Electrical issue becoming a docking problem

[Hatteras58]

Today we had our third experience not being able to connect to shore power in a marina with ‘upgraded’ electrical (i.e., NEC 2015 or newer). I won’t pretend to understand the problem but it’s apparently related to GFCI sensitivity at the dock pedestal. Whatever the explanation, we must have enough stray current that we immediately trip the 50A breaker on the pedestal upon connection. Again, this is the third marina we’ve been to where we’ve had the choice of leaving or powering up with generator or inverter. Is an isolation transformer my least expensive fix? If they modernize the electrical at my home marina, we’re screwed! Any comments?

[Captain Ralph]

Something is leaking to the green wire, using your green wire in place of the white wire or your white and green wires have been tied (strapped) together.

When the GFI senses any current on the green wire, it faults and trips the dockside service breaker.
Green - ground for fault current only. White for neutral or return current only.

An isolation transformer may not correct this issue.
It would be smarter and safer to find the fault.

Try this to help isolate and find the option causing the error.

Plug into the dock with every ships breaker off. After every move, check the dock breaker. Works best with 2 people.

Turn on the ships service breakers, then panel enable switches.
Then turn on one option breaker.
Turn that option breaker off, and turn on the next option breaker.
Turn that option breaker off, and turn on the next option breaker.

If during one at a time testing, the dock service GFI does not trip, then next step;
Turn on the A/C water pumps on first and leave on, then each A/C option.
Run your A/Cs.
Not tripping? continue;
Then, one option breaker on and leave on and turn on the next one.
Some where, some option will trip the dock GFI breaker.

Most of the time, I have found white and green wires have been tied at the gen-set or inverter.
More evident on 115Vac than 230Vac equipment when the 230Vac equipment is not in error.
These should only be tied while the gen-set or inverter are active and off of the dock.

Other issues I have found are an A/C compressor leaking to the frame, an A/C compressor capacitor leaking to the metal enclosure box, an option truly leaking fault current (battery chargers most common).

This is going to take some time but still the quickest and least expensive DIY way to find your issue.
Other ways are to isolate your boat from the dock, then test green & white wires with an OHM meter.

[dar636]

Hello-

I had the same issue on my 76 YF and used the one breaker at a time method, in my case it was the 110v water heater tripping dock power. Good luck,

[Bob Quinn]

Hello-

I had the same issue on my 76 YF and used the one breaker at a time method, in my case it was the 110v water heater tripping dock power. Good luck,

I saw a similar situation with a hot tub heater.
If the internal heating element corrodes, it then leaks current to ground, hence the GFCI does what it is supposed to do.

I believe I have heard things like hair dryers or other electric heating elements may for some reason cause trips - this I can not explain, just hearsay.

[Hatteras58]

Capt Ralph, thanks for taking the time to give me this detailed instruction. Greatly appreciated and I will be on this immediately. Hopefully, something obvious wiil show up. Thanks again

[SKYCHENEY]

An isolation transformer is not the cheapest fix but it is the best fix. Once you install it, you won't have to worry about tripping any of those marina systems ever again; no matter what new equipment gets installed on the boat.

[Captain Ralph]

An isolation transformer is not the cheapest fix but it is the best fix. Once you install it, you won't have to worry about tripping any of those marina systems ever again; no matter what new equipment gets installed on the boat.

I'm concerned this would be just be a patch to get plugged into the dock.
If there is fault current on the ships green wire somewhere, it would still not be correct and may continue not be safe on board.

Further, some transformer installations do pass the green wire all the way thru and the dock breaker would continue to trip if fault current was still on the green wire.

[Pascal]

Indeed adding an isolation transformer is the best solution but also the most expensive. Reason it works is that with a transformer you don’t bring the neutral on board so you can’t trip the new GFCIa

Usually testing breakers one a time will not work for a very simple reason : single pole breakers do not interrupt neutral and it is the neutral when connected to ground that will cause the problem

To isolate the guilty appliance you need to physically unplug or disconnect each appliance.

Start with oven, cooktop, fridge, washer etc. don’t over look some of the 220v stuff like oven which may still use 120v with neutral for timers or lights. Non marine inverters are also prime suspects.

Generator should not cause the issue as the rotary switch also cuts the neutral. Generator are designed to bind G to N anyway

[Captain Ralph]

Indeed adding an isolation transformer is the best solution but also the most expensive. Reason it works is that with a transformer you don’t bring the neutral on board so you can’t trip the new GFCIa

Usually testing breakers one a time will not work for a very simple reason : single pole breakers do not interrupt neutral and it is the neutral when connected to ground that will cause the problem

To isolate the guilty appliance you need to physically unplug or disconnect each appliance.

Start with oven, cooktop, fridge, washer etc. don’t over look some of the 220v stuff like oven which may still use 120v with neutral for timers or lights. Non marine inverters are also prime suspects.

Generator should not cause the issue as the rotary switch also cuts the neutral. Generator are designed to bind G to N anyway

With all due respect to Pacal, I do have different opinions.

Pending the installation of the transformer, the ground wire may still connect fault currents from the boat to the shore service and trip the service GFI.

It is not neutral that trips a Ground Fault Interrupt breaker. It could be fault current on the ground wire.

When testing single pole breakers, on the USER side of the panel, at least electricity is removed from the option outlets or devices. Not a complete catch all but a good safe start.

Yes neutral to ground is a common problem, not the only problem that causes GFIs to trip.

Better marine and RV inverters have set-up or strapping options that determine how or when ground and neutral are tied together. This may need further investigation to insure the installation is per required spec.
Non marine or RV inverters (UPSs) where neutral and ground are always tied should not be on board.

Yes, Gen-sets with complete (4 pole) isolation breakers or transfer switches are exempt.
Interesting how many 2 & 3 pole transfer switches are out there.

Bottom line; GFI systems are designed to improve safety around wet locations where electricity is present. It can still be a challenge interfacing different technologies together.
It is a wave of the future that should not be patched or covered up but fixed correctly.

If anybody has any concerns about the electric options on board your boat, please consult with a real & certified marine electrician.

[Hatteras58]

Sounds like we need to investigate this situation much deeper with help from a competent electrician. We did, however, test the AC systems (120 and 240V) per Captain Ralph's instructions and did not find a single problem with any of the breakers or the A/C units. What we found was that if the Outback inverter is ON when you turn on the power at the pedestal, the dock power trips immediately. This does not happen at our home marina which has not upgraded the electrical to the 2015 or newer code. If we turn the inverter off prior to turning on the dock power, the connection is not lost. I am not qualified to explain this problem, but I will say that one of the 5-position rotary switches in the main panel recently started chattering loudly when the boat is on inverter power. Any connection to the GCFI-dock power issue? Who knows at this point.

Once again, I do appreciate the feedback on my original post.