Marine Grade Wire

Last Changed 2/11/2007

The best wire to use in mobile environments is stranded wire. Solid wire is prone to get brittle and break when it is subjected to the flexing in a mobile environment.. The best wire is marine grade wire. Marine grade wire is made up of finer strands of wire that are tinned to prevent corrosion. Marine grade wire costs a bit more but then we are dealing with expensive equipment like our trailers and trucks.

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Stranded wire is not suitable for attaching to screw based connections, like terminal strips. The connections to our inverter/charger use set screw lugs where the wire is inserted into the lug and then compressed with a side set screw. In this situation, stranded wire does not need a lug on the end of the wire.

Wire Size

We often think of wire gauge and a general current rating like #12 wire for 20 amps. We really should account for the distance the wire runs also. Below are tables for 12 Volt and 120 Volt ratings. For example take the need to carry 15 amps at 12 Volts; to go only 10 feet, #10 wire would be fine. However to go 30 feet, #6 wire would be proper.

These tables are based upon a 3% voltage loss. The factor that determines the current/distance is the resistance of the wire per foot. Since 3% of a 120 Volt circuit is 10 times the 3% loss of a 12 Volt circuit, and the resistance is the same for the same gauge wire, a 120 Volt circuit can be up to 10 times the length of a 12 Volt circuit using the same gauge wire.

Using larger wire will mean the wire will heat up less. You need to consider this if you try to stuff too many wires running at their upper current limits in a conduit or other enclosed space.


Wire Size for Distance 12 Volt Systems (feet)
Current Amps	Wire Size AWG#
16	14	12	10	8	6	4	3	2	1	0	00
5	8	14	24	38	61	96	-	-	-	-	-	-
10	4	7	12	19	30	48	76	-	-	-	-	-
15	-	4	8	13	20	32	51	64	-	-	-	-
20	-	-	6	10	15	24	38	48	61	-	-	-
30	-	-	-	6	10	16	25	32	41	51	-	-
40	-	-	-	-	8	12	19	24	30	38	48	-
55	-	-	-	-	-	9	14	18	22	28	35	44
70	-	-	-	-	-	-	11	14	17	22	28	35
80	-	-	-	-	-	-	-	12	15	19	24	30
95	-	-	-	-	-	-	-	-	13	16	20	26
110	-	-	-	-	-	-	-	-	-	14	18	22
125	-	-	-	-	-	-	-	-	-	-	15	20
145	-	-	-	-	-	-	-	-	-	-	-	17

Wire Size for Distance 120 Volt Systems (feet)
Current Amps	Wire Size AWG#
Current Amps	16	14	12	10	8	6	4	3	2	1	0
5	88	142	226	360	573	-	-	-	-	-	-
10	44	71	113	180	287	456	-	-	-	-	-
15	29	47	76	120	191	304	483	-	-	-	-
20	-	35	57	90	143	228	362	457	-	-	-
30	-	-	-	60	96	152	241	305	384	-	-
40	-	-	-	-	72	114	181	228	288	363	-
55	-	-	-	-	-	83	132	166	209	264	-
70	-	-	-	-	-	-	103	131	165	208	262
80	-	-	-	-	-	-	-	114	144	182	229
95	-	-	-	-	-	-	-	-	121	153	193
110	-	-	-	-	-	-	-	-	-	132	167
125	-	-	-	-	-	-	-	-	-	-	147

Disclaimer: The information in this site is a collection of data we derived from the vendors and from our personal experiences. This information is meant as a learning guide for you to make your own decisions Best practices and code should always be followed. The recommendations we make are from our personal experiences and we do not receive any compensation for those recommendations.

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