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GFCI / Galvanic Isolator Problem
OK, troubleshooters, see if you can point me in the right direction.
A customer came into the yard with a severely (and I do mean SEVERELY) eroded sail drive unit...It's a J-1o9 / Yanmar...fairly new, maybe 6-9 mos...even smells new. He had brought the boat to SF from Santa Barbara several months ago and docked her at a local marina. Divers had never noticed anything amiss during routine cleaning either in Santa Barbara or here, and his zinc(s) were always reported to be in reasonable condition, and were replaced when necessary. However, he, for some reason moved his boat to another private marina, or dock, and that's when the fun began.
I immediately suspected he had a Galvanic Isolator problem...that is, no Isolator; but in fact he does, a good one too, though I forget the brand at the moment...don't know about capacitors, they're usually fairly large, and I 'm reasonably sure this unit doesn't have one, but it does have a rather elaborate monitoring system. All well and good, except...
Whenever I plug into the yard's power, I trip the GFCI. Not the AC breaker, but the GFCI. I know this should point me squarely at a leakage between the neutral and ground. There are only three AC branch circuits: Water heater, Battery charger, and Outlets. So I dutifully removed each of the neutrals in turn from their buss until I could get the power to stay on long enough to think I had it (water heater) licked. Disconnected the heater, re connected the others, but no cigar...stays on long enough for me to turn on the charger on but that's it
Anyway, this can't be that difficult...I'm probably not seeing the forest for the trees. Any and all suggestions welcome.
BTW, I measure >5m between neut and gnd with main AC ON; >40M when off.