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Old 04-18-2019, 03:46 PM   #2
STB
Guru
 
City: Gulf coast
Join Date: Aug 2016
Posts: 2,271
I think you want the galvanic isolator as close to the shore power inlet as is reasonably possible given the need to keep it dry, etc.

In some sense, it doesn't matter where it is, as long as it isolates the boat's ground from the earth ground(*), thereby preventing your boat's zincs (or less noble metals in useful components!!!) from getting consumed protecting your neighbors' boats that share the same earth ground.

There may be other reasons that aren't coming to my mind, but i think the big reason one wants it close to the shore inlet is just to prevent it from accidentally getting bypassed. If any ground bypasses it, by intention or accident, since they are all tied together, everything has bypassed it.

(*) One does want the boat's ground to be tied to the shore ground for safety reasons, which is why the galvanic isolators only isolate up to ~1.4V -- allowing the ground to function normally for safety beyond that. In this way, they provide isolation for the low voltages stray currents that cause corrosion -- but a ground path for the high voltage electrical problems that could otherwise kill someone.
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