Larry,
You are correct, but the correct method of connecting an isolation
transformer is to use the safety earth at the dock only on the primary side
which must be isolated from the hull.
Steve

"Larry" wrote in message
...
"Russell" wrote in news:1150664559.195111.128480
@h76g2000cwa.googlegroups.com:

Since my post a few days ago, spoke to our marine electrician and the
on-staff electrical expert retained by the Harbor office. We are going
to have to install an isolation transformer in our dock box. This will
cost about $1,000 after parts, labor and some mods to the box. All 90
boats in our harbor that got the notices have to do this, move, or
unplug or disconnect the AC ground from the DC, not a good option.
So, now I see the West Advisor says that apparently solves the marina's
issue with the AC, but unless we separate all the underwater stuff,
like the through hulls, we still are subject to DC corrosion. Can this
be true? What is the real solution to the AC, the DC, the safety and
the corrosion problem? Is there one? We are one of 90 modest boats from
about 28-48 feet, mostly 1970's through 1990's vintage. We all have to
get these transformers now, but the issue is what else do we need to do
once we are on the transformer?



As long as the AC ground on the dock is connected to the DC ground, and
therefore all the underwater metal parts of the boat, the electrolysis
problems caused by your boat being connected to the earth and all the
other boats so connected WILL CONTINUE UNABATED, isolation transformers
or no isolation transformers! It's a BATTERY made up of your metal
parts, the seawater as electrolyte and the marina metal parts, including
the bottom of the harbor the marina is grounded to! You have, by
shorting your plate of the battery to the marina plate of the battery,
SHORTED OUT THE ELECTROLYSIS BATTERY and its plate is going to be EATEN
in the process. AC power is not required to accomplish this, only
CHEMISTRY, basic battery chemistry.

Now, the secondary winding of the isolation transformer HAS NO GROUND
WHATSOEVER, if it is an isolation transformer it isolates its AC power
from GROUND. So, you may touch ANY grounded anything, including the AC
power ground wire of the power company itself, from EITHER side of the AC
output winding of the isolation transformer and you WON'T GET SHOCKED!
That's why we call it an ISOLATION transformer....it isolates the AC
power going to the boat from GROUND.

Once the AC power supply to the boat has no ground connection,
whatsoever, you can fully disconnect the boat from shore ground,
altogether, and noone will get a shock UNLESS THEY CONNECT THEMSELVES
STRAIGHT ACROSS THE TWO OUTPUT WIRES OF THE ISOLATION TRANSFORMER WHERE
THE POWER HAPPENS. There are NO other circuits for current to flow
through!

The only connection from the primary side to the secondary side of an
isolation transformer is MAGNETISM IN THE CORE. There are special
insulating tapes put between the core of the transformer and the windings
to PREVENT any path between them.

Geez....this ISN'T ROCKET SCIENCE! Disconnect the damned shore ground
from the boat and install the isolation transformer with no secondary
ground and it'll be JUST FINE FOR ALL!

Once the isolation transformer is between the boat and the power company,
the boat only needs TWO WIRES!..the ones to the secondary 120VAC winding!