SIX weeks and zincs are TOAST - Page 4 - SailNet Community
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post #31 of 57 Old 11-09-2017
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Re: SIX weeks and zincs are TOAST

I have a procedure I use when doing corrosion surveys. It might be worth a look

Corrosion Testing

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post #32 of 57 Old 11-10-2017
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Re: SIX weeks and zincs are TOAST

Quote:
Originally Posted by MarkSF View Post

I was a little uncertain how to do the grounding on the charger. It has two, one for the charger itself, and one for the chassis. The main ground is connected to the boat ground bus. The case ground I connected to the through-hull bonding system, as that's how the old charger was. Is this the normal approach? This seemed to be the way the Pro Nautic manual suggested.
Your charger has a negative terminal, which carries charger current, and a chassis ground, which carries ZERO current unless there is an internal fault in the charger. Chassis gronding wire can be no smaller than one wire GA below the chargers DC negative...

Chassis ground needs to be able to carry the full current of the charger, in a failure/fault, and thus it needs to be bonded to your main DC neg bus or at the ships single ground point (most often the engine).

Grounding / Earthing the charger at a seacock can be dangerous especially with the small bonding wires and the inherent corrosion of bonding wires in bilges. If the charger were to develop a fault, especially in fresh water, where it might not be able to trip the breaker, it could create a dangerous situation.

Green or green with yellow stripe "bonding wires" should never every carry DC current unless there is a fault. I see far too many folks pick up a green bonding wire and use it as DC negative, a very bad practice..... The installation of a marine battery charger is one of the more often incorrectly done installs on boats primarily because it seems so easy...

Installing a Marine Battery Charger

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post #33 of 57 Old 11-10-2017
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Re: SIX weeks and zincs are TOAST

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Originally Posted by boatpoker View Post
How do you know the difference between AC and DC leakage, by looking at the zincs?

It had long been thought that AC did not cause any corrosion activity but that has been disproven, it does but it is so slow that you'd likely never notice. Leaking AC can kill you but unlikely it will cause any corrosion.
Bingo! AC causing corrosion is one of the more common misunderstandings in the marine environment..

Quote:
Originally Posted by boatpoker View Post
I've seen leaking DC cause propellers, shafts and rudders disappear within two weeks two weeks of an amateur "electrician" playing with his electrical system.
How about less than 24 hours for DC from nearly new (installed in the spring before launch) to this... This DC corrosion event was caused by a DIY failed solder joint..... D'oh.....

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post #34 of 57 Old 11-10-2017
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Re: SIX weeks and zincs are TOAST

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Originally Posted by Maine Sail View Post
...Chassis gronding wire can be no smaller than one wire GA below the chargers DC negative...
Interesting. Of the four inverter/chargers we have owned (Trace, Prosine, Outback, Victron), none of their chassis ground lugs could take one AWG size below the 4/0 DC negative wire connecting them to the batteries. About 6AWG is the maximum that will connect to the ground lug.

Quote:
Originally Posted by Maine Sail View Post
Chassis ground needs to be able to carry the full current of the charger, in a failure/fault, and thus it needs to be bonded to your main DC neg bus or at the ships single ground point (most often the engine).
This has always been a bit of confusion to me. How does the main DC neg bus differ from the battery DC neg post? On our boat, there is a 2/0 wire from the negative battery terminal to the negative bus at the panel.

Our boat also has engines electrically isolated from the water, with the indirect exception of the raw water feed. There is no electrical connection through the transmission/prop. We also have no external ground plate. The engine block is connected electrically directly to the starting battery, and to the house DC negative only through an ACR when charging and the batteries are combined. The alternators are isolated ground leading directly back to the house battery.

Both the panel negative bus and the closest engine are 20' away from the inverter/charger. So why can't I save a 20' run of large cable and connect the chassis ground to the negative battery terminal, which is only 3' away from the inverter/charger?

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post #35 of 57 Old 11-10-2017
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Re: SIX weeks and zincs are TOAST

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Originally Posted by Maine Sail View Post
This DC corrosion event was caused by a DIY failed solder joint..... D'oh.....
More details about where a solder joint was used, and how it led to that failure is something I'm interested in learning. Can you elaborate?

Mark

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post #36 of 57 Old 11-11-2017
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Re: SIX weeks and zincs are TOAST

Quote:
Originally Posted by Maine Sail View Post
Your charger has a negative terminal, which carries charger current, and a chassis ground, which carries ZERO current unless there is an internal fault in the charger. Chassis gronding wire can be no smaller than one wire GA below the chargers DC negative...

Chassis ground needs to be able to carry the full current of the charger, in a failure/fault, and thus it needs to be bonded to your main DC neg bus or at the ships single ground point (most often the engine).

Grounding / Earthing the charger at a seacock can be dangerous especially with the small bonding wires and the inherent corrosion of bonding wires in bilges. If the charger were to develop a fault, especially in fresh water, where it might not be able to trip the breaker, it could create a dangerous situation.

Green or green with yellow stripe "bonding wires" should never every carry DC current unless there is a fault. I see far too many folks pick up a green bonding wire and use it as DC negative, a very bad practice..... The installation of a marine battery charger is one of the more often incorrectly done installs on boats primarily because it seems so easy...

Installing a Marine Battery Charger
Mine has a negative AC terminal, an AC input ground, AND a case ground. See page 8 of the ProNautic 1220P manual. It tells you to connect the case ground to the bonding system. Given that the AC ground is connected to the D.C. Neg bus, why don't I just jump the case ground to the AC ground?

Edit : oh I see, because the gauge wouldn't be sufficient.

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Last edited by MarkSF; 11-11-2017 at 01:47 AM.
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post #37 of 57 Old 4 Weeks Ago Thread Starter
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Re: SIX weeks and zincs are TOAST

Follow up - As of last fall's haul out (2018) I'm STILL having this issue. the two new Aluminum anodes were badly pitted after only 3 weeks in the water!

I recently cleaned up the Leece-Neville 90A alternator.The oil breather for the Universal M25 exited behind the alternator, and any vapor would be drawn up into the alternator and over the diodes where it would condense. Airflow for the alternator goes through the body toward the pulley. There was a good deal of soot in amongst the diodes, so I cleaned the works with WD40 and then compressed air.

you can see that it's awfully dark in there...

I also installed an oil catch can and routed the breather there rather than behind the alternator.


(Don't snicker, it's a 33 year-old engine... and it's paid for!)

I just installed 2 new Navalloy Aluminum Anodes, and have ordered a Corrosion Reference Electrode so that I can continue to dig into the problem. I will post an update if I recall.
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“(Don't snicker, it's a 33 year-old engine... and it's paid for!)“

Actually you should be proud - your engine looks better than most. Am looking from a tiny photo on my phone, but it looks clean, dry, no oil or rust. Very nice!
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Re: SIX weeks and zincs are TOAST

Looks a bit like ours (1982 raw water cooled)...





We don't seem to have zinc issue, but don't have quite as much going on in our engine compartment. Hope your re-routing solves it!
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post #40 of 57 Old 4 Weeks Ago
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Re: SIX weeks and zincs are TOAST

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Originally Posted by eherlihy View Post
Follow up - As of last fall's haul out (2018) I'm STILL having this issue. the two new Aluminum anodes were badly pitted after only 3 weeks in the water!
.
Is your boat "bonded"? If so do you also have metal tanks or things connected to the ground circuit? If you do check to be sure all those grounds are in good condition or things like a fuel tank level monitor will pass current into the bonding etc and out the shaft to the water
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