Marine Grade Wire and Cable

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Wire and Cable

"Why pay marine prices when the automotive product looks pretty much the same?" Good question; and one we hope you will never have to answer the hard way!

Most boaters have encountered the failure of equipment due to corrosion or poor connections. Most boat fires are directly related to a faulty electrical system. A non-operative bilge pump, due to wire corrosion or terminal failure, can cause a boat to sink. Wiring used aboard boats is subjected to four operating conditions not generally encountered ashore - vibration, the ever present salt-laden moisture in the atmosphere, contamination by various chemicals-particularly oil, diesel, dirty bilge water, and exposure to ultraviolet rays from sunlight.

Electrical Wire When installing solar panels and wind generators, high quality marine grade electrical wire must be used to get peak power from those devices. Each strand of wire offered by e-Marine has a tin coating for corrosion resistance (note the silver look to each strand). Ordinary automotive wire can suffer a loss of conductivity due to corrosion after only a few months in a marine environment. Corrosion takes place when water enters the wire jacket and insulation.

How to Determine the Wire Gauge To Use

Common practice is to allow up to 3% voltage drop across a DC circuit.

Length (feet): Determined by measuring the length of the conductor from the positive (+) power source connection to the electrical device and back to the negative (-) power source connection.

Current ( amps ): Determined by adding the total amps on a circuit.

Formula: Use the following formula and Table A to determine the proper wire size (National Fire Protection Agency and Coast Guard require that the next larger wire size be used when the calculated CM area falls between the two wire sizes).

CM=(K x I x L) / E

CM = Circular Area of Conductors K = 10.75 (Constant representing the mil-foot resistance of copper) I = Current (amps) L = Length (feet) E = Voltage drop (in volts)

Example. Question: A bilge pump draws 10 amps. The positive run is 11 feet from the power panel, including the float switch. The negative run is only 10 feet. What size is the wire?

Answer: Using the formula to reach the correct answer:

CM = (10.75 x 10 (amps) x 21 (total length of run))/ 0.36 (3% of 12v) = 6,271

Table A shows that 12 AWG wire has a CM area of 6,500 and is the correct choice.

Table A

AWG	AWG CM Area	Amp Capacity Outside Engine Space	Amp Capacity Inside Engine Space
18	1,600	20	17
16	2,600	25	21
14	4,100	35	30
12	6,500	45	38
10	10,500	60	51
8	16,800	80	68
6	26,600	120	102
4	42,000	160	130
2	66,500	210	178
1	83,690	245	208
1/0	105,600	285	242
2/0	133,100	330	280
3/0	167,800	385	327
4/0	211,600	445	378

Table B - Wire Size for 3% Voltage Drop at 12V

	5 Amps	10 amps	15 amps	20 amps	25 amps	30 amps	40 amps	50 amps	60 amps	70 amps	80 amps
Length
15 feet	16	12	10	10	8	8	6	6	4	4	4
20 feet	14	12	10	8	8	6	6	4	4	4	2
25 feet	14	10	8	8	6	6	4	4	2	2	2
30 feet	12	10	8	6	6	4	4	2	2	2	1
40 feet	12	8	6	6	4	4	2	2	1	1/0	1/0
50 feet	10	8	6	4	4	2	2	1	1/0	1/0	2/0
60 feet	10	6	6	4	2	2	1	1/0	2/0	2/0	3/0
70 feet	10	6	4	2	2	2	1/0	2/0	2/0	3/0	3/0
80 feet	8	6	4	2	2	1	1/0	2/0	3/0	3/0	4/0
90 feet	8	4	4	2	1	1/0	2/0	3/0	3/0	4/0
100 feet	8	4	2	2	1	1/0	2/0	3/0	4/0	4/0