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Old 02-01-2012, 18:24   #181
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Re: Neighbor dumping raw AC into water?...what to do?

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Originally Posted by s/v Beth View Post
Perhaps. But I learned alot about boat electronics from this thread, esp from Nick.
Thanks guys.
Ya, tis an ill wind.
Also, with my recall, it is good to refresh.
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Old 02-01-2012, 18:51   #182
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Re: Neighbor dumping raw AC into water?...what to do?

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If you want to keep the rig separate from the DC system, one DC negative connection that many people overlook is the VHF antenna mount.

The coax shield is connected to DC negative in the radio and it's also connected to the barrel connector on the mount.

I insulated the mount from the mast with nylon spacers, and it didn't affect the radio performance at all.

I did the same thing with the masthead mount for the Bullet M2HP transceiver.

Rig is electrically grounded with a Dynaplate and has no connection whatsoever to the DC or AC system.

As the boat was built in Denmark, it came with a GFI breaker and no AC grounding system, and I'm leaving it that way.
+1

Forgot about the antenna grounds.

Learned a lot on thei thread. Thanks all.

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Brad
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Old 02-01-2012, 19:02   #183
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Re: Neighbor dumping raw AC into water?...what to do?

Note that you can get zincs for free. Or at least the cost of scrap zinc.

Our boat yard has a huge pile of them. Take what you want and pay a small amount for the recycling $$ they would have gotten.

I'm planning to hang a couple from the midship cleats. We have an iron keel. In our case, it's probably best to have them near the keel and not on the forestay and backstay.

Anyone know a good way to attach a wire so it insulated into the zinc and doesn't corrode? I'm thinking melting the zinc in one spot and pushing the wire in. either that, or using liquid elecrical tape. (That stuff realy stinks, but I won't smell it underwater.)

Regards,
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Old 02-01-2012, 19:18   #184
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Re: Neighbor dumping raw AC into water?...what to do?

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Note that you can get zincs for free. Or at least the cost of scrap zinc.

Our boat yard has a huge pile of them. Take what you want and pay a small amount for the recycling $$ they would have gotten.
Zinc anodes cost only a few dollars. Are you really so cheap that you would entrust your boat to a few depleted anodes that you found on a scrap heap? Not to mention going to the trouble of melting them down to attach a wire?

Jeezus, just buy a few new ones.
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Old 02-01-2012, 19:19   #185
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Re: Neighbor dumping raw AC into water?...what to do?

Brad, I'm told that used zincs are often no longer really effective, porosity, chemical conversion, something happens and if you've ever noticed the way a really old one crumbles? Not the place to save beer money.

Also, zinc vapors are something you do not want to breath. If you're going to be torching it, melting it, welding on galvanized metals, etc., you want to treat it the same way you would treat lead or asbestos dust. Full protective gear or positive ventilation.

Not to be paranoid, but since it is so easy to avoid some toxins, why not?
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Old 02-01-2012, 19:32   #186
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Re: Neighbor dumping raw AC into water?...what to do?

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Brad, I'm told that used zincs are often no longer really effective, porosity, chemical conversion, something happens and if you've ever noticed the way a really old one crumbles? Not the place to save beer money.

Also, zinc vapors are something you do not want to breath. If you're going to be torching it, melting it, welding on galvanized metals, etc., you want to treat it the same way you would treat lead or asbestos dust. Full protective gear or positive ventilation.

Not to be paranoid, but since it is so easy to avoid some toxins, why not?
Good advice. I have hung an old zinc overboard and whether it was too porous or I had a bad connection it didn't seem to do much. Next time I'll use a new one!
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Old 02-01-2012, 19:51   #187
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Re: Neighbor dumping raw AC into water?...what to do?

So I googled "buy zinc ingots" and the top hit was someplace called rotometals.com. Offering $2.29/lb and less and even free shipping. Buy a nice big ingot, bolt up some cable...

Actually I liked where Nick is going wrt galvanic isolators and more equipment meaning more failure modes. The simple answer is just don't plug the boat into the AC at all, and keep out of those problems entirely.

Or as Bob Marley said, "No woman no cry".
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Old 02-01-2012, 23:18   #188
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Re: Neighbor dumping raw AC into water?...what to do?

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So I googled "buy zinc ingots" and the top hit was someplace called rotometals.com. Offering $2.29/lb and less and even free shipping. Buy a nice big ingot, bolt up some cable...
It is just as possible to overprotect a boat as it is to underprotect one. Just adding anodes willy-nilly is not a particularly good idea. Especially if you are talking about big ones.
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Old 03-01-2012, 04:08   #189
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Quote:
Originally Posted by hellosailor
So I googled "buy zinc ingots" and the top hit was someplace called rotometals.com. Offering $2.29/lb and less and even free shipping. Buy a nice big ingot, bolt up some cable...

Actually I liked where Nick is going wrt galvanic isolators and more equipment meaning more failure modes. The simple answer is just don't plug the boat into the AC at all, and keep out of those problems entirely.

Or as Bob Marley said, "No woman no cry".
Fastbttms is right... too many zincs is as bad as too little.

Not using shorepower is a very quick fix. This would have been my first step in I were in the OP position.

The nice thing with an isolation transformer is that your boat is not plugged into the shore power. Only the transformer is plugged in and it is isolated from your boat. Think of he transformer as a power generating source just like the genset. The only difference is that you switch diesel with an electric magnet powered from shore as input to he "generator".

cheers,
Nick.
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Old 03-01-2012, 05:27   #190
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Re: Neighbor dumping raw AC into water?...what to do?

Well folks...I'm still not understanding just how stray AC current causes galvanic corrosion. I need to read some more in Niger Calder's book about it, but its on the boat some 8 hour drive away. Plus even stray DC leakage would in my reasoning cause the leaking boat to lose material from it's underwater metal since it(the leaking boat) is the anode and not the cathode. I always thought it was the other way around..ie. the leaking boat causes the neighboring boats to lose material. And all this assumes one is pluged into shore power establishing a common ground(and electron pathway) with the leaking boat and AC and DC ground are one of the same.

And another problem I've always had is the statement that too many zincs are as bad as too few. I understand that over zincing will cause one to lose zincs at a faster rate however I suspect that an equilibrium is established at some point and the rate of lose will be the same as putting the "correct" amount of zinc on the boat in the first place.

Sorry about being so dense on this, but even years ago when in EE undergraduate classes I always had to get back to simple basics to understand the more complex.
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Old 03-01-2012, 06:43   #191
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Re: Neighbor dumping raw AC into water?...what to do?

It has to be understood that stay currant and galvanic corrosion are 2 different things. As the results are similar many get them mixed up.Even though the result (lost metal) may appear the same the cause is different.

Galvanic corrosion is the result and an electrical potential difference between metals. When different metals are in an electrolyte (water) ions can flow from 1 metal to the other. (the direction of flow depends on the metals) The trick is to keep the electrical potential in balance so as to stop the current flow. This is why a bonding system is used, the bonding wire keeps all metals at the some potential (in theory) Adding too much zinc can cause things to become more out of balance. You want X mass of zinc to protect Y mass of boat metal. Once again keeping a good balance. In a perfect world you should not have any zinc wastage at all, the zinc is there to protect when things get out of balance. I often see boats come out of the water with zincs several years old and no wastage. These boats have a good balance and or good bonding system.
To explain the galvanic isolator think of your boat as one cell in a battery. Each other boat in the slips near you are the other cells. The AC ground wire can connect these "cells" together. if the other boats do not have the same electrical potential as yours current will flow from one to the other. The isolator stops DC flow through the AC shore ground wire isolating your boat from this marina "battery" Like others have said it can be limited and will only stop DC flow not AC flow. This is when the isolation transformers are so good they completely isolate your boat from the shore system.
Stay current is just that, an electrical fault trying to find a path to ground. Damage is most likely from DC not AC as others have said.
Hope this might help some who are having trouble understanding some of this. It is fairly simple in theory but can get tricky in practice.
The trick to trouble shooting is to be systematic in your approach to fault finding. It is detective work but but not all that hard.
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Old 03-01-2012, 06:50   #192
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Re: Neighbor dumping raw AC into water?...what to do?

* deleted *
Wayne too quick for me

cheers,
Nick.
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Old 03-01-2012, 08:25   #193
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Re: Neighbor dumping raw AC into water?...what to do?

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I had a similar problem a few years back. An underfunded sea scout sailboat across the fairway from me replaced its dead charger with a cheap automotive charger. Suddenly, everybody within 20 meters of that boat was losing zincs. A Bayliner in the next slip over from him even lost its trim tabs due to electrolysis. (Owner wasn't aware how to prevent electrolysis in trim tabs.)

When the scoutmaster refused to take responsibility for the damage that was being done to neighboring yachts, the neighborhood committee began unplugging his boat every night.

Every night.

Problem solved.
Why unplug it EVERY night when you can sink it one time then like a nice neighbor when the owner see;s it you can give him
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Old 03-01-2012, 09:05   #194
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Re: Neighbor dumping raw AC into water?...what to do?

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IANAL but I watched law and order "and" Miami Vice

- did you know about stay currents?
- yes
- would you say stray currents are a common occurrance?
- somewhat
- are there ways to shield against damage?
- yes
- were you advised to try them?
- yes

- Did you try them?
- No. But that guy is a meanie!
- (judge) Just answer the questions please
- do other people use these methods?
- yes
- (judge) dismissed. next case...
- but judge! There is no justice!
- I said next case...
- but judge! You are wrong!
- citation for contempt. Pay $200 do not pass go - Lunch!
It seems like many on this thread believe that an isolation transformer fully mitigates the leakage current problem. It will provide protection for metals on the boat, but serious leakage currents left uncorrected can kill you.

I prefer to find the source, measure their magnitude, and eliminate them.

Here is some documentation on the subject:

http://www.google.com/url?sa=t&rct=j...8uofNQ&cad=rja

Hot Marina - Lethal AC Ground Faults

http://www.iaei.org/magazine/2007/07...hock-drowning/

http://bluesea.com/files/resources/t...und_Faults.pdf
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Old 03-01-2012, 09:11   #195
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Re: Neighbor dumping raw AC into water?...what to do?

FYI & FWIW, virtually all electrocution drownings occur in freshwater, not saltwater.
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