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Old 14-06-2009, 10:59   #1
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Galvanic Isolator Installation

Since I have rewired my boat and added a VERY expensive Maxprop, I have decided to add a galvanic isolator. The wiring diagrams shows the GI in the green wire circuit between the shore power and the AC double pole breaker. On my boat, the SP goes to a terminal block way up in a narrow space (then to the breaker) and the Green ground wire terminal then has another green wire that goes to the boats DC neg buss. The space where the term block is very hard to get to and no place to maount the GI. However the green grounding wire that goes to the boats DC Neg buss is an easy reach.
Is there any reason the GI cannot be installed between(inserted) in the AC ground wire and the Boats DC neg buss connection? Single 30A SP circuit.
Seems the principal is to isolate the AC ground from the DC Neg buss with the GI.

And, there are $98 GI's (Yandina), $198 GI's (Guest and Newmar) and $398 GI's (ProSafe One). All 30A versions.
Will one work as well as the other?
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Old 14-06-2009, 18:44   #2
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The basics: The safety ground wire is designed to go from the shore power inlet to the AC safety ground bus. All AC loads on the boat have their safety ground wire tied to that same AC safety ground bus. This provides a redundant circuit back to the source, usually a transformer outside of the marina, for fault current. This redundant path will then trip a circuit breaker should a fault occur. In accordance with ABYC E-11, the vessel B- ground is to be electrically connected to the safety ground bus using a single conductor.

I am concerned with your comment: "However the green grounding wire that goes to the boats DC Neg buss is an easy reach." as, on the surface, it does not appear that your boat is wired in accordance with the basics above.

Since the first thing that your safety green wire "sees" after leaving the shore power inlet is the AC safety ground bus, you can put the GI any where along the conductor.

As far as the different manufacturer's of GI, you will get what you pay for. Either a GI with a monitoring system to ensure the integrity of the safety ground wire or a "fail-safe" are permitted by ABYC A-28. The "fail-safe" models are built of more robust components and are the ones that I recommend. The manufacturer with the most robust units, in my opinion, are those from Dairyland Electrical Industries: DEI Marine - Products

Hope this helps.
Charlie
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Old 14-06-2009, 19:31   #3
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GI

Quote:
Originally Posted by CharlieJ View Post
I am concerned with your comment: "However the green grounding wire that goes to the boats DC Neg buss is an easy reach." as, on the surface, it does not appear that your boat is wired in accordance with the basics above.

Since the first thing that your safety green wire "sees" after leaving the shore power inlet is the AC safety ground bus, you can put the GI any where along the conductor.

Charlie
Yes, I misspoke. It is wired correctly I believe. I will put the GI in the circuit path that runs from the AC safety groung to the Boats B- (DC neg buss)
Thanks
ps I looked at DEI but they appeared to be a UK only company. I will keep looking. Now I see they are US. My first search turned them up in the UK.
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Old 15-06-2009, 05:46   #4
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Quote:
Originally Posted by redcobra View Post
Yes, I misspoke. It is wired correctly I believe. I will put the GI in the circuit path that runs from the AC safety ground to the Boats B- (DC neg buss)
Put the GI between the shore power inlet and the safety ground bus. There is one tie between the safety ground bus and the vessel ground. Do not install the GI there. Remember; you are installing the GI to block galvanic currents from using the AC safety ground wire in the shore power cord as the conductor.

OK??

Best regards,
Charlie
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Old 15-06-2009, 06:04   #5
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Quote:
Originally Posted by CharlieJ View Post
Put the GI between the shore power inlet and the safety ground bus...
See also Marinco's Guide to AC Electrical Systems:
http://www.marinco.com/files/media/g...r%27sGuide.pdf
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Old 15-06-2009, 08:12   #6
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Got it Charlie. Thanks
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