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Old 04-03-2012, 03:11   #16
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Re: Why We Don't Leave Our Boat Plugged In

You can always hand another zinc anode over the side, like "zinc grouper" or "hanging anode".

We have a fish zinc, like the one in this link: Zinc Grouper and hand it up clipping it to the shrouds whenever we're in a marina. It worked wonders to our prop zinc lifetime! And the fish still hasn't corroded to nothing after 3 years.

You can also use a bigger cousin of this fish: http://www.boatzincs.com/hanging_anode_zinc.html if the fish corrodes too quickly.

P.S. Just don't forget to take it down when underway
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Old 04-03-2012, 03:18   #17
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Re: Why We Don't Leave Our Boat Plugged In

My other half says that as a proper solution you should really get a galvanic isolator. Most likely there is a stray current in the shore's ground, so you want to isolate ship's ground from shore's.

They don't call galvanic isolators "zinc savers" for nothing.
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Old 04-03-2012, 06:02   #18
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Re: Why We Don't Leave Our Boat Plugged In

You may want to install a galvanic isolator on your ground plug it will let AC go through but will eliminate the DC dripping into your boat and reduce the zincs erosion.
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Old 04-03-2012, 07:05   #19
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I hung one of the zinc groupers over the side clipped to a chainplate which is connected. Meter moved a little but not Significantly better when plugged in. Yeah galvanic isolator is probably the way to go but my future plans for this boat don't involve marinas so I may hold off on that expense.
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Old 04-03-2012, 07:19   #20
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Re: Why we dont leave our boat plugged in

Quote:
Originally Posted by DotDun View Post
I believe any good quality digital meter will work.
http://assets.fluke.com/appnotes/ele...r/B0269b_u.pdf
Indeed; but you still need a (Ag/AgCl) reference electrode.
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Old 04-03-2012, 09:37   #21
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Re: Why We Don't Leave Our Boat Plugged In

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Originally Posted by bazzer View Post
Any idea where I can get a Reference electrode ?
for example:

Corrosion Reference Electrode
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Old 07-03-2012, 10:07   #22
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Re: Why we dont leave our boat plugged in

I agreee with the two-wire solution. Americans seem to be "ground-obsessed." There is no such thing as "ground," especially on a boat. The water, especially in a marina, is just a big electro-chemistry experiment. Don't participate. Make no electrical connection to anything that might get wet. Treat both wires of AC shorepower (black and white) as HOT. Neither one is "ground" or even "neutral" in any reliable sense. The green wire is used to sense current where there should be none and should be connected to any metal chassis of any electrical device that you might touch but nothing else.
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Old 07-03-2012, 13:07   #23
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Re: Why We Don't Leave Our Boat Plugged In

You are a physicist and you believe this? How is it then that electrical engineers, electricians, authorities and experts on this subject do not accept your two wire solution? Your solution was what came before the three wire system, and is the reason for electrocutions and fires on boats. It was also the reason for many electrocutions and fires ashore. That third wire is there specifically to provide a path for current back to ground, instead of going through your body. It is used not just on boats but anywhere AC electricity is used. This provides a much higher level of safety.

The only truth in your comment is:
Quote:
Treat both wires of AC shorepower (black and white) as HOT. Neither one is "ground" or even "neutral" in any reliable sense.
Yes they are both hot. And if there is a fault where one or the other is inadvertently connected to a metal casing or metal part of the boat, then the current has no way to get back to ground until someone accidentally touches something that is metal and now HOT!. Without the green wire, it has nowhere to go except through you.

Been there, done that, and fortunately lived to talk about it.
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Old 07-03-2012, 13:10   #24
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Re: Why We Don't Leave Our Boat Plugged In

The problem with galvanic isolators is when they go out (and they do) it does damage from what I hear.
I think another problem is the common means of bonding the DC ground to the AC ground. If there is fault with the marina wiring or the guy beside you has a cheap 1960's type 2 prong auto motive charger, it is quite possible to cross hot with neutral that way. It will give stray currents a path to less noble metals. If you are bonded this way, try un-bonding AC ground to the DC. Generally it is done at the engine block or in your panel.

As far as the 2 wire solution...Are you nuts? If everyone did that, the whole harbor would be hot enough to cook fish!
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Old 07-03-2012, 14:01   #25
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Re: Why We Don't Leave Our Boat Plugged In

Galvanic isolators do fail. But the current (no pun intended) standard requires them to have a status monitor that alerts the operator to a failure, or they must be a fail safe isolator, meaning they must only fail in the conducting mode. This preserves the integrity of the green wire.

Part of the problem here is that many people do not think of the AC, DC, Bonding and lightning protection as separate systems. To correctly install and understand how it all works one needs to think of them as separate, and only connected together at one place. To add to the confusion, the concept of bonding all metal fittings in contact with the water is still very controversial. That is why some people advocate cutting the green wire. They do not understand how these systems work separately. If you don't want to bond, then don't bond. But don't ever cut the third (green wire) in the AC system. See diagram that shows how AC, DC and Grounding system are connected. Does not include a lightning protection system. http://newboatbuilders.com/images/circuit8.jpg

And I quote:
Quote:
As far as the 2 wire solution...Are you nuts? If everyone did that, the whole harbor would be hot enough to cook fish!
This is why a major part of my boat builders web site is devoted to electrical systems.

One top of all that a lot depends on whether you have a fiberglass, wood, or metal boat. So it can all be rather intimidating. That's why I have always told boat owners and builders, that unless they have a strong electrical background, or anything beyond a 12V DC system, do not DIY you boat's electrical system. Hire an electrical engineer to design it and a certified marine electrician to install it.
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Old 07-03-2012, 14:16   #26
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Re: Why We Don't Leave Our Boat Plugged In

Personally, I feel my way is the safest...I keep DC separate from AC. Secondly...no bonding. Third, a healthy investment in solar to keep the systems running if I need them to while I'm away from the vessel. Third, I unplug the shore power at my boat. Not just shut it off at the dock breaker. That way the ground is disconnected too. No chance of a hot cross over to neutral which is where the ground is connected at the harbor panel. Lastly hang a grouper over the rail. Not only does it add protection, it gives you a real world look at whats going on in the water. JMHO.
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Old 07-03-2012, 15:40   #27
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Re: Why We Don't Leave Our Boat Plugged In

Ike:

I never advocated cutting the green wire. Read my last sentence. But bear in my mind it's purpose -- to detect current in either AC line from the chassis back to the source. There are several other comments from guys who get it -- the source (or sink) is not some fictitious "ground" -- it is the other end of the power source -- the negative terminal of the battery for instance. If you are connected to shore power your green wire goes back to the source of that shorepower. If you are running on an inverter it goes back to the inverter. The problems that arise result from tying these various sources together (often backwards) by connecting their green (fault sensing) wires together as if they were a common "ground."

Keeping the DC and AC sources separate as Celestial Sailor suggests is sound. I would go further and have nothing connected to shorepower and the local electro-chemistry experiment except my battery charger, with all three wires of course, the shore's green wire connected to the charger chassis and nothing else. Then run everything on the boat from a(n) inverter(s). The green wires of any AC appliances on board go back to the inverter, not to the shore power system.

Lastly, I would note comments from some Europeans who have very little of these problems. They know that the brown and blue are both hot (+ and - 120v, 180 degrees out of phase and that the green (and yellow over there) is a fault sensor, not a "ground."

Finally, connecting anything electrical to the water is just asking for trouble.
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Old 07-03-2012, 15:48   #28
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Re: Why We Don't Leave Our Boat Plugged In

Oh, one other thing -- you only see three wire plugs (in the US) on things that have a metal case. If the two hot wires (black and white) are completely encased and insulated and there is nothing for them to short to, then the third prong and green wire are considered to be unnecessary. UL thinks so, anyway.
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Old 07-03-2012, 16:23   #29
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Re: Why We Don't Leave Our Boat Plugged In

One other thing not mentioned yet. It is a good idea to have ground fault outlets on the boat. If something does go wrong on the boat or in the harbor, those babies start popping.
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Old 07-03-2012, 18:49   #30
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Re: Why We Don't Leave Our Boat Plugged In

Oh Yeah
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