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Old 07-16-2019, 06:34 PM   #1
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Break your bonds expert says

Are marinas today worse as far stray currents than past years?
So it it getting worse or are people today more aware.

https://www.westmarine.com/WestAdvis...unding-Systems

Quote:
Bonding and Electrolytic Corrosion Due to Hot Marinas
Do not bond any thru-hulls or other immersed metal that can be electrically isolated. Specifically, keep your metal keel/ballast, your metal rudder shaft, your engine/prop, and all thru-hulls electrically isolated, from each other, and from the engine.

It's worth understanding the reason. In an increasing number of marinas, there are substantial DC electric currents running through the water. If your bits of immersed metal are bonded, the electric current will take the lower resistance path offered by your boat in preference to the water near your boat, and the current will flow into one of your bits of metal, through your bonding wires, and then out another bit of metal. The anodic bit of metal or thru-hull that has the misfortune to be on the "out current" side of the current running through your bonding system will also become "out metal" and will disappear, sometimes rapidly.

Your zinc is only intended to protect against the modest galvanic potentials and therefore currents that are caused by the dissimilar metals that are immersed and electrically connected together on your own boat. Your zinc is incapable of supplying enough galvanic potential to protect against substantial DC currents that may be flowing in the water. These DC currents in the water will cause electrolytic corrosion to your bonded thru-hulls or metal parts.
I disconnected all through hull years ago, but I did leave the struts and shaft log bonded and the rudder posts and rudders. I have never seen any corrosion on anything.
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Old 07-16-2019, 06:45 PM   #2
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Most people are better educated today, and we have far better new coverage.
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Old 07-16-2019, 08:09 PM   #3
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Everything metal on my boat is bonded (except the prop shaft) to a large aluminum transom anode. Plate lasts 2 or 3 years and I replace it. No sign of deterioration.

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Old 07-16-2019, 08:17 PM   #4
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I also just read that article and noticed same away from bond everything together idea.
now this needs interpretation,
"The key factor here is that the yacht's electrical system is connected to seawater ground at one point only, via the engine negative terminal or its bus."
appears directed at shaft to prop bonding, however if you have twins, should you bond both or just one?
"So now, you are annoyed with the inconsistencies"
Bond the DC negative to the green ground of AC, but now you need a Galvanic Isolator to protect from shore power carrying a DC current. But then if your boat has an AC leak to ground would it not go out the DC bonding into other boats through water.
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Old 07-16-2019, 10:13 PM   #5
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Great article.

Leaves me with more questions than answers.

For example, I use the Groco flanged seacocks that has a stainless steel ball and stem in it. Is the ball electrically isolated from the bronze base with seals? I'll have to check with Groco.

And will the Boat US insurance surveyor accept the non bonded underwater fittings in the survey that they do every 10 years on older boats?
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Old 07-16-2019, 11:35 PM   #6
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Article is >20 years old.
Author is renowned sailor and inventor, but is just another EE
Everything in my boat has been connected together for >35 years. It is still floating.
I am not aware of any sinkings at my marina due to corroded through-hulls, shafts, struts, etc.

Conclusion? Pass me another Corona
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Old 07-16-2019, 11:39 PM   #7
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Quote:
Originally Posted by SoWhat View Post
Article is >20 years old.
Author is renowned sailor and inventor, but is just another EE
Everything in my boat has been connected together for >35 years. It is still floating.
I am not aware of any sinkings at my marina due to corroded through-hulls, shafts, struts, etc.

Conclusion? Pass me another Corona
I agree, except pass me a Stella
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Old 07-17-2019, 05:21 AM   #8
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I asked a noted expert about bonding and his reply was along the lines of, "As a licensed ABYC surveyor, I can not suggest or recommend removing your bonding system. But (Whisper) nothing on my boat is bonded." I promptly removed the whole bonding system from my sailboat, which I expected to keep forever. I'd remove it from our trawler but we'll have to sell it in a few years and I don't want a flap with the buyers survey.
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Old 07-17-2019, 09:52 AM   #9
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If you put two different metals in salt water, you have a battery. The least noble metal on the scale will deteriorate. Bronze has zinc in its mix so the bronze will happily give up its zinc. Bonding runs the current generated by this battery into a sacrificial zinc which is designed to deteriorate.

Having an aluminum boat that’s 45 years old and so far the only galvanic damage was when a PO used carbon shaft packing (slaps forehead), I am a firm believer in bonding. Buy yourself a silver anode and use your multimeter to test the current at all your expensive fittings. That is the only accurate way to determine if you should be bonded.

The galvanic transformer is to compensate or correct stray dc current and an isolation transformer is to isolate the vessel from AC shore power.
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Old 07-17-2019, 10:47 AM   #10
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Anyone want to forward a theory on how marina water is alive with DC?
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Old 07-17-2019, 11:15 AM   #11
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Quote:
Originally Posted by Xsbank View Post
Having an aluminum boat that’s 45 years old and so far the only galvanic damage was when a PO used carbon shaft packing (slaps forehead), I am a firm believer in bonding.
Since you have experience with this and have an aluminum boat, may I ask what your through hull materials are and what other metals you have electrically connected to the hull?

I ask because I understood isolating metals was preferable to a bonding system on aluminum hulls. I don't recall my source off the top of my head, but it was either Michael Kasten or Nigel Calder (or both).

This stuff gives me a headache.
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Old 07-17-2019, 12:54 PM   #12
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Quote:
Originally Posted by diver dave View Post
Anyone want to forward a theory on how marina water is alive with DC?
Exactly I was wondering the same thing, it caught my eye as a reason for debonding which I had not yet thought of, so I started the thread.

Bad boat wiring decaying in bilges from ever older boats sitting in slips?
boats are both DC and AC but only the dock is AC.

I have a few DC wires in bilges for the bilge pumps. I have junction blocks below the floor. They typically dont get wet.
Can seawater or something else rectify dock AC or industrial machine AC leakage into DC currents in the water at marinas?
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Old 07-17-2019, 04:31 PM   #13
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Quote:
Originally Posted by sdowney717 View Post
Exactly I was wondering the same thing, it caught my eye as a reason for debonding which I had not yet thought of, so I started the thread.

Bad boat wiring decaying in bilges from ever older boats sitting in slips?
boats are both DC and AC but only the dock is AC.

I have a few DC wires in bilges for the bilge pumps. I have junction blocks below the floor. They typically dont get wet.
Can seawater or something else rectify dock AC or industrial machine AC leakage into DC currents in the water at marinas?
In residential the neutral (white) is bonded to the ground (green). That practice has carried over to some boat AC panels. Marinas as well if they have the neutral bonded to ground?
I once had to re-wire a house as the homeowner saved money hiring a friend who worked with electronics where the neutral is switched, Black (power) is always on.
The recommendation is to bond green ground to DC-. The only reason is for your on board safety.
DC current theory? what if you have a copper strap the length of the boat to which you apply whatever you want to bond at convenient points. That strap is cut. now you have a DC- searching for a DC- battery terminal and the only other item bonded is the shaft or rudder post. Will it trickle out and return through another item on the bonding circuit? I don't know, sounds like it could.
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Old 07-17-2019, 07:21 PM   #14
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Quote:
Originally Posted by Soo-Valley View Post
In residential the neutral (white) is bonded to the ground (green). That practice has carried over to some boat AC panels.
Contrary to ABYC and potentially lethal if (as it should be) the DC negative and AC gound are bonded.
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Old 07-17-2019, 07:28 PM   #15
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Forgot the word “not”.
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Old 07-17-2019, 08:08 PM   #16
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There should never be an AC neutral to ground bond on a boat where it is getting power from a remote location, like the shore power. That bond should only exist for a power origination on the boat, such as a generator or a isolation transformer. And when the gen is off, that bond needs to be broken, which naturally occurs if you have a gen selector switch that breaks open the neutral and hot wires together, which it should be doing.

Reason is you dont want multiple return paths for currents, since if the neutral wire, which carries current is attached on the boat to the green ground wire, then the green ground wire is carrying current back to its origination along with the neutral white wire, which means a ground fault condition has happened and a hot marina, but hot with AC power.

A defective device or appliance plugged into an outlet, or a defective hard wired appliance could create that kind of bond joining the white neutral to the green ground inside itself.

I could easily imagine people installing a gen switch and they only disconnect the black hot wires thru a gen selector switch, and they leave all the neutral white wires joined together, cause people with a little bit of knowledge know to join all white wires together on AC systems, and only switch the hot black side.
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Old 07-17-2019, 08:55 PM   #17
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some quick North American standard terminology;

Grounded load current conductor: White
Panel or equipment grounding conductor: Green
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Old 07-18-2019, 09:34 AM   #18
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All through hulls on my boat are welded aluminum (I’m keel cooled) with stainless ball valves and the only other metal is a 2 1/2” stainless shaft and a 36” stainless wheel. Above-water, recent additions like the new bilge discharge and poop vents are plastic.
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Old 07-18-2019, 09:34 AM   #19
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Quote:
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...Bronze has zinc in its mix so the bronze will happily give up its zinc...

I thought brass had zinc and bronze had tin and/or other metals?

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Old 07-18-2019, 10:42 AM   #20
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Lots of different alloys .....
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