I posted this on another bulletin where a contributor had bonded all
his underwater metal with 1" copper straps and needed to test. Copied
here for anyone having electrolysis problems.

An ohm meter is a poor way to check bonding connections. I use a 12
volt lamp and make a probe using a screwdriver. Hook a long enough
wire to the positive terminal of the starting battery and then poke
the screwdriver into each of the through hull fittings and make sure
the lamp lights. An ohm meter is only testing the circuit at micro-
amps.

The following applies mainly to boats left in the water. Trailered
boats rarely spend enough time in the water for electrolysis to be a
problem.

ELECTROLYSIS 101. I've worked with electrolysis for 18 years
including live-aboard on a steel yacht for 14. We have sold thousands
of our galvanic isolators and handle numerous emails/phone calls daily
on electrolysis situations.

BONDING STRAPS

Although your copper straps look impressive they are totally
unnecessary. The wire at the most only carries a few milliamps and
there is no concern for voltage drop so the copper only needs to be
heavy enough to resist deterioration from oxidation. A 10 gauge
copper wire is more than adequate. I use non stranded 10 gauge bare
copper wire for my installations, being careful to secure it so it is
not subject to flexing from boat motion. Non stranded wire has much
less surface area and avoids the cavities between the strands where
moisture and corrosion/oxidation can progress.

THEORY

Electrolysis only happens when two dissimilar metals are immersed in
an electrolyte and connected together. The dissimilar metals have
different electrolysis voltages so if you connect them together
current flows through the connecting wire one direction and through
the water the other. As the current leaves one metal to travel to the
other, it causes metal to come off one surface and be deposited on the
other like battery plates so the higher voltage metal suffers
electrolysis. Electrolysis can also occur when an adjacent structure
or boat is injecting DC current into the water and that current goes
in one end of your boat and out the other on its way to the
destination. This can cause electrolysis even though your boat is not
an offender.

PROTECTION

There are basically 2 ways to reduce electrolysis. The PREFERABLE one
is to DISCONNECT the electrical circuit. If this can't be done, the
second method is to provide a sacrificial anode (Zinc) so it
deteriorates rather than your expensive equipment.

a) DISCONNECTING

Electrolysis cannot occur on an isolated piece of metal in salt
water. It is all at the same voltage but if it is isolated no current
can flow so there is no electrolysis. When it is connected to another
piece of metal, ESPECIALLY if the other piece is a different metal,
you just created a shorted battery and electrolysis will start. By
following the wrong advise and bonding everything in the boat you are
creating batteries where it is unnecessary and making electrolysis
problems worse.

ANN-MARIE'S RULE #1. Only bond underwater items that are showing
symptoms of electrolysis. If it ain't broke, DON'T fix it. Once you
bond it unnecessarily you have CREATED the circuit rather than
DISCONNECTING it. You are now stuck with providing Zincs since you
have removed the first line of protection.

Although some through hulls appear to be isolated due to sitting in
fiberglass and using non-metallic tubing, they quite often are not and
WILL need bonding. For example the raw water cooling inlet for an
inboard engine is in fact connected to the engine block by the salt
water in the tubing and may need bonding so the current flows though
copper rather than the water and in/out of the through hull.

b) SACRIFICIAL ZINC

There are situations where different metals cannot be disconnected and
you are stuck with putting zincs on them to provided a target for the
electrolysis. Zincs have a higher electrolytic voltage than marine
metals so it is the first to deteriorate.

Keep in mind that the zinc will CREATE electrolysis (favorable
electrolysis since the zinc is being eaten up). Putting zincs where
they were not needed will still cause the zincs to erode away since
they create the battery situation where none may have existed.

The range of protection a zinc can supply to other metals bonded to it
is limited by the conductivity of the water. In salt water you get
coverage for a radius of about 4 to 6 feet. A zinc on the stern of a
14 ft boat where everything is bonded is only protecting half the
boat. This range gets even less in fresh water and may reduce to only
inches. Often magnesium is substituted for zinc in fresh water to
provide an even higher voltage to push through the fresh water.

USE A CONDOM

Over 90% of our customers electrolysis problems are created by the
shore power connection. You could theoretically disconnect the ground
connection in the shore power and avoid electrolysis (and in some
cases this is a solution) but ABYC regulations require the AC ground
be connected to the DC ground so an electrical fault on the boat won't
electrocute swimmers in the vicinity.

When you connect your underwater metal to the shore power ground you
have "bonded" with every other boat on the docks who have the same
connection. Now electrolysis currents are free to flow anywhere in
the marina and it only takes one boat with a 12 volt DC leakage to eat
up every boat within a wide radius even though the offender has zero
electrolysis evidence.

Your protection is a Galvanic Isolator in the ground connection of the
shore power lead. You don't have to purchase ours (although they are
typically less than 1/2 the price of our competitors). Any Galvanic
Isolator that meets AYBC specifications will do - they are not rocket
science and extremely reliable. We have sold thousands, all on
unconditional warranty and have never had a return due to failure.

Feel free to ask general interest questions here or email me if you
prefer.

On Jan 6, 6:06 am, "Steve Lusardi" wrote:
Andina,
I found your synopsis of this issue very good. This problem is not
understood by most people. Please explain what a Galvanic Isolator is.
I
find absolutely no reason to connect shore earth to your boat, ever.
There
should be a ships earth and it should never be the hull, either on the
AC
side or the DC side. The ships earth should be isolated from the hull.
There should be an LED mounted in an obvious location connected
between the
hull and ships earth. Normally this LED would be off, unless there is
a DC
leak to the hull. This would then allow the LED to turn on and alert
the
crew to locate the fault immediately. On the AC side, an isolation
transformer is a necessity. The ships safety earth is then bonded to
neutral
at the panel only and the main ships ckt breaker should be of the GFI
type.
Steve

REPLY from ANDINA.

A Galvanic isolator consists of back to back diodes which still
provide an electrical path for AC current but block DC voltages up to
about 1 volt. So the ground protection for electrical faults is
retained but the small DC voltages that cause electrolysis are
blocked. ABYC specifications require that the Galvanic Isolator be
able to carry 130% of rated current continuously. This is required
because if an appliance on a boat was wired incorrectly and using the
ground instead of the neutral, the total current would be flowing
through the isolator. Should the isolator then fail under load, the
AC would now be connected directly to the ground that has become
disconnected from the shore ground. This puts 120 volts AC on all the
underwater items on your boat which can KILL SWIMMERS IN THE VICINITY.

Your statement that:-

I find absolutely no reason to connect shore earth to your boat, ever.

is very dangerous without explanation.

Omitting this connection can kill people.

On most boats you cannot isolate the DC ground from the underwater
metal because the starter motor is bolted to the engine block which in
turn connects to the propeller shaft and the water. So without the
ground, an internal failure of the battery charger could put 120 or
230 volts AC on your DC ground and into the water.

Relying on indicators or alarms is not a satisfactory solution, it
only takes milliseconds to kill someone.

Relying on a GFI Circuit breaker is not satisfactory. In salt water
the current flowing though a GFIC can kill a swimmer before the GFIC
can trip.

Now I agree that the probability of these worst case scenarios is
remote, however the consequences are grim. The ABYC specifications
err on the conservative side to avoid leaving the risk/consequence
decision up to the boat owner.

If using an isolation transformer the risk is miniscule. Isolation
transformers are extremely reliable, the only risk would be an
uninformed installer making an error in wiring up equipment. Without
the isolation transformer and with no ground you are betting the
reliability of your equipment against the life of swimmers in the
vicinity of your boat.

Regards,

Ann-Marie Foster,



On Jan 5, 11:49*am, Andina Marie wrote:
I posted this on another bulletin where a contributor had bonded all
his underwater metal with 1" copper straps and needed to test. *Copied
here for anyone having electrolysis problems.

An ohm meter is a poor way to check bonding connections. *I use a 12
volt lamp and make a probe using a screwdriver. *Hook a long enough
wire to the positive terminal of the starting battery and then poke
the screwdriver into each of the through hull fittings and make sure
the lamp lights. *An ohm meter is only testing the circuit at micro-
amps.

The following applies mainly to boats left in the water. *Trailered
boats rarely spend enough time in the water for electrolysis to be a
problem.

ELECTROLYSIS 101. *I've worked with electrolysis for 18 years
including live-aboard on a steel yacht for 14. *We have sold thousands
of our galvanic isolators and handle numerous emails/phone calls daily
on electrolysis situations.

BONDING STRAPS

Although your copper straps look impressive they are totally
unnecessary. *The wire at the most only carries a few milliamps and
there is no concern for voltage drop so the copper only needs to be
heavy enough to resist deterioration from oxidation. *A 10 gauge
copper wire is more than adequate. *I use non stranded 10 gauge bare
copper wire for my installations, being careful to secure it so it is
not subject to flexing from boat motion. *Non stranded wire has much
less surface area and avoids the cavities between the strands where
moisture and corrosion/oxidation can progress.

THEORY

Electrolysis only happens when two dissimilar metals are immersed in
an electrolyte and connected together. *The dissimilar metals have
different electrolysis voltages so if you connect them together
current flows through the connecting wire one direction and through
the water the other. *As the current leaves one metal to travel to the
other, it causes metal to come off one surface and be deposited on the
other like battery plates so the higher voltage metal suffers
electrolysis. *Electrolysis can also occur when an adjacent structure
or boat is injecting DC current into the water and that current goes
in one end of your boat and out the other on its way to the
destination. *This can cause electrolysis even though your boat is not
an offender.

PROTECTION

There are basically 2 ways to reduce electrolysis. *The PREFERABLE one
is to DISCONNECT the electrical circuit. *If this can't be done, the
second method is to provide a sacrificial anode (Zinc) so it
deteriorates rather than your expensive equipment.

a) DISCONNECTING

Electrolysis cannot occur on an isolated piece of metal in salt
water. *It is all at the same voltage but if it is isolated no current
can flow so there is no electrolysis. *When it is connected to another
piece of metal, ESPECIALLY if the other piece is a different metal,
you just created a shorted battery and electrolysis will start. *By
following the wrong advise and bonding everything in the boat you are
creating batteries where it is unnecessary and making electrolysis
problems worse.

ANN-MARIE'S RULE #1. *Only bond underwater items that are showing
symptoms of electrolysis. *If it ain't broke, DON'T fix it. *Once you
bond it unnecessarily you have CREATED the circuit rather than
DISCONNECTING it. *You are now stuck with providing Zincs since you
have removed the first line of protection.

Although some through hulls appear to be isolated due to sitting in
fiberglass and using non-metallic tubing, they quite often are not and
WILL need bonding. *For example the raw water cooling inlet for an
inboard engine is in fact connected to the engine block by the salt
water in the tubing and may need bonding so the current flows though
copper rather than the water and in/out of the through hull.

b) SACRIFICIAL ZINC

There are situations where different metals cannot be disconnected and
you are stuck with putting zincs on them to provided a target for the
electrolysis. *Zincs have a higher electrolytic voltage than marine
metals so it is the first to deteriorate.

Keep in mind that the zinc will CREATE electrolysis (favorable
electrolysis since the zinc is being eaten up). *Putting zincs where
they were not needed will still cause the zincs to erode away since
they create the battery situation where none may have existed.

The range of protection a zinc can supply to other metals bonded to it
is limited by the conductivity of the water. *In salt water you get
coverage for a radius of about 4 to 6 feet. *A zinc on the stern of a
14 ft boat where everything is bonded is only protecting half the
boat. *This range gets even less in fresh water and may reduce to only
inches. *Often magnesium is substituted for zinc in fresh water to
provide an even higher voltage to push through the fresh water.

USE A CONDOM

Over 90% of our customers electrolysis problems are created by the
shore power connection. *You could theoretically disconnect the ground
connection in the shore power and avoid electrolysis (and in some
cases this is a solution) but ABYC regulations require the AC ground
be connected to the DC ground so an electrical fault on the boat won't
electrocute swimmers in the vicinity.

When you connect your underwater metal to the shore power ground you
have "bonded" with every other boat on the docks who have the same
connection. *Now electrolysis currents are free to flow anywhere in
the marina and it only takes one boat with a 12 volt DC leakage to eat
up every boat within a wide radius even though the offender has zero
electrolysis evidence.

Your protection is a Galvanic Isolator in the ground connection of the
shore power lead. *You don't have to purchase ours (although they are
typically less than 1/2 the price of our competitors). *Any Galvanic
Isolator that meets AYBC specifications will do - they are not rocket
science and extremely reliable. *We have sold thousands, all on
unconditional warranty and have never had a return due to failure.

Feel free to ask general interest questions here or email me if you
prefer.

On Sun, 6 Jan 2008 08:12:46 -0800 (PST), Andina Marie
wrote:

On Jan 6, 6:06 am, "Steve Lusardi" wrote:
Andina,
I found your synopsis of this issue very good. This problem is not
understood by most people. Please explain what a Galvanic Isolator is.
I
find absolutely no reason to connect shore earth to your boat, ever.
There
should be a ships earth and it should never be the hull, either on the
AC
side or the DC side. The ships earth should be isolated from the hull.
There should be an LED mounted in an obvious location connected
between the
hull and ships earth. Normally this LED would be off, unless there is
a DC
leak to the hull. This would then allow the LED to turn on and alert
the
crew to locate the fault immediately. On the AC side, an isolation
transformer is a necessity. The ships safety earth is then bonded to
neutral
at the panel only and the main ships ckt breaker should be of the GFI
type.
Steve

REPLY from ANDINA.

A Galvanic isolator consists of back to back diodes which still
provide an electrical path for AC current but block DC voltages up to
about 1 volt. So the ground protection for electrical faults is
retained but the small DC voltages that cause electrolysis are
blocked. ABYC specifications require that the Galvanic Isolator be
able to carry 130% of rated current continuously. This is required
because if an appliance on a boat was wired incorrectly and using the
ground instead of the neutral, the total current would be flowing
through the isolator. Should the isolator then fail under load, the
AC would now be connected directly to the ground that has become
disconnected from the shore ground. This puts 120 volts AC on all the
underwater items on your boat which can KILL SWIMMERS IN THE VICINITY.

Your statement that:-

I find absolutely no reason to connect shore earth to your boat, ever.

is very dangerous without explanation.

Omitting this connection can kill people.

On most boats you cannot isolate the DC ground from the underwater
metal because the starter motor is bolted to the engine block which in
turn connects to the propeller shaft and the water. So without the
ground, an internal failure of the battery charger could put 120 or
230 volts AC on your DC ground and into the water.

Relying on indicators or alarms is not a satisfactory solution, it
only takes milliseconds to kill someone.

Relying on a GFI Circuit breaker is not satisfactory. In salt water
the current flowing though a GFIC can kill a swimmer before the GFIC
can trip.

Now I agree that the probability of these worst case scenarios is
remote, however the consequences are grim. The ABYC specifications
err on the conservative side to avoid leaving the risk/consequence
decision up to the boat owner.

If using an isolation transformer the risk is miniscule. Isolation
transformers are extremely reliable, the only risk would be an
uninformed installer making an error in wiring up equipment. Without
the isolation transformer and with no ground you are betting the
reliability of your equipment against the life of swimmers in the
vicinity of your boat.


Good advice.

Bottom line: unless an isolation transformer is (properly) installed,
the shore power green grounding wire should ALWAYS be connected to the
boat's AC ground, preferrably through a galvanic isolator.

Chuck


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Andina Marie wrote in news:8810ac1d-6d25-48fb-b03f-
:

A Galvanic isolator consists of back to back diodes which still
provide an electrical path for AC current but block DC voltages up to
about 1 volt. So the ground protection for electrical faults is
retained but the small DC voltages that cause electrolysis are
blocked.

Assuming, of course, that nothing in the boat hooked to the AC line, like
AC compressors, fan motors, battery chargers, AC-powered refridgeration
and lighting has absolute NO LEAKAGE that will forward bias any of those
diodes.

This dirty little secret has trashed many boats I know of with diode
galvanic isolators. Even the slightest AC leakage, not even enough to
trip a good GFCI, forward biases the diodes in both directions 60 times a
second, allowing galvanic current to flow through the forward biased
diodes during every AC peak in the same direction.....completely negating
the flow-stop protection the diodes were supposed to provide.

Almost ANY motor sitting for years in the marine seawater environment has
some small leakage, more than enough to forward bias galvanic isolator
diodes without causing any noticable GFCI trips or any kind of shocking
experience because of the working circuit grounds. The DC galvanic
current flows right along with the leakage current to marina grounds and
to the other boats, completing the circuits.

The cure isn't cheap....but is cheaper than new propulsion, rudders,
posts, shafts, through hull fittings and labor...ISOLATION TRANSFORMERS
to take the boat completely out of the AC line loop. Now only
magnetically coupled to the power grid, the boat IS isolated....but not
cheaply with high profit diodes.

http://www.charlesindustries.com/main/iso_guard.html
http://www.defender.com/product.jsp?path=-1|328|303336&id=614209 $567
(120/240VAC 30A)
http://tinyurl.com/yus7an (West Marine but probably only 120VAC) $495

30A of isolated AC certified for boats. How much is a new shaft and
screw, installed?

It's a fair trade....

Shhhh.....don't tell anyone....You can also use it to boost 120VAC to
120VAC/240VAC to run the European equipment the boat came
with!.....shhhh. Did I say that?

Shhhh....you can also use it to run 120VAC outlets off 240VAC supplies
outside the USA, too, if you use the 120/240 models. They make great
boost drop transformers, properly breakered in/out.


Larry
--
As the price of Monopoly money rises, at some point it will equal
Federal Reserve Private Bank fake banknotes in value!

Larry is correct. If you have an older boat that has accumulated fine
salt deposits over the years, AC leakage to ground can diminish the
effectiveness of Galvanic Isolators. You can test very easily after
installing the galvanic isolator. If the AC voltage you read across
it is more than about 0.3 volts you are starting to lose isolation.
Typically the worst case loss is only up to about 50% as the DC rides
through on one of the AC polarities when the diodes go into
conduction. On the other polarity of the AC it is bucking the DC.

You can solve this problem with a Galvanic Capacitor. It is just a
large capacitor that you put in parallel with the Galvanic Isolator so
the AC goes through it instead of the isolator. Some manufacturers
include a capacitor in the isolator but so far as I can see, not a
single manufacturer will tell you the capacity of it and since the
space occupied in their isolators is inadequate I feel sure they are
just putting in a small token capacitor so they can say it is there.

Our isolators have no capacitor. If you find you need one, we sell a
Galvanic Capacitor that is rated for 5 amps AC continuous that you
connect in parallel with the isolator. This would permit up to 5 amps
ground leakage before it compromises the galvanic isolator efficiency.

On Mon, 7 Jan 2008 06:49:19 -0800 (PST), Andina Marie
wrote:

snip

Our isolators have no capacitor. If you find you need one, we sell a
Galvanic Capacitor that is rated for 5 amps AC continuous that you
connect in parallel with the isolator. This would permit up to 5 amps
ground leakage before it compromises the galvanic isolator efficiency.

With 5 amps of leakage current, there is a serious problem that ought
to be fixed aside from any compromising effect on galvanic isolation.
Sounds like an electrocution waiting to happen. All it takes is a
corroded (or non-existing) grounding connection to the cabinet of a
refrigerator.

However, a functioning GFCI will trip immediately with 5 amps of
leakage through the green grounding conductor. Most will trip with a
thousandth of that current (5-6 mA).

Chuck

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You are correct Larry. I designed my own isolation transformer, because I
couldn't find one that met all my needs, but even building it myslf was not
inexpensive. My xformer is capable of both 50 and 60 Hz, is capable of
handling input power from 100 to 280 Volts. Input is phase and neutral, no
safety earth. The output has 5 voltage steps manually selectable. The output
winding is 230 volts with a center tapped neutral. Neutral is then tied to
ships earth along with both generator neutrals. Its rating is 10 KW. My
biggest problem was inrush current. This was resolved by employing a 300 W,
220 V light bulb in series with the primary and a 100 amp shunt around the
lamp. This works perfectly where the user starts the xformer with the shunt
disconnected and after secondary voltage is detected then engaging the
shunt. Primary idle current, with no secondary load and without ferro
resonant caps on the primary is .3 amps with 230 Volt input, so it is very
efficient. The xformer case measures 25" W, 15" H and 17" D and it weighs 94
Kgs. This size was necessary because the galley and hot water is all
electric. I carry only diesel fuel for safety reasons. I have to repeat
myself here. There is absolutely no way to protect your hull from other
boater's electrical faults if you connect shore safety earth to your boat.
Of course there are safety risks, but they can be mitigated. Here is an
interesting note. I designed two Isolation Transformers, this 10 KW model
and an automatic 5 KW model. They were shown at the London Boat Show a few
years back. I received "0" interest. People will not invest a dime to
correct a problem they do not understand. Stupidity has its just rewards.
Steve


"Larry" wrote in message
...
Andina Marie wrote in news:8810ac1d-6d25-48fb-b03f-
:

A Galvanic isolator consists of back to back diodes which still
provide an electrical path for AC current but block DC voltages up to
about 1 volt. So the ground protection for electrical faults is
retained but the small DC voltages that cause electrolysis are
blocked.

Assuming, of course, that nothing in the boat hooked to the AC line, like
AC compressors, fan motors, battery chargers, AC-powered refridgeration
and lighting has absolute NO LEAKAGE that will forward bias any of those
diodes.

This dirty little secret has trashed many boats I know of with diode
galvanic isolators. Even the slightest AC leakage, not even enough to
trip a good GFCI, forward biases the diodes in both directions 60 times a
second, allowing galvanic current to flow through the forward biased
diodes during every AC peak in the same direction.....completely negating
the flow-stop protection the diodes were supposed to provide.

Almost ANY motor sitting for years in the marine seawater environment has
some small leakage, more than enough to forward bias galvanic isolator
diodes without causing any noticable GFCI trips or any kind of shocking
experience because of the working circuit grounds. The DC galvanic
current flows right along with the leakage current to marina grounds and
to the other boats, completing the circuits.

The cure isn't cheap....but is cheaper than new propulsion, rudders,
posts, shafts, through hull fittings and labor...ISOLATION TRANSFORMERS
to take the boat completely out of the AC line loop. Now only
magnetically coupled to the power grid, the boat IS isolated....but not
cheaply with high profit diodes.

http://www.charlesindustries.com/main/iso_guard.html
http://www.defender.com/product.jsp?path=-1|328|303336&id=614209 $567
(120/240VAC 30A)
http://tinyurl.com/yus7an (West Marine but probably only 120VAC) $495

30A of isolated AC certified for boats. How much is a new shaft and
screw, installed?

It's a fair trade....

Shhhh.....don't tell anyone....You can also use it to boost 120VAC to
120VAC/240VAC to run the European equipment the boat came
with!.....shhhh. Did I say that?

Shhhh....you can also use it to run 120VAC outlets off 240VAC supplies
outside the USA, too, if you use the 120/240 models. They make great
boost drop transformers, properly breakered in/out.


Larry
--
As the price of Monopoly money rises, at some point it will equal
Federal Reserve Private Bank fake banknotes in value!

"Steve Lusardi" wrote in news:fma6k9$ijg$00$1
@news.t-online.com:

People will not invest a dime to
correct a problem they do not understand. Stupidity has its just rewards.
Steve


This is absolutely true. Trying to explain it to them only makes them
angry. Unlike usenet, I keep it shut on the docks...(c;

On Feb 2, 6:23*am, Larry wrote:
"Steve Lusardi" wrote in news:fma6k9$ijg$00$1
@news.t-online.com:

People will not invest a dime to
correct a problem they do not understand. Stupidity has its just rewards..
Steve

This is absolutely true. *Trying to explain it to them only makes them
angry. *Unlike usenet, I keep it shut on the docks...(c;

Just a comment/question about GFCIs.

The typical North American GFCI operates when there is an unbalance
beteen the amount of AC flowing in the live and flowing in the neutral
wire. That unbalance may be due a potentially dangerous leakage to
ground (or in this case the boat/water) but not necessarily. That
unbalance operation is the reason that GFCIs are not recommneded for
use in domestic situations for fridges and freezers. You can come home
to a fridge of bad food!

Not that we should not use them and also understand how and why they
operate to provide safety, but it's almost as if the designation
'Ground Fault Current ...... ' is a misnomer. In Europe and elswhere
understand they are called RCDs.

I liked the discussion about isolation transformers. What sort of
wattage ratings would be typical; realizing that when the boat is at
the wharf unused there may be a minimum load, due to a little bit of
battery top up, maybe a fridge and a small bilge pump (itself often on
12 or 24 volt DC boat supply) that may cut in occasionally. Perhaps
intermittently 500 watts?????

We have on hand, for example several hefty transformers (basically one
to one ratio, with a few extra volt taps) each capable of at least 250
watts or more. Have often considered using them as isolation and minor
voltage adjustment devices. Also as mentioned, properly arranged,
transformer/transformers can be used to 'match' land voltages of
around 230v OR 115v to the boat.

Terry,
Your questions are right on target. In Germany, the main breaker must be
GFI. Therefore all loads within the distribution will be GF protected. In my
experience, there are only two types in Europe a .030 Amp and a .3 Amp
breaker. They do measure that load current matches return current. If there
is an imbalance, then there must be another return path to safety earth. In
Europe you will never see those in-line AC filters whose case is screwed to
the equipment frame exactly for that reason, as they bleed to frame(safety
earth). On a boat, they are very useful and if a more sensitive was
available, I would use that.

Isolation transformers can be made very elaborately or very inexpensively,
depending on the application. Most importantly is the way you connect the
safety earth wire from the shore outlet to your boat. I will not ever
connect it, but to do that is illegal. If you must connect it, it must
connect only to the transformer frame and NOT anywhere else. Your ship
ground is from the centertap of the secondary winding. To determine how
large the transformer should be, add all the loads that could be
simultaneously connected and add 20%.

Isolation transformer problems and there are a few. One, when connecting the
boat to the shore connection and the transformer is larger than 1KW, you
will very likely pop the ckt breaker for the feed because of inrush current.
Two, efficiency can be a big issue, so electric use can be significantly
higher. You cannot use an Auto Transformer for an isolation role. They are
the typical step down transformers used to reduce 220 volt power for 110
volts loads. Another problem that I encountered is that the ones that I
found were not suitable for marine use, even the ones so labeled.

Problem solutions: In rush can be contained by using a common incandescent
light bulb in series with the primary and after start, shorting past the
lamp. Two, if idle current is higher than you wish, make the primary winding
Ferro-resonant, by adding the appropriate capacitance in parallel with the
winding. If you want to know how, contact me off-line and I will tell you. I
decided to design and build my own, because I could not find one that met
all my requirements. I am very happy to state that my transformer met all my
requirements, is easy to use and very economical.

My requirements:
Accept input voltage between 100 Volts and 260 Volts (Japan = 100 V / UK =
260 Volts).
Adjustable output voltage = (end of dock low voltage syndrome)
Single phase only, output = 115 Volt secondary end to center tap and 230
Volt secondary end to end.
Power needed = 10 KW
Ferro Resonant primary selectable for both 50 Hz and 60 Hz.

Steve

"terry" wrote in message
...
On Feb 2, 6:23 am, Larry wrote:
"Steve Lusardi" wrote in news:fma6k9$ijg$00$1
@news.t-online.com:

People will not invest a dime to
correct a problem they do not understand. Stupidity has its just
rewards.
Steve

This is absolutely true. Trying to explain it to them only makes them
angry. Unlike usenet, I keep it shut on the docks...(c;

Just a comment/question about GFCIs.

The typical North American GFCI operates when there is an unbalance
beteen the amount of AC flowing in the live and flowing in the neutral
wire. That unbalance may be due a potentially dangerous leakage to
ground (or in this case the boat/water) but not necessarily. That
unbalance operation is the reason that GFCIs are not recommneded for
use in domestic situations for fridges and freezers. You can come home
to a fridge of bad food!

Not that we should not use them and also understand how and why they
operate to provide safety, but it's almost as if the designation
'Ground Fault Current ...... ' is a misnomer. In Europe and elswhere
understand they are called RCDs.

I liked the discussion about isolation transformers. What sort of
wattage ratings would be typical; realizing that when the boat is at
the wharf unused there may be a minimum load, due to a little bit of
battery top up, maybe a fridge and a small bilge pump (itself often on
12 or 24 volt DC boat supply) that may cut in occasionally. Perhaps
intermittently 500 watts?????

We have on hand, for example several hefty transformers (basically one
to one ratio, with a few extra volt taps) each capable of at least 250
watts or more. Have often considered using them as isolation and minor
voltage adjustment devices. Also as mentioned, properly arranged,
transformer/transformers can be used to 'match' land voltages of
around 230v OR 115v to the boat.