The zincs on the drive shaft ahve disappeared in the past 3 years. I keep the dock power on to charge the batteries, which allow the Adler Barber DC refrigerator to keep the beer cold. Two years ago, in an attempt to solve the zinc problem, I installed a galvanic isolator in the dock power ground line (the green wire). It did not solve the zinc problem. In reading articles on the subject, many people recommend removing the ground wire from the AC ground to the DC ground. I did that this spring and will see if my zinc problem is solved or not. Any Comments??
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3 years?
If your zincs lasted three years i think you're doing better than average! I wouldn't worry - just replace them every other year or more.
If your zincs lasted three years i think you're doing better than average! I wouldn't worry - just replace them every other year or more.
You don't have a problem!
Last year I used 75% of two zincs (large). On my previous boat (no shore power) one zinc would barely last a year. They are sacrificial and are doing their job. I recommend replacing them annually as part of your spring commissioning. You don't want to run the risk of you zinc disintegrating to the point it might fall off!
Last year I used 75% of two zincs (large). On my previous boat (no shore power) one zinc would barely last a year. They are sacrificial and are doing their job. I recommend replacing them annually as part of your spring commissioning. You don't want to run the risk of you zinc disintegrating to the point it might fall off!
Zincs, and stuff
Three years is a TON! Your zincs are working, but you should have them replaced when they appear to be about half spent. They are actually just about at the end of their useful life, at that point. You are correct that there are many good reasons to eliminate the connection between your AC ground (green wire), and your common DC ground. Among the most important is that, assuming that your common ground is somehow in contact with the water surrounding your boat (through the engine, shaft and prop, for instance), should you have a short to ground in one of your AC appliances (this is what the green wire is there for), you will be sending full voltage AC into the water around you. This can have bad consequences for anyone swimming, as well as those zincs! Assuming that your AC wiring, and that of the dock, is up to snuff, you want that current to safely travel to ground through the green wire.
Three years is a TON! Your zincs are working, but you should have them replaced when they appear to be about half spent. They are actually just about at the end of their useful life, at that point. You are correct that there are many good reasons to eliminate the connection between your AC ground (green wire), and your common DC ground. Among the most important is that, assuming that your common ground is somehow in contact with the water surrounding your boat (through the engine, shaft and prop, for instance), should you have a short to ground in one of your AC appliances (this is what the green wire is there for), you will be sending full voltage AC into the water around you. This can have bad consequences for anyone swimming, as well as those zincs! Assuming that your AC wiring, and that of the dock, is up to snuff, you want that current to safely travel to ground through the green wire.
The real question!
Ray: I guess the real question is when did they go away? If they have been gone for the past couple of years you need to get them checked more often. If they lasted for 3 years, it does not sound like you have much of a problem. I would have your strut, shaft
Ray: I guess the real question is when did they go away? If they have been gone for the past couple of years you need to get them checked more often. If they lasted for 3 years, it does not sound like you have much of a problem. I would have your strut, shaft
Ray, Are you saying, you haven't had "any" zincs
in the past 3 years?...That is not good!?.... and whether you are tied into shore power or not it is still VERY important to have zincs. You can still get problems from disimilar metals in the water (Galvanic Corrosion) as opposed to "stray current corrosion". But they are all due to electrolysis. Go to the link below and carefully read it. It is an *excellent" paper on Zincs and corrosion etc. PS...Are you in Salt Water...or Fresh Water....because there is a lot of difference in the two with regards to galvanic corrosion and you should be purchasing different (Magnesium) Zincs for Fresh water due to the fact that in fresh water there is less electrolyte activuty thus the need for a less noble metal (magnesium)
in the past 3 years?...That is not good!?.... and whether you are tied into shore power or not it is still VERY important to have zincs. You can still get problems from disimilar metals in the water (Galvanic Corrosion) as opposed to "stray current corrosion". But they are all due to electrolysis. Go to the link below and carefully read it. It is an *excellent" paper on Zincs and corrosion etc. PS...Are you in Salt Water...or Fresh Water....because there is a lot of difference in the two with regards to galvanic corrosion and you should be purchasing different (Magnesium) Zincs for Fresh water due to the fact that in fresh water there is less electrolyte activuty thus the need for a less noble metal (magnesium)
Re; zinks and grounds
First to address the ac/dc ground system. All the elec systems books and guides say NEVER put the ground systems together. I know they sound the same but ar'nt. they should be treated as totally seperate entities. with no wires common to each system. now the zinks, you can get electrolisis even if you have no ac on your boat. all it takes is one boat on your dock to have an improper system to put stray voltage in the water and do a lot of damage. for the cost of a zink about 4$ its not worth the risk to not change it every season. Pretty cheap insurance against the chance the leaking boat is going to show up at your dock this year.
First to address the ac/dc ground system. All the elec systems books and guides say NEVER put the ground systems together. I know they sound the same but ar'nt. they should be treated as totally seperate entities. with no wires common to each system. now the zinks, you can get electrolisis even if you have no ac on your boat. all it takes is one boat on your dock to have an improper system to put stray voltage in the water and do a lot of damage. for the cost of a zink about 4$ its not worth the risk to not change it every season. Pretty cheap insurance against the chance the leaking boat is going to show up at your dock this year.
Grounds???
The following was copied from sailmag.com concerning their article from this months issue. Re: "Installing Shore Power" (April): It's important to ground the AC system to the boatÕs DC system negative. Start at the grounding bus bar that came with the AC panel and run a #8 or #10 AWG green wire to the DC negative connection (usually it's at the starter) on the engine. This wire is required under American Boat and Yacht Council Standard E-8, ensures that if a fault in the AC system gets into the DC system, it cannot introduce a hazardous level of AC voltage into the water or create a shock hazard on board. No comment by me, but see link for info.
The following was copied from sailmag.com concerning their article from this months issue. Re: "Installing Shore Power" (April): It's important to ground the AC system to the boatÕs DC system negative. Start at the grounding bus bar that came with the AC panel and run a #8 or #10 AWG green wire to the DC negative connection (usually it's at the starter) on the engine. This wire is required under American Boat and Yacht Council Standard E-8, ensures that if a fault in the AC system gets into the DC system, it cannot introduce a hazardous level of AC voltage into the water or create a shock hazard on board. No comment by me, but see link for info.
Agree with James
Every book or expert I have talked to notes that the ABYC recommends otherwise, but says not to combine the grounds. If you really research the issue, you will see that there is no perfect solution, and that each carries its dangers. But, assuming that the ground wire system (green) is functional in the marina, clearly the safest thing is not to combine this green wire with your DC ground. And, it is not just a matter of zincs, but safety, as well. There are similar disagreements as to whether or not a boat should have a bonding system. There is responsible opinion on both sides, backed up by reams of experience. Each side tends to hold its opinion very firmly. The ABYC says to bond, probably because it finds itself in a position where it has to have an opinion. Many experts disagree. My boat is quite system intensive, has extensive electronics and electrical equipment, and I live aboard. When I am at a dock, I am plugged in, 24/7. I still have my original shaft, prop, and strut, with no electrolysis, (BIG knock on wood!) and get reasonable life out of my zincs. The boat is not bonded.....and I think I will leave it that way! By the way, galvanic corrosion can occur even when every boat and the marina's electrical systems are perfect, as long as there are dissimilar metals in salt water. Electrolysis is one thing, and galvanic corrosion is quite another. Use zincs!
Every book or expert I have talked to notes that the ABYC recommends otherwise, but says not to combine the grounds. If you really research the issue, you will see that there is no perfect solution, and that each carries its dangers. But, assuming that the ground wire system (green) is functional in the marina, clearly the safest thing is not to combine this green wire with your DC ground. And, it is not just a matter of zincs, but safety, as well. There are similar disagreements as to whether or not a boat should have a bonding system. There is responsible opinion on both sides, backed up by reams of experience. Each side tends to hold its opinion very firmly. The ABYC says to bond, probably because it finds itself in a position where it has to have an opinion. Many experts disagree. My boat is quite system intensive, has extensive electronics and electrical equipment, and I live aboard. When I am at a dock, I am plugged in, 24/7. I still have my original shaft, prop, and strut, with no electrolysis, (BIG knock on wood!) and get reasonable life out of my zincs. The boat is not bonded.....and I think I will leave it that way! By the way, galvanic corrosion can occur even when every boat and the marina's electrical systems are perfect, as long as there are dissimilar metals in salt water. Electrolysis is one thing, and galvanic corrosion is quite another. Use zincs!
But Tim.....Eventually the DC ground of your boat
will find its way to the AC ground from the dock (through the water). So the theory is to just tie them at ONE location on your boat. This way their Voltage potential levels between the 2 are the same thus no current is flowing thus no current electrolysis..... That's the theory at least.... I think I've read what boat manufacturers might wire to be the safest wiring for lowering potential AC "electrical shock" into the water is not the best for Electrolysis......But like the experts say....I am not sure what is best.(I'm not even 100% sure what my boat is...I'll check thsi weekend........).. But I think ALL experts agree.....use zincs on all metals that have a potential to touch seawater and especialy ones that is comprised of 2 different types of metals. And attach it as close to the metal you are trying to protect and replace often
will find its way to the AC ground from the dock (through the water). So the theory is to just tie them at ONE location on your boat. This way their Voltage potential levels between the 2 are the same thus no current is flowing thus no current electrolysis..... That's the theory at least.... I think I've read what boat manufacturers might wire to be the safest wiring for lowering potential AC "electrical shock" into the water is not the best for Electrolysis......But like the experts say....I am not sure what is best.(I'm not even 100% sure what my boat is...I'll check thsi weekend........).. But I think ALL experts agree.....use zincs on all metals that have a potential to touch seawater and especialy ones that is comprised of 2 different types of metals. And attach it as close to the metal you are trying to protect and replace often
James, Show me!
James I think you are extremely wrong. Sorry for the strong acusation but this is a serious thing. I ask you to show me in which books on what page it says to seperate them! The AC ground should be tied to the DC negitive. The thing you never do is tie the AC negitive to Dc negitive. I really didn't want to get in this because if you don't understand electricity this is a hard explaination. Don't remove the AC ground wire from the DC. If you do, The DC is grounded to the water outside the boat, if there is a problem with the AC grounding, there is then a potential fron the AC to the DC which is a real shocker!! All your grounding should be tied together ( AC, DC, Lightning) to the exterior of the hull. This eliminates potential between them and thus no current flow. If you are grounded to different places on the hull, you have created a very expensive battery out of your boat. The Galvanic isolator should only be connected from the green wire to the shore power connection.It should not be tied to the DC system. Nigel Caldwell on Page 156 of his book Boatowners Mechanical and electrical Manual shows this in a circuit diagram. It is confusing in the first portion of his book because he has to explain each system first. On page 155 he brings it all together under the title "The Common Grounding Point". If you don't understand it get a professional, not only for your health but your boats health. Zincs are cheap. They do their job. Expect to change them on your yearly maintenence list. sincerely r.w.landau
James I think you are extremely wrong. Sorry for the strong acusation but this is a serious thing. I ask you to show me in which books on what page it says to seperate them! The AC ground should be tied to the DC negitive. The thing you never do is tie the AC negitive to Dc negitive. I really didn't want to get in this because if you don't understand electricity this is a hard explaination. Don't remove the AC ground wire from the DC. If you do, The DC is grounded to the water outside the boat, if there is a problem with the AC grounding, there is then a potential fron the AC to the DC which is a real shocker!! All your grounding should be tied together ( AC, DC, Lightning) to the exterior of the hull. This eliminates potential between them and thus no current flow. If you are grounded to different places on the hull, you have created a very expensive battery out of your boat. The Galvanic isolator should only be connected from the green wire to the shore power connection.It should not be tied to the DC system. Nigel Caldwell on Page 156 of his book Boatowners Mechanical and electrical Manual shows this in a circuit diagram. It is confusing in the first portion of his book because he has to explain each system first. On page 155 he brings it all together under the title "The Common Grounding Point". If you don't understand it get a professional, not only for your health but your boats health. Zincs are cheap. They do their job. Expect to change them on your yearly maintenence list. sincerely r.w.landau
Another thought for Tom
The thinking that I have read regarding coupling the grounds notes that the AC ground (green) should NEVER carry current, as opposed to the AC neutral, which does. The only time the ground will carry current is when an appliance has a short that goes to the case, or somesuch. The ground wire is connected to the case to give such current a path to ground, without passing through the unsuspecting boatowner (or landowner,as the case may be). That would be the only time the green wire would be energized, and one would be most thankful for its presence, in such an event. But, if the AC ground is connected to the DC ground, and assuming that the DC ground is in contact with the water (as it usually is), then if the AC ground is energized, that current would pass directly into the water, increasing the potential for electrocution, not to mention electrolysis. It is not a problem generated by a poor DC ground. On the other hand, if the AC ground (green wire) is grounded ashore, through a correct shore power installation, it causes no problem, just as in a house. The reason that some advocate connecting the two grounds is so that the AC ground will always have a path to ground in the event that the shorepower wiring is not up to snuff, and the green wire is not connected to a shore ground. But, you can determine whether or not this is so by simply setting your multimeter on AC volts, and then putting one probe in the hot wire opening in your AC outlet, and the other in the ground. If you measure voltage, there has to be a complete circuit, and a connection to ground. If not, go yell at the Marina Manager! On the other hand, if your grounds are tied together on board your boat, you will ALWAYS be at the risk of an AC short going to ground through the water. Addtionally, some boats have their DC systems just run to and fro from their batteries, without connecting their common ground to the water. I don't think I would like to have an AC short energize my DC negative wires.......!
The thinking that I have read regarding coupling the grounds notes that the AC ground (green) should NEVER carry current, as opposed to the AC neutral, which does. The only time the ground will carry current is when an appliance has a short that goes to the case, or somesuch. The ground wire is connected to the case to give such current a path to ground, without passing through the unsuspecting boatowner (or landowner,as the case may be). That would be the only time the green wire would be energized, and one would be most thankful for its presence, in such an event. But, if the AC ground is connected to the DC ground, and assuming that the DC ground is in contact with the water (as it usually is), then if the AC ground is energized, that current would pass directly into the water, increasing the potential for electrocution, not to mention electrolysis. It is not a problem generated by a poor DC ground. On the other hand, if the AC ground (green wire) is grounded ashore, through a correct shore power installation, it causes no problem, just as in a house. The reason that some advocate connecting the two grounds is so that the AC ground will always have a path to ground in the event that the shorepower wiring is not up to snuff, and the green wire is not connected to a shore ground. But, you can determine whether or not this is so by simply setting your multimeter on AC volts, and then putting one probe in the hot wire opening in your AC outlet, and the other in the ground. If you measure voltage, there has to be a complete circuit, and a connection to ground. If not, go yell at the Marina Manager! On the other hand, if your grounds are tied together on board your boat, you will ALWAYS be at the risk of an AC short going to ground through the water. Addtionally, some boats have their DC systems just run to and fro from their batteries, without connecting their common ground to the water. I don't think I would like to have an AC short energize my DC negative wires.......!
Yes Ollie....this is another fine mess we have
gotten ourselves into !.....LOL.....R.W.Landau has is right and yes Tim all your scenario's are valid....I guess every one hopes that if there 'is" a short to ground that it will blow a circuit breaker somewhere. But that isn't always the case and you can still have a low current under (0.1amps) running through the water from an incorrectly wired boat/dock that could zap (
gotten ourselves into !.....LOL.....R.W.Landau has is right and yes Tim all your scenario's are valid....I guess every one hopes that if there 'is" a short to ground that it will blow a circuit breaker somewhere. But that isn't always the case and you can still have a low current under (0.1amps) running through the water from an incorrectly wired boat/dock that could zap (
A good article!
My degree is Electrical Engineering and I have a small boat with no AC. But if I did, I would wire it as presented in this article. See link below. Mark Kissel Kittiwake 98H240
My degree is Electrical Engineering and I have a small boat with no AC. But if I did, I would wire it as presented in this article. See link below. Mark Kissel Kittiwake 98H240
Thanks, Mark
I wired my 272 for shore power according to the diagram shown in the WM advisory--including the GFCI outlets and aint dead yet... nor have I electrocuted any fish ;<) My gratitude to all for a good discussion. Tom
I wired my 272 for shore power according to the diagram shown in the WM advisory--including the GFCI outlets and aint dead yet... nor have I electrocuted any fish ;<) My gratitude to all for a good discussion. Tom
Tim
I would much rather a short ground to water than through me. That is the reason you do it. r.w.landau
I would much rather a short ground to water than through me. That is the reason you do it. r.w.landau
Another good discussion
Here is a link to another excellent article on grounds and zincs, etc. Note that AC is not commonly causing galvanic corrosion, but the green AC ground attaches you to all the other boats in the marina and their DC current leaks, if present. Galvanic isolators are supposed to eliminate your spending your zincs to protect the guy in the next slip - don't know why it didn't work in your case!
Here is a link to another excellent article on grounds and zincs, etc. Note that AC is not commonly causing galvanic corrosion, but the green AC ground attaches you to all the other boats in the marina and their DC current leaks, if present. Galvanic isolators are supposed to eliminate your spending your zincs to protect the guy in the next slip - don't know why it didn't work in your case!
In an effort to bring some clarity....
....to this discussion, I went to the boat and dived into my personal Bible, Nigel Calder's book. By the time I returned to cyberspace, the two terrific articles by Honey (West Advisor
....to this discussion, I went to the boat and dived into my personal Bible, Nigel Calder's book. By the time I returned to cyberspace, the two terrific articles by Honey (West Advisor
After sleeping on it...
I think that I probably have more confidence in a marina's wiring job than do most boaters, because, in the marina I manage, we are meticulous with this. We cannot afford not to be, as we have really high electrical demands with a luxury commercial sportsfishing fleet, lots of mega-yachts with high demands at 220 v, and lots of freezers and AC units. We have less than 10 sailboats!!! Ouch!!! But we have a large staff including our own electrician and two outside electrical consultants, one American and one Mexican, to make sure of the quality control of our electricity. We are always doing some maintanance which, by the way, recently included renewing all the grounding cables. But, it is true that not all marinas can afford to be as thorough as we have to be, and I will hark back to my recommendation that all boaters learn to simply check the power and polarity at their docks, using their multimeters. As for my pondering whether to change my system, I think that (apart from some of the DC and RF grounds mentioned in the Honey article), I will continue to leave my grounds separate, and continue to check the AC in whatever marina I happen to visit.
I think that I probably have more confidence in a marina's wiring job than do most boaters, because, in the marina I manage, we are meticulous with this. We cannot afford not to be, as we have really high electrical demands with a luxury commercial sportsfishing fleet, lots of mega-yachts with high demands at 220 v, and lots of freezers and AC units. We have less than 10 sailboats!!! Ouch!!! But we have a large staff including our own electrician and two outside electrical consultants, one American and one Mexican, to make sure of the quality control of our electricity. We are always doing some maintanance which, by the way, recently included renewing all the grounding cables. But, it is true that not all marinas can afford to be as thorough as we have to be, and I will hark back to my recommendation that all boaters learn to simply check the power and polarity at their docks, using their multimeters. As for my pondering whether to change my system, I think that (apart from some of the DC and RF grounds mentioned in the Honey article), I will continue to leave my grounds separate, and continue to check the AC in whatever marina I happen to visit.
Tim, Thanks
Thanks for considering all the input and not being as abrasive as I was in response to your idea. I do apologize for my abrasive tone. There is one thing that can still get you into trouble concerning the previous subject. If you use a charger that is connected from the AC source to the DC system, make sure it is an isolation charger/inverter. Some of the older chargers/inverters were not of this type. If they fail, the DC system is subject to the negative AC. Thus have 110v in you DC system. I am glad that your marina is concerned about the quality of power to your boats. For the record, I still think it is best to have a common ground for every power/lightning/corrosion (one subject to power)source. I also think that bonding to thru hulls is asking for electrolysis (galvanic type). There is no current flow unless they are connected. When a bonding wire is connected to the thru hulls, it completes a circuit that allows the different metals to become a battery with just the different metals from the boat. I think it is better not to ground thru hulls. They are insulated from the rest of the boat by the rubber hoses. Good sailing r.w.landau
Thanks for considering all the input and not being as abrasive as I was in response to your idea. I do apologize for my abrasive tone. There is one thing that can still get you into trouble concerning the previous subject. If you use a charger that is connected from the AC source to the DC system, make sure it is an isolation charger/inverter. Some of the older chargers/inverters were not of this type. If they fail, the DC system is subject to the negative AC. Thus have 110v in you DC system. I am glad that your marina is concerned about the quality of power to your boats. For the record, I still think it is best to have a common ground for every power/lightning/corrosion (one subject to power)source. I also think that bonding to thru hulls is asking for electrolysis (galvanic type). There is no current flow unless they are connected. When a bonding wire is connected to the thru hulls, it completes a circuit that allows the different metals to become a battery with just the different metals from the boat. I think it is better not to ground thru hulls. They are insulated from the rest of the boat by the rubber hoses. Good sailing r.w.landau
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