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Store Home / Wire & Cable / Connectors / Wire Protection / Electrical / Custom Cables / Technical / Specials |
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TECHNICAL INFO
(links below open in a new window) |
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Marine Electrical Info |
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ABYC Elecrical Standards |
Some common marine electrical regulations |
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Marine Color Codes for Wiring |
Color code chart for marine wiring |
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US Coast Guard Boatbuilder's Handbook |
USCG electrical regulations, and basic wiring diagrams |
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Cable Sizing for Marine Applications |
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When calculating voltage drop always use TOTAL round trip distance of wire run positive terminal of the source, to the load, and back to source's negative terminal
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3% Voltage Drop Tables 12V, 24V, 36V |
Use 3% voltage drop for any “critical application” affecting the safety of the vessel or its passengers: bilge pumps, navigation lights, electronics, etc |
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10% Voltage Drop Tables 12V, 24V, 36V |
Use 10% voltage drop for any “noncritical applications: windlass, cabin lights, etc.... |
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Conductor Sizes Specifications |
Technical data of cable sizes |
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Allowable Amperages for Single Conductors |
Max allowable amps for 105C single conductor calbes |
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Allowable Amperages for Multiconductor |
Max allowable amps for 105C multiconductor cables |
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| 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.
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Table A - (based on 105°C insulation rating)
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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 |
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Other Useful Formulas & Info |
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DC Electrical Conversion Formulas |
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Amps= Watts / Volts |
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Watts= Volts x Amps |
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Volts = Watts / Amps |
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