HELP Current on ground wire when on Generator

Oct 26, 2010
1,881
Hunter 40.5 Beaufort, SC
As measured with a clamp on meter.

When the Power Selector Switch is on Shore Power every thing checks out fine. Current on Black (hot) and White (Neutral) match and there is 0 current on Green (Ground). The Ground and Neutral are not connected on the boat.

When the Power Switch is on Generator there is .340 Amps on the Green ground wire. The Ground and the Neutral are bonded together at the generator. Is this a problem particularly from a safety standpoint? Is there something in the generator that is causing this that is normal?

Your perspectives are welcome. In the attached sketch. Black is Hot, Orange is Neutral (white wouldn't show up) and Green is ground. The top sketch is with the Selector Switch is in Shore. The bottom sketch is when the selector switch is in Generator.
001.jpg
 
Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Just a thought - if there is a fault in one of the on board electrical devices and if the galvanic isolator is open the egc (green) cannot conduct anything. Verify that the isolator is not interrupting the equipment grounding conductor.
 
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Feb 14, 2014
7,399
Hunter 430 Waveland, MS
One way to verify your Galvanic Isolator, per Charles's thought.

Disconnect your shore power, then check the Green wire again.

_____
I also assume your Generator was NOT running, when you Changed the Selector Switch.
Jim...
 
Oct 26, 2010
1,881
Hunter 40.5 Beaufort, SC
Have checked the Galvanic Isolator per the instruction with the ProSafe30 manual. It reads 1211ma in one direction and 1089 ma in the other direction. So I don't think the galvanic isolator is open. The manual says it should approximately .8 to 1 amp and within 10% of each other. Just a little off of that but I'm not sure my clamp on is precise enough for that.

Also, when on shore power, the black and white (hot and neutral) read the same amps, as they should if there is no stray ground current. When on Generator Power, the black and white wires are off by about .3 amps. This corresponds to the
340 milliamps I am reading on the ground wire. It seems there is something in the generator circuit that is causing some leakage or it is inherent in the way the generator is internally wired or controlled or possibly some "circulating current" that occurs because the white and green are bonded at the generator?

@JamesG161 No the generator was not running but even if it was, the rotary selector switch is a "break befor make" type so it shouldn't make any difference.

I don't recall if the shore power cable was connected when I was checking the generator currents so I will go back and check it that way. I see that since the rotary switch only breaks the black and white wires, if the shore power was still plugged in, the green wire to the generator and the green wire to the shore are still connected through the galvanic isolator all the way back to the shore power grounding point (about 100 yards). Huh - I'll have to check that and do these tests with the shore power cable disconnected. Maybe @Maine Sail can weigh in on this.
 
Oct 26, 2010
1,881
Hunter 40.5 Beaufort, SC
@Charles Erwin Thanks for the tip. Even though I think the Galvanic Isolator is not open and checks out per post 4. I will take the galvanic isolator out of the circuit and see if maybe the 340 milliamps shows up when connected to shore power with it out of the circuit. Hadn't thought of that possibility.
 
May 17, 2004
5,025
Beneteau Oceanis 37 Havre de Grace
What appliances / devices are running when you make the measurements? Is It the same devices either way?
 
Oct 26, 2010
1,881
Hunter 40.5 Beaufort, SC
What appliances / devices are running when you make the measurements? Is It the same devices either way?
All AC devices were on except the water heater. Same devices were on either way. I didn't have the water heater on because when it is on (with cold water in the tank) along with the the battery charger and Air Conditioner it is right at 29.5 Amps and I didn't want to be tripping breakers while I was doing the testing.
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
What type of Inverter/Charger do you have?
On my boat the ICG come into play on the Green Wire.
Jim...
 
Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Yes - take the isolator out of the calculus. I do not see that the egc (green) is bonded to DC neg but if these are not bonded the isolator is not doing anything for you anyway.

Remember if no load then no current. If generator is off then no source current either. So with generator on turn off the loads (devices) one by one in turn to see which of the loads is implicated.
 
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Feb 10, 2004
3,917
Hunter 40.5 Warwick, RI
Dan, FWIW, my Ship-Shore switch breaks all 3 wires. But if the shore cable is the cause of the 340mA, it would seem that there must be another path between the shore and the boat for the current to flow. Water return? I think you need to verify that the shore cable is not the cause of the 340mA current. IMO that magnitude of current could eat up all kinds of metal really fast.
 
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Jan 4, 2010
1,037
Farr 30 San Francisco
I think this is OK. Once your boat is floating, away from the dock how to handle on board Hot Neutral and GND?
In the shore power situation ground and neutral are tied together somewhere back at the service entrance to the marina and there is a ground rod shoved deep into the ground. Once your boat is on its own what to do? What it seems has been done here is the replicate that situation at the generator. Neutral and ground are tied together and to the vessel ground. If you really worry hire a marine electrician to run through the system and double check it.
 
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