"hot" marina poll

[sailorboy1]

To me what I a seeing and which I pretty much always believed is that people blame the marina system for their or others boat system problems.

[Garrettw]

Originally Posted by boatpoker

So a "hot boat" neighbour problem not a "hot marina" problem.
An inexpensive galvanic isolator will resolve that problem.

I might submit that a significant wiring fault, even if a boat is the root cause, can be a marina problem.

Those numbers are with my galvanic isolator installed and working. An isolation transformer would be the next logical option in this case.

[Maine Sail]

Originally Posted by boatpoker

As a retired ABYC certified marine electrician and certified marine corrosion tech I have heard this term "hot marina" many times. It then takes me 10 minutes of questions and explanations to sort out what the speaker actually means. I find it is a term generally used by those with little knowledge of marine electrics or corrosion. Much like the other frequently misused term "electrolysis" which simply cannot occur on boats.

Bingo!

[donradcliffe]

Originally Posted by Johan Leopard51

Recently our fibreglass yacht was on yard for antifoul and some work. Somebody noticed they got shocked when touched a metal part, think it was prop shaft.

With boatyard power switched off but cable still connected, still happens. With boatyard cable physically disconnected from yacht, no shock. That tells me that the boatyard AC supply has very bad earth (so our yacht acts as earth). Am I wrong?

In the marina we bleed a lot of metal and I suspect same thing : that shore power earthing is terrible.

It is part of reason I want to install as much solar as the flybridge of cat can handle : so that yacht can be “off grid” no cable to shore at all unless HAVE to connect. Power consumption while at rest is very small.

Happened to me in a Thai boatyard. The cause was the yard's extension cord I plugged the boat into had crossed wires.

[fstbttms]

Originally Posted by sailorboy1

To me what I am seeing and which I pretty much always believed is that people blame the marina system for their or others boat system problems.

This.

[OldManMirage]

Reposting in the correct forum...

On my Endeavour 32 the original owner had cut out all the AC wiring. Left all the parts but no wire !

I re-wired everything except for the shore power receptacle. I removed that and covered the hole. All my modest AC needs are met by a 1000 watt inverter.

But I will say that at the last marina I was in, the Rudder Club, my shaft zinc disappeared after a few months. I was cleaning the hull and noticed it gone. This was after a winter where I had not dove on the boat for probably 6 months.

I replaced it as soon as possible and then shortly after I moved to different marina. The zinc is now over a year old and still looks good. But yes, I will replace it at next haulout, hopefully in the next few weeks.

Also, not saying it was the marina, could easily have been a neighbor.

[Montanan]

Originally Posted by boatpoker

In my opinion ... There is no debate against established, proven science

Reference link:

The Science Behind Electric Shock Drowning
Nov. 16, 2018
Internal research reveals more about ESD and helps to identify the real Zone of Danger in electrified water.
Michael S. Morse

https://cc.bingj.com/cache.aspx?q=el...gBWjsMVfwWKtzX

Snipet:


What We Know

Dr. Morse has personally evaluated several cases in which individuals in fresh, salt, and chlorinated water have died as a result of electrical current flow in the water, presumably from either electrically induced ventricular fibrillation or electrically induced muscle paralysis that causes ESD.

The science behind ESD is simple. A current source, such as an energized broken wire touching a body of water, allows current to flow in the water. The current then seeks its way through the water to ground. A swimmer in the water passes through the flow of current and becomes part of the invisible circuit between source and ground. The current flow through the swimmer causes a level of muscle contraction that he or she cannot control or override, leading to electrically induced paralysis and resultant drowning. ESD is different from electrically induced ventricular fibrillation, which requires a much greater current. In electrically initiated ventricular fibrillation, the current flow must traverse the heart muscle.

Over the years, many have observed that ESD seems to be most prevalent in freshwater environments, concluding that this is because the conductivity of the human body is higher than that of the surrounding fresh water (leading to current flow along the path of least resistance, being through the body of the swimmer). The most accurate statement is not that “current follows the path of least resistance” but rather that current follows all paths in inverse proportion to the resistance of the path. This would imply that the geometry of the environment and the location of source and ground would play a significant role in path resistance. Physics tells us that the current will not divert in great proportion to a more conductive human body if the overall path to ground is longer, representing greater resistance than other paths."


Each vessel in a marina and each conductive pathway through a vessel in a marina is subject that "current follows all paths in inverse proportion to the resistance of the current path."

An isolation transformer mitigates the current pathway. Utilize proper protection. Allow stray currents to follow an alternate pathway.

[Panope]

Does wearing a dry suit protect against electric shock?

[peter57]

Originally Posted by boatpoker

I completely understand that but we have several posters implying here that it is the marina at fault, not themselves or their neighbours boats.

Calling it a "Hot marina" issue is false and misleading.

One night we (a slight party) arrived back from the Casino to a marina (not naming) at a mates boat and as everyone was boarding I could see a glow in the water coming from the boat on the next finger, it was his 240v power lead that had pulled out of its connection and landed in the drink, to our amazement that it had not tripped the circuit breaker.

[Johan Leopard51]

Originally Posted by sailorboy1

To me what I a seeing and which I pretty much always believed is that people blame the marina system for their or others boat system problems.

Maybe there are two versions of “hot”. One is bad wiring of supply from marina as in phase rotation or live and neutral swapped, voltage and/or frequency out of specification.

The other is that the reticulation of the whole subnet your cable originates from has no earth or bad earth. That will mean your vessel might, for the entire mini-grid, represent the path of least resistance.

I am sure my wiring is not perfect, but the situation I sketched where our boat on outhaul would shock you if you touched prop shaft and boatyard plug was connected (whether on or off, connected ensured the shock) can only point to the boatyard earth is bad or absent. No cable, no shock from prop shaft. That test is obviously easy on dock.

A good earth is so easy and in marina setup it should be especially easy given the likely saltwater damp terrain. When we do earth pits for large solar and storage systems we sink 16 copper rods of around 1.5m so that their tops are 60cm below ground, cross connected with bare copper cable on two exits and filled with a special soil. We’re far from ocean and last one I got 0.6 ohms at my transformer inside the building. I think the standards require maximum of 2 ohms at a MV substation and a bit more further down the reticulation.

You could reasonably expect your shore power to test under 5 ohms. What they get at their utility connection point is NOT the one to rely on, as the earth reticulation to where your shore power connects to can easily be bad (or stolen copper). You want to look at the earth at distribution board where your shore power cable connects.

We have a permanent mooring and I’ve wondered whether I shouldn’t just sink a private earth in the marina floor by way of one large rod and connect to that. It should work???

[sailorboy1]

over 2,000 people have read this thread but apparently only 18 have ever been in a marina based on the poll votes

[Redboat]

Electric Shock Drowning: Causes and Prevention by Dr G.S. Cargill, Lehigh University · Department of Materials Science and Engineering

Pages 35 - 44 discusses, with diagrams, the ways a marina can be "hot" which I interpret to mean enough potential current leakage from AC to shock a person and drown them. I know there was a fatality in my marina a few years back of a swimmer getting electrocuted.

Some causes are due to problems on a boat, others due to a problem on the marinas poewer poles.

[boatpoker]

Originally Posted by Redboat

Electric Shock Drowning: Causes and Prevention by Dr G.S. Cargill, Lehigh University · Department of Materials Science and Engineering

Pages 35 - 44 discusses, with diagrams, the ways a marina can be "hot" which I interpret to mean enough potential current leakage from AC to shock a person and drown them. I know there was a fatality in my marina a few years back of a swimmer getting electrocuted.

Some causes are due to problems on a boat, others due to a problem on the marinas poewer poles.

The problem with this thread is the question in the first post is overly vague.

Some cannot distinguish between ESD and electrolytic corrosion and have blamed "hot marinas" for rapid depletion of their anodes.

So are we talking about ESD or anode depletion ? ... depending on the issue there are different answers.

[sailorboy1]

Originally Posted by boatpoker

The problem with this thread is the question in the first post is overly vague.

I don't think my question is vague at all and that it is very straight forward. Not the questions fault that people make claims etc. for something they even understand.

[boatpoker]

Originally Posted by sailorboy1

I don't think my question is vague at all and that it is very straight forward. Not the questions fault that people make claims etc. for something they even understand.

People on this thread are are using the term to define two different, largely unrelated scenarios (ESD & anode depletion/corrosion). Please define your understanding of a "hot marina".