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Old 29-10-2010, 18:12   #1
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Galvanic Isolators

As most of you have already read, galvanic isolators are discussed in this month's Sail Magazine. Ever since I found my zincs nearly gone after only 1.5 years in fresh water, I have been worried about "scavenger boats". This article only fueled the flames.

My question for you is... What product/company do you trust? Article highlighted Guest/Marinco isolators. I am not an electrician, but am fully aware that like most things in life there are Chevy's and there are Cadillac's.

Todd
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Old 29-10-2010, 18:45   #2
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These are without a doubt the best. magazines tend to favor the advertisers products.
Home | DEI Marine
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Old 29-10-2010, 19:45   #3
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I recently got the one that one that was on eBay. I don't think a galvanic isolator is that complex a product. But take my opinion here with a hefty grain of salt. I haven't much experience with them at all.

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Old 29-10-2010, 21:16   #4
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The DEI GI that Wayne referenced is the only one I will install. They are absolutely superior to everything else on the market. This company has been in the GI business for years protecting pipelines and all manner of underground and underwater structures. There product is designed to fail safe; i.e., if the unit is hit by a surge, it will fail shut. You will still have a lifesaving connection to safety ground but you will no longer have GI.

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Old 29-10-2010, 21:23   #5
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I guess I'm old fashioned, nothing but an isolating transformer will do for me, of course I have an aluminium boat so I need to be sure there is no way stray currents can make their way on board.
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Old 30-10-2010, 09:31   #6
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This will probably be frowned upon, but I made my own GI after seeing an article in PBO on how to do this. Its rated for 50amps, (more than adequate for UK marina's), but has no indicators or failsafe. I rarely use shore power now that I have a decent wind geny fitted.
Having read alot on GI's since I made my own, a proper failsafe model with LED fault indicators is on next years budget
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Old 30-10-2010, 10:06   #7
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Quote:
Originally Posted by Wakadui View Post
As most of you have already read, galvanic isolators are discussed in this month's Sail Magazine. Ever since I found my zincs nearly gone after only 1.5 years in fresh water, I have been worried about "scavenger boats". This article only fueled the flames.


Todd
Todd,

You say your zincs are going in Fresh Water?? That water couldn't be too fresh. Mine has lasted 22 years in fresh water. Now I know many say you should use manganese anodes in fresh water but here in the Great Lakes everyone uses zincs and I have not heard of anyone having a problem. It's really a surprise to Great Lakes sailors when they head south and the anodes disappear.
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Old 30-10-2010, 10:22   #8
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There's nothing seriously wrong if zincs are disappearing in fresh water

Dave
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Old 30-10-2010, 12:00   #9
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If your zincs are going in 1.5 years then you're all good. That's a very slow rate of wastage (mine are gone in 4 months, and that with an isolation transformer), but since they're wasting at all, you know they're working. Don't worry, be happy.
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Old 30-10-2010, 17:44   #10
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Galvanic isolators and isolation transformers do not protect the boat from stray current through the cable TV and telephone wires.
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Old 31-10-2010, 16:23   #11
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Galvanic isolators and isolation transformers do not protect the boat from stray current through the cable TV and telephone wires.
Neither cable TV nor telephone devices are connected to boat ground. Hence, there will not be galvanic problems from these connections.

Stray current tranverses the boat due to bonding the thru hulls.
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Old 04-11-2010, 06:14   #12
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Neither cable TV nor telephone devices are connected to boat ground.
Not generally, but connection does happen and these connections to land must be investigated as part of a corrosion survey.

Quote:
Stray current tranverses the boat due to bonding the thru hulls.
Incorrect. If a vessel had unbonded through hulls and the through hulls were in bilge water, an errant B+ connection in the bilge water (failed submersible pump, failed bilge pump float switch, failed insulation on the conductor) would cause stray current corrosion on the through hulls.

There is a lot of "dock knowledge" that is just plain wrong in dealing with galvanic and stray corrosion issues.

Charlie
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Old 04-11-2010, 06:30   #13
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Not generally, but connection does happen and these connections to land must be investigated as part of a corrosion survey.


Incorrect. If a vessel had unbonded through hulls and the through hulls were in bilge water, an errant B+ connection in the bilge water (failed submersible pump, failed bilge pump float switch, failed insulation on the conductor) would cause stray current corrosion on the through hulls.

There is a lot of "dock knowledge" that is just plain wrong in dealing with galvanic and stray corrosion issues.

Charlie
I don't disagree. My statements are from a 'no equipment faults' POV.
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