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 maintain operating
voltage when remote fixtures and/or exit signs are connected to the emergency lighting
TABLE A – Important Electrical Installation Information
12 volt system
t e c h n i c a l data
6 volt system
wire gauge
total watts on
wire run
#12
#10
#8
wire gauge
total watts
on wire run
#6
#12
#10
max. length of wire run (feet)
6
7
8
10
12
14
16
18
20
21
24
25
30
35
40
48
50
75
100
125
150
175
200
225
250
378
324
283
226
178
162
133
119
113
108
89
86
75
65
53
44
43
28
21
17
14
12
10
10
9
600
515
450
360
283
257
212
189
180
171
141
136
120
103
85
70
68
45
34
27
23
19
16
16
14
#8
#6
max. length of wire run (feet)
955
818
716
570
450
409
338
300
286
273
225
216
190
164
135
112
108
72
54
43
36
31
27
25
22
1518
1301
1138
910
715
650
538
477
455
434
357
344
303
260
214
178
172
115
86
69
57
49
42
40
36
6
7
8
10
12
14
16
18
20
21
24
25
30
35
40
48
50
75
100
125
150
175
200
225
250
94
81
70
56
44
40
33
30
28
27
24
21
19
15
13
11
11
7
5
4
3
3
2
2
2
150
129
112
90
70
64
53
47
45
43
38
34
30
25
21
17
17
11
8
7
5
5
4
4
3
238
204
179
143
112
102
84
75
71
68
60
54
48
39
33
28
27
18
14
11
9
8
6
6
5
379
325
284
227
178
162
134
119
114
108
95
86
76
63
53
44
43
29
21
17
14
12
10
10
9
Values not shown in Table A may be calculated using the following formulas:
Length (Feet) = Table B Constant Value
I. Maximum
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.
II. Maximum Load (Watts) = 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.
TABLE B – Constant Values per Voltage System Wire Size (Maximum Voltage Drop 5%)
system
wire size
constant
6 volt
#12
534
#10
849
system
wire size
constant
12 volt
#8
350
#6
2148
#12
2137
#10
3397
32 volt
#12
15197
#10
24157
#8
38423
#8
5403
24 volt
#6
8590
#4
13660
#12
8548
#10
13588
48 volt
#6
61090
#4
97140
#12
34193
#10
54353
#8
86452
#8
21613
#6
34363
#4
54641
110 volt
#6
137454
#4
218565
#12
179575
#10
285450
#8
454025
#6
#4
#2
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
2
3
4
5
6
7
8
9
10
N
multiply distance by
1.333
1.500
1.600
1.670
1.714
1.750
1.777
1.800
1.818
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.
992