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Old 14-07-2013, 18:13   #16
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Thanks for the link, I'll check that out. I apologize for the brevity in my previous reply, I can be more long winded now.

It's my understanding that the green wire provides an easy (easier than through me) path to ground for stray current that has managed to find its way out of the circuit. Most of the sources I've read say that the engine lug (through the engine, transmission, and prop shaft to the water) is usually the "common ground" used. If the green wire is doing its job of shunting stray electrons into the water (and away from me), then the current can shock swimmers and fishes, and cause premature deterioration of metals on, outside, or near my boat.

That deterioration, electrolysis, general rotting of metal parts seems to be a product of the green wire doing its job.

Is this a correct assumption, or do I have it wrong?
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Old 14-07-2013, 18:21   #17
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There is a running debate on this. ABYC reccomends connecting the engine into the AC protective earth , this is done not to establish a path to earth , via seawater , but to add the engine into the protective circuit. That is of an AC hot site touches the engine , the AC fuses will trip.

To my understanding ABYC does not require a specific AC ground to seawater , the AC ground is established via the shore power lead , back to a common earth neutral point established at the premises.

In many countries code actually recommends not establishing any " local " AC grounds to prevent earth loops etc.

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Old 15-07-2013, 07:42   #18
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Re: No Breakers For AC

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Originally Posted by nolandinsight View Post
Thanks for the link, I'll check that out. I apologize for the brevity in my previous reply, I can be more long winded now.

It's my understanding that the green wire provides an easy (easier than through me) path to ground for stray current that has managed to find its way out of the circuit. Most of the sources I've read say that the engine lug (through the engine, transmission, and prop shaft to the water) is usually the "common ground" used. If the green wire is doing its job of shunting stray electrons into the water (and away from me), then the current can shock swimmers and fishes, and cause premature deterioration of metals on, outside, or near my boat.

That deterioration, electrolysis, general rotting of metal parts seems to be a product of the green wire doing its job.

Is this a correct assumption, or do I have it wrong?
The green wire is intended to provide a direct path to shore ground...not thru the water. It is there to avoid serious injury or death from electrocution.

A 'galvanic isolator' is a bit of a misnomer, since it is intended both to reduce electrolytic corrosion from stray low voltage DC currents entering the water (since these cause corrosion faster than AC currents) and, if it has a capacitor, to bleed off low-level AC currents directly to the shore ground via the green wire. There is some controversy as to whether or not the capacitor is a good idea; some believe it is not because it can mask AC leakages which really should be identified and corrected.

Here's a good primer on galvanic isolators, including a discussion of ABYC standards and how to test individual isolators.

Testing A Galvanic Isolator Photo Gallery by Compass Marine at pbase.com

Bill
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Old 15-07-2013, 10:37   #19
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I understand now, thank you very much!
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Old 16-07-2013, 07:09   #20
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Re: No Breakers For AC

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Update: found the "breaker panel". Anyone remember these?
Showing our age by knowing what these are.
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Old 16-07-2013, 14:46   #21
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Re: No Breakers For AC

"It's my understanding that the green wire provides an easy (easier than through me) path to ground for"
That is a realithy of it, yes. The ground wire does provide an easy path to ground. Whether that path should be provided, is the debate that's gone on for so many decades.
So in the case of a person, unregulated pleasure vessel? You decide on whether it should provide an easy path, intermingled with the bonding system or anything else. Or, whether it should just be a "safety ground" to prevent your electrocution.

In this day and age you might think plastic tool housings, two-wire "grounded" polarized AC cords, and other ideas have made mixing water and AC somewhat safer. Years ago I was using a "double insulated" power tool on an extension cord that had gotten damp from overnight dew on the grass. Guess what gave me a tingle anyway?

So after a few other odd mishaps, I just treat all AC wires as live and hostile, until proven otherwise. And if I'm working on a circuit, the breaker panel or cutoff gets padlocked before I work on it. Learned that the hard way too.
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Old 16-07-2013, 15:50   #22
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Re: No Breakers For AC

Instal a proper AC circuit board for a number of reasons, mostly safety and convenience.

How many circuits you set up will be dependent on how much load you anticipate on each circuit and not necessarily where each circuit is running. Give larger load things that are also important their own circuits, like battery chargers. This also makes it convenent to kill the power just to that one device when you need to service it.

GFCI outlets are really important on a boat. All of them need this protection.

Always use double pole breakers rated for AC on AC circuits.

I tag out an AC circuit when I am working on it by putting a piece of yellow electrical tape over the breaker.
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