Wire Size Guide/Charts

Proper wire size is absolutely critical to insure that your heater works properly. Undersized wire is the single biggest mistake made when installing our heaters. To function properly, these heaters must be wired with the proper size wire, and grounded properly, this cannot be stressed enough.

Battery performance is dramatically reduced in low temperatures as well. A battery that is required to operate continuously at 0 degrees F will provide about 60% of its capacity.

Wire size in Direct Current is VERY important. In low voltage systems (12, 24, 36 and 48VDC) the overriding concern is power loss. Wire must not be sized merely for the ampacity, because there is less tolerance for voltage drop (except for very short runs). For example, a 1V drop from 12V causes 10 times the power loss of 1V drop from 120V. See the chart below to determine the maximum run with each gauge wire at a specific voltage.

The numbers represent the maximum number of feet that wire can be ran without exceeding a 2 % loss. An example would be: A 12 volt heater, pulling 40 Amps, using a 10 gauge wire, could be ran a maximum of 2.8 feet. You can go twice the distance where a 4% loss is acceptable. A 4% loss however is not recommended by DC Thermal and will result in less than desirable results with our heaters.

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12 Volt 2% Wire Loss Chart

AMPS	14 ga.	12 ga.	10 ga.	8 ga.	6 ga.	4 ga.	2 ga.	1/0 ga.
1	45	70	115	180	290	456	720
2	22.5	35	57.5	90	145	228	360	580
4	10	17.5	27.5	45	72.5	114	180	290
6	7.5	12	17.5	30	47.5	75	120	193
8	5.5	8.5	15	22.5	35.5	57	90	145
10	4.5	7	12	18	28.5	45.5	72.5	115
15	3	4.5	7	12	19	30	48	76.5
20	2	3.5	5.5	9	14.5	22.5	36	57.5
25	1.8	2.8	4.5	7	11.5	18	29	46
30	1.5	2.4	3.5	6	9.5	15	24	38.5
40			2.8	4.5	7.0	6.5	18	29
50			2.3	3.6	5.5	9	14.5	23

24 Volt 2% Wire Loss Chart

AMPS	14 ga.	12 ga.	10 ga.	8 ga.	6 ga.	4 ga.	2 ga.	1/0 ga.
1	90	140	230	360	580	912	1440
2	45	70	115	180	290	456	720	1160
4	20	35	55	90	145	228	360	580
6	15	24	35	60	95	150	240	386
8	11	17	30	45	71	114	180	290
10	9	14	24	36	57	91	145	230
15	6	9	14	24	38	60	96	153
20	4	7	11	18	29	45	72	115
25	3.6	5.6	9	14	23	36	58	92
30	3	4.8	7	12	19	30	48	77
40			5.6	9	14	23	36	58
50			4.6	7.2	11	18	29	46

36 Volt 2% Wire Loss Chart

AMPS	14 ga.	12 ga.	10 ga.	8 ga.	6 ga.	4 ga.	2 ga.	1/0 ga.
1	135	210	345	540	870	1368	2160
2	67.5	105	172.5	270	435	684	1080	1740
4	30	52.5	82.5	135	217.5	342	540	1160
6	22.5	36	52.5	90	142.5	225	360	579
8	16.5	25.5	45	67.5	106.5	171	270	435
10	13.5	21	36	54	85.5	136.5	217.5	345
15	9	13.5	21	36	57	90	144	229.5
20	6	14	16.5	27	43.5	67.5	108	172.5
25	7.2	11.2	18	28	46	72	116	184
30	4.5	7.2	10.5	18	28.5	45	72	115.5
40			11.2	18	28	46	72	116
50			9.2	14.4	22	36	58	92

48 Volt 2% Wire Loss Chart

AMPS	14 ga.	12 ga.	10 ga.	8 ga.	6 ga.	4 ga.	2 ga.	1/0 ga.
1	180	280	460	720	1160	1824	2880
2	90	140	230	360	580	912	1440	2320
4	40	70	110	180	290	456	720	1160
6	30	48	70	120	190	300	480	772
8	22	34	60	90	142	228	360	580
10	18	28	48	72	114	182	290	460
15	12	18	28	48	76	120	192	306
20	8	14	22	36	58	90	144	230
25	7.2	11.2	18	28	46	72	116	184
30	6	9.6	14	24	38	60	96	154
40			11.2	18	28	46	72	116
50			9.2	14.4	22	36	58	92

72 Volt 2% Wire Loss Chart

AMPS	14 ga.	12 ga.	10 ga.	8 ga.	6 ga.	4 ga.	2 ga.	1/0 ga.
1	270	420	690	1080	1740	2736	4320
2	135	210	345	360	580	912	1440	3480
4	60	105	165	270	426	684	1080	1740
6	45	72	105	180	285	450	720	1158
8	33	51	90	135	213	342	540	870
10	27	42	72	108	171	217	435	690
15	18	27	42	72	114	180	288	489
20	12	21	33	54	87	135	216	345
25	10.8	16.8	27	42	69	108	174	276
30	9	14.4	21	36	57	90	144	231
40			16.8	27	42	69	108	174
50			13.8	21.6	33	54	87	138

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