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Thread: Dock and Amps

  1. #1
    Steve Myers's Avatar
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    Default Dock and Amps

    While inspecting a dock using a clamp method as shown by James Shafer in
    http://www.icomia.com/library/ICOMIA....asp?BK_ID=251
    or
    http://www.halifaxharbor.net/Marina%...g%206%2004.pdf
    I get a reading of .501 amps clamping the feed to the dock, which includes 2 undgrounded conductors, one grounded (neutral) and a grounding conductor while operating a 1500 watt hairdryer in one outlet.
    This is a new commerical 14 slip dock with no shore powers, just outlets and lights, and no load at the time of the test. It has one lighting circuit and two separate outlet circuitis.
    This dock is bonded to ground.
    see link for detail wiring information: http://www.ameren.com/LakeOzarks/ADC...ectrInstal.asp
    NEC 2005 with AHJ changes as listed online.
    I shut off the load and reading remains, fluctuating between .359 and .501.
    I throw the mains feeding the dock and the current readings remain.
    I had a similiar dock recently showed .10 amps but when the power was turned off, the reading left.
    All outlets on both docks checked correctly for polarity and grounding.
    My guess and that is what it is a guess, is that I am seeing a reading because by bonding the dock to the service and requiring a grounding electrode at the seawall the amp reading is coming from the service wiring. Whether it is stray voltage or just a better grounding system I don't know.
    My question: Does this present a danger?
    In the case of the commerical dock it is a 4 wire subpanel.
    In the .10 amp case it is a 3 wire circuit with GFCI protection from an older house that is probably has the neutrals and grounds on a common bus.
    Any insight with answers or additional test I can perform to ensure the safety of the dock owners and their guests would be appreciated.
    Mr Shafer's Marina Inspection procedure calls for using a clamp meter on the ungrounded legs and grounded and EGC at the same time. Looking for 0.00 under a load like the 1500 watt. If the reading any other than 0 the power is finding another route back, ie. water, dock, cables, etc.
    But on the commerical dock the reading is there load or no load, power or no power.
    Also, at both docks we also checked voltage gradient using leads that held 1' apart and connected to ac volt meter touched to the water at various points and positions around the dock and inside the wells. There were no reportable readings. (.0010 to .0030 ac volts).

    Similar Threads:
    Inspection Referral SOC

  2. #2
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    Default Re: Dock and Amps

    My question: Does this present a danger?
    Yes.
    Being a certified "land lubber" and having no experience with docks, I can't help you but if the readings are accurate and I understand you correctly, you have enough of a problem to kill somebody.
    First, I would use a different meter to verify to make sure it is not a defective meter.
    One thought, since the issue continues without the power on, could you be getting power bleed from another source, like another dock or vessel?
    Good luck and don't go swimming there!

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  3. #3
    Rod Hummel's Avatar
    Rod Hummel Guest

    Default Re: Dock and Amps

    There has been increasing evidence over the last 10 years that unexplained drownings near and at marinas were really the result of shock or electrocution.

    Many times the cause is, as noted above, improperly wired vessels, or even other marinas in the area with the same issue.

    Are there private docks nearby?

    r


  4. #4
    Steve Myers's Avatar
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    Default Re: Dock and Amps

    There are private docks across the cove, about 100' from the commerical dock. The other is a private dock with docks on both side. There are now 29,000 privately owned docks on the Lake of the Ozarks.
    I use James Shafer's method of checking for voltage gradient in the water with leads that 1' apart. There was no reportable voltage in the water at either dock.


  5. #5
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    Default Re: Dock and Amps

    I would not trust the voltage gradient test to EXCLUDE a problem. You might use it to demonstrate that a problem exists but your amperage reading would be much more indicative of a problem and it's magnitude. As I understand it voltage gradients are transient and in continuous flux and vary in intensity in proportion to the distance from the source. Again, I'm no expert by any means but it looks like you have a bonfide issue that appears to be originating from another source.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  6. #6
    chris mcintyre's Avatar
    chris mcintyre Guest

    Default Re: Dock and Amps

    This thread is over my head as far as electrical goes, so this link may or may not be of any relevance.

    The Case of Stray Voltage in a Lake


  7. #7
    Rod Hummel's Avatar
    Rod Hummel Guest

    Default Re: Dock and Amps

    One of the best discussions on this issue is contained in Nigel Calder's Boatowner's Mechanical and Electrical Manual. I can't reference it at the moment....have lent it to my brother.

    This has one of the best texts I've seen on AC/DC wiring in reference to marinas, boats, and best practices related to the instant problem.

    You may have saved someone's life with your discovery!

    r


  8. #8
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    Default Re: Dock and Amps

    Quote Originally Posted by chris mcintyre View Post
    This thread is over my head as far as electrical goes, so this link may or may not be of any relevance.

    The Case of Stray Voltage in a Lake
    Very interesting.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  9. #9
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    Default Re: Dock and Amps

    Steve,

    After reading through this several times (paragraphs would have made it easier to read) I will start here:

    Quote Originally Posted by Steve Myers View Post
    I get a reading of .501 amps clamping the feed to the dock, which includes 2 undgrounded conductors, one grounded (neutral) and a grounding conductor while operating a 1500 watt hairdryer in one outlet.

    This is a new commerical 14 slip dock with no shore powers, just outlets and lights, and no load at the time of the test. It has one lighting circuit and two separate outlet circuitis.
    If I am understanding you correctly, you have:
    - power to the dock
    - no shower power pedestals
    - one lighting circuit with no lamps on at the time
    - two SEPARATE receptacle outlet circuits - not on a multiwire circuit
    - you are measuring 0.5 amps clamped around that feed (cable, in conduit, whatever)

    Here are my first questions based on my above understanding:
    - Did you measure the current in each circuit conductor, individually, going to the dock?
    - If so, which one(s) measured what?
    - If not, did you then go back and disconnect each conductor one-by-one to eliminate which one(s) changed the amp draw, indicating that they are part of the problem?

    Clamping around a conduit or cable with multiple circuits and getting a reading simply indicates there is a current flow SOMEWHERE ... without giving us any idea of WHERE that SOMEWHERE is.

    First thing I would do would be to measure reading you took the first time (to get a current current reading), then measure the lighting circuit conductors, record that reading, disconnect the lighting circuit conductors and re-take your first reading - is there any difference?

    Leave the lighting circuit disconnected if there is no difference.

    Repeat with one of the receptacle circuits.

    Repeat with the other receptacle circuit.

    For the one(s) you find a reading on, and the ones which cause a reading in the conduit or cable, measure what is on which conductor: hot, neutral, ground.

    With the above readings, we may be able to make some educated guesses as to what you are measuring and why you are reading what you are.

    For example, if NONE of the conductors produces any measurable reading and you leave them all disconnected, and, with all disconnected, you still get a reading on the entire conduit or cable, then either something is introducing a current flow from what should be "dead" ends at the lighting fixtures or receptacle outlets.

    If you disconnect the conductors from BOTH the line side feed and the lighting fixtures and the receptacle outlets and you STILL are reading current on the conduit or conductors, then the current is being induced by outside sources (possibly magnetic fields from power lines? I am reaching for straws here if this is what you end up with as nothing else makes sense with both ends disconnected).

    If ANY conductor makes that reading on the conduit or cable drop to almost 0 amps, then there is something wrong ON THAT ONE CIRCUIT, and maybe even THAT ONE CONDUCTOR ... but at this point we simply do not know enough information to be able to make even guesses.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  10. #10
    Steve Myers's Avatar
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    Default Re: Dock and Amps

    Quote Originally Posted by Jerry Peck View Post
    Steve,

    After reading through this several times (paragraphs would have made it easier to read) I will start here:



    If I am understanding you correctly, you have:
    - power to the dock
    - no shower power pedestals
    - one lighting circuit with no lamps on at the time
    - two SEPARATE receptacle outlet circuits - not on a multiwire circuit
    - you are measuring 0.5 amps clamped around that feed (cable, in conduit, whatever)

    Here are my first questions based on my above understanding:
    - Did you measure the current in each circuit conductor, individually, going to the dock?
    - If so, which one(s) measured what?
    - If not, did you then go back and disconnect each conductor one-by-one to eliminate which one(s) changed the amp draw, indicating that they are part of the problem?

    Clamping around a conduit or cable with multiple circuits and getting a reading simply indicates there is a current flow SOMEWHERE ... without giving us any idea of WHERE that SOMEWHERE is.

    First thing I would do would be to measure reading you took the first time (to get a current current reading), then measure the lighting circuit conductors, record that reading, disconnect the lighting circuit conductors and re-take your first reading - is there any difference?

    Leave the lighting circuit disconnected if there is no difference.

    Repeat with one of the receptacle circuits.

    Repeat with the other receptacle circuit.

    For the one(s) you find a reading on, and the ones which cause a reading in the conduit or cable, measure what is on which conductor: hot, neutral, ground.

    With the above readings, we may be able to make some educated guesses as to what you are measuring and why you are reading what you are.

    For example, if NONE of the conductors produces any measurable reading and you leave them all disconnected, and, with all disconnected, you still get a reading on the entire conduit or cable, then either something is introducing a current flow from what should be "dead" ends at the lighting fixtures or receptacle outlets.

    If you disconnect the conductors from BOTH the line side feed and the lighting fixtures and the receptacle outlets and you STILL are reading current on the conduit or conductors, then the current is being induced by outside sources (possibly magnetic fields from power lines? I am reaching for straws here if this is what you end up with as nothing else makes sense with both ends disconnected).

    If ANY conductor makes that reading on the conduit or cable drop to almost 0 amps, then there is something wrong ON THAT ONE CIRCUIT, and maybe even THAT ONE CONDUCTOR ... but at this point we simply do not know enough information to be able to make even guesses.
    I appreciate the systematic approach to locating the source.
    Next week I plan to further investigate.

    So far the original inspection:
    1st- I clamped the conduit (H-H-N-G) with a 1500 watt load. The test is looking for anything other than zero. It indicates the power is going somewhere but not returning. .500 amps reading.
    2nd- I used the disconnect at the seawall which eliminate power to the dock, but .500 amps remained.

    The dock is bonded with #6 green stranded conductors from disconnect panel to Grounding Electrode to ramp to dock to all stiff arms.

    GEC had about .200 amps it by itself.

    My best guess is I believe the grounding electrode at the seawall may be providing a better oath to ground than one of 10 other services of the condos. There are 3 new docks installed at this condo complex, it is the one in middle that shows these readings.

    I had a hot dock call this summer where an boat lift installer was shocked, but not injuried. The dock was wired according to Ameren Electric requirements. (http://www.ameren.com/LakeOzarks/ADC...escription.pdf)
    The panel feeding the dock was 4' from the AC unit. When the AC unit came on the GEC was hot. The panel didn't have a good ground to service so the path followed was to the lake through the bonding conductor.

    I have found similar problems on older homes that have 3 wire service panels, grounding and grounded conductors on common bus. Then when the dock service is wired I show power coming on the grounding system to the lake that should be going to the service. It is taking all paths, and the dock installation seems to win.

    I do suspect stray voltage from a neutral-ground source.


  11. #11
    Roger Frazee's Avatar
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    Default Re: Dock and Amps

    Hi Steve

    Lake of the Ozarks eh? I learned to ski on that lake. Had a cabin in Indian Creek on the Gravios Arm.

    I don't want to fault the author but his article has a lot to be desired for reasons Jerry pointed out. He shows no method of finding the source of the current.

    Turning off the mains on the service does remove the source voltage to the marina. However it does not isolate the neutral. It remains bonded to the grounding system of the Marina. First thing I would do is clamp that service neutral at the service panel or service disconnect and see if there is current on it with the main on and absolutely no load operating not even a freakin battery charger. Record any current on the neutral. Then turn the mains off and see what happens with the current on the neutral.. If you have that .5 amps either way then you need to to have the utility come out and check their end. Tell them you have current on the neutral at the SE with power removed from the Marina.

    If you have an electrician handy I'd have him start isolating the grounding electrode system while monitoring the the neutral at the SE.

    With power off at the SE about the only circuit path that will allow current flow will be over groundING conductors or grounded conductors.

    I am also not quite clear where you are clamping. Is it load side of a single ocpd service disconnnect on the feeder to the panelboard (sub-panel) for the dock ? That's how I'm understanding anyway.

    If you have that current flow on the neutral at the service disconnect I'd move to the grounding electrode conductor (s) and clamp them and see if you have current flow with the mains off. If you do then have an electrician disconnect the grounding electrode(s) while you clamp the service neutral at the disconnecting means. See if the current goes away. If not then check for any television or data grounding conductors and disconnect them from their earth grounding points while you monitor the service neutral. Make sure you monitor the service neutral at the service equipment not at a downstream panelbaord. And be careful current on the grounding system can hurt you if the fault is serious enough.


  12. #12
    Roger Frazee's Avatar
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    Default Re: Dock and Amps

    My best guess is I believe the grounding electrode at the seawall may be providing a better oath to ground than one of 10 other services of the condos. There are 3 new docks installed at this condo complex, it is the one in middle that shows these readings.
    Sorry I did not refresh the page to see your last reply.

    What your saying here is that the current is flowing to earth and not from earth to the service equipment. That is part of the mystery... is it coming or going... It is highly unlikely that current is going out with the mains off.

    If it is going to earth then it is an external source if your mains is opened. It could be coming in on coax or other comm cable that is grounded to the dock electrode system.

    I'd clamp the service neutral and start isolation of systems and see if current on the service neutral changes with the mains off.

    For example if you disconnect the electrode grounding conductor that .2 amps likely will now show up on the service neutral if it is leaving going to earth. If it is coming in from earth then the current on the service neutral should decrease by .2 amps.

    Last edited by Roger Frazee; 12-26-2009 at 12:11 AM.

  13. #13
    Steve Myers's Avatar
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    Default Re: Dock and Amps

    Upon reinspection today:
    Ungrounded L1- .21 amp with one light on.
    Ungrounded L1- .00 amp with light off.
    Ungrounded L2- .00 no load
    Grounded (N)- .12 with light on
    Grounded (N)- .10 with light off
    Grounding Conductor- 1.10 to .80 amps (load or no load)

    Conduit clamped- .42 to .70 amps (varied little load or no load)

    Disconnected Grounding Conductor from Dock
    and disconnected main at service-
    Conduit clamped- .10 amps
    Grounding Conductor to GCE at seawall- 1.10 amps.

    Disconnected Grounding conductor at Main.
    Grounding Conductor to GCE at seawall- .20 amps

    Discovered that the Main Service disconnect does not have GCE.
    Grounded and Grounding Conductors bonded at Main Service.

    Will have the Condo management contact electrician and disconnect power to docks until situation remedied. (note this condo complex is new and unoccupied)


  14. #14
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    Default Re: Dock and Amps

    Quote Originally Posted by Steve Myers View Post
    Upon reinspection today:
    Ungrounded L1- .21 amp with one light on.
    Grounded (N)- .12 with light on
    Right there you know *something* is wrong as you should have the same .21 amps through the L1 and its neutral.

    Grounded (N)- .10 with light off
    Which means almost the entire light load current went *somewhere* other than where it was supposed to (it is not going through its return neutral leg).

    Will have the Condo management contact electrician and disconnect power to docks until situation remedied.
    Excellent recommendation.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  15. #15
    Roger Frazee's Avatar
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    Default Re: Dock and Amps

    Quote Originally Posted by Steve Myers View Post
    Upon reinspection today:
    Ungrounded L1- .21 amp with one light on.
    Ungrounded L1- .00 amp with light off.
    Ungrounded L2- .00 no load
    Grounded (N)- .12 with light on
    Grounded (N)- .10 with light off
    Grounding Conductor- 1.10 to .80 amps (load or no load)

    Conduit clamped- .42 to .70 amps (varied little load or no load)

    Disconnected Grounding Conductor from Dock
    and disconnected main at service-
    Conduit clamped- .10 amps
    Grounding Conductor to GCE at seawall- 1.10 amps.

    Disconnected Grounding conductor at Main.
    Grounding Conductor to GCE at seawall- .20 amps

    Discovered that the Main Service disconnect does not have GCE.
    Grounded and Grounding Conductors bonded at Main Service.

    Will have the Condo management contact electrician and disconnect power to docks until situation remedied. (note this condo complex is new and unoccupied)
    You certainly have current going somewhere it shouldn't.

    As Jerry said it looks like your neutral current has found an alternative path to the transformer.

    I am having some trouble understanding all your tests but it isn't necessary for a long analysis of those on my part. And it could be I am having a bit of trouble with the configuration of the service and your terminology. The electrician should be able to sort things out and locate the objectionable current and reason neutral current appears to be finding a "better" path to the transformer than through the service equipment.

    It would be great if you could get back to the board with the results found by the electrician. And if he was able to find a solution.

    In the mean time I would like to look your results over with a clear understanding of your tests and the service configuration for the commercial dock. Is it essentially the same as the amergen drawing you linked to ?

    I am understanding that you have a single service disconnect (OCPD) enclosure. Then a 4 wire feeder from that service disconnect to the dock panel board. There is no supplemental electrode at the SE.

    At the dock panel board you have a GEC to a ground rod at a seawall or maybe it is to the rebar in the sea wall.

    That panelboard has a main breaker and 15 or 20 amp branch circuits to lights and receptacles.

    When you say "grounding conductor" in your tests you mean the egc of the feeder for the dock panelboard.

    When you use the terms "disconnect main at the service" you mean opening the SE disconnect not the dock panel board main breaker.

    When you use the terms "disconnect grounding conductor from the dock and disconnected main at service " you mean disconnecting the feeder egc from the terminal bar in the dock panelboard and opening the SE disconnect not the main breaker in the dock panelboard.

    Your clamping the PVC conduit of the feeder when you say "conduit clamped".

    I'm confused where your disconnecting the grounding conductor when you say "disconnected grounding conductor at MAIN" is that at the SE or the dock panel? I think you mean the SE.

    Just like to look at the test results with a 100% understanding ...


  16. #16
    Steve Myers's Avatar
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    Default Re: Dock and Amps

    Here is a quickly done diagram.




  17. #17
    Roger Frazee's Avatar
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    Default Re: Dock and Amps

    Upon reinspection today:
    Ungrounded L1- .21 amp with one light on.
    Ungrounded L1- .00 amp with light off.
    Ungrounded L2- .00 no load
    Grounded (N)- .12 with light on
    Grounded (N)- .10 with light off
    Grounding Conductor- 1.10 to .80 amps (load or no load)

    Conduit clamped- .42 to .70 amps (varied little load or no load)
    Thanks for the drawing that helps a lot.

    These were the first tests from what I understand before you disconnected anything.

    These tests were done at the dock panelboard.

    As Jerry pointed very little current on the grounded leg of the light circuit is returning on the feeder neutral. but the question is ... is it at least returning to the neutral bar of the dock panelboard. So a measurement would have been nice on the grounded leg of the branch circuit serving that light. And a measurement on the egc of that lighting circuit to see if current was using the egc due to neutral to egc connection somewhere.

    If that current is not there then you have a neutral to ground bond via the dock metal or something. If it showed up as .21 amps on the branch circuit grounded leg then what happended to it at the feeder neutral? This suggests possible bonding of the neutral and ground at the dock panelboard and the current is using the feeder egc to return to the service equipment and transformer. But if both neutral and egc of feeder are good you would expect a more even split than .12 and 1.10.

    But the issue is how come 1.10 amps on the feeder egc with no loads operating.

    Ok at this point you disconnect the feeder egc at the dock panel board. Still 1.10 amps flowing on the feeder egc. Looking at the diagram at that point in the design of the grounding system you have the gec to the ground rod and dock bonding wires from the required metal on the dock. Only low impedance path to the transformer is the egc of the feeder.
    In other words the dock bonding and the gec to the ground rod converge on the feeeder egc. So at this point you know that with power off current is entering the GES and possibly the dock bonding wires and flowing to the transformer over the EGC of the dock panelboard feeder. I would have suspected 1.10 amps at the service equipment on the feeder egc also. Ok so now you disconnect the feeder egc at the service disconnect and the current falls to .20 amps on the gec to the dock panelboard ground rod. Good bet at this point that the 1.10 amps is entering from an exteranl source via the ground rod for the dock panel. When you opened the low impedance path at the service equipment the current could no longer flow to the transformer.

    If I was the electrician I would disconnect the GEC and the dock bonding wire at that ground rod for the dock panelboard. It looks like from your diagram that both are connected to the ground rod itself. With everything reconnected I'd clamp the egc of the feeder at the service equipment and see what I have for current. Then I would operate the light again and see what I have for current on L1 and grounded (N).If the current for the lighting load still doesn't show itself or the light fails to work then suspect neutral to ground connection to the dock metal and the lighting load current was using the bonding wires to flow to the ground rod gec then to the feeder egc then to the service equipment and transformer.

    It would also be nice to know the wattage of the light your operating. It appears to be one about 25 watts.

    I am suspecting that your measurement of 1.10 to .80 amps on the feeder egc is also including the lighting load when it was operating. This would could be either neutral to ground connection load side of the dock panelboard or neutral to ground bond at the dock panelboard.

    So my best thinking is you have current entering the GES via the ground rod and possible improper bonding of dock panelboard or neutral to ground connection on that lighting load branch circuit.

    I'll try to make up a drawing to show what I just discussed as it is not easy to follow. I'll try to post in a day or so.


  18. #18
    Steve Myers's Avatar
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    Default Re: Dock and Amps

    Just to put a perspective on what I encounter daily here is some photos of yesterday's discovery:





  19. #19
    Roger Frazee's Avatar
    Roger Frazee Guest

    Default Re: Dock and Amps

    Steve

    Thanks for sharing those photos....I'm LMAO at the moment.

    Hey .. that last photo of the receptacle screwed to the dock metal can be an issue of unwanted current on the bonding wires and metal of the dock if neutral and ground are touching in that box. This is a common issue and gives the results your getting on that commercial dock with the disappearance of the grounded leg current on that lighting branch circuit.

    Of course there is a lot more wrong with that installation....

    I especially like the knockout hole, with romex entering, covered in that junction box with what looks like duct seal...in a feeble attempt to waterproof ....people sure get resourceful.


  20. #20
    Roger Frazee's Avatar
    Roger Frazee Guest

    Default Re: Dock and Amps

    I fish your lake quite often in bass tournaments. I see those types of electrical installations from my boat. Actually makes me want to go up and warn the owners.

    I swear I've pitched a jig on those docks your showing.....


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