Dock ground fault experience

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danderer

danderer

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Joined
Jan 28, 2015
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709
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Infinity
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Kadey Krogen 48
Stopped recently at Indian Creek Yacht and Country Club. They redid their docks in the last year or so and now all power pedestals implement the 2017 standard with 30 mA ground fault protection. This is the first time with this boat that we have encountered that standard.

When we arrived the manager greeted us.* He was pulling a rather substantial cart. As I understand it the cart is a portable isolation transformer with the ability to display the leakage encountered.

He plugged it into the pedestal and we plugged into the cart. He then had us energize circuits one at a time to verify we would have no problems. Once we demonstrated we were good we could then plug into the pedestal.

Very, very neat. He said they bought the cart after having some number of boaters insist the problem couldn’t be THEIR boat.

We now know the only leakage we have is 8 mA when the inverter is energized. That is a research project for another day.
 
Interesting that the marina went as far as buying a diagnostic tool to let you see what your leakage was on the various AC circuits throughout your boat.

I have faced this a number of times over the years. It is a result of marinas upgrading their electrical systems and installing GFCI protection (or a similar acronym) to their power supply. Boats being wet develop faults so they trip these new protective devices. The only way to solve it is to trace down the offending circuit and fix it. Or install your own isolation transformer.

I have a bit of a problem with the whole concept of shore power GFCI protection. I don't think it is bringing an additional element of safety to our boating world unlike GFCIs installed in galleys and heads which I totally support. But they are here to stay and we need to adapt to live with them.

David
 
FT PIERCE city Marina used to have you come to the fuel dock to test your boat before putting you out on the new docks.

Not sure after they just renovated the fuel dock.
 
Isn't the idea behind shore power GFCI to reduce the risk of electric shock drowning? If our boats put enough current into the water to trip the shore side GFCI then without the shore side GFCI wouldn't we putting persons in the water nearby at risk? As I understand it it is more of a problem in fresh water than salt water but can still happen in salt water.

Electric Shock Drowning: A Silent Killer just one of many links turned up.

DavidM said:
Interesting that the marina went as far as buying a diagnostic tool to let you see what your leakage was on the various AC circuits throughout your boat.

I have faced this a number of times over the years. It is a result of marinas upgrading their electrical systems and installing GFCI protection (or a similar acronym) to their power supply. Boats being wet develop faults so they trip these new protective devices. The only way to solve it is to trace down the offending circuit and fix it. Or install your own isolation transformer.

I have a bit of a problem with the whole concept of shore power GFCI protection. I don't think it is bringing an additional element of safety to our boating world unlike GFCIs installed in galleys and heads which I totally support. But they are here to stay and we need to adapt to live with them.

David
Click to expand...
 
#1 We have always had customers tell us that their boats AC system was not the issue.

#2 They always blame it on the marina.

#3 We have always found the customer boat to be the issue with regard to AC leakage.

If the shore based GFI trips, your boat has an issues even if it's just a small bit of leakage.
 
Great solution by the marina. Many (mostly older) inverters would throw a quick spike when being connected, then would settle down (clearly a non-electrician's explanation, please don't quote me...). The spike was well within the tolerances of older dock connections. The newer GFCI standard trips before the inverter "settles down." Solution, by a compliant inverter. Or put in your own isolation transformer.

Many boats are now finding that they have other wiring issues (for example, using the same "ground connection" for AC and DC circuits, which is a Bozo no-no). I know it has been a PITA for many boat owners, but after a few years of this I think we will all be safer.
 
Robster_in_edmonds said:
Many boats are now finding that they have other wiring issues (for example, using the same "ground connection" for AC and DC circuits, which is a Bozo no-no).
Click to expand...

And this is one of the reasons why we have so many marine electrical issues, a lack of understanding of the actual safety standards.

AC (green) and DC ground are supposed be bonded on-board the vessel under both ABYC (even with an ELCI) and the ISO/RCD standards, though ISO/RCD allows an exception if a whole boat RCD is fitted.

AC Green/Grounding and AC Neutral/White are not to be bonded on board unless inverting, generating or you have an isolation transformer installed..
 
Our boat would trip the ELCI on a dock as soon as we plugged it in, a friends boat did the same. It took a lot of time and work to get them fixed. There were multiple problems on both boats. Now they both work fine on a protected dock.
 
A test I've seen marina personnel perform that would be easy to replicate on your own. Male and female plugs to fit your shore power cord and the marina. 3 wires with the outer sheath stripped leaving insulated conductors. Pull some slack in all three and create loops. Using a high quality multi meter such as a Fluke with three digits to the right of the decimal place measure the current on all 3. If HOT and NEUTRAL are the same and safety GROUND is zero you're good to go. If not, then not. If not turn off everything then enable one circuit at a time until the fault reappears. there's your problem.
 

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danderer said:
Stopped recently at Indian Creek Yacht and Country Club. They redid their docks in the last year or so and now all power pedestals implement the 2017 standard with 30 mA ground fault protection. This is the first time with this boat that we have encountered that standard.

When we arrived the manager greeted us.* He was pulling a rather substantial cart. As I understand it the cart is a portable isolation transformer with the ability to display the leakage encountered.

He plugged it into the pedestal and we plugged into the cart. He then had us energize circuits one at a time to verify we would have no problems. Once we demonstrated we were good we could then plug into the pedestal.

Very, very neat. He said they bought the cart after having some number of boaters insist the problem couldn’t be THEIR boat.

We now know the only leakage we have is 8 mA when the inverter is energized. That is a research project for another day.
Click to expand...




All the Inverters I know of have a draw when energized even when nothing is plugged in, the better(more expensive) the inverter generally the smaller the draw. 8ma would be within the realm of what it prob draws at rest. I’d look into it with research online and maybe a multimeter just to be sure but I wouldn’t search to much. 8ma may just be the cost of doing business for that model.
 
Jmarsh203 said:
All the Inverters I know of have a draw when energized even when nothing is plugged in, the better(more expensive) the inverter generally the smaller the draw. 8ma would be within the realm of what it prob draws at rest. I’d look into it with research online and maybe a multimeter just to be sure but I wouldn’t search to much. 8ma may just be the cost of doing business for that model.
Click to expand...
This isn't a question of power draw. It's leakage; power drawn that's not returned via the neutral and instead returned via some other path to ground.
 
Friday Harbor Municiple Marina had several isolation transformers bolted to hand trucks that they used to plug in boats that were unable to plug in without tripping the breakers. The staff brought it out, plugged the boat in and chained the transformer cart to the dock.

Excellent marina customer service.
 
Happened to us a couple of months ago at the Marathon Marina in the Keys. We're waiting on the electrician to come out and take a look at our boat.
 
We were proactive in that we assumed our 1989 vessel would pop the ELCI breakers- so we installed an isolation transformer onboard to solve 2 problems:

  • Change the input from twin 30A to a single 50A split into 2 legs.
  • prevent problems with new ELCI pedestals.
 
Pau Hana
You do know that if you were leaking AC into the water column before installing the isolation transformer, you still are. Your boat will not trip the 30mA RCD on the pedestal but any leakage is still leaking.
 
CharlieJ said:
Pau Hana
You do know that if you were leaking AC into the water column before installing the isolation transformer, you still are. Your boat will not trip the 30mA RCD on the pedestal but any leakage is still leaking.
Click to expand...


As far as I know, we aren't leaking anything per what we have been told by marine staff testing the area.
 
CharlieJ said:
Pau Hana
You do know that if you were leaking AC into the water column before installing the isolation transformer, you still are. Your boat will not trip the 30mA RCD on the pedestal but any leakage is still leaking.
Click to expand...

How can AC be leaked into the water with an isolation transformer wired correctly?

With an isolation transformer, earth is no longer ground on the boat so where is the AC from the boat returning to through the "water column"?
 
Last edited:
My Post #15
Pau Hana
You do know that if you were leaking AC into the water column before installing the isolation transformer, you still are. Your boat will not trip the 30mA RCD on the pedestal but any leakage is still leaking.
Click to expand...

@syjos questioned my logic:
How can AC be leaked into the water with an isolation transformer wired correctly?
Click to expand...

You are absolutely correct. I filed that erroneous factoid away years ago and never even questioned it until your challenge when I had to draw out the circuit and discovered there cannot possibly be a water path with its resulting electrical field. The only exception would be for a short to the case in which case the water path would come into play and an electric field would develop. Very unlikely.

Proof once again that we may know a lot but we don't know everything.

Thanks for setting me straight.
 
Electrical leaks on a boat are a danger to your boat in the form of electrolysis as well as neighboring boats. My experience is in saltwater. Zincs, in heat exchangers as well as running gear get eaten quickly. Then the next softer metal begins to get eaten. The new standard for shore power is actually doing boaters a favor by exposing stray current.
 
I'm going through zincs like candy on Halloween. I've been at a marina going on 2 month now. Before that we were on the hook quite a bit. I scrape the bottom once a month and have been replacing shaft and rudder zincs each month too. Wondering if my zincs are protecting the whole marina.
My understanding is the the "leak" comes through the shore powers ground. And the latest is what eats up the zincs. Is that correct? Would a galvanic isolator stop this?
Pic shows a one month old and a new zinc20200814_112940.jpeg
 
Talk to your neighbors to see if they are having the same issue. The sources could be, shore power, someone else's boat, your boat or any combination.
 
Pmcsurf1 said:
I'm going through zincs like candy on Halloween. I've been at a marina going on 2 month now. Before that we were on the hook quite a bit. I scrape the bottom once a month and have been replacing shaft and rudder zincs each month too. Wondering if my zincs are protecting the whole marina.
My understanding is the the "leak" comes through the shore powers ground. And the latest is what eats up the zincs. Is that correct? Would a galvanic isolator stop this?
Pic shows a one month old and a new zincView attachment 106515
Click to expand...

A good galvanic isolator should stop other boats from "borrowing" your zinc from the interconnected green ground wire.

An Isolation Transformer is the ultimate protection against galvanic corrosion, swimmer shock hazard and leaks to earth. You will be able to plug into any marina pedestal without fear of tripping ELCI - GFCI breakers, reverse polarity etc.

Full disclosure, I am biased since I am a dealer for Victron Isolation Transformers.
 
Thanks for the full disclosure.
I've heard they are heavy and expensive. Whats the install like? Plug and play or super involved?
 
Last edited:
Pmcsurf1 said:
Thanks for the full disclosure.
I've heard they are heavy and expensive. Whats the install like? Plug and play or super involved?
Click to expand...

The 3600 watt Victron Isolation Transformer weighs 50 lbs and cost around $650 - $700.

Install can be easy depending on space availability. The 3 AC wires (black, white, green) between the shore inlet and breaker panel is cut and the transformer wired between the two.
 
I'm sure I'm confused. What is the difference between Isolation Transformer and a galvanic isolator?
I've heard the transformers weigh hundreds of lbs and cost 3 to 4 thousand dollars.
 
Pmcsurf1 said:
I'm sure I'm confused. What is the difference between Isolation Transformer and a galvanic isolator?
I've heard the transformers weigh hundreds of lbs and cost 3 to 4 thousand dollars.
Click to expand...

A galvanic isolator is wired into the green ground wire coming into your boat between the shore inlet and the breaker panel. The isolator creates a one way path in the ground wire with diodes to prevent other boats from using your zincs but still allow shorts to dissipate to ground.

An isolation transformer consists of a primary and a secondary coil winding that are electrically separated by a main insulation. Capacitive coupling allow transmission of electricity between the windings without an actual electrical connection between the windings. The isolation transformer becomes the power source and earth is no longer ground.

The galvanic isolator protects the ground wire only in an AC system. The isolation transformer protects all three incoming AC wires.
 
Syjos,
Great info. Thanks for taking the time. I was looking at galvanic isolator for around $400. I'd rather spend a little more and get the whole shooting match.
I've got 50 amp service coming in from bow and stern. I just need to install before the panel.
Would the 3600 work for 50 amp?
 
Is that 50a 125/250v? The 30a 125v isolation transformers are not to spendy. However, and please correct me if I’m wrong, a 50a 125/250v isolation transformers is $2000+and weighs in at 235 lbs.
 
tiltrider1 said:
Is that 50a 125/250v? The 30a 125v isolation transformers are not to spendy. However, and please correct me if I’m wrong, a 50a 125/250v isolation transformers is $2000+and weighs in at 235 lbs.
Click to expand...
Hope I didn't get scammed. I just bought on Amazon.
Weight little over 50lbs. I've heard Vicron is reputable co. I'm replacing 2 zincs a month so I hope this helps. Screenshot_20200817-211634_Amazon%20Shopping.jpeg
 
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