555.34(A) 100mA GFPE
- Thread starter Pdan
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cadpoint
Senior Member
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- Durham, NC
If you search here in MH, there's a few great posts on Marina's.
The one main point I forgot about but was made about the wiring of a boat: IE is the wiring is Hot and common
and the Boat is common and they bleed power, and the poster had basically walked from any future work due to this!
The one main point I forgot about but was made about the wiring of a boat: IE is the wiring is Hot and common
and the Boat is common and they bleed power, and the poster had basically walked from any future work due to this!
"I imagine its to limit potential current leakage from the feeder that could end up traveling thru the water as its parallel path."
I agree that a break in the feeder cable jacket and insulation or a short in the power pedestal could cause a current leakage, but since the 100mA GFPE is used for protection of equipment (busbar in the pedestal), I'm not seeing the relevance.
I agree that a break in the feeder cable jacket and insulation or a short in the power pedestal could cause a current leakage, but since the 100mA GFPE is used for protection of equipment (busbar in the pedestal), I'm not seeing the relevance.
synchro
Senior Member
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- Chicago, IL
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- EE
There will be a cumulative leakage current into the water from multiple boats even though each one has a leakage less than the 30 mA necessary to trip the GFPE in their pedestal. Apparently that's one reason for having a 100 mA feeder GFPE , as well as for leakage from a feeder itself into the water as was mentioned above.
With a 120/240V system, the leakage current to the water from one phase can effectively cancel leakage current to the water on the other phase within the current transformer of the.feeder's GFPE. And so using 2-pole 100 mA GFPE can allow even more than 100 mA of leakage on each phase through the water, as long as the difference in their currents is less than 100 mA. That is not really a good thing. Leakage currents in the water create a voltage gradient across the water. Fresh water is more of a problem than salt water because it typically has a higher resistivity than the human body does, and therefore a body will shunt a larger portion of the local current flow than in salt water.
A 120/208V 3-wire system would produce only a limited amount of leakage cancellation within the feeder GFPE even when the leakages on each phase are equal. Complete cancellaton would require no leakages into the water from line to the earth, but only leakages through the water between L1 and L2. That's not going to happen in a marina with a system that has a grounded neutral .
With a 120/240V system, the leakage current to the water from one phase can effectively cancel leakage current to the water on the other phase within the current transformer of the.feeder's GFPE. And so using 2-pole 100 mA GFPE can allow even more than 100 mA of leakage on each phase through the water, as long as the difference in their currents is less than 100 mA. That is not really a good thing. Leakage currents in the water create a voltage gradient across the water. Fresh water is more of a problem than salt water because it typically has a higher resistivity than the human body does, and therefore a body will shunt a larger portion of the local current flow than in salt water.
A 120/208V 3-wire system would produce only a limited amount of leakage cancellation within the feeder GFPE even when the leakages on each phase are equal. Complete cancellaton would require no leakages into the water from line to the earth, but only leakages through the water between L1 and L2. That's not going to happen in a marina with a system that has a grounded neutral .
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Thats interesting, are you sure the breakers are designed that way?
What about the conductors supplying the pedestal?
Is that the case with onboard AC wiring as well as DC?
Its been a while since I looked over 33 CFR Sections 183.401 - 183.460 and the ABCY
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