House GFI trips with boat shore power cord

[Cal33-2_Owner]

This may have already been discussed, but my search didn't find anything.

The Shore power on my sail boat works fine at the dock. Now that the boat is out of the water and at the house, I can not get the shore power to work. Yesterday I purchased an brand new extension cord adapter for 15A 125V. I will get a shore power light on the panel, no indication of reverse polarity, looks good. Switch the Boat panel AC main on, dead... GFI on the house (20A) is tripped. Thoughts?

 

[Bill Roosa]

Try turning off all the sub CB on the boat and then turn on the main AC. If the main does not cause the gfi to trip then turn on each sub CB till you get a trip. Also check the GFI at the house for a loose ground wire at the outlet box and at the CB box.

 

[Cal33-2_Owner]

all 3 sub switches already off, I have tried 2 different gfi's around the house and one directly off the fuse panel in the basement to see if it was a bad gfi, same result with all 3 gfi's. On the main AC panel, there are 3 subs, If they are off, what is energizing when I turn the main AC on? How do I figure that out? Why would the system work well while in the water, but not on land?

 

[KD3PC]

galvanic isolator? transfer switch/ or something else wired between the power inlet and the AC panel?

 

[Charles Erwin]

If you have a green white connection on board the boat the return will pass via both and your house GFI will trip. It would work on the water because the typical 30 amp shore power supply is not GFCI protected.

In any case - plug the shore power cord into the receptacle at the boat. Go to the other end of the cord and test to see if there is continuity between white (neutral) and safety green (grounding) pins. If so you need to find and eliminate that connection. Battery charger, water heater, microwave are typical culprits.

By the way how do you plug 30 amp cord into your 15/20 amp house receptacle?

Charles

 

[LeoLambert310]

If you have a GFI on the boat you'll have to trip as you can not have 1 GFI feed power to the second.

 

[uncledom]

I would need to see a wiring diagram but, I would think your boat does not have an isolation transformer. This in essence lifts the ground and forces the GFCI to see all power as just between the hot and neutral. It would never trip on a fault on the secondary side of the transformer. I would guess that there is a load or loads that are wired directly to the buss so that as soon as the main breaker goes on that load or loads are energized. My battery charger/inverter and my galvanic isolator are both wired this way. I have read that galvanic isolators can cause a GFCI to trip when there is a problem.

 

[twalker H260]

If I recall correctly promariner and a few other brands of galvanic isolator a have an issue with their monitoring systems tripping the gfi circuits.

 

[LeoLambert310]

OK if you have looked he had no problems with the power at the dock but only when he set it up at home.. now most home outlets are GFIed and as I stated you can not feed power from one GFI to the second the system will trip. I found this out at some docks that had only 15amp power and the system tripped, I tripped the boats GFI's and shore power was ok to the charger but no 110volt to the cabin outlets.

 

[Ken Cross]

I've found sometimes series GFCIs trip, but not always. The ones I've seen inside have a simple inductive pickup with both power and return. When power and return don't mirror each other out of phase, they trip. I'd like to know why that causes one GFCI to trip when in series?

Ken

 

[Cal33-2_Owner]

I suspect the AC switch itself at this point (or maybe the On light or the Test switch). See the attached photo ACswitch.jpg. The house GFI still tripped when only the switch was wired (Blacks to accessories removed in this photo, I then removed all accessory whites and greens from the bus bar, no help). I can not find a wiring diagram for a Carlingswitch on line. Is this wired correctly? What is the resistor I have ?'ed.

 

[Ron20324]

I hope you are making a wiring schematic of your system. I see a few problems in there. If it was mine, I'd wire the line ground right to the breaker, then jumper it back to that buss bar. Usually ring terminal are used, though it looks like you used spade tips with the bent ends. /// I doubt that IS a "resistor", as you'd short to neutral when operated. Maybe that's your GFI problem, though I suspect SOMEWHERE you have a green and neutral connected via a wire path- a no-no on board ship. /// It is kind of dark in there, but is the the light on the right the reverse polarity light? My light is wired across ground and neutral, so as to light up when neutral become energized. /// Also, I'd find a way to get some of those wires off the breaker lugs.

 

[uncledom]

If they are current GFI outlets and they are not faulty, you should be able to plug ten of them one after the other without any trips. If a properly installed and working GFI outlet or device trips there is an imbalance between the hot and neutral conductors. There is no reference to ground. There is an assumed leakage to ground, possibly through a human, and so the circuit trips open for safety. In reality if you were to take a light bulb or other load and wire to the hot prong of the outlet or device and run the neutral to the panel neutral directly it would cause the GFI to trip due to a percieved imbalance. It can only compare the current between the hot and neutral directly connected to the Line side of the GFI outlet or device.

 

[uncledom]

Cal33 I think that is for the breaker power indicator lamp. Disconnect it and see if the lamp goes out. Maine Sail probaly knows this by heart. My question is this, GFI trips as soon as the main breaker only is turned on? If so I think my first response is going in the right direction. You need to see what is connected to the main breaker load side but does not have a means of disconnect other than the main breaker. Maybe there is a fuse or inline popout circuit breaker button that is not an on/off switch. Look to those devices.

 

[Captain Bucknut]

Any chance you may not have continuity between the AC and DC systems? If that is the case, when plugged to shore your ground will seek continuity through the water. Once out of the water there is nowhere to go, possibly causing the GFCI to trip. Quick check the continuity from the battery to the shore power L clip in the socket.

 

[Maine Sail]

That breaker is a double pole 30A with a 65VAC reverse polarity trip coil (left side with green grounding wires) and surge arrester (red circle). If that breaker detects a reverse polarity situation it will trip the line & neutral breaker.

There are many things on a boat that can cause a 4-6mA GFCI to trip and the number one is quite often an on-board neutral (white) to grounding (green) bond.

Sadly there are far too many hacked together marine AC systems out there that it is really impossible to say what is causing your GFCI to trip. Start by unplugging the vessel and checking for continuity across the White/Neutral Bus and the Green/Grounding Bus. There should be no continuity.

Possible causes:

On-board Neutral to Earth bond
Water heater
Improperly wired inverter
Non Marine Inverter
Inverter transfer switch too slow
Galvanic Isolator (with auto testing circuit)
Non-Marine battery charger
Improper system wiring


Beyond that do yourself a favor and replace your homes 120V 15A outlet with a NEMA L5-30R so you can use your standard shore power cord. While it won't be able to provide 30A on a 15A circuit the shore cord will be better protected.

Put it all in a nice watertight box on the exterior of the house and have your electrician install a 30mA ELCI in the homes AC panel for that circuit and your "trip" problem is most likely gone.

Still keep in mind that your GFCI is telling you something. It is telling you that you need to figure out the problem before moving forward with anything.

The boat should be wired properly, even when on the hard, and using an extension cords and adapters is not the best method for providing shore power.

 

[Ken Cross]

After I posted this I see Main Sail spoke up. He basically picks up where I left off, so I'd still do the following:

Do Main Sail's continuity check, then:

• I'd begin by disconnecting the hot wire (black) where it connects to the GFCI and check if you still get a trip. If so the issue is with the shore power cord, connectors or the wire from the shore power input to the point it connects to the GFCI.
  
  
• If not, connect it back up and go downstream by disconnecting the black load side of the GFCI and try again. With the load disconnected and it doesn't trip, you have a real problem on your load side and you need to find it for safety reasons.
  
  
• If it does trip with the load disconnected, reconnect the load and disconnect the green ground on the left-hand side of the photo. and try again. If it no longer trips the problem appears to be caused by the GFCI itself.
  
  
• If the problem turns out to be caused by the GFCI, you need to determine if the GFCI is working properly and is designed to send a small current to the static ground, or if it's faulty. at that point, I'd suggest trying to contact the manufacturer. (or possibly someone else can jump in here???)

I hope this makes sense.
Ken