wrote:
Russell wrote:
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?

You should also be able to install an isolator on your boat, if it does
not already have one, and be in compliance of isolating the ground to
electrolysis.

If an isolator will not function properly in the marina then there is a
problem with the marinas wiring, which sounds highly suspect to start
with.

Ask for the details of how the hired electrician has determined that
your boat is causing problems and let us know what he says. What kind
of measurements did he do?

Regards
Gary


I agree.

Even though we usually think of galvanic
isolators as protection from a corrosive
galvanic couple set up by an unprotected
boat nearby, it's worth remembering that
they also work the other way.

If an unprotected boat installs a
galvanic isolator, then nearby boats,
even those without galvanic isolators,
will not lose their zinc to the
unprotected boat through the shore power
grounding connector.

Chuck

wrote in news:1150690300.254639.300810
@u72g2000cwu.googlegroups.com:

The boat still needs 3 wires just like before. One side of the
secondary of the isolation transformer will now go to the BOATS ground
system, including the green ground wire on the boat. The secondary of
the isolation transformer is treated the same way as your generator
system when feeding the boat.

Regards
Gary




My point being the boat is no longer connected to MARINA GROUND,
eliminating the electrolysis problem.

The damned cheap marinas should be built with them in every dock post...

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!

There is another issue that hasn't been addressed by the group. That issue
is in-rush current when connecting an isolation transformer. The problem can
be severe if the transformer is correctly sized. I use a transformer that I
had custom made for me in Ankara, Turkey. It is 10 KW and it can use shore
power from 100V to 280V on either 50 or 60 Hz so it is usable anywhere in
the world. The problem is how to keep the in-rush current from popping the
service breaker and one answer is a light bulb in series with the primary.
Once power has been applied, simply throw a shorting switch bypassing the
light bulb before using a load.
Steve

"Larry" wrote in message
...
"Glenn Ashmore" wrote in news:tbnlg.112499$Ce1.112216
@dukeread01:

Definitely mount it on the boat. Once you make a place for it to mount
wiring it up is simple but I wish I could find a Charles transformer
for
less than $500. I need two and the best price I have found is $670
each.



Hmm....50A service at 120VAC = 6 KVA.

http://www.charlesindustries.com/main/ma_iso_bost.html
16" x 15" x 12" and weighs 155 lbs....about as much as one passenger.

Can't put it in the bilge where it'll rot in the wet, but try to keep it
as low as possible and near centerline so you don't lean over too far.

Here....justification!:

http://www.charlesindustries.com/main/ma_iso_bost.html

"The Isolation Transformer
The ABYC defines an Isolation Transformer as a
transformer installed in the shore power supply circuit on a
boat to electrically isolate all AC system conductors, including
the AC green grounding conductor on the boat from the
AC system conductors of the shore power supply.
If we are bringing AC shore power aboard to an
electrical panel on a boat, a marine grade Isolation
Transformer should always be used in the shore power
circuit where it comes aboard, and before it reaches the
AC distribution panel or any other device aboard.
The AC shore power current passes through the
transformer's primary windings only, and induces a
current in the secondary windings, which supply the
boat. Primary and secondary windings are insulated
from each other, and a ground fault on the shore side
will not involve our boat.
At its simplest form, a transformer consists of two
coils of wire in close proximity but electrically isolated
from each other, usually wrapped around a common
metal core to contain the magnetic fields produced. If an
alternating current is applied to one of the coils, it will
induce a similar current in the other coil.
Most transformers are designed to step voltage up
or down by having differing numbers of turns in the
two coils. An isolation transformer has the same number
of turns in each coil, serving only to isolate the boat
from the shoreside power, but to give the same voltage.
An Isolation Transformer is used because the shoreside
AC power is referenced to ground. If you are connected
to the earth and you touch the "hot" lead of a normal
shoreside AC service, you will get shocked.
The isolation transformer removes the ground
reference from the ship's service. Neither of the two
sides of an AC circuit on the boat is at ground potential.
Therefore you must contact both sides of the onboard
supply to shock yourself."

I had a diver under the boat today. This boat was in the yard ten weeks
ago. New shafts, props, all new zincs everywhere (tabs, rudders,
shafts, transom, etc.). The diver reports the ZINCS ARE GONE!!! Even
most of the bolts are gone or just hanging. How can this be happening?
If it is another boat, what can I do to find it or to protect against
it without exposing anyone on my boat to AC shock. In the meantime, we
are unplugging from shore power, which is scary, although our bilges
are pretty dry. I read all the posts, but am still confused on whether
it is AC or DC related, and if the isoloation transformer has any
impact. Oh, one more thing. We had a new computerized charger installed
a while back. I wonder if it were wired incorrectly would that cause
the zincs to go like this?

Russell wrote:
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?

"Steve Lusardi" wrote in
:

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


Correct. The boat must NOT be connected to dock ground to stop the
underwater fizzing...(c;

"Steve Lusardi" wrote in
:

It is 10 KW and it can use shore
power from 100V to 280V on either 50 or 60 Hz so it is usable anywhere
in the world.

The modern way of creating a wide ranging, DC to radio frequency
isolation "transformer" isn't a transformer at all......

Whatever input AC voltage and frequency is available over a very wide
range is simply "consumed" by a full wave bridge rectifier and low
frequency DC filter, the same as the power supply in your desktop
computer. The resultant unregulated DC, now from 80 to 400VDC is fed to
a high-powered switching inverter, like your battery-powered inverter,
that feeds off whatever DC is available from the rectifier-filter. Its
output frequency is crystal-controlled, its output sinewave is sampled,
measured and the results are fed back to the inverter's control IC, which
determines the pulse width of the inverter's high powered, high voltage
transistor switching array. Over the range of loads from no load to the
capacity of the unit, output is a virtual sinewave at exactly 60 Hz,
voltage regulated to be rock steady. Because such electronics uses a
high frequency switching system with very lightweight toroid
transformers, unlike the old magnetic transformers, you don't need a fork
lift to haul them down the dock, even though they will create 10KW or
more of stable AC power, completely isolated from the power company and
ground.

This is exactly how the new inverter gensets, like my Honda EU3000i 3KW
work. The "generator" is a very high frequency, permanent magnet, 6
phase alternator built into the flywheel of a 6.5 hp, 1-cyl, computer
controlled by the inverter, engine. It looks just like the stator
windings on an outboard motor it was copied from. Being very high
frequency, in the kilocycle range, the size of the magnetic parts becomes
very small and lightweight. The inverter behind the power outlets merely
rectifies and filters it into DC to run the modified sine inverter from,
instead of rectifing the AC line in the paragraph above.

Switchers are very neat, very efficient pieces of electronic art....(c;

"Russell" wrote in news:1150917215.062248.50070
@p79g2000cwp.googlegroups.com:

I had a diver under the boat today. This boat was in the yard ten weeks
ago. New shafts, props, all new zincs everywhere (tabs, rudders,
shafts, transom, etc.). The diver reports the ZINCS ARE GONE!!! Even
most of the bolts are gone or just hanging. How can this be happening?
If it is another boat, what can I do to find it or to protect against
it without exposing anyone on my boat to AC shock. In the meantime, we
are unplugging from shore power, which is scary, although our bilges
are pretty dry. I read all the posts, but am still confused on whether
it is AC or DC related, and if the isoloation transformer has any
impact. Oh, one more thing. We had a new computerized charger installed
a while back. I wonder if it were wired incorrectly would that cause
the zincs to go like this?



It is DC related because your underwater metal parts are hooked directly
to the electrical system on the dock's ground wire. This amounts to
running a wire from your engine block and underwater metals to every
other boat's underwater metals and the entire bottom of the bay. This
results in some horrific electrolysis currents, you zincs trying to
provide noble metal to protect the whole marina, not just your skeg and
prop, eating it away at an amazing pace. When the zinc was gone, the
next least noble metal started to be used as the underwater battery plate
in the shorted system.

Get a digital multimeter from someone. Unplug the boat at the dock post.
Put the digital multimeter on DC volts. Put one lead of the meter on the
boat's now-open ground pin in the boat power plug. Put the other meter
lead on the ground lug (or the metal electrical box bare metal which is
the same point). You will now measure the DC potential difference
between your boat's underwater metal parts, hooked to the ground pin of
the boat's power plug...and the rest of the world hooked to the marina
ground, including every other boat that's wired like yours is.

This voltage will be around 1-2 volts DC, not AC. Any AC voltage you can
measure at this point indicates something is bad wrong with the marina's
electrical system. There should be no AC voltage between their ground
and your boat's connection to seawater...the underwater metals that are
"grounded" to AC ground.

If you want to see how much current flows when the boat's plugged in,
switch the digital multimeter to DC amps. The internal low-resistance
shunt in the multimeter is a virtual short, allowing the boat and AC
power system to conduct like it was plugged in. That current you see is
why your zincs are eating away just before the nice prop was.....

Many problems are caused by the boaters themselves. One boat has a
faulty battery charger leaking between the DC output and the charger's
ground back to the dock. This results in some DC voltage applied to that
boat's underwater metal parts, much more voltage than just zincs can
produce and, probably the wrong polarity. His boat is now acting like a
PLATING MACHINE!....using your zincs to plate his prop! Some other boat
hasn't had a zinc in years so his boat causes a big potential difference
to yours and others. To find the offender, you need one person standing
watching your DC voltmeter reading high and another person going down the
dock, NOT SWITCHING BREAKERS ON AND OFF, but unplugging boats, one after
another. FRS walkie talkies make this job much easier than yelling
between you. When you unplug the offender, the voltage back on your dock
drops drastically. THAT guy is eating everyone's zincs and props. Show
the marina dockmaster who has a very good reason to get him OFF YOUR GRID
as it's eating the marina's electrical system, too!

Let us know which boat has the flea market automatic battery charger when
you find him..... Japanese battery chargers some have POSITIVE DC hooked
to AC ground!....the only AC ground point on his boat so it doesn't short
his batteries to operate that way. His prop is +14.2V above
yours!...lotsa ground current flows!

Russell wrote:
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?

Russ,

I've never heard such garbage in my life. Lets get this straight, they
have a problem with their wiring, and they want you to pay for it? No
way.

While on the subject, would someone please explain the difference
between an Isolation Transformer and a Galvanic Isolator? Do they do
different things? Is one better to have than the other?

Thanks,

Gary