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post #11 of 23 Old 03-01-2019
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Re: Ground on a boat?

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Originally Posted by bigdogandy View Post
Kriss - follow the big black cables from the battery to where they terminate. Should be on the engine block, or a large bus bar that connects to the engine block. Thatís your ground.

It is most likely a bad mistake to connect to the green wires. Those are usually either for AC grounding or for bonding metal through hulls together (unless a previous owner did something creative with green wire!) and in either case are dangerous to rely on as a ground for any DC system.

I learned the hard way on this kind of thing, and really wish I had gotten a qualified marine electrician to do the work and educate me along the way.

Be careful.
This is incorrect. The AC ground (green) must be bonded (joined) to the DC negative.

The hysterical laughter you hear as you drive a way in your"new" boat ..... is the seller.
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post #12 of 23 Old 03-01-2019
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Re: Ground on a boat?

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Originally Posted by krisscross View Post
Yes, that 4AWG green wire connects to the black cable bus bar next to the engine block and connected to it.
I would connect the ground wires for the wind generator and itís mast to that ground bus bar, with a separate wire for each that is the same size as the positive feed from the wind generator. Use good quality marine crimp connectors with heat shrink on all connectors.
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post #13 of 23 Old 03-01-2019
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Re: Ground on a boat?

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Originally Posted by boatpoker View Post
This is incorrect. The AC ground (green) must be bonded (joined) to the DC negative.
I suspect he meant that the green Earth ground / bonding conductors should never be used to carry DC equipment current. We see this mistake often...
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post #14 of 23 Old 03-01-2019
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Re: Ground on a boat?

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Originally Posted by Maine Sail View Post
I suspect he meant that the green Earth ground / bonding conductors should never be used to carry DC equipment current. We see this mistake often...
Thanks Mainesail....that is what I meant.

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post #15 of 23 Old 03-01-2019
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Re: Ground on a boat?

There's a bit of confusion here ...

The AC and DC grounds are separate.

They are also connected.

This is more than a little confusing, but it's also the same way house wiring is done. In a house, the white (neutral) wire is connected to the same place as the bare ground wire.

However, it's _where_ they are connected that is important. Electricity will always follow the path of least resistance. In a properly installed system, the ground is connected to the neutral, but it never carries any current unless something goes wrong.

The upshot being, it _does_ make a difference exactly how you connect grounding wires to the DC negative. You need to ensure you do it in a manner that will not cause current to flow along the ground wires under normal operating conditions. This may be very simple in your case, but if it seems confusing at all, I highly recommend that you pay a marine electrician for an hour of his time to explain the safest way to connect everything.
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Re: Ground on a boat?

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Originally Posted by BillMoran View Post
There's a bit of confusion here ...

The AC and DC grounds are separate.

They are also connected.

This is more than a little confusing, but it's also the same way house wiring is done. In a house, the white (neutral) wire is connected to the same place as the bare ground wire.

However, it's _where_ they are connected that is important. Electricity will always follow the path of least resistance. In a properly installed system, the ground is connected to the neutral, but it never carries any current unless something goes wrong.

The upshot being, it _does_ make a difference exactly how you connect grounding wires to the DC negative. You need to ensure you do it in a manner that will not cause current to flow along the ground wires under normal operating conditions. This may be very simple in your case, but if it seems confusing at all, I highly recommend that you pay a marine electrician for an hour of his time to explain the safest way to connect everything.
No, No, No ! .... The neutral is never connected to the ground on board other than automatic switching at a source. i.e. inverter or generator. Doing otherwise may kill someone.
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Re: Ground on a boat?

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No, No, No ! .... The neutral is never connected to the ground on board other than automatic switching at a source. i.e. inverter or generator. Doing otherwise may kill someone.
You're correct. I wasn't saying that it was ... but I can see how my comparison to house wiring could easily be confused in that way. Thanks for clarifying.
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post #18 of 23 Old 03-01-2019
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Re: Ground on a boat?

Pictures say a thousand words. Would somebody post a simple schematic to clear this up?
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post #19 of 23 Old 03-02-2019
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Re: Ground on a boat?

The bonding system, wires that connects all the below water through hulls together, is there so every fitting has the same electrical potential. The theory is that if everything is bonded together, they will all have the same electrical potential and a single piece won't act as a sacrificial anode. Otherwords, you won't be setting up a weak battery and having a through hull disappear. The bonding system is NOT AN ELECTRICAL GROUND. Have had boats that are bonded and ones that aren't. Haven't seen a problem with either set up.
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post #20 of 23 Old 03-02-2019
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Re: Ground on a boat?

Soon as the AC side comes up, the answer is, get a pro.
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