Marina GFP Concerns

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.

Ground-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/