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Old 07-11-2019, 05:54 PM   #1
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Excessive amperage leak?

I've been helping out in the marina and was checking new arrivals for power leaks into the water. A transient trawler read 300 mA on one cord and 600 mA on the other (Fluke 323, which reads to tenths of an amp). We advised the boat owner. It was hot outside, no swimming allowed around the docks....we let him stay plugged in. The boat left early the next morning. So what do other marinas consider excessive leakage?
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Old 07-11-2019, 06:40 PM   #2
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The NEC requires no more than 30 mAmps of leakage at an individual slip or 100 mAmps for a dock. I believe human muscles lock up around 60mAmps and then you get ESD, electro shock drowning. Even if you don’t allow swimming around the docks, what happens when someone trips and falls in the water and you allowed a boat with 600 mAmps or even 300 mAmps to be plugged in?
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Old 07-11-2019, 06:47 PM   #3
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That is the reason marinas are installing ELCI breakers. Either on their own or government mandate.
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Old 07-11-2019, 06:58 PM   #4
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Rufus, with respect, why are you doing checks if nobody told you what the limits are? Huge waste of time, imho.
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Old 07-11-2019, 07:33 PM   #5
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We were using the Fluke 323 as recommended by the state. Per the state, anything that registers on the Fluke is too much...the minimum it reads is 100 mA. So 100mA is the default limit. That seemed high to me, so I was wondering if other marinas are using a lower value (and a different meter). And yes, the trawler/looper in question should have been unplugged. The owner told us he had been tripping ELCI breakers on previous stops, hired a marine electrician to fix it at the previous marina, and thought it had been repaired....now he knows it's not.
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Old 07-11-2019, 08:45 PM   #6
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The NEC changed in 2011 and required marinas to go to ELCIs if they are new or doing major work to the electrical system. The NEC of 2017 now requires the same for residential docks. Using a clamp on meter probably is not accurate enough. The state marinas around here have computerized systems that can tell you what your leakage current is. My boat used to trip them when we bought it. The surveyor didnít even check for it. I would plug into my dock at home where I had installed 5 mAmp GFCIs and without anything being turned on the GFCSs would trip. I decided to replace the electrical panel because I needed more circuits. I used a portable GFCI to test the boat as I worked on it. The original wiring was 2 30 amp inlets with only 1 30 amp main breaker. The other inlet was directly wired into the main bus bar. All of the neutrals were on 1 bus bar. It took a couple days of ringing out the wiring to determine which neutrals went with which hot wires. I added a second neutral bus bar and seperated the shore power 1 neutrals from the shore power 2 neutrals. A few other miscellaneous fixes and the 5 mAmp GFLCIs no longer tripped. It was a lot of work but it was worth it since we can now go to the newer wired marinas and not trip the breakers.
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Old 07-11-2019, 09:19 PM   #7
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The real danger is fresh water which is not very conductive. Current will preferentially go through your body back to the dock. Saltwater is usually more conductive than a human, so there is less of a risk.
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Old 07-12-2019, 05:44 PM   #8
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Rufus: If you were clamping the entire shore cord, that is only the preliminary test. To truly determine if a particular boat is leaking current into the water column you have to use a break out adapter that allows the test to be performed by clamping L and N (120V shore power) or L1, N, & L2 (240V shore power). In this way the test is emulating the method used by the pedestal residual current device (RCD).

The levels we use for absolute maximums are: <100mAAC in fresh water and <500mAAC in saltwater. These levels are safe, but they will trip a 30mAAC pedestal RCD or an ELCI installed aboard.
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Old 07-12-2019, 06:07 PM   #9
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We were using the Fluke 323 as recommended by the state. Per the state, anything that registers on the Fluke is too much...the minimum it reads is 100 mA. So 100mA is the default limit. ....
The 324 is a much better choice. Reading 0.1 A on a 400 Amp fixed range is sub-optimum. The 324 has a 40Amp range.
What state is this?
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Old 07-14-2019, 06:18 AM   #10
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We clamp the whole cord as there's not time to get more specific. The state is Michigan. And given the extremely high water levels with some marina docks going under water, there have been reported electrical issues with some infrastructure.
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Old 07-14-2019, 09:00 AM   #11
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Ok, I have a twin 30 amp system, and it is easy to plug the boat into a GFCI extension cord, and it will NOT trip the GFCI breaker, so I can be certain the leakage is under 6 milli amps.

I kind of wonder if your testing method is flawed clamping on the cable with all the wires in it being measured.

And a few years ago, I rewired the entire AC system. And I dont have any odd AC equipment, just fridge, Microwave, water heater, AC-Heat pump, stove, toaster, electric grill, two built in electric wall heaters, generator, an AC windless and about 20 outlets, battery charger-converter, etc... just typical stuff and some of it is pretty old, like the princess oven and cruisair heap pump and battery charger, all from 1971.
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Old 07-14-2019, 09:45 AM   #12
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..,,

The levels we use for absolute maximums are: <100mAAC in fresh water and <500mAAC in saltwater. These levels are safe, but they will trip a 30mAAC pedestal RCD or an ELCI installed aboard.


Ahhh; .5Amps of stray current is safe? Not if a human is in that path, swimming or not!!
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Old 07-14-2019, 10:01 AM   #13
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Even 30 mili amp is too high, if your in the water and getting shocked. ELCI is for equipment protection, not personal protection which is set much lower at 6 ma. And for good reasons, as it will not kill you when you get shocked.
I just have a higher standard on my boat.
My square-D panel also has most of its breakers as GFCI - AFCI breaker protection for the boats AC circuits, and I dont get nuisance trips or lets say its rare. I left the fridge as no gfci protection for obvious reasons.

I have read some of the installs combine multiple slips into a single ELCI breaker, so you could have a string of boats all under the 30 ma limit, but the combined leakage rate will trip the breaker killing power to them all.

If they are going to do it, every slip should be protected by its own ELCI breaker, but preferably someday they will also go with the the GFCI 6 ma rating on the boat itself as in the individual circuits as I did. Having the higher standard is easy to do, and it also will show up any problems quicker than the 30 ma standard, which you can meet and have it still be deadly.

Just yesterday, I reinstalled my heat pump which is on a 6 ma GFCI-AFCI breaker, and I accidentally brushed the back of my hand on the compressor wire in the control box as it was running. I barely felt a thing thru my sweaty hand and the power was instantly cut off preventing me getting shocked. And if you know anything about these compressors, the back emf can boost the voltage over 300vac on some of the compressor wiring, yet I was fine. I guess one bad thing, it makes me more lazy about being safe with the AC wiring! But good thing is my careless dumb stuff I sometimes do wont kill me.

Another point lets say your ground wire is compromised, a gfci circuit is a comparator to current potentials between hot and neutral, so it will still trip off and save your life, even with a poor ground connection or even a broken ground.
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Old 07-14-2019, 10:46 AM   #14
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With every magic, there is a price to pay. GFCI save lives, no doubt about that. It takes about 10nF of capacitance to ground to trip a 5mA device. All normal wiring methods add some capacitance from L's to G. Also, MOV based TVSS add more capacitance. Further, line surges from outside add to the baseline reactive currents. A 2kV common mode pulse, feeding a downstream surge arrestor will likely trip the GFCI.
A long feeder, protected by even a 30mA device may trip, even though there is no ground fault.
A couple of lessons:
Apply the GFCI as close to the ground fault threat as possible.
Use power loss monitors on reefers and freezers.
Apply panel mounted TVSS systems upstream of GFCI protectors.
Optimally, a TVSS design will use gas tubes as well, to vastly reduce normal ground currents caused by MOV's.
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Old 07-14-2019, 11:10 AM   #15
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An isolation transformer will mask electrical issues on a boat and eliminate the effects.
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Old 07-14-2019, 11:47 AM   #16
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diver_dave:
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Ahhh; .5Amps of stray current is safe? Not if a human is in that path, swimming or not!!
It won't be pleasant, but research shows that it will not kill the nominal human. I suggest that you review the following documents:
1. USCG FY2006 Grant
In-Water Shock Hazard Mitigation Strategies
Final Report October 1, 2008

2. Electric Shock Drowning: Causes and Preventin; G.S. Cargill

It is the voltage gradient developed in the water column by AC leakage that will cause electric shock drowning. A voltage gradient of 2V/ft, in salt or fresh water, will be lethal for a human that is in the water and parallel to the equip-potential lines.

Freshwater streams and lakes has a conductivity of 0.01-0.2 Siemens/m and saltwater has a conductivity of 5.5 S/m so a steeper gradient will be produced in fresh water than in sea water for a constant source of leakage.

That all said, ABYC settled on an ELCI limit of 30mAAC to trip in < 100mS which ensures that the leakage cannot develop the lethal voltage gradient in either fresh or salt water. The NEC is using the 30mAAC limit and trying to come to grips with implementation that is safe and cost effective hence the vacillation in the mitigation strategies put for in the NEC commencing with the 2011 edition.
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Old 07-14-2019, 11:49 AM   #17
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Quote:
With every magic, there is a price to pay. GFCI save lives, no doubt about that. It takes about 10nF of capacitance to ground to trip a 5mA device. All normal wiring methods add some capacitance from L's to G. Also, MOV based TVSS add more capacitance. Further, line surges from outside add to the baseline reactive currents. A 2kV common mode pulse, feeding a downstream surge arrestor will likely trip the GFCI.
A long feeder, protected by even a 30mA device may trip, even though there is no ground fault.
A couple of lessons:
Apply the GFCI as close to the ground fault threat as possible.
Use power loss monitors on reefers and freezers.
Apply panel mounted TVSS systems upstream of GFCI protectors.
Optimally, a TVSS design will use gas tubes as well, to vastly reduce normal ground currents caused by MOV's
All points spot on!
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Old 07-14-2019, 12:16 PM   #18
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An isolation transformer will mask electrical issues on a boat and eliminate the effects.
Yep...

A isolation transformer solves issues by eliminating the possibility of leakage current back to shore.

Most leakage current issues seem to be inadvertant ground neutral connections in a boats AC panel.

When a isolation transformer is installed you intentionaly bond neutral to ground in your boats AC panel, and isolate the shore conductors.

Leakage problem solved.
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Old 07-14-2019, 12:16 PM   #19
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An isolation transformer will mask electrical issues on a boat and eliminate the effects.




All the line to neutral issues, remain issues. Such as overloads, L to N shock hazards, and shorts due to bad wiring. SOME of the L and N issues may go away, such as common mode surges, and maybe some RF type noise. You are still left with L to Gnd shock hazards though. Assuming you bonded the secondary N to gnd.
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Old 07-14-2019, 12:47 PM   #20
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All the line to neutral issues, remain issues. Such as overloads, L to N shock hazards, and shorts due to bad wiring. SOME of the L and N issues may go away, such as common mode surges, and maybe some RF type noise. You are still left with L to Gnd shock hazards though. Assuming you bonded the secondary N to gnd.
I do not believe you are correct.

I have been stewing over a real scenario where you would get current running through the water in a primary or a parallel path.

I suppose... That IF a branch circuit failed in a mode where...

A. The neutral conductor opened
B. The ground conductor opened
C. The ground conductor also shorted to seawater

That is the only failure mode where I can see any through the water leakage.

Yes, just like in a house if

a. The neutral was open
b. The ground wire was open
c. The load side of the open neutral was shorted to the appliance case

then you could get a shock hazard on a appliance case, but circuit protection is traditionally based on a single failure happening.

I’m easy to convice that I’m incorrect, just share the logic of your thinking and if it makes sense electrically, then well...it makes sense.
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