I guess you'll have to warn the thousands of hull divers working electrocution-free in saltwater marinas for decades in this country.
Stray current in the water
- Thread starter JBP-PA
- Start date
The boat is on Lake Erie, last I checked it was (sort of) freshwater.I guess you'll have to warn the thousands of hull divers working electrocution-free in saltwater marinas for decades in this country.
Stray current in a marina in fresh water is just as dangerous as in salt water. I personally know of people and their dogs who've been killed by stray current in a marina on a lake.
--__Peggie
--__Peggie
Stray AC current in freshwater is considerably more dangerous than in saltwater as saltwater is a better conductor of electricity than the human body, on the other hand the human body is a better conductor electricity.
Relevant article here: A Preventable Dockside Tragedy | BoatUS
Mr. Ritz addressed our club at a general meeting to encourage us to counter this threat. That was a few years ago, and since then we have rewired all five head walks and added new ELCI breakers for all shore power outlets.
Yeah, they are very sensitive and occasionally trip when something is *marginal in a boat's AC system, but we feel the protection is worth having. We also ban recreational swimming in the marina.
Visiting divers/scrubbers all insist (and always have done so) on unplugging boats on either side of the one they are working on. We are about 20 miles away from the site of the tragedy mentioned, and also on the river. i.e. in fresh water.
While the % risk is low, it seems worth preventing such a death as much as possible.
*Speaking of marginal, several boats initially found that their OEM hot water tank heater coil was the culprit when their power post started mystery-tripping with the new sensitive breakers.
Mr. Ritz addressed our club at a general meeting to encourage us to counter this threat. That was a few years ago, and since then we have rewired all five head walks and added new ELCI breakers for all shore power outlets.
Yeah, they are very sensitive and occasionally trip when something is *marginal in a boat's AC system, but we feel the protection is worth having. We also ban recreational swimming in the marina.
Visiting divers/scrubbers all insist (and always have done so) on unplugging boats on either side of the one they are working on. We are about 20 miles away from the site of the tragedy mentioned, and also on the river. i.e. in fresh water.
While the % risk is low, it seems worth preventing such a death as much as possible.
*Speaking of marginal, several boats initially found that their OEM hot water tank heater coil was the culprit when their power post started mystery-tripping with the new sensitive breakers.
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I guess you'll have to warn the thousands of hull divers working electrocution-free in saltwater marinas for decades in this country.
True for all AC currents in water.
The key is do NOT Ground yourself.
Jim...
In fresh water it doesn’t matter whether you’re touching a ground or not. You’re more conductive than the fresh water around you, so if there’s an AC leak nearby the current will go through you to get to ground.
True for all AC currents in water.
The key is do NOT Ground yourself.
Jim...
Electric Shock Drowning (ESD) is essentially a problem in freshwater only. It simply isn't an issue in saltwater.
The answer to Freshwater is still Grounding.
The Freshwater must still conduct AC through your body to a Ground.
How far from a good ground can be calculated.
Jim...
Just to add something not at all important on this.
As you move away from the source of the voltage in water, the conductance goes up with the cube of distance because the half sphere water volume away from the source is expanding and hence charge carriers increase with the cube of distance. At some distance away from the source, the conductance is so high that for all purposes, its zero ohms to earth ground so basically ground.
In salt water, the conductance is already about 1000X higher than clean fresh water. So in salt water, the voltage goes to zero very quickly because the conductance increases so fast with distance. Or in other words, the resistance goes to zero very quickly. Where resistance is zero, there is zero voltage drop.
But in fresh water with much lower conductance, the voltage can extend out a much larger distance before its effectively zero. You dont need to be touching any ground, the danger is having your body where there is a voltage gradient or field.
That distance might be a bunch of feet in freshwater so a swimmer can get close enough to the source where there is still a voltage potential over distance (ie, voltage gradient or field). Its the AC voltage potential difference across your body that kills. The current might be very low, not enough to cook anything.
Remember that the conductance increases with the cube of distance away from the source so it also means that a swimmer might feel nothing and the within a short distance, encounter a field (potential across the body) that messes with the heart.
In salt water, the distance are so small that the swimmer would almost need to be touching the hot electrode.
As you move away from the source of the voltage in water, the conductance goes up with the cube of distance because the half sphere water volume away from the source is expanding and hence charge carriers increase with the cube of distance. At some distance away from the source, the conductance is so high that for all purposes, its zero ohms to earth ground so basically ground.
In salt water, the conductance is already about 1000X higher than clean fresh water. So in salt water, the voltage goes to zero very quickly because the conductance increases so fast with distance. Or in other words, the resistance goes to zero very quickly. Where resistance is zero, there is zero voltage drop.
But in fresh water with much lower conductance, the voltage can extend out a much larger distance before its effectively zero. You dont need to be touching any ground, the danger is having your body where there is a voltage gradient or field.
That distance might be a bunch of feet in freshwater so a swimmer can get close enough to the source where there is still a voltage potential over distance (ie, voltage gradient or field). Its the AC voltage potential difference across your body that kills. The current might be very low, not enough to cook anything.
Remember that the conductance increases with the cube of distance away from the source so it also means that a swimmer might feel nothing and the within a short distance, encounter a field (potential across the body) that messes with the heart.
In salt water, the distance are so small that the swimmer would almost need to be touching the hot electrode.
This website has a good description of the Electroshock Drowning which occurs in freshwater. As has been repeatedly stated in this thread, ESD is not a big issue in saltwater, however, it is a big issue in freshwater and one does not need to be connected to ground in order to die from ESD.
ESD & FAQ
WHAT IS ELECTRIC SHOCK DROWNING? Electric Shock Drowning (ESD) is the result of the passage of a typically low level AC current through the body with sufficient force to cause skeletal...
www.electricshockdrowning.org