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From: Arild Jensen (no email)
Date: Mon Jun 11 2007 - 10:56:04 EDT
-----Original Message-----
From: Gene Gruender
I have a good friend who drowned recently due to just this type of stray
current in a marina. They never were able to determine where it came from.
I will never again swim around a bunch of boats in a marina.
Gene Gruender
Sun Chaser
There is very good reasons for why most marinas are posted - NO SWIMMING!
Al it takes is one transient boat with faulty wiring. Or a correctly
wired boat with one household appliance aboard.
UL/CSA certification requires household appliances to have the white and
green wires tied together and connected to the metal shell.
In a perfectly wired boat completely compliant with ABYC this single item
will now dump AC current into the water.
WHY??
Because the return current that normally follows the white wire back to
shore now splits between the white and green wire at the point where they
are tied to the metal shell of the appliance.
The current following the green wire now goes to the ground bus and then
to the bonding system that ABYC requires to be installed in boats. From
there the current exits into the water and tries to return to the ground
rod located next to the marina power transformer. Result - any swimmes in
the water can experience muscular paralysis. And that only requires a few
milliamperes. Less current than wha tis needd to induce cardiac arrest.
Muscular paralysis stops the swimmer from breathing and moving their limbs
to swim. - Result, they drown; even though they did not suffer a heart
attack.
Anchored boats with a genset running can also create a similar situation.
If current is dumped into the water at one end of th eboat the stray current
will atempt to return to the genset by way of any convenient thru hul
lfiting. Anyone swimming in proximity to the hull may get into this strema
of current flowing back t othe genreator from a thru hul lfiting located at
the extreme end of the boat - as an example Or maybe from one side of boat
to the other.
For instance, runnign the genset to drive A/C or charge batteries and then
someone decides to clean the hull while boat is anchored.
regards
Arild
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