Russell wrote:
Thanks all. Here is more info. I called the harbor master's office.
They had a consultant test all the boats in the marina. Over 100 boats
were found to have the same situation as mine and we were all given ten
day notices, to correct, unplug from shorepower or remove the boat from
the marina. The test showed "power cord ground terminal grounded to
through-hulls". I am not sure how they tested, but isn't the same
ground connected to the shafts? And if the AC ground goes to the engine
DC ground post, as ABYC requires, and I assume all our boats comply,
then wouldn't the AC ground by definition then be connected to anything
on the ground strap which is everthing metal on my boat, including the
through hulls. This is all very confusing and seaches on Google bring
up a lot of data, but not a consensus. I would think, to comply with
the marina demand, we would all have to break any connection between
any metal in the water and the AC ground. But to do that, we would have
to remove the AC ground from the engine DC ground, and that is very
dangerous and violates ABYC and every other code. Any ideas?

chuck wrote:
Andina Marie wrote:
Russell wrote:
We have been eating up zincs, and just had to replace both props. Had
the marina check and they said the power cord gound terminals on our
twin inboard were grounded to the thru hulls. This is in sal****er.
Any ideas on what could be going on, why this is an issue and what to
do to correct it?
For safety reasons, the ABYC specifications call for the shore power
cord to be grounded to the DC ground
OK

which
includes the underwater
metal attached to the engine(s).

I don't think ABYC actually requires this part. It
is often done, but not always.

There is an increasing number of new boats that
are designed with electrically isolated props and
shafts. Without a connection to the shore power
ground, there is little chance for galvanic
currents to be set up with a neighboring boat. In
fact, even through-hulls can be electrically isolated.

It is actually a safe and trouble-free approach,
but it requires an insulating shaft coupler. And,
of course, some special attention to an RF ground,
if there is one. Usually a capacitor with high
reactance at 60 Hz can effectively isolate the
grounding plate.

Chuck

Your cheapest protection is a galvanic isolator. They are on sale for
under $100 at Defender
http://www.defender.com/product.jsp?path=-1|328|303336&id=605562
One isolator can handle a 50 amp shore cord or two 30 amp.

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Hello Russell,

I'm completely baffled!

First, it is nearly impossible and quite a pain to
determine where a power cord ground terminal is
connected to the water unless the boats were
boarded by the consultant. I strongly doubt they
were able to actually establish that claim.

Second, I have no idea why grounding at the
through-hull would trouble the marina or their
consultant. After all, the green wire is grounded
on shore. I suppose they had no suggestions as to
where it "should" be grounded.

Third, taking your posting literally, it appears
the consultant tested the boats, and not the
marina's wiring.

I would think that as a marina customer, you
should be entitled to more of an explanation. For
example, can the marina or the consultant cite any
authority or standard that supports their action.
If there are 100 of you, take up a small
collection and hire your own consultant. You may
even have a legal case. ;-(

To the best of my knowledge, there is no authority
or standard to which boats must adhere in their
wiring. The NEC's jurisdiction is thought to stop
at the dock pedestal. The ABYC standards are
voluntary, although insurance companies may
require compliance with them.

Good luck.

Chuck







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