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.

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 insolated 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 nuetral
at the panel only and the main ships ckt breaker should be of the GFI type.
Steve

"Andina Marie" wrote in message
...
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 Sun, 6 Jan 2008 08:05:44 -0800 (PST), Andina Marie
wrote:

....
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.
....
Regards,

Ann-Marie Foster,


Do you have a reference supporting the lethality of GFIs
to swimmers, Ann-Marie?

Brian Whatcott Altus OK

I run an Isolation transformer and I use an air starter.
Steve

"Andina Marie" wrote in message
...
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,