Next message: (no name): "Re: lv-ab: suggestions for upgrading the AC circuitry?"
I believe there are two schools of thought here, due to two different
problems that can occur depending on whether you hook them together or
not.
If you are taking AC power from the marina, and you tie their ground to
your boat's DC ground, i.e., engine, keel, etc., then if the marina's
"ground" is not at the same "ground" potential as the water around you,
you risk not only plating your propeller to the dock, but also
electrocuting anyone in the water around your boat.
On the other hand, if you do not tie them together then you are in
danger of becoming the missing link yourself between your onboard AC
appliances and anything that is tied to your boat's DC ground.
I was doing some electrical work on a friend's 56' aluminum one-time
America's Cup contender in Portland Maine, and noticed that when I
touched the green safety ground coming directly from the dock power to
an aluminum bulkhead I got a nice fat blue spark. I did not measure it,
but judging from the energy of the spark each time I touched the wire to
the bulkhead, there was considerable voltage and current involved
there. In his case the price could have been that his entire boat would
end up plated to the dock, so I left it disconnected and recommended
that he consult with the dockmaster to figure out why their "ground" was
so far about earth potential. I wish I could tell you the outcome, but
I never heard.
I think an isolation transformer for power, and everything grounded to
the hull/DC ground, might provide good all-round protection.
Dick
> While we are on the subject of AC and grounds, what is everyones opinion of
> tieing the AC ground and the DC bonding system together.
>
> Caulder (Sp?) in his book advocates them being tied together, other opinion
> I have heard says not to.
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