Hello there halibutslayer,

I think there is a little misunderstanding about what a
galvanic isolator does. If constructed the usual way with
four diodes, the isolator will conduct AC AND DC, except
that until the voltage exceeds about 1.5 volts, it doesn't
conduct at all (simplification of course). Depending on the
design rating of the diodes and heat sink, it may conduct 30
or 50 or 200 amps AC, DC, or both, forever! Now this is an
isolator without any capacitors.

Add a capacitor and what happens? It will still conduct 30
or 50 or 200 amps AC, DC, or both, forever. What changes? It
will now conduct AC without the 1.5 volt threshold kicking
in. But depending on the capacitor chosen, the AC voltage
drop could be even more than 1.5 volts. Could be less. Who
knows? What does it matter? AC voltage can and does vary by
a lot more than a few volts without jeopardizing the safety
of the vessel. So there simply does not seem to be a safety
issue associated with making sure there is not a 1.5 volt AC
threshold, while allowing some other unspecified AC voltage
drop. No difference will be seen in the way fuses and
breakers and GFIs work, with or without a capacitor.

So are there any benefits to not having a capacitor? Maybe.
There is no such thing as a galvanic AC current, I guess,
but there can be an AC electrolytic current. Research
suggests these currents may be even more damaging than DC
currents. So from a corrosion perspective, it would be good
to block them from getting into the boat's green wire. An
isolator without a capacitor would at least block the
lower-voltage AC, but would allow the higher-voltage AC to
pass (once the 1.5 volt threshold was exceeded).

So where is the benefit to adding the capacitor? None that I
can see.

The only ways to fully provide for onboard safety and also
eliminate galvanic and electrolytic currents from traveling
through the green wire are to use an isolation transformer,
or don't bring shore power aboard.

Usually, a simple galvanic isolator is sufficient.


Regards,

Chuck