VOLTAGE DROP TABLE - FOR 6 & 12 VOLT SYSTEMS
The National Electrical Code limits
voltage drop to a maximum of 5% of
nominal. The table shows the maximum
length of a given battery circuit,
assuming that the total load is
concentrated at the end of the load
circuit. If loads are uniformly spaced (equal
watts, equal distances) along the circuit path,
all of these distances may be increased,
based on the number of heads or fixtures
on a given circuit. This may permit a savings
by the use of a smaller wire size (see wiring
distance formula table below).
Wiring Distance Formula Table
Number of Heads 2
3
4
5
6
Multiply Feet by 1.33 1.5 1.6 1.67 1.71
For example, a 36 foot long, 6 volt circuit
has 7 watt heads spaced 12 feet apart.
According to the voltage drop table, #10
wire must be used at 43 feet for a 5%
voltage drop. But, multiplying the 27 feet for
#12 wire by 1.5, a 401/2 foot wire run is acceptable. Therefore, #12 wire may be used and
still meet the 5% voltage drop limitation. Wire
size determinations can be made for non-uniformly spaced loads. But for ease and safety,
it would be advisable to use the voltage drop
tables. For a precise determination of the
maximum length of wire run for a concentration load (before applying the adjustment for
uniformly distributed loads), divide the total
load in watts into the constant at the bottom
of each row. (Example: the maximum wire
run for #12 wire on a 12 volt system, with a
44 watt load, is 2267÷44, or 51 feet.)
Conversely, the maximum load on a run of
known length (before applying the adjustment) may be determined by dividing the
length into the constant. (Example: On a 12
volt system, a 38 foot run of #12 wire can be
loaded to 2267÷38 = 60 watts; on #10 wire,
3604 ÷38 = 94 watts.)
Project Name
Catalog #
6 VOLT SYSTEM
12 VOLT SYSTEM
Total
Watts on
Wire Run
12
10
8
6
12
10
8
6
6
7
8
10
12
14
16
18
20
21
24
25
28
30
32
35
36
40
42
48
49
50
54
56
60
64
70
72
75
80
84
88
90
96
100
104
108
112
120
125
126
128
132
136
144
150
152
156
160
162
168
175
176
180
184
192
198
200
Constant
94
81
70
56
47
40
35
31
28
27
23
22
20
19
17
16
15
14
13
11
11
11
10
10
9
8
8
7
7
7
6
6
6
6
5
5
5
5
4
4
4
4
4
4
4
3
3
3
3
3
3
3
3
3
3
3
2
2
567
150
128
112
90
75
64
56
50
45
43
37
36
32
30
28
25
25
22
21
18
18
18
16
16
15
14
12
12
12
11
10
10
10
9
9
8
8
8
7
7
7
7
6
6
6
6
6
5
5
5
5
5
5
5
4
4
4
4
901
238
204
179
143
119
102
89
79
71
68
59
57
51
47
44
41
39
35
34
29
29
28
26
25
23
22
20
19
19
18
17
16
16
15
14
13
13
12
11
11
11
11
10
10
10
9
9
9
9
8
8
8
8
8
7
7
7
7
1432
379
325
284
227
189
162
142
126
113
108
94
91
81
76
71
65
63
57
54
47
46
45
42
40
38
35
32
31
30
28
27
25
25
23
22
21
21
20
19
18
18
17
17
16
15
15
15
14
14
14
13
13
12
12
12
11
11
11
2277
377
323
283
226
189
162
141
126
113
108
94
90
81
75
70
64
63
56
54
47
46
45
42
40
37
35
32
31
30
28
27
25
25
23
22
21
21
20
18
18
18
17
17
16
15
15
15
14
14
14
13
13
12
12
12
11
11
11
2267
600
515
450
360
300
257
225
200
180
171
150
144
128
120
112
103
100
90
86
75
73
72
66
64
60
56
51
50
48
45
43
41
40
37
36
34
33
32
30
28
28
28
27
26
25
24
23
23
22
22
21
20
20
20
19
18
18
18
3604
955
818
716
573
477
409
358
318
286
272
238
229
204
191
179
163
159
143
136
119
117
114
106
102
95
89
82
79
76
71
68
65
63
59
57
55
53
51
47
45
45
44
43
42
39
38
37
36
35
35
34
32
32
31
31
29
29
28
5730
1518
1301
1138
911
759
650
569
506
455
433
379
364
325
303
284
260
253
227
217
189
186
182
168
162
151
142
130
126
121
113
108
103
101
95
91
87
84
81
76
72
72
71
69
67
63
60
60
58
57
56
54
52
51
50
49
47
46
45
9109
Wire Gauge (in feet)
Fixture Type
Wire Gauge (in feet)
12/05/11
© 2012
LSI INDUSTRIES INC.