marina shore cords clamp meter testing issue

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PYC

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So i have a Fluke 369 A/C leak detection clamp meter that i have been using to check our shore cords at our marina. I have some issue that have left some electricians and myself puzzled...

-I clamp the whole shore cord and get 350 mA reading , ...theoretically meaning i have major current leakage issue..
-When i clamp the white and black wire from "inside " the pedestal, i get 0 mA, as i should, so no current leakage is going into the water?
-When clamping just the green ground wire i get that same 350mA reading. This is where we get stumped......what does this mean? where do we go from here?

-i have cut each breaker off on the boat one at the time until ALL breakers are off and still get same ground readings..including while main breakers off (boat is completely dead but still plugged to shore power...if unplugging boat from shore power cord, all readings are zero...naturally )
-probing some of the ground wires (green) on the boat buss bar gives same 350 mA readings... So SOMETHING has to be feeding in that ground wire somehow??
- no continuity readings when probing electrical outlet on boat to shore plug hook up
-was told this meter only reads "downstream" measurements by Fluke but electricians say differently
-all surrounding boats have minimal readings.


-according to Fluke (and electricians) this meter and test can only test leaking current by clamping hot and neutral wires only.....but they have an article on the fluke website stating different??? and that you CAN clamp all wires (hot, neutral and ground together)


Any help would be great, just want to be able to understand whats going on and if there is an issue, be able to point the finger at the right party.
 
Did you take measurements with the Filter both on and off?
Does the 350ma ( leakage measurement) change when the load changes?
 
Do all of the boats have their shore power EGC bonded to the non-current carrying metal parts of the boat that are in contact with the water?

If this is the only one, then the boat is acting as a grounding electrode and is providing a parallel path for the service neutral current via the EGC and the service main bonding jumper.

If they all have that bond, then is there something different about this boat that would make it a better grounding electrode? For example, this boat has a metal hull and the others have fiber glass hulls.

If not, I don't have any idea.
 
I would say the current is not originating from the cable feed, it is a return path from a different source via the ground wire. Try turning off other local sources to see if it disappears.
 
With the shore cord unplugged from the pedestal, I suggest that the voltage be measured between the ground pin of the plug and the ground terminal of the pedestal outlet. If a significant voltage is present (say a few volts or more) it could be due to voltage drop on the neutral of the service conductor and/or power company lines which are upstream of the neutral/EGC bond in the main panel. If so, then connecting the plug would cause a current to flow through the cord's ground wire, along the lines of what Don mentioned in his post above.
 
ELA said:
Did you take measurements with the Filter both on and off?
Does the 350ma ( leakage measurement) change when the load changes?
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I have not played with the filter, readings will stay constant on the ground wire weather everything is on or off
 
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synchro said:
With the shore cord unplugged from the pedestal, I suggest that the voltage be measured between the ground pin of the plug and the ground terminal of the pedestal outlet. If a significant voltage is present (say a few volts or more) it could be due to voltage drop on the neutral of the service conductor and/or power company lines which are upstream of the neutral/EGC bond in the main panel. If so, then connecting the plug would cause a current to flow through the cord's ground wire, along the lines of what Don mentioned in his post above.
Click to expand...
Would this issue not cause similar high readings on multiple boats, if this were the case?
don_resqcapt19 said:
Do all of the boats have their shore power EGC bonded to the non-current carrying metal parts of the boat that are in contact with the water?

If this is the only one, then the boat is acting as a grounding electrode and is providing a parallel path for the service neutral current via the EGC and the service main bonding jumper.

If they all have that bond, then is there something different about this boat that would make it a better grounding electrode? For example, this boat has a metal hull and the others have fiber glass hulls.

If not, I don't have any idea.
Click to expand...
i will get some more details as i am new to this marina, the likely culprit seems to be a issue on the boat side wiring?... i was always taught there should never be anything on a ground wire unless there is an issue, but have found in searching , minimal readings can be normal?, so with that thought, is this something we should be concerned about with Electric Shock Drownings? or is the ground doing whats its suppose to be doing and the root cause needs to be found?

My main concern is the pedestal itself as far as my job goes. Being able to eliminate this from any blame is my aim, however i would like to gain more knowledge about the subject to help guide our boat owners possibly in the right direction be it some issue on their boat. So thanks everyone for your help!
 
I agree with hillbilly1.

You are measuring something external to the boat, and possibly external to the pedestal.

Ignore any circuitry on the boat and think of it as a large electrode sitting in the water, connected via the EGC.

You are measuring current from this electrode.

You might be detecting a fault in the circuit feeding the pedestal, or you might be detecting 'normal' earth currents caused by the utility multi earth neutral system, or you might be detecting current caused by a break in a high voltage concentric neutral. If your meter can detect DC you might even be detecting galvanic corrosion (doubtful on several levels but possible).

IMHO this requires further investigation because even if there isn't an issue with the boat or the marina wiring, it could be a shock hazard for anyone in the water.

I note that the OP is a property manager, not an electrician. I'd suggest that the OP needs to understand this issue but that a qualified electrician perform any investigation beyond the normal property manager's role.

Jon
 
Is there ground fault protection for the feeders supplying the pedestals (required in newer installations).? If not, then the ground wire in the pedestal where leakage is present might be connected to neutral, possibly somewhere upstream of the pedestal if not inside of it. (If the feeder had ground fault protection then it would trip with a 350 mA ground fault). A neutral could have a few volts on it relative to local earth potential, which would cause current to flow if it were connected to metal parts submersed in the water.
 
winnie said:
I agree with hillbilly1.

You are measuring something external to the boat, and possibly external to the pedestal.

Ignore any circuitry on the boat and think of it as a large electrode sitting in the water, connected via the EGC.

You are measuring current from this electrode.

You might be detecting a fault in the circuit feeding the pedestal, or you might be detecting 'normal' earth currents caused by the utility multi earth neutral system, or you might be detecting current caused by a break in a high voltage concentric neutral. If your meter can detect DC you might even be detecting galvanic corrosion (doubtful on several levels but possible).

IMHO this requires further investigation because even if there isn't an issue with the boat or the marina wiring, it could be a shock hazard for anyone in the water.

I note that the OP is a property manager, not an electrician. I'd suggest that the OP needs to understand this issue but that a qualified electrician perform any investigation beyond the normal property manager's role.

Jon
Click to expand...
i do thank you for the info, I haven't been able to find "marine" electricians knowledable about this type issue in my area, i just keep hitting dead ends, hence my attempts to reach out to those do
 
synchro said:
Is there ground fault protection for the feeders supplying the pedestals (required in newer installations).? If not, then the ground wire in the pedestal where leakage is present might be connected to neutral, possibly somewhere upstream of the pedestal if not inside of it. (If the feeder had ground fault protection then it would trip with a 350 mA ground fault). A neutral could have a few volts on it relative to local earth potential, which would cause current to flow if it were connected to metal parts submersed in the water.
Click to expand...
No these are not GFI, early 1990's build
 
PYC said:
i do thank you for the info, I haven't been able to find "marine" electricians knowledable about this type issue in my area, i just keep hitting dead ends, hence my attempts to reach out to those do
Click to expand...

You might try finding an electrician family with issues of 'stray current' on farms.

Good luck!

Jon
 
hillbilly1 said:
I would say the current is not originating from the cable feed, it is a return path from a different source via the ground wire. Try turning off other local sources to see if it disappears.
Click to expand...
By "local sources" are you referring to surrounding power pedestals or going back to sub and main panels?
 
synchro said:
Is there ground fault protection for the feeders supplying the pedestals (required in newer installations).? If not, then the ground wire in the pedestal where leakage is present might be connected to neutral, possibly somewhere upstream of the pedestal if not inside of it. (If the feeder had ground fault protection then it would trip with a 350 mA ground fault). A neutral could have a few volts on it relative to local earth potential, which would cause current to flow if it were connected to metal parts submersed in the water.
Click to expand...
PYC said:
No these are not GFI, early 1990's build
Click to expand...
And so without ground fault protection on the feed to the pedestal, the ground wire (ECG) in the pedestal could be connected to neutral somewhere and the pedestal would still provide power. Further invertigation would be needed to determine if such miswiring could be the cause of your observed current in the ground wire.
 
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