Shore Power tripping GFCI outlet

[Bayhouse]

2003 330 express

At my empty lot (with dock/boat), I have metered electric and a line running underground to the bulkhead. At the panel, there is an outlet and that underground wire plugs into the outlet so basically I have a very long extension cord.

With a GFCI outlet at the panel, with all AC switches turned off, when I flip the shore power switch the GFCI trips.

I put a regular outlet (no GFCI) and everything works great, but obviously this is not very safe.

I tried a small GFCI pig tail between the shore power and the long extension cord - trips the GFCI with the main.

Note, I do have a 30 to 15amp converter in line.

The cord and the shore power plug on the boat are both new and the connections in there are clean but the problem continues.

No problems at marinas with 30amp service.

Any suggestions about where to start?

 

[Meanwhile]

I can sympathize. I ran my shore power to an outlet that had a 40' reel and it kept popping the GFCI. I switched to another circuit that is also a GFCI and a much longer cord, it works all the time. I think some GFCI's are better than others.

 

[seasick]

Bayhouse said "I tried a small GFCI pig tail between the shore power and the long extension cord - trips the GFCI with the main. "

If you tried a small GFCI pigtail connected to the shore power and NOT the extension cord, did it trip. If yes, you have a problem with the shore power. If no, your extension cord is bad.
If you plug in the extension cord at the dock and plug in the short GFCI adapter at the boat but NOT the boat outlet, does it trip?
I assume the 30 to 15 amp converter you mentioned is just a device to go from a 30A twist lock receptacle to a standard duplex receptacle. It that true? What plug is on the short GFCI cord? If it is standard duplex, then the test I mentioned would now also include the 30A to 15 A adapter cable and that could be bad.

Based on my experiences, the most likely culprit is the wiring and outlet at the shore power point followed by a defective GFCI outlet in the boat.



As you also noted, it is not a good idea to override or eliminate the GFCI receptacle

 

[wspitler]

Try cycling your galvanic isolator switch. (under the starboard aft gunnel in the cockpit) It must be on for the ground circuit to be completed. I assume you have tried another load source such as a power tool or light to eliminate the boat as a source of the problem and the GFCI does not trip?

 

[seasick]

Try cycling your galvanic isolator switch. (under the starboard aft gunnel in the cockpit) It must be on for the ground circuit to be completed. I assume you have tried another load source such as a power tool or light to eliminate the boat as a source of the problem and the GFCI does not trip?

It was not clear to me if the tripping occurred when shore power was connected but nothing plugged in or it trips when something was plugged into the AC receptacle. I assumed the first case.

 

[wspitler]

It was not clear to me if the tripping occurred when shore power was connected but nothing plugged in or it trips when something was plugged into the AC receptacle. I assumed the first case.

I think I understood that it didn't trip the GFCI until the boat's AC master was selected to "on" even though all of the switches on the AC buss were selected off. (no loads) That would happen, I believe, if there was a problem with the Galvanic isolator or it was selected off.

 

[dogdoc]

I am not clear on exactly how your situation is wired. A schematic/ wiring diagram from the pole to boat would help clear that up. What I think is happening is when you plug your shore power cord into a 15 amp gfi outlet the gfi trips. The way a gfi works is it measures the current from the hot and then back from the neutral. If at some point in the circuit there is a current loss of 5ma or greater the gfi trips. This is usually a short to ground and does not have to be much to lose 5ma. The gfi will not trip unless there is a load applied. You could plug something into the gfi outlet, night light, battery charger anything and see if it trips this would indicate a problem before the boat. If not then the problem is from the plug to the boat and somewhere on the boat there is a short to ground. Not sure of your location but if it is salt water plenty of opportunity for small shorts to cause a 5ma drop.

 

[seasick]

A GFCI does not need a ground wire in order to trip properly. A GFCI simply trips when a fault is detected on the neutral wire . It is also legal to wire a GFCI with out a ground but the wiring changes a bit.
So I am not sure why a galvanic isolator would cause the device to trip. I need to do some research.
On exterior GFCI failures, the causes are mixed; they usually fail due to water intrusion/corrosion or insect nests.In these cases the GFCI trips as soon as power is turned on. Nothing has to be plugged into it.

At the dock, a bad extension cord is often the problem. All it takes is a single quick dunk in sea water of the female end of the cord to start corrosion and current leakage.
Knowing the exact configuration of cables and devices and when the receptacle trips will help.

 

[Bloodweiser]

Are you going from dock gfci to a Boat gfci ? I

 

[seasick]

If he had to use a 30A to 15A adapter, that tells me that he has a standard 30A twistlock receptacle but wanted to plug in a standard 3 prong extension cord.. The code for marina wiring does not require ground fault for the 30 or 50 amp service. 115V 15 amp is a different story. The assumption is that a shore power connection would be to a 'shore power' wired vessel and that would have protection for standard receptacles. In addition, the shore power would have polarity reversal detection.

These types of connections using non protected adapter pig tails are dangerous for several reasons, the most important is that the connection of the two cords is not weather resistant nor mechanically protected from separating even a small amount. That junction can get wet and create stray currents or shorts. The shore power has a 30 amp breaker but the extension cord can't handle anywhere neat the amount of current. The result can be overheating and fire. I have seen boats burn due to the use of residential (cheap) extension cords.
So if you are going to connect to a shore power 30A connector, use a shore power cord. If you don't have a shore power receptacle on the vessel, use the pig tail GFCI adapter on the boat protected from the elements or running water ( like when it rains). A better solution for connecting a non shore power equipped boat to power is to have a standard GFCI receptacle at the dock and run a good high quality heavy gauge extension cord sized for max load and also for cable length.

 

[Bayhouse]

Thanks all, to clarify some questions:

The boat has factory installed 30amp shore power (recently replaced plug) and I'm using a 30 amp Marinco shore power cord for the boat connection from the extension cord.

On the male side of the 30amp shore power cord, I'm plugging into a Marinco 30amp to 15amp pigtail adapter to the extension cord.

That pigtail connects directly to the extension cord from the panel.

I've tried both a regular 15amp GFCI outlet at the panel as well as this 15 amp GFCI power block between the extension cord and the pigtail adapter.

If I plug everything together in all scenarios, the boat CB only trips when I flip the main shore power CB on the panel to the on position.

I have used the extension cord for power tools with the power block GFCI and have had no issues tripping the circuit.

I am exclusively in salt water,

There are GFCI outlets on the boat, both in the cabin and at the helm.

The panel does have reverse polarity detection, have no idea if it works.

I think the galvanic isolator switch is binary, if it's off, I wouldn't even get power to the boat. In my case, I have power until I flip the mains.

Thanks all for the help, keep it coming.

 

[seasick]

The isolator is on the ground wire not the neutral. In ir out, you can still have power.
I am not clear on what trips when you " plug everything together in all scenarios, the boat CB only trips when I flip the main shore power CB on the panel to the on position.:

That breaker is not a GFCI device. It says you have a short or excessive load. When it trips are all the other 110v switches off? If not, turn everything off and see if the main trips

Also, are you saying that you have a shore power cord running from the boat to the dock but at the dock you had to use a converter to connect to dock power ( in that case, I would assume the shore receptacle is not a 30A twist.

And finally, you say that you replaced your shore power plug. I suggest you take take that thing apart and see if something got messed up with the wiring

 

[SkunkBoat]

Start with what you recently replaced...30 A shore power plug on boat...correct Hot/Neutral/Ground?

 

[RussGW270]

I would not have found the bad batteries if my shore power had not tripped, but.. the toggle is broken, so I have a new 30amp arriving tomorrow. I ordered it straight from Paneltronics and was 85 bucks with like 3-day shipping included. I am measuring the shore power cables we have. The previous owner was nice enough to give us the cables, but I do not think we are getting true 30amps. They have/had an adapter for the cable, and so I think it is doing, maybe 20amps max... not really 30 amps. Going to see how long the cable is and order a full cable that length, keep the adapter as a spare or use it for the house connections when under the cover.

 

[seasick]

If any of the outlets or plugs in the shore connection look like standard residential plugs, you can't (shouldn't) draw 30 amps. They are not rated for it. The theoretical max current is set by the dock circuit and what size breaker it has.
That said, regular extension cords may be rated for MUCH lower currents so be careful. If you draw more than they are rated, they will heat up, may melt, and may catch fire. They will also add voltage drop and that can make things even worse. They will not unless hey melt and short wires will noy cause your boat main breaker to trip with nothing turned on.

 

[Bayhouse]

Start with what you recently replaced...30 A shore power plug on boat...correct Hot/Neutral/Ground?

I had the same problem with the old shore power plug and am confident that it's wired correctly.

 

[Bayhouse]

Update. Had the electrician out and he did some work in the box. It was not pretty whoever jury-rigged the old setup and I'll spare the details. He re-wired to code, switched existing outlet to GFCI and added a new GFCI outlet.

I can now run shore power on the boat without tripping the main shore power CB or the GFCI - great news! My panel gauge is showing 120/60.

However, now my battery charger (ProNautic 1250c3) is reporting an "Under Voltage" fault.

Manual reports "If Under Voltage LED stays illuminated for longer than 20 seconds the batteries are heavily discharged" - I don't believe this is the case, i have a monitor on the batts and it reads 12.2 (been a couple of days since last use). Getting hit with the tropical storm today so can't check with a VM.

 

[seasick]

If your batteries measure 12.2 volts at the battery and when using a decent voltmeter, your batteries are very discharged. Resting voltage when charged should be about 12.6 or so depending on the battery type'
One other question; When you measured the voltage was the battery charger on? If so, something is wrong there also.