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Old 05-13-2019, 09:07 PM   #1
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Default Stray voltage

Here we go. Been a while. I have a full Marina to attend to. Problem is 46 volt ac variance from neutral to ground. Granted this is a 100' plus and smaller marina that houses close to 100 yachts and smaller boats, all with shore power 30amp up to dual 3phase 100 amp services. I am leaning toward a complete marina survey. Check every shore power tower,distribution load center(1200+/- amp), and transformer connection. Using thermal and other equipment as required. Keep in mind I am not a marine electrician. We have had divers getting shocked from the boats while trying to clean them. All because of 1 boats electrical earth/cathode system. Is there anything specific I should be looking for? I have found 1 issue 1 boat's power cord was missing its neutral post, using ground instead. Still didn't drop neutral to ground voltage maybe 2-3vac. Help. Thank you all.
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Old 05-13-2019, 09:09 PM   #2
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I have never worked on a marina before.


But, it sounds like you have a solid plan. I'd start at the service and branch my way out, verifying all connections and bonding jumpers were intact and in good shape, etc etc.
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Old 05-13-2019, 09:16 PM   #3
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Thanks Cow, I was thinking working from final point of use back, not from source out. Any difference in doing this?? Aside from possibly find the problem area faster going in the reverse direction?
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Old 05-13-2019, 09:21 PM   #4
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You should verify the integrity of the equipment ground back to the service neutral. Put an ammeter on the main bonding jumper and see if there is a significant amount of current flowing on the grounds. If so, you can measure each feeder ground separately to see if it is any one in particular.

Also you can put a load on a ground and measure the fall of potential across it to see how conductive it is compared to what you would expect for the length and conductor type.
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Old 05-13-2019, 09:22 PM   #5
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This is a totally different topic but is for the same marina. The power company has removed their 3 phase regulator bank already resulting in 8vac to end of dock. 480v 3 phase feeds this critter and the transformers on the individual docks step it down to 1200 amp disconnect systems.
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Old 05-13-2019, 09:24 PM   #6
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You have given really vague information, and this is a pretty large task. Just start going through stuff. Two main things to look out for are a device in the field shorted through a resistance that is heating up your ground or an open neutral somewhere.

Start disconnecting loads to isolate it. Sit down with a map, figure what you expect to see and begin isolating it. Once you know which service, you can then find a device. That is likely where you will stop, as someone has a fault in their boat.
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Old 05-13-2019, 09:24 PM   #7
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Thanks Cool Will. The thought of checking individual grounds in the main distro room escaped me!!!
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Old 05-13-2019, 09:31 PM   #8
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Understood sparkiez. The marina is complex seeing their is no mapping on paper:-( didn't want to bore the crew with the specifics of yacht dual 50amp synchronization, or the same for 3 phase. And yes didn't throw in the 750kva 3 phase power company distibution system either, I belive incoming is 14.4 or the parallel 500mcm copper feeder cable, or the main break down of each dock platform. As mentioned no mapping ever put to paper.
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Old 05-14-2019, 12:04 AM   #9
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Your first assignment is to draw up a single line for the whole complex. Label everything accordingly. Take your time and do it right. Double check. Starting at the source, take measurements working toward the load, and where they change lift the wire and meg it. Assuming you're in a salt air environment, check all connections for corrosion, especially the neutral, and grounds.
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Old 05-14-2019, 02:37 AM   #10
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Don't get your heart set on it being just one fault somewhere,
And that fixing that will bring it all back to normal.
For it could well be a series of little issue's, many fold.
You know how complex earthing and neutral systems can be
The problem could even well be external to the marina
And instead in a nearby local location that shares the same earth plane.
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Old 05-16-2019, 09:43 PM   #11
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I want to thank all so much. Being of such a small crew of 1 electrician, for 2,400 acres this task will have to be out sourced to Gulf Power and other entities. I thank you all!! A task I would love but can only split myself so much. Thank you all so much again. Will report on the found issues. Yes I feel their is a issue on the ground issue shared or not. Thank you again. Will keep you informed.
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Old 05-17-2019, 03:46 AM   #12
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They insisted on making garage door opener outlets gfi protected even though they are way up there on the ceiling and nobody ever got shocked from one, but certainly there have been a record number of deaths from electrocution near to or at marina's when either people merely swim , or divers go down to scrape the moss off the boats. But they don't require all shore power to have GFI circuit protection , even though , if required, not only would all those deaths be reduced to near zero, but our buddy Taz would have a much easier time of finding out the selected lousy boats that are leaking current , simply by the fact that they would be complaining the circuit breakers are tripping all the time. Man I hate Code Making Panelists. They insist on expanding AFCI to the entire dwellings, but won't touch the places where enhanced protection from either arc faults or ground faults really would make a difference. And save lots of lives. The old guys were good though. They made us put gfi's onto pool equipment. That was cool. That was back when CMP's were good guys and not bought up by the greedy manufacturer's . Now they are poop.
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Old 05-17-2019, 05:55 AM   #13
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This site has some good info, its an actual problem compared to a dreamed up problem like some things you deal with.

https://www.electricshockdrowning.or...resources.html

I didn't think about it until I read it there, but what might be a tingle you'll pull off of on land can screw up your swimming enough that you drown - it's not the shock but the drowning that kills. The problem is worse in fresh water because salt water is a much better conductor, so the voltage gradient in the water is smaller in salt water.

@macmikeman, now you did it, now you have to keep working until Hawaii adopts the 2017 NEC or at least the 2014. The 2014 NEC requires GFI at 100ma on main marina feeders, unless all branch circuits and feeders are GFCI protected. The 2017 lowers the requirement to 30ma

Quote:
Originally Posted by NEC 2017
555.3 Ground-Fault Protection. The overcurrent protective devices (OCPDs) that supply the marina, boatyards, and commercial and noncommercial docking facilities shall have ground-fault protection not exceeding 30 mA.
http://www.mikeholt.com/download.php...ds_2014NEC.pdf

https://www.mikeholt.com/download.ph...55_2017NEC.pdf

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Old 05-18-2019, 09:55 PM   #14
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@splatz Has any distance in footage from a marina been recorded?? Fresh water compaired to salty? On the tingling"light shock" sensation? Have their been voltage variances sampled? Our marina is approximately 10+/- miles from a gulf of Mexico inter coastal opening. They rent jet skies, pontoon(yeah the aluminum ones)boats, Yolo paddle boarding, airplane(water plane) flights. So a ton of back and forths from land to water. Thank you all so much.
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Old 05-19-2019, 12:02 AM   #15
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@Taz069 I am afraid I can't answer any of those questions ... I am pretty sure the voltage gradient could be present out as far as the furthest metallic parts, plus a little further - probably to the end of the furthest prop.
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Old 05-19-2019, 08:42 PM   #16
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@splatz. Thank you! Outside edge of the variance value and distance. And percentages for water integrity/dialoution. Will work on that avenue as well. Thank you.
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Old 05-19-2019, 09:41 PM   #17
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Taz .,, I have deal some marina docks system but the basic grist is check the grounding conductor to make sure they are properly grounded and clean connections

I know you have a lot of 120 volts system in there but for mine 240 volt system ( yuh line to neutral system ) we dont have GFCI on them yet but most common one I ran into are 20 or 30 amp circuits single phase the three phase I will discuss that in little bit.

are you running full single phase or all the docking stations are wired on three phase circuit?

check the current between the neutral and ground conductor to make sure it is reading correct and you may have to rig up a probe to float on water to read the ground conductor to the water to get some stray voltage if you are getting more than just couple volts then you have issue cropping up and if you are getting it and if your tester can detect the DC current then I would pinpoint to one of the vessels that have corrosion protection system not working correctly.

oh by the way salt water do conduct electricity more further than fresh water ( depending on how clean the water is but if mixed then it will lean toward to salt water side) so it will read much lower voltage than fresh water is so just be aware of that.

I will do as other say on the posting start at the source to make sure it is good then work it way out.

You may have to kill the power of each section of marina dock system to see how much voltage it drop ( start at the main feeder area to get the grist of set up ) if you still getting the same voltage as you kill each section then try shut off the main source either main breaker or ask POCO to pull the transfomer fuses to see if that go away if no change then you may have other source that getting voltage .,,

you may have to check any vessel if they are on generator mode that may cause the issue ( I have see it couple time allready )

But please cordation between yourself and POCO and marina opeterator to set up a plan to get that stubborn bug.

wish ya the luck to get that one.
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