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Marina GFP Concerns
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Marina Ground Fault Leakage Current and the NEC®

by Ed Lethert, Electric Shock Drowning Safety Specialist

My activities include working with individual marinas in helping them to understand the causes of ESD and implementing methods for mitigating the danger; I've spent much time considering Section 555.3 of Article 555 of the NEC.

A key part of the mitigation process includes provision of ground-fault protection at the pedestals where shore power is made available to watercraft. I fully endorse the 2011 (and 2014) NEC requirement for ground-fault protection not exceeding 100 mA, and encourage marinas to consider installing this protection at their shore power pedestals. I've always been a little skittish about having 100 mA GFP protection upstream of the pedestals that could result in annoying, inconvenient, and unnecessary nuisance trips.

Article 555 of the 2014 NEC, "Marinas and Boatyards," has been re-titled in the 2017 edition to "Marinas, Boatyards, and Commercial and Noncommercial Docking Facilities." Along with the new title, there are important changes and additions including a very important revision. The revised rule, Section 555.3, has reduced the maximum permitted ground-fault protection from 100 mA to 30 mA and applies that requirement to all overcurrent protective devices (OCPDs) installed in any facility covered by Article 555.

Anyone involved with marina electrical installations and their operation must consider the potential negative consequences that could result if this new rule is not applied thoughtfully and reasonably in the field, especially as it relates to shore power service to watercraft. It is also important to note that Article 555 makes no distinction between freshwater and saltwater marine environments, even though there are significant differences, electrically speaking.

ELCIGround-fault protection of 30 mA at the pedestal receptacle is fine, even a good thing. ELCIs (Equipment Leakage Circuit Interrupters) on newer boats are designed to trip at 30 mA. Now all boats at that facility would have the equivalent of ELCI protection.

Preliminary field measurements performed by me last Summer raise important questions regarding the application of ground-fault protection to marina feeders and mains. While limiting overall ground-fault protection to 30mA for an entire facility may not be a problem for private docks and very small commercial facilities, it portends big (possibly insurmountable) challenges for medium and large commercial marinas where false tripping of circuit breakers would become a massive and unmanageable nuisance.

A quote from a recent email thread reads as follows: "…the real life application of this ridiculously low standard is being felt by several marinas in Washington. I would encourage anyone who wants to see the effect of 30 mamp on a dock of 100 boats call ----- ------ marina….zero power! They have stopped a massive power upgrade (2 million$) to their facility because of this issue ….how does that make the marina safer? Another one of our member marinas has a cheater box that isolates problems in order to maintain power for boats that do not have a problem greater than 30." Extending rules and regulations beyond practical limits all too often produces negative results where practical necessity encourages the defeating or bypassing of the very measures intended to protect.

30 mA ground-fault protection at the pedestal makes good sense and will provide a greater degree protection than the currently required 100 mA. I believe (and hope) that this was the intent of the ABYC who appears to have played a role in arriving at the 30 mA number. The fact remains that feeders serving multiple receptacles must have higher trip levels—at least 100 mA, possibly higher. Existing installations may require rewiring of existing feeders to serve fewer pedestals. Main breakers should be equipped with adjustable ground-fault protection or ground-fault monitoring equipment adjusted to accommodate the real-world conditions for the specific installation.

Additional measurement activity is planned for this summer season to help in determining leakage current norms for typical marina installations. The results will be posted on my website when they become available.

It is likely that field experience with the 2017 rule will necessitate a rewrite of 555.3 for the 2020 NEC. In the meantime, engineers, designers, contractors, inspection authorities, and marina operators will likely find this new requirement a significant challenge. Careful planning, design, and coordination of distribution architecture will be required for new facilities, and for upgrades to existing facilities. Field measurements made after installation could require modifications or adjustments to an initial design.

A FINAL COMMENT
PLEASE keep in mind that compliance with codes and safety standards will help to protect an individual that inadvertently enters the water around a dock or boat equipped with electric power. Compliance with codes and safety standards should NEVER be perceived as a “green light” for recreational swimming or other in-water activities around such docks or boats. The 2017 NEC reinforces this position by including a new requirement (in new section 555.24) that mandates warning signs at all approaches to dock facilities where electricity is in use. It even goes so far as to specify the minimum acceptable wording. These warning signs, along with proactive education of the public, are a great and inexpensive way to enhance personal protection for marina customers and staff—and reduce a marina owner’s exposure to liability claims.

Read the full article here:

About Ed. Ed Lethert is an Electric Shock Drowning Safety Specialist living in Minneapolis, Minnesota. He has devoted much of his time in recent years to addressing issues associated with electric shock drowning (ESD). He's a retired electronic technician, technical consultant, electrical project manager, and electrical instructor. His activities include promoting awareness of ESD with presentations to marina associations, sheriffs departments and other groups, promoting the installation of ESD warning signs, distribution of ESD educational materials, etc. Ed is a member of the Electric Shock Drowning Prevention Association.

elethert@gmail.com
http://www.electricshockdrowningmn.com/
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Comments

  • Now that I'm aware of this electric shock drowning hazard around marinas. And it looks like there is no really 100% safe solution yet devised. I glad the NEC has included warning signs of the hazard. Because I was thinking who knows which of their 2% of boats are causing the hazard without carrying around your meter. All I come up with a lame way to identify these dangerous boats to look for electrocuted fish floating near these boats ? Thanks for the warning and interesting problem for the experts to solve. It's at the same par of discussions about unwanted current around pools & heated farm ponds during the winter.

    Lloyd Voo  May 16 2017, 10:54 pm EDT
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  • Marinas that are replacing plain shore power pedestal breakers with the now finally available 30 mA trip GFCI breakers have been having a really bad time of it, maybe 2% of the boats have too much leakage, and are tripping the breakers every time the breakers are switched on. This is often not just from miss-wiring Neutral to Ground connections. Any older boat built in China/Taiwan is going to have trouble we have found. Boats can have inadvertent fault or designed in by mistake Ground to Neutral ties onboard that will instantly trip a GFIC in any boat manufactured anywhere. But often we find the more troublesome "cross talk" of parallel wired boats with a single wire for each individual conductor is the problem, not miss-wiring or faults. Older China and Taiwan built boats for example have AC outlets run with 3 individual single wires, for all the feeder wires and branch circuits. They trip GFCI breakers because of inductance between the long parallel wire runs. Now boat owners wish the shipyards had bought cable like we use here in the USA instead of wired with single wires right off the spool, and not the sheathed cable assemblies like we commonly buy here that are slightly twisted and inside a thin but further separating thermoplastic jacket, so as to not cross talk enough to leak current to each other and trip a GFCI.

    The only solution to these boat's woes is to install an isolation transformer on the shore power feeder right after the boat's shore power breaker. Typically an isolation transformers 50 A 125/240 Vac 12 KW like we usually use are 250 Lbs and $1200 wholesale, like we shipped over for all the yachts we used to build in China and Taiwan. 30A 120 Vac Isolation transformers are 75 lbs and $450 wholesale at the bottom price range. Now days on any USA boat work you want to use American Boat and Yacht Council approved (hospital grade double shielded) transformers, a bit more money to be sure to pass an insurance survey.

    This works because the shore power only goes as far as the transformer, not throughout the boat with all the miles of parallel wires increasing inductive coupling. Output of the transformer goes to the panel on the existing wires, and even if you have G to N ties, it doesn't matter at all, it is always a balanced load to the shore power source. Much safer for fresh water boats, if wired wrong with a N-G tie or a N-G fault. Note that a galvanic isolator does nothing to protect swimmers from ESD. Galvanic isolators do prevent corrosion problems, a much more complicated subject.

    If weight is a problem, there is only one manufacturer making Torroidal units now, they are lighter than the usual really heavy steel transformers as mentioned above, might be more feasible for smaller boats. Twice the price I'm sure, although I have not priced the company yet. Might be a better solution for smaller boats.

    First thing if a boat in a marina that has converted to GFCI shore power breakers and they are a problem, is to chase down all the G to N ties with the ohms setting on a multimeter after the inverter N to G tie is disconnected. These are sometimes from a N-G bond jumper in the panel for some wrong reason, or most commonly an outlet that has a N-G short behind it. But then if that does not fix it, and you are still reading 10,000 ohms or less, the only cure is an isolation transformer.

    One could put the transformer in a box on the dock, as a portable unit for each boat, but as there are not any UL listed under water-proof assemblies, this is not going to be a good idea if it gets kicked off the dock!

    John  May 11 2017, 10:23 pm EDT
    Reply to this comment

    • Reply from: David Rifkin   May 11 2017, 11:11 pm EDT
    I have never heard of "leakage" caused by running single conductors instead of a boat cable with all conductors inside a sheath. I would be interested in more information on how this appears as a leak and causes a GFP to trip.

    We have never not found the actual source of leakage in excess of the 30ma trip on the pedestal GFP. Grounded neutrals are one cause on boats using shorepower with no transformer. But in older boats the leakage is usually caused by motor winding insulation breakdown over the years. A/C compressors are the prime culprit.

    What we do is clamp the shore cord and cycle AC loads to find which ones contribute to the leakage. This can also be done with a leakage testing clamp meter onboard.

    The ground to neutral resistance specification in E-11 of the ABYC standards is >25,000 ohms. Not sure where the 10k comes from.

    If a transformer is installed, there MUST be a grounded neutral connection on the secondary side. So on all boats with a transformer the G-N resistance on the secondary should be near zero. That's normal for these boats.

    The new high frequency switching transformers (now accepted by ABYC standards) are true lightweights. I think the 30amp is under 12 pounds. But they cost 4-5 times what a conventional transformer costs.

    The 2% of the boats that are tripping pedestal GFPs represent a danger to anyone who might end up in the water around that boat. They must be repaired before plugging into any marina system (for example, you don't accommodate a leaking boat by disabling ground fault protection or plugging it into a conventional pedestal with no GFP).
    Reply to David Rifkin

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