Hubbell Lighting Buyers Guide\ 9 — Technical (Hubbell Lighting Inc)

5% Voltage Drop Table

6 and 12 Volt Systems

Isofootcandle curves are based on illumination at 87-1/2% of nominal battery voltage (end of battery life.) Illumination levels at the beginning of the discharge cycle (Beam penetration) will be approximately 20% greater than shown. 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.)

DISTRIBUTED LOAD CIRCUIT DISTANCE ADJUSTMENT 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, 6V circuit has 7W 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 40-1/2 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 12V system, with a 44W load, is 2267 ÷ 44 = 51W; on #10 wire, 3604 ÷ 44 = 82W.)

Total Watts on Wire Run	6 Volt Circuit Length Wire				12 Volt Circuit Length Wire
	Wire Gauge				Wire Gauge
	12	10	8	6	12	10	8	6
6	94	150	238	379	378	600	955	1518
7	81	129	204	325	324	515	818	1301
8	70	112	179	284	283	450	716	1138
10	56	90	143	227	226	360	570	910
12	44	70	112	178	178	283	450	715
14	40	64	102	162	162	257	409	650
16	33	53	84	134	133	212	338	538
18	30	47	75	119	119	189	300	477
20	28	45	71	114	113	180	286	455
21	27	43	68	108	108	171	273	434
24	24	38	60	95	89	141	225	357
25	21	34	54	86	86	136	216	344
28	20	32	51	81	81	129	206	325
30	19	30	48	76	75	120	190	303
32	16	26	42	67	66	106	168	268
35	15	25	39	63	65	103	164	260
36	14	23	37	59	59	94	150	238
40	13	21	33	53	53	85	135	214
42	13	21	34	54	54	86	136	217
48	11	17	28	44	44	70	112	175
49	11	18	29	46	46	73	117	186
50	11	17	27	43	43	68	108	172
54	10	16	25	40	40	63	100	159
56	9	15	24	38	38	60	96	153
60	8	14	22	35	35	56	90	143
64	8	13	21	33	33	53	84	134
70	8	13	20	32	32	51	82	130
72	7	11	18	29	29	47	75	119
75	7	11	18	29	28	45	72	115
80	6	10	16	26	26	42	67	107
84	5	10	16	25	25	40	64	102
88	6	9	15	24	24	38	61	97
90	6	9	15	24	24	38	60	95
96	5	8	14	22	22	35	56	89
100	5	8	14	21	21	34	54	86
104	5	8	12	20	20	32	51	82
108	4	7	12	19	19	31	50	79
112	4	7	12	19	18	30	48	76
120	4	7	11	17	17	28	45	71
125	4	7	11	17	17	27	43	69
126	4	7	11	17	17	27	43	68
128	4	6	10	16	16	26	42	67
132	4	6	10	16	16	25	40	65
136	3	6	9	15	15	24	39	62
144	3	5	9	14	14	23	37	59
150	3	5	9	14	14	23	36	57
152	3	5	8	14	14	22	35	56
156	3	5	8	13	13	21	34	55
160	3	5	8	13	13	21	33	53
162	3	5	8	13	13	21	33	53
168	3	5	8	12	12	20	32	51
175	3	5	8	12	12	19	31	49
176	3	4	7	12	12	19	30	48
180	2	4	7	11	11	18	30	47
184	2	4	7	11	11	18	29	46
192	2	4	7	11	11	17	28	44
198	2	4	7	11	11	17	27	43
200	2	4	6	10	10	16	27	42
Constant	567	901	1432	2277	2267	3604	5730	9109

5% Voltage Drop Table - Page 8