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post #1 of 7 Old 05-19-2011 Thread Starter
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Wiring a galvanic isolator

I have Glendinning cables which come in the transom and connect to a dedicated circuit breaker box in the lazarette. From there, the power goes to the main panel at the nav station. I am going to add an isolator before the breaker box. My thought is to open the box, remove the ground and add a piece of 10g green ground wire to exit the box, run to the isolator and then another from the isolator to return to the box and reconnect to the breaker post. This would keep me from having to open the shielding around the current cables that are nicely run into the back of the breaker box.

In order to do this, I would have to splice the extension onto the end of the existing cable inside the breaker box. I would use proper marine grade connectors, but I've always thought that splicing 110v wires was a bad idea.

Any thoughts or alternatives?


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post #2 of 7 Old 05-19-2011
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You are likely to need to make two splices in the ground wire to make the connection to the Galvanic Isolator. One to go from the box to the GI, and one from the GI to box.

If it were my boat, I would find a spot to mount the GI somewhere convenient in the lazerette. I would then cut about a foot of the outer jacket (there is no shielding) off of the power cable between the shore power connector and the breaker box, cut the ground wire in the middle of where you removed the outer jacket, crimp two appropriately sized lugs onto the ground wire, and button it up. Actually, this is what I did!

I found a spot in the lazerette that is above the hatch, so it is unlikely to get very wet, unless I capsize. In which case I'll be dealing with other issues...


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The return wire from the GI would not really need a splice, it would go from the GI directly to the breaker directly. If I open the jacket, I was concerned that there wouldn't be enough length to reach the GI in its only available mounting location.


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post #4 of 7 Old 05-19-2011
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I'm not at all sure of the spacing on your boat, but I would suggest disconecting the shore power form the breaker box. Install a new junction box, or a larger box, and then run the shore cable wires to the isolator, adding a new piece of wire (possibly cut from the one you have, if that works out long enough) to tie the new box back to the existing breakers.

In AC electrical work, and most land-based codes, you don't run splices in the AC wiring. Everything is joined inside boxes, and only continuous wire runs go from box to box. I have no idea what marine codes call for but would expect the same underlying logic to apply.

Either a new water-tight box, or a larger one for the breakers.

A conventional landlubberly electrical supply house actually SHOULD have waterproof boxes, they would be referred to as "explosion safe/proof" or "BOM" Bureau of Mines /DOT certified for use in explosive atmospheres (i.e. around gasoline and methane) if you can't find plain old fashioned "exterior" waterproof ones. Waterproof/exterior stuff usually isn't quite as waterPROOF.
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post #5 of 7 Old 05-19-2011
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On land it would be NEMA 4 Water Tight & Dust Tight - Indoors/Outdoors

Or NEMA 4x Water Tight, Dust Tight, & Corrosion Resistant - Indoors/Outdoors

Lot of nice plastic ones at good prices as you dont want to know what a SS one cost


The explosive deal is a whole nother deal and much stricter on land

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post #6 of 7 Old 05-19-2011
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Quote:
Originally Posted by Minnewaska View Post
The return wire from the GI would not really need a splice, it would go from the GI directly to the breaker directly. If I open the jacket, I was concerned that there wouldn't be enough length to reach the GI in its only available mounting location.
Why not run new wire of adequate length? 8/3 (which is what I have for the connection between my shore power inlet, and the breaker panel) is $2.64/ft here (shipping included). You might need 20', which would be $53...

The GI probably cost you $200.

Also, if you choose to do it the way I suggest, seal the ends of the outer jacket where you cut into it for the GI. Try to keep moisture from wicking up the strain relief (which is usually twine). I used rubber splicing tape to do this, but silicone would probably be OK.
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post #7 of 7 Old 05-22-2011
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Here's a post with pictures of an installation.

Installing a galvanic isolator - Yachting and Boating World Forums
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