Steve Lusardi wrote:
I don't want to rain on your parade here, but bad shore power is very common
and the guy next door is not causing it. The problem is that there is at
least one consumer on your distribution transformer that has a current leak
to safety ground. In an ideal world that leak should flow to earth through
the neutral to safety earth connection at the distribution transformer, but
as you are in a marina and your hull earth is a lot better than the corroded
earth rod at the transformer, the energy leak is flowing through your hull.
That is the reason for using an isolation transformer. In any case never
connect the shore point safety earth to your hull. Do exactly like your
neighbor did, connect only phase and neutral. On your boat make certain all
safety earth connections connect to your hull only. It is just as safe for
YOU, but the dock has a serious SAFETY issue. Any person touching a dock
earthed point and the water could be shocked. This is NOT code, but the
shock is significantly less on your wallet.
Steve

wrote in message
oups.com...
There is another thtread about someone with a bad shore power
connection and what to do with it. I agree, the guy has no right to
endanger others. I consider myself to be a fairly knowledgeable person
but had never had my boat in a marina and never had shore power so I
was not familiar with the dangers. When cruising, we stayed in a
marina for the first time. I decided to swim to check my prop for
fouling as I always did.
The water felt really strange, sorta tingly all over. My shaft zinc
that had just been installed a month ago was nearly gone. I was in
mask and snorkel looking at it trying to figure it out when it suddenly
occurred to me, ELECTRICITY! I swam away from the boats without
touching anything and got out of the water at the shore. Sure enough,
the guy next to me had a bizarro shore power cord with two prongs, just
regular zip cord.




Hello Steve,

I would caution strongly against using the
water-earth path in lieu of the green equipment
grounding conductor. Ever.

The purpose of that conductor is to provide a low
impedance path for the purpose of clearing a
ground fault.

In proper wiring, the impedance is no more than a
few ohms and the fault is cleared at a breaker.
Fault current does NOT flow through the earth.

By contrast, the water-earth path may have a
resistance of 25 ohms or more for salt water, and
tens of thousands of ohms or more for fresh water.
This path will NOT clear a ground fault. It will
not trip a 20 A breaker. Witness the 120 volt
power cords dropped off a dock without tripping a
breaker!

If one has a problem with wiring impedances in the
marina, deal with it by getting the wiring
inspected. Ask the marina operator when it was
last checked. Yell. Scream. Buy your own tester
and tell the marina what you measured. Tell the
other boaters. Take names and publish on the
Internet. But don't throw out the safety net
because even with corroded connections, the wiring
may still allow a ground fault to be cleared.

If there is a problem with a nearby source (boat
or otherwise) then an isolation transformer would
be a good idea.

But even with an isolation transformer, always use
approved wiring practices. There is probably no
more thoroughly reviewed standard than the NEC.
The ABYC standards for AC wiring are similarly solid.

And install GFCIs for the smaller ground fault
currents that won't trip a regular breaker but can
electrocute.

Good luck.

Chuck



















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