of 5% of nominal. Circuit runs must be of sufficient capacity to
TABLE A - IMPORTANT ELECTRICAL INSTALLATION INFORMATION
12 VOLT SYSTEM
TOTAL WATTS
ON WIRE RUN
#12
6
378
8
283
7
WIRE GUARD
94
450
716
1138
8
70
570
450
409
338
300
180
108
24
6
189
113
21
1518
818
212
119
20
955
257
133
18
600
283
162
16
#6
360
178
14
#8
515
226
12
#10
MAX. LENGTH OF WIRE RUN (FEET)
324
10
6 VOLT SYSTEM
TOTAL WATTS
ON WIRE RUN
286
171
89
273
141
225
1301
#12
7
910
10
650
14
715
477
455
434
357
112
179
284
162
84
134
75
119
71
43
24
178
102
45
27
227
112
47
28
325
143
53
30
24
379
204
64
33
21
238
70
40
20
150
90
44
18
#6
129
56
16
#8
MAX. LENGTH OF WIRE RUN (FEET)
81
12
538
WIRE GUARD
#10
114
68
38
108
60
95
25
86
136
216
344
25
21
34
54
86
30
75
120
190
303
30
19
30
48
76
40
53
85
135
214
40
13
21
33
53
35
65
48
103
44
50
70
43
75
31
16
10
250
36
19
10
225
43
23
12
200
54
27
14
175
72
34
17
150
108
45
21
125
112
68
28
100
164
27
16
9
25
14
22
260
35
178
15
48
172
11
50
115
100
57
150
69
49
175
42
200
40
225
36
250
12
6
4
2
14
8
4
2
17
9
5
2
21
11
5
3
29
14
7
3
43
18
8
4
44
27
11
5
63
28
17
7
125
39
17
11
75
86
25
10
6
3
10
5
9
Values not shown in Table A may be calculated using the following formulas:
I. Maximum Length (Feet) = Table B Constant Value
Maximum Load (Watts)
Example: Find the maximum circuit length for #8 wire on a 24 volt system with an 80 watt load.
Maximum Length (Feet) = 21613 ÷ 80 = 270 feet.
Table B Constant Value
Maximum Length (Feet)
Example: Find the maximum circuit load for 540 feet of #12 wire on a 32 volt system.
Maximum Load (watts) = 15197 ÷ 540 = 28 watts.
II. maximum Load (Watts) =
SYSTEM
TABLE B – CONSTANT VALUES PER VOLTAGE SYSTEM WIRE SIZE (MAXIMUM VOLTAGE DROP 5%)
6 VOLT
WIRE SIZE
CONSTANT
#12
534
#10
849
12 VOLT
#8
350
#6
2148
#12
2137
#10
3397
32 VOLT
SYSTEM
WIRE SIZE
CONSTANT
#12
15197
#10
24157
#8
38423
#8
5403
24 VOLT
#6
8590
#4
13660
#12
8548
#10
13588
48 VOLT
#6
#4
61090 97140
#12
34193
#10
54353
#8
21613
#6
34363
#4
54641
110 VOLT
#8
#6
#4
#12
#10
#8
#6
#4
#2
86452 137454 218565 179575 285450 454025 721875 1147850 1824900
Uniform Loads
The maximum circuit length data in Table A (and derived from Table B) assumes that 100% of the load is concentrated at the end of the run.
If equally sized loads can be equally spaced along the run, maximum circuit length can be increased by the multipliers shown in Table C.
TABLE C - MULTIPLIERS FOR EQUALLY SIZED, EQUALLY SPACED LOADS (MAXIMUM VOLTAGE DROP 5%)
NUMBER OF FIXTURES
MULTIPLY DISTANCE BY
2
2
1.333
3
3
1.500
4
4
1.600
5
5
1.670
6
6
1.714
7
7
1.750
8
8
1.777
9
9
1.800
10
10
1.818
N
N
2n /(n +1)
Information republished is for reference only. Local codes and the local authority having jurisdiction are the most reliable sources to
ensure code compliance.
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