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Discussion Starter · #1 ·
I was having some issues with electrolysis on my sailboat so I installed a galvanic isolator with a led monitor and turned it on and it said I had no problems with the ground( no leds on ) . so the other day I shut off all my breakers on the boat to replace my leaking water heater I started to remove the wires and they were still hot so I unplugged shoreline . I replaced the
water heater and every thing was fine,but I still wondered why my wiring was hot when I turned off all breakers. I went to the hardware store and purchased a receptacle tester and found my hot and neutral were reversed so I started at the marina plug and guess what the hot and neutral were reversed, so that is fixed. My question is with the hot and neutral reversed at the marina side
would this be causing my electrolysis problem? Thanks Mark
 

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I would wonder about the power still on after the breaker is off. Its hooked to something. Yeah, I like that tester to check out the marina wiring. If your post was wrong, what else is wrong. I dont know how many electric cords I have pulled out of the water. People just unhook there boat and throw it on the dock hot and expect it to stay there.
 

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I agree with badsanta. If you shut off all the breakers and the system is still hot you have a serious problem. Convential wisdom until recently has always been that galvanic corrosion is a DC problem, but some recent studies have shown that stray AC may also cause it. But worse yet, stray AC will kill you. You need to get this fixed. The marina needs to have their dock system checked out thoroughly. You need to make sure the polarity is correct on your boat. And you need to check out those breakers to see that they are working correctly. One last thing. when you unplug the shore power cord, unplug BOTH ends. Then you know for sure it's dead!
 

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Don't swim around that ship.
When we move or limbs, we are operating at a few milli-volts.
120 V AC will paralyse you and it will be horrible.
It is the principle of electro-fishing and it is very effective.
 

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Discussion Starter · #5 ·
I have fixed the the marina shore power and the breakers are working fine and I have checked every plug receptacle and all is ok, I just need to know if that was what was causing my outdrive to be eaten away Thanks Mark
 

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I was having some issues with electrolysis on my sailboat so I installed a galvanic isolator with a led monitor and turned it on and it said I had no problems with the ground( no leds on ) . so the other day I shut off all my breakers on the boat to replace my leaking water heater I started to remove the wires and they were still hot so I unplugged shoreline . I replaced the water heater and every thing was fine,but I still wondered why my wiring was hot when I turned off all breakers.
If you've turned off the main shorepower breaker, NONE OF THE AC WIRES, other than the ones between the AC panel and the shore power inlet should be hot.

If any still were hot, YOU HAVE A PROBLEM.


The MAIN AC PANEL on a boat should have TWO BREAKERS for the shorepower connection—one for hot and one for neutral. If yours doesn't have a double breaker on the SHOREPOWER FEED to the AC PANEL—you need to fix that. The reason for the two breakers is to prevent the boat's internal AC wiring from being energized in the case of a reverse polarity problem on the shorepower post. Not fixing this may get someone killed.

I went to the hardware store and purchased a receptacle tester and found my hot and neutral were reversed so I started at the marina plug and guess what the hot and neutral were reversed, so that is fixed. My question is with the hot and neutral reversed at the marina side
would this be causing my electrolysis problem? Thanks Mark
It is possible, but there could also be so many other problems with this electrical system, it can't really be determined from what you've said.
 

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The problem was reversed polarity at the marina receptacle and IMDDMC clearly states in his post that this problem has been fixed. Come-on people read the posts. I will agree with Dawg that the main should be a double pole breaker, disconnecting the neutral and hot when "off".
The elctrolysis is caused through the gound wire so reversing polarity will not effect it.
 

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Ebs-

If he had all the breakers on his boat off, and was still getting live AC at the hot water heater, his AC panel design has a serious flaw. The electrolysis issue is far less important IMHO, since that won't generally kill you stone cold dead—a bad AC panel design will.
 

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Dawg read the 1st post. With reverse polarity at the marina plug his breakers were switching the neutrals so he would still have power on the hots. The only "design flaw" is that he appears to have only a single pole main breaker when it should be a double pole. The reverse polarity problem was repaired and he verified that his receptacles are proplerly wired with the tester. He did not indicate whether the main was a single pole or a double pole but I agreed with you it should be a double pole switching the hot and the neutral.
Salt water marinas are notoriously bad for stray currents and a galvanic isolator is really his solution for that problem.
 

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Mark, you indicate your problem is fixed but I suggest you read this Electrolysis as it may prove helpful to you regarding your question about electrolysis.

The simple answer to your only question is yes.

ebs I am having difficulty in understanding how the circuit is being completed if all the breakers are off, even if they are single pole breakers. If the polarity is reversed, then when the breaker is off, the wire acting as the neutral would be open. The only other conductor left would be the ground to carry the current, which in essence would be a direct short causing a breaker to trip someplace. What am I missing? Or do you think the current from the water heater is going to ground in the sea and not using the grounding conductor?
 

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FarCry—

If the shorepower pole had reverse polarity as indicated, and the OP's boat only has a single breaker for the AC main inlet, rather than the highly recommended double breaker setup, then the RP situation would leave the normally neutral and uninterrupted line hot. Given that he didn't short the line directly to ground, it is really, really unlikely that he'd draw the 30 amps required to trip the shorepower post breaker. Shorting an AC line to the point where it is drawing 30 amps is going to be rather spectacular. :)
 

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SD,
I still don't understand how the circuit is completed causing the OP to get shocked. Do you?

Can we break this down into facts and see where I am missing something?

1) There was a RP situation.
2) Normally black=hot and white=neutral and green=ground.
3) With RP once it gets on Mark's boat the white wire should be uninterrupted and would be, in this case, carrying power to a termination on one side of the heating element in the water heater
4) The black wire, now serving as neutral, would be terminated on the water heater possbly ahead of a factory installed switch, maybe then on to a factory reset/breaker which probably then goes to the line side of a Tstat and then eventually it will be connected to the other side of the heating element
5) The breakers are all off on the boat and the water heater is connected to one of them
6) Current will flow from the shore post on the white wire to the heater through the heating element and out the heater on the black wire to the panel on the boat.
7) If the breakers are off then the circuit as described is open and the heater should not operate
8) If the water heater is internally bonded from the factory (neutral and ground connected) in this case the white/hot is directly connected to a ground and is indeed a direct short. The current draw of the heater would be irelevent and should either cause something to melt or, to be dramatic, be something rather spectacular:).
9)If the heater is wired with the factory wriring bonding just the external metal parts to the grounding conductor (green) and back to the post then there shouldn't be any potential to get shocked unless there is a less restrictive path to ground then through the ground wire.

Heading to Jost for the day, I'll check back much later. Perhaps after some painkillers this will make more sense to me!!!!!!!!!!!!!!!!!!!





FarCry—

If the shorepower pole had reverse polarity as indicated, and the OP's boat only has a single breaker for the AC main inlet, rather than the highly recommended double breaker setup, then the RP situation would leave the normally neutral and uninterrupted line hot. Given that he didn't short the line directly to ground, it is really, really unlikely that he'd draw the 30 amps required to trip the shorepower post breaker. Shorting an AC line to the point where it is drawing 30 amps is going to be rather spectacular. :)
 

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If he was grounded at all, even if not very well grounded, the now hot NEUTRAL wire would still shock him. He didn't say how he discovered the wires were still hot... and if he accidentally shorted the hot "neutral" wire to ground, he'd still get a shock... That is why I say this is such a dangerous situation, and that his AC installation is dangerous and defective—as it doesn't appear to have a double breaker for the main AC shorepower feed coming into the boat.

You're making the assumption, which is probably faulty, that he was shocked by the "hot" and "neutral" wires, but the ground wire is still a viable path back for the electricity, since a galvanic isolator is merely a set of diodes that blocks low voltage current from passinganything above about 1.2-1.4 Volts, whether DC or AC will pass through a galvanic isolator with no trouble.

A galvanic isolator does not interrupt the ground path at all. It merely prevents very low level voltage currents from being able to pass it... galvanic currents are generally driven by voltages below ONE volt. If they're above ONE volt, the problem is pretty serious.
SD,
I still don't understand how the circuit is completed causing the OP to get shocked. Do you?

Can we break this down into facts and see where I am missing something?

1) There was a RP situation.
2) Normally black=hot and white=neutral and green=ground.
3) With RP once it gets on Mark's boat the white wire should be uninterrupted and would be, in this case, carrying power to a termination on one side of the heating element in the water heater
4) The black wire, now serving as neutral, would be terminated on the water heater possbly ahead of a factory installed switch, maybe then on to a factory reset/breaker which probably then goes to the line side of a Tstat and then eventually it will be connected to the other side of the heating element
5) The breakers are all off on the boat and the water heater is connected to one of them
6) Current will flow from the shore post on the white wire to the heater through the heating element and out the heater on the black wire to the panel on the boat.
7) If the breakers are off then the circuit as described is open and the heater should not operate
8) If the water heater is internally bonded from the factory (neutral and ground connected) in this case the white/hot is directly connected to a ground and is indeed a direct short. The current draw of the heater would be irelevent and should either cause something to melt or, to be dramatic, be something rather spectacular:).
9)If the heater is wired with the factory wriring bonding just the external metal parts to the grounding conductor (green) and back to the post then there shouldn't be any potential to get shocked unless there is a less restrictive path to ground then through the ground wire.

Heading to Jost for the day, I'll check back much later. Perhaps after some painkillers this will make more sense to me!!!!!!!!!!!!!!!!!!!
 

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I think ebs answered my question , that's what I needed to know .As I said before the the ac double breaker has been fixed shoreline has been fixed I want
to thank everybody for there help except saildog , I was just trying to get some help I thought that was what this forum was all about, not getting screamed at. [EDIT]
 

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Imdd :

What do you expect from a twin-hull dog?
He does it all the time... the opening Saildog Salvo is often enough to keep you away. It often works.
Not this time, I hope.

I will help you.
Particularly if you have an engine problem, I'll be glad to advise if it's within my remit.

I never use shore power directly to the boat's wiring. I have a shore power line, and it's an orthodox plug-board type, but it does not connect to the ship's AC bus. I keep that separate. I never use the ship's AC wiring. I have never trusted it, really.

If you are leaking those sort of voltages though, it will cause havoc with corrosion. Using an orthodox plug-board really should end the problem as it cannot leak to the ship's earth... well, not easily anyway. It might be worth a try, at least until you find the problem. For battery charging in the meantime, just plug in an orthodox battery charger. Don't leave it unattended though.
Remember to kill the charger power before pulling the charger leads off the battery. I have painful recollections of neglecting that advice.
.
 

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LMDDMC—

Can you please point out where you said you replaced the original setup with a double breaker. AFAICT, you never did. I was emphasizing this for your safety... [EDIT]
 

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What you are missing Far cry, is that if he has stray current causing galvanic corrosion, he has a ground fault somewhere. So when he switches off his single pole breaker the neutral is still hot and current is flowing through the ground fault to the green grounding wire. So his system is still hot. If he has a double pole breaker it breaks both the hot (black) and neutral (white) and stops all current flow. If he still has a hot system after that, it means that something on his boat is direct wired to the hot side of the breaker panel, not through the breaker. This is a life threatening situation not just a corrosion problem. He needs to get that checked out.
And as I said in my post before, yes, AC can result in stray current corrosion. But if after you shut every thing down, you still have stray currents then they are coming from someone else's boat or from the dock side shore power. He needs to check the water around his boat for current.
 

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Farcry, if the polarity is reversed and the breakers are turned off the circuit would not be created through the normally hot and neutral, but between the neutral and ground. With correct polarity and the breakers off, there is no potential between any of the conductors and you will not get an electrical shock.
 

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It was a pleasure to read Peikenberry's response as he used the correct terminology in a well considered answer to the issue.

As soon as I here someone use the term "electrolysis" as applied to marine corrosion I immediately know that they are not knowledgeable about the issue. The info below is from an article on my web site.

ELECTROLYSIS: Chemical changes in a solution or electrolyte due to the passage of electric current.

Electrolysis is a current (pun intended) subject of docktalk around our yacht club and there seems to be some confusion about it. Much of the confusion stems from the misunderstanding or incorrect use of terms related to marine electrical issues.

As you can see from the definition above, electrolysis is what happens to the electrolyte (water), not what happens to any metallic components. This term has come to be applied to virtually all marine corrosion but what we are really talking about is two separate issues. Be wary if your marine surveyor uses the term electrolysis, he probably does not know what he is talking about.

1. Galvanic corrosion: Corrosion that occurs at the anode of a galvanic cell.

You may remember high school science class where a battery was created by connecting two dissimilar metals with wire and immersing the whole contraption in water thereby activating magnetic fields and causing current to flow.


On a boat with bronze, aluminum, galvanized and stainless steel that are connected with grounding wires and immersed in the lake...... you accomplish the same thing. The more noble metal is the "cathode", the less noble, the "anode". In this process the less noble metal gives up electrons to the more noble thus weakening the metal, otherwise known as "galvanic corrosion".

The "sacrificial" anodes on your shafts, trim tabs etc. are supposed to sacrifice themselves thereby protecting expensive metal parts. This is why it's important to keep your anodes or "zinc's" in good condition and never paint them.

A vessel suffering from galvanic corrosion is usually the source of it's own problem, although two vessel's linked by shore power grounds can create a galvanic cell between two very close boats.

2. Stray Current corrosion: Corrosion that results from a battery or other external DC electrical source causing a metal in contact with an electrolyte (water) to become anodic with respect to some other metal in the same electrolyte.

In simple terms a wire touches something it shouldn't, like a faulty bilge pump float or degraded wiring lying in the bilge sending current into the water, causing one metal to give up electrons and corrode. Again any vessel suffering from this type of corrosion is likely the master of it's own disaster but the culprit could also be a neighboring vessel. This type of corrosion can can eat metals at an alarming rate. I know of one 42' motoryacht that lost both shafts, both rudders and both propellers in a space of less than two weeks.

Complicating this picture somewhat is the fact that DC can be super-imposed on your AC wiring through the common ground on board or the ground we all share on the dock. As all vessels in the marina are connected through shorepower grounds there is potential for widespread damage. Aside from concerns of corrosion there is also serious potential for electrocution if shorepower cords are allowed to lie in the water let alone the fools that leave their shorepower cord plugged in at the dock while they go out for an afternoon cruise.

Recent tests have shown that AC currrent from shorepower in the water can also cause corrosion to underwater parts. This has been a long argued issue by people who know a lot more about this than me. ABYC has long required that the AC and DC grounds should be bonded however this means that with a fault AC can be introduced to the entire system. New Ground fault protection systems, galvanic isolators, isolation transformers and impressed current systems are some of the various methods attempting to combat corrosion.

Salt water is generally regarded as a more serious breeding ground for marine corrosion as the salt makes it more conductive however, polluted fresh water can be even more conductive with the right contaminants.


With our aging fleet of pleasure craft it's likely that at some time, less than expert hands have played with your electrical system. If your vessel is suffering from any electrical faults or unusual corrosion consult with an American Boat and Yacht Council Certified marine electrical technician with specific corrosion control training or give me a call and I will try to set you up with an expert in this field.


The info below is from an article on my web site
 

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boatpoker,

Great piece, except for one thing:

1. Galvanic corrosion: Corrosion that occurs at the anode of a galvanic cell.

You may remember high school science class where a battery was created by connecting two dissimilar metals with wire and immersing the whole contraption in water thereby activating magnetic fields and causing current to flow.
It's not the "activating [of] magnetic fields" that causes current flow. What causes current to flow is the loss of electrons by the anode (the less noble of the two metals), and a gain of electrons by the cathode. The loss of electrons is known as "galvanic corrosion." Aka: "Oxidation." (The gain by the cathode is, curiously, known as "reduction." Go figure.)

A magnetic field will result, but it is an effect, rather than a cause.

Jim
 
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