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how thick gauge should the common negative/neutral cable to be?


how thick gauge should the common negative/neutral cable to be?

Old 08-09-2013, 07:22 PM
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Default how thick gauge should the common negative/neutral cable to be?

I am re-tidying all my cables while outboard is off. going to be using 3x 'Brass Bus Bar', one for the back to supply negative to bilge pumps and lights at the back so i'd only need to run positive cable thru the boat, 2 at the front for common positive and negative.

because all the power gonna be shared. (items will be individually fused AFTER the positive come out of the 'Bus bar') question is. I've got a very THICK high flow cable that runs from battery to the front positive bus bar, do I need the same gauge/thickness cable for the negative main/common/shared cable as well that goes to bus bar ? will need to as thick as the positive one?

vcreation is offline  
Old 08-09-2013, 07:34 PM
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Old 08-09-2013, 07:39 PM
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Short answer - yes.

Longer answer - it looks like you have a branched ground return path. The segment between our ground bus bar near rge battery and the battery must be capable of carrying the max current load, and should be sized the same as the "positive" side cable that runs from your battery to the positive side distribution bar.

The segment that connects the ground bus bar for your electronics and the other bus bar "might" be able to be smaller, as it will only carry the return current for the loads connected to the "electronics" bus bar, and not the loads from the pumps/lights.

To be safe use the same gauge. Or, do the math and ruthe load calculations to make sure you have sufficient gauge wire for the overall load and desired voltage drop over the length of the run.

Check out a text like one from Charlie Wing on DC electrical principals.

Also, make sure you have a properly sized fuse or breaker on your positive supply wire, ideally within 7" of the battery.
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Old 08-10-2013, 05:49 PM
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Blue Seas has a calculator to help determine wire size

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Old 08-10-2013, 06:50 PM
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If the positive and negative cables going to the bow of the boat are different sizes then either one is too big and/or one is too small.

The only exception is if the boat is Aluminium which could account for a smaller negative wire.
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