Adding Simple Shore Power??
 

I meant the opposite. For the cost of the outlets, why would you not
have them? Do you have to argue for having life preservers or fire
extinguishers?

--

Roger Long



"Jeff" wrote in message
...
Roger Long wrote:
I wouldn't have expected to see "GFI" and "argument for" in the
same sentence.

Why? Is there something wrong with them? All of the outlets on my
boat are GFCI's; I assume they provide some protection.

Adding Simple Shore Power??
 

Roger Long wrote:
I meant the opposite. For the cost of the outlets, why would you not
have them?

I agree, but I never cease to be amazed by the seemingly obvious
truths that are proven false.

Do you have to argue for having life preservers or fire
extinguishers?


Well, I could argue against them. For example, my reading of Maine
law a few years ago was that it requires children under 12 to wear a
PFD even while down below, sleeping in their cabin. I don't even
think it specified "underway."

Adding Simple Shore Power??
 

Roger Long wrote:
Walking around the dock holding a live plug in your hand is dumb,
dumb, dumb. If you trip and go into the water, you're just going to
flounder around conscious and wondering why your hand won't reach for
the dock edge, and your feet won't kick. Bad way to die.

--

Roger Long

Roger that Roger:
Especially if you are prone to trip over things like me. Ups......
Darn, fell in again.....
poof!
Bob

Adding Simple Shore Power??
 

chuck wrote in news:1vpRf.11533$S25.11273
@newsread1.news.atl.earthlink.net:

I agree: a plastic case on a double-insulated pot ought to be pretty
safe. What I really had in mind though was an appliance that had the
equipment grounding conductor connected to the case. Some electric
drills and other power tools possibly found on boats still use metal
cases and three-prong plugs. As for the mast, for many of us, the mast
is IN the galley, along with the engine, and most everything else. :))



The drop-in-cord is still a 3-prong grounded AC feed. I don't understand
about connecting shore ground to the engine block and underwater metal
parts or the mast. The 3-prong grounded-through-the-drop-cord case of
the 120V fridge-from-Walmart is at ground potential. The only voltage
that's going to be on its case to the engine block in your boat is the
electrolysis DC potential between the metal conduit under the dock all
rusted out and leaking and your zincs, which will be fizzing away
protecting the rotting conduit if you connect their ground to your engine
block.

Is your mast grounded to the engine? Most are just floating to make sure
and lightning strike holes the hull to sink the whole thing so they can
sell you a new boat. Measure resistance between the mast and the
negative terminal on any 12V light near it. I bet it's an open circuit.
Grounding straps running through fiberglass boats costs them money to
install. You just know they're not going to do it, right?

I don't understand how grounding the AC line to the boat's DC circuit is
going to be "safer". If you get between AC "hot", the black wire, and
the boat's ground to the seawater, you get a shock limited by the
resistance of the connection to the seawater, which isn't much. If you
ground the AC line to all the boat's equipment, you get a shock with only
you as the resistance limiting the current that's going to kill you, just
like at home! How is that "safer"?? I'll be glad to come to your boat
and hold onto AC ground or neutral in one hand and the engine block in
the other, any time....grounded or not. I won't get shocked.

If we were interested in AC line safety, every marina would simply be
FORCED, the only way to make it happen, to comply with an NEC requirement
to install ground fault interrupters to all dock breaker panels out there
in the little post out front. Noone would ever get shocked, again,
unless they got right across the AC line to neutral. Of course, noone
would have any AC power in the boat, either, because the leakage of all
those old rusty fridges, water heaters and battery chargers would trip
the hell out of all the dock GFIs, plunging the boats in the dark,
too!...(c; Don't worry, noone at the marina or NEC cares.

Someone sent me a picture of total stupidity. This guy is standing in
his bare feet on a metal stepladder in the middle of a swimming pool in
his bathing suit. He's drilling a hole in the ceiling for something with
a metal-cased old electric drill. If you follow the cord back you see
it's plugged into a little brown 2-wire extension cord. You can see the
ground pin on the drill's electric cord sticking out in mid air. Totally
Stupid is right!...(c;

Adding Simple Shore Power??
 

Well Larry, I know from previous posts that this issue troubles you.

What the analysis hinges on is what happens when the boat next to you
connects the 120 volt hot wire to his DC ground system (prop, etc. below
the water). Did you skip that part of the post? Did you tune it out
because you know in your heart the the guy on the boat next to yours
would never do such a thing?

Your view (rhetoric aside) seems to be that in the above example, the
water will provide a return path to the shore power connections and
what? trip a breaker? or just create a whopping electric field between
the prop and whatever is the lowest resistance path back to the shore
power ground connection? Or maybe you have some other analysis of what
happens. You really can't ignore that part of the analysis and then
conclude there is no safety hazard.

The scenario I've tried to describe considers that the shortest path
from the prop of the boat in the next slip to the shore power grounding
point MIGHT be through YOUR prop to your DC ground system (engine or
whatever it is connected to on the boat).

Even if that path is not the one with the LOWEST resistance, it may
still provide sufficiently low resistance to cause electrocution if
someone touches both the engine and the green shore power grounding
conductor. Does that bit of Ohm's law trouble you after all these years? ;)

Of course it is true that if there are no other boats in sight, and no
other opportunities for messed-up wiring near your boat, you will have
no problems with shock hazards. Think about what you're saying for a
moment, Larry. You agree that galvanic currents can pass through the
water from boat to boat even though these are less than a couple of
volts, but you are positive that 120 VAC currents would never do so
between the same two pieces of metal. How do you explain that? Ohm's law
again?

To keep this reasonable short, I'm lumping salt water and fresh water
analysis together, even though the problem is more serious with fresh water.

Chuck




Larry wrote:
chuck wrote in news:1vpRf.11533$S25.11273
@newsread1.news.atl.earthlink.net:


I agree: a plastic case on a double-insulated pot ought to be pretty
safe. What I really had in mind though was an appliance that had the
equipment grounding conductor connected to the case. Some electric
drills and other power tools possibly found on boats still use metal
cases and three-prong plugs. As for the mast, for many of us, the mast
is IN the galley, along with the engine, and most everything else. :))




The drop-in-cord is still a 3-prong grounded AC feed. I don't understand
about connecting shore ground to the engine block and underwater metal
parts or the mast. The 3-prong grounded-through-the-drop-cord case of
the 120V fridge-from-Walmart is at ground potential. The only voltage
that's going to be on its case to the engine block in your boat is the
electrolysis DC potential between the metal conduit under the dock all
rusted out and leaking and your zincs, which will be fizzing away
protecting the rotting conduit if you connect their ground to your engine
block.

Is your mast grounded to the engine? Most are just floating to make sure
and lightning strike holes the hull to sink the whole thing so they can
sell you a new boat. Measure resistance between the mast and the
negative terminal on any 12V light near it. I bet it's an open circuit.
Grounding straps running through fiberglass boats costs them money to
install. You just know they're not going to do it, right?

I don't understand how grounding the AC line to the boat's DC circuit is
going to be "safer". If you get between AC "hot", the black wire, and
the boat's ground to the seawater, you get a shock limited by the
resistance of the connection to the seawater, which isn't much. If you
ground the AC line to all the boat's equipment, you get a shock with only
you as the resistance limiting the current that's going to kill you, just
like at home! How is that "safer"?? I'll be glad to come to your boat
and hold onto AC ground or neutral in one hand and the engine block in
the other, any time....grounded or not. I won't get shocked.

If we were interested in AC line safety, every marina would simply be
FORCED, the only way to make it happen, to comply with an NEC requirement
to install ground fault interrupters to all dock breaker panels out there
in the little post out front. Noone would ever get shocked, again,
unless they got right across the AC line to neutral. Of course, noone
would have any AC power in the boat, either, because the leakage of all
those old rusty fridges, water heaters and battery chargers would trip
the hell out of all the dock GFIs, plunging the boats in the dark,
too!...(c; Don't worry, noone at the marina or NEC cares.

Someone sent me a picture of total stupidity. This guy is standing in
his bare feet on a metal stepladder in the middle of a swimming pool in
his bathing suit. He's drilling a hole in the ceiling for something with
a metal-cased old electric drill. If you follow the cord back you see
it's plugged into a little brown 2-wire extension cord. You can see the
ground pin on the drill's electric cord sticking out in mid air. Totally
Stupid is right!...(c;

Adding Simple Shore Power??
 

As a simple experiment, just use a 12 VAC filament transformer (do they
still call them that?) and measure the current from one prop to the next
with the other wire clipped to the green grounding conductor. It's tough
to measure DC resistance in water because the surface areas of the
conductors get drawn into the act and the current tends to polarize the
path at the electrodes. But the 12 VAC route gives you exactly what you
would get with at 120 volts with no risk.

On breaker tripping, there've been an awful lot of power tools
(connected and running) dropped into sal****er that never tripped their
breakers. Extension cords (hot) are found hanging in the water routinely
at some marinas. So by all means give it a test. But please just use 12
VAC and measure the current. We can just multiply by ten to get the 120
VAC current.

I'm with you 100% on isolation from galvanic currents.

Turns out that the lethal situation for swimmers in the presence of
these strong fields is far worse in fresh water than in sal****er,
contrary to one's initial expectation. In sal****er, the current is so
overwhelmed with little high-conductivity paths around the swimmer that
virtually no current passes thru the swimmer.

In fresh water, the swimmer looks like a low resistance "short" in the
middle of the field (he bends the field, actually) and concentrates the
current through himself!

Keep us posted on results.

Chuck

Adding Simple Shore Power??
 

chuck wrote in news:wV3Sf.4616$sL2.2779
@newsread2.news.atl.earthlink.net:

We can just multiply by ten to get the 120
VAC current.

I don't think it's linear, actually. The curve would be more log-like.
The transformer would show it, though.


Turns out that the lethal situation for swimmers in the presence of
these strong fields is far worse in fresh water than in sal****er,
contrary to one's initial expectation. In sal****er, the current is so
overwhelmed with little high-conductivity paths around the swimmer that
virtually no current passes thru the swimmer.


This is why I don't think I'm in any danger ungrounded like that. The
same principle of the swimmer being a greater resistance is true of our
underwater prop. The path DOWN under the offending boat in your scenario
is much easier than trying to get the current to go from his little prop
to our little prop sideways away from the giant ground 15' under the
keel. The current distribution is going to be massive down but very
little sideways. Unless I'm DIRECTLY connected between the underwater
metal and AC ground or neutral, I'm completely insulated from any path,
whatsoever! Even if his boat is turning the water blue with current, If
I just touch the engine block, I'm totally isolated. If I'm touching an
insulated appliance, I'm totally isolated. The scenario becomes very
absurd, very fast, not a normal condition that might happen. The one
engine-to-AC line possibility might be if I touch the engine and the
water heater's grounded case simultaneously. There might also be a
current path through the fresh-water-cooling loop the water heater
connects to the engine with. If this loop is conductive, the heater is
already semi-grounding the engine block to the AC line, but I've never
seen any evidence it makes a difference. We moved the water heater out
of the engine room into the portside deep locker to get the heater out of
the way of engine belt and impeller maintenance on the front of the
Perkins. I never thought of this current path through the hot water
heating hoses before this morning. Interesting. Being fresh water
contaminated with antifreeze I'm not sure what its resistance would be.

There's no galvanic current to the dock through that hose I can
measure....

Adding Simple Shore Power??
 

Your measurements will tell the story, Larry.

We tend to believe that salt water is a great conductor. Compared to
fresh water, it is some orders of magnitude better. Compared to metal
conductors, salt water is many orders of magnitude worse. Dirt and sand
are even worse conductors than salt water.

Here's an even simpler experiment. Take a couple of one foot lengths of
copper pipe attach a 20 foot wire to each and connect the wires to an AC
voltmeter. Drop the pipes into the water with say 20 to 40 feet of
separation. If your boat is in a marina, there is a chance you'll detect
an electric field in the water with this setup. If you find one around
your boat, switch the meter to AC current and see if any current flows.
Because the "probes" are not dissimilar metals, any current you detect
will not be due to a galvanic couple. Now connect one of the "probes" to
the AC grounding conductor while leaving it in the water. Remeasure the
voltage and current. Does it drop to zero?

In the other experiment, you'll be creating an electric field.

Next step is to consider that happens to conductors in electric fields.

But if you've got a copy of either of Beyn's books handy (The 12 Volt
Doctor's Practical Handbook, or The 12 Volt Doctor's Practical Handbook
for the boat's electric system) you can read up on these fields.

Chuck

Larry wrote:
chuck wrote in news:wV3Sf.4616$sL2.2779
@newsread2.news.atl.earthlink.net:


We can just multiply by ten to get the 120
VAC current.


I don't think it's linear, actually. The curve would be more log-like.
The transformer would show it, though.


Turns out that the lethal situation for swimmers in the presence of
these strong fields is far worse in fresh water than in sal****er,
contrary to one's initial expectation. In sal****er, the current is so
overwhelmed with little high-conductivity paths around the swimmer that
virtually no current passes thru the swimmer.



This is why I don't think I'm in any danger ungrounded like that. The
same principle of the swimmer being a greater resistance is true of our
underwater prop. The path DOWN under the offending boat in your scenario
is much easier than trying to get the current to go from his little prop
to our little prop sideways away from the giant ground 15' under the
keel. The current distribution is going to be massive down but very
little sideways. Unless I'm DIRECTLY connected between the underwater
metal and AC ground or neutral, I'm completely insulated from any path,
whatsoever! Even if his boat is turning the water blue with current, If
I just touch the engine block, I'm totally isolated. If I'm touching an
insulated appliance, I'm totally isolated. The scenario becomes very
absurd, very fast, not a normal condition that might happen. The one
engine-to-AC line possibility might be if I touch the engine and the
water heater's grounded case simultaneously. There might also be a
current path through the fresh-water-cooling loop the water heater
connects to the engine with. If this loop is conductive, the heater is
already semi-grounding the engine block to the AC line, but I've never
seen any evidence it makes a difference. We moved the water heater out
of the engine room into the portside deep locker to get the heater out of
the way of engine belt and impeller maintenance on the front of the
Perkins. I never thought of this current path through the hot water
heating hoses before this morning. Interesting. Being fresh water
contaminated with antifreeze I'm not sure what its resistance would be.

There's no galvanic current to the dock through that hose I can
measure....

Adding Simple Shore Power??
 

chuck wrote in news:3XfSf.4771$sL2.2554
@newsread2.news.atl.earthlink.net:

Here's an even simpler experiment. Take a couple of one foot lengths of
copper pipe attach a 20 foot wire to each and connect the wires to an AC
voltmeter. Drop the pipes into the water with say 20 to 40 feet of
separation. If your boat is in a marina, there is a chance you'll detect
an electric field in the water with this setup. If you find one around


WHOA! Last time I created this kind of electric field, we used an old
telephone generator in the lake I grew up on! We got busted by the game
warden just as we were filling the minnow buckets with fish the field had
stunned....(c;

(Works great, by the way...(c;)