Help needed with Reverse Polarity & breaker Issue

[Domroberge]

Hi everyone!

For the second summer in a row, the breaker located at GFI electrical box in the forward sail locker keeps on tripping periodically when connected to shore power. When I hauled out the sailboat last fall of 2023, I discovered a serious discolouration/oxidation around the Frigoboat plate under the boat. See Pictures! During this time, the reverse polarity light on the main panel comes on very faintly when the sailboat is connected to shore power. We suspected that our sailboat is either affected by stray current at the marina, or that we have some type of electrical leak from our boat.

This past spring prior to launch, I had the Frigoboat plate changed. The technician recommended that we also install a Dynaplate. This was done in addition to changing my magnesium anodes (we sail in fresh water) on the sail drive again this year.

Despite these changes, our sailboat GFI breaker on-board the sailboat kept on tripping this summer, and I have noticed similar discolouration of the hull when diving under the boat while at anchor this summer. I have been working with an ABYC certified electrician, but the root cause hasn't been found yet.

The issue started after I had our 4 AGM house batteries changed to 3 Victron lithium batteries with a new Victron changer/inverter for the house batteries.

The engine battery and 4 AG batteries for my windlass and bow thruster are still charged by a separate charger.

Our sailboat is a 2011 Jeanneau 50DS

Has anyone seen this type of problem? Can anyone suggest a way to diagnose the problem?

[smac999]

a dim rev pol light is normally caused by a bad or lose netreal wire. as the voltage drop causes a few volts drop in the white wire. which causes a few volts between white and green which lights up the light dim.

easily checkable with a volt meter to see if you have real rev pol or not, or just a few volts loss on the white. under more load the voltage diff will increase and it will get brighter.

if the gfi started triping right after the inverter install then it's probably a inverter wiring issue. many are installed wrong and then they trip elci / gfi breakers

[GordMay]

Blue Sea Systems has an explanation of the RPI faint illumination phenomenon:
“AC Reverse Polarity False Indicators”
➥ https://www.bluesea.com/support/arti...lse_Indicators

Originally Posted by BSS

“... It is possible for such a circuit to faintly illuminate the Reverse Polarity light even though the circuit is properly wired. It is useful for boaters to understand how this can occur...”

[Domroberge]

Will check.. thanks a lot for the feedback!

[danno7]

The explanation for the reverse polarity light is probably one issue, but the GFCI could be a different issue. A GFCI typically measures the current in the HOT wire and compares that to the current in the NEUTRAL wire. I do not know if they will trip if the voltage on the NEUTRAL is different than GROUND; it might.

If the GFCI problem only happens when on shore power and not when inverter powered, that could be a clue.

I am wondering if the inverter has Neutral not connected to Ground? If the neutral is not connected to ground when the power is from the inverter (shore power is completely disconnected) then the GFCI will never trip. Try this... disconnect from shore power, turn the inverter off, and measure the resistance between the neutral and ground on the GFCI?

What have you got plugged in to the GFCI?

[GordMay]

A Ground Fault Circuit Interrupter [GFCI] offers personal protection against lethal [fatal] electrical shock, or electrocution.


The NEC defines a GFCI as "a device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds some predetermined value that is less than that required to operate the overcurrent protective device of the supply circuit."

A GFCI protection device operates on the principle of monitoring the imbalance of leaving [ungrounded ‘hot’] and returning [grounded neutral] current, through the current transformer. When the imbalance reaches between 4mA to 5mA, the solid-state circuitry opens the switching contacts, and de-energizes the circuit.
It does not monitor the grounding conductor, and so it will still operate, in a 2-wire circuit, without a ground.

According to a study*, conducted by the American Society of Home Inspectors [published in IAEI News, November/December 1999], 21% of GFCI circuit breakers, and 19% of GFCI receptacles tested did not provide GFCI protection. Yet, the circuit remained energized!
In the examined cases, failures of the GFCI sensing circuits were mostly due to damage to the internal transient voltage surge protection [metal-oxide varistors], that protect the GFCI sensing circuit. This damage resulted from voltage surges, from lightning and other transients.
In areas of high-lightning activity, such as Southwest Florida, the failure rate for GFCI circuit breakers was more than 57%.
* “It’s Time We Update UL-943 Again” ~ IAEA News [September 5, 2017]
➥ https://iaeimagazine.org/2017/julyau...-ul-943-again/

See also:

“What a ground fault circuit interrupter does and what it does not do”
➥ https://electrical-engineering-porta...terrupter-gfci

“GFCI Basics” ~ EC&M Magazine
➥ https://www.ecmweb.com/content/artic...11/gfci-basics

[danno7]

So it seems Gord agrees with me and answers the unknown I posed about the ground wire. A GFCI does not care about the ground voltage or current.

This takes me to the point of the inverter neutral not connected to ground. A GFCI in this situation will never trip. You can connect the hot wire directly to ground, and nothing will happen. There is no return path for the current in the hot wire.

If the ground in the inverter is not connected to the return, it must be a faulty GFCI. If the neutral is connected to ground, you could have the GFCI operating normally and tripping because something connected to it is faulty. Or it could be a bad GFCI.

This is all dependent on some item you are not aware of and thus not telling us, or us not understanding the whole picture .