wrote:
chuck wrote:
Terry K wrote:
Hmm.

Seems to me GFCIs pop if there is a difference between hot and neutral
wire currents. Don't rely on ground. If all the current that comes in
doesn't return the way it's supposed to, it turns off. It's a
differential amp that does it and toroidal coil assemblies. The test
button might need earth, so it can trip the circuit by cheating. Proper
ones don't.

GFCIs work at 125 volts only so they are usually
not the sole solution.

The Earth should not be electrified, nor the Sea neither. It's bad
enough that we might inadverdently offer the possibility for current to
flow into the earth by touching a live wire, but if the power company
hadn't hooked the earth to the power line, it's wouldn't have any where
to leak to whilst electrocuting you.

Aboard, if metal parts are earthed, earth the plug,
Disagree. Any appliance with a 3-prong plug will
lose the protection built into it if the ground
wire is not connected, unless it is protected by a
GFCI. But if that appliance develops a ground
fault (hot wire shorted directly to metal case) it
will not trip the GFCI unless some one or thing
provides a path to earth. Meanwhile, if it is,
say, an electric drill (3-prong plug), you are
walking around your boat holding the hot 125 vac
wire in your hand!

Surely we don't want to be suggesting that people
"game" the wiring system and thereby disable
built-in protections.

Chuck



otherwise, it
don't matter. Sea water in the bilge sort of grounds wet stuff, but
it's moot.

There are several possible faults that are best protected by
contradictory means. It's a question of probability and risk
assessment.

It's your boat. Read your insurance documents for electrical
requirements, survey report required? Marinas don't seem to care. Old
boats may be grandfathered. Fire is the real danger.

Terry K

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I dont even have any connections for shore power so am not sure how my
boat was making any sort of connection. I'd never spent any time in a
marina so didnt know swimming near other boats was an issue till then.


It's difficult to speculate intelligently, but AC
is thought to be much less of a problem in causing
galvanic corrosion than DC, so I would concentrate
on finding a DC current path to explain the rapid
zinc depletion. Being in the field of an impressed
current system on a larger vessel could do it, for
example.

AC fields in salt water usually don't cause safety
problems for swimmers because the swimmer's body
is effectively shorted out by the much greater
conductivity of the surrounding seawater. Imagine
(but don't do it!) standing on an insulating
surface and touching a bare, hot 120 VAC wire with
both hands 1 foot apart. Since the resistance of
the wire is so much less than the body's
resistance, you feel nothing and live to tell
about it. A swimmer in a strong electrical field
in sal****er experiences the same effect. In fresh
water, however, you'd be toast.

Chuck

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