NFPA Journal

This summer, when millions of us gas up the boat and head out on the water for some much needed R&R, the last thing on our minds will be electric shock drowning. Even so, year after year we see tragedies reflected in headlines as vacationers are killed or injured when they unknowingly jump into electrified water around marinas and docks.

This was a major area of discussion for Code Making Panel 7 during the 2020 NEC® first draft meeting in January. Experts experienced in the manufacture, installation, and inspection of electrical equipment and systems used in and around marinas met to discuss the hazards, their causes, and suggested solutions. At the core of the discussion was “why?”—why is there electricity in the water? And what role can the NEC play in safeguarding people while allowing vessels to connect to shore power?

It would be easy to point fingers at one entity or another as the source of the problem, but one fact that all sides agree on is that a marina environment can be brutal. Equipment is subjected to constant dampness or outright submersion. Waves and tides produce constant motion that applies pressure to equipment. Eventually, something is going to give, whether it’s on the vessel or part of the marina. It’s a given that ground faults occur—on docks, on boats, and in the equipment and appliances that populate these environments.

A 2014 report published by the Fire Protection Research Foundation and prepared in cooperation with the American Boat and Yacht Council was referenced in the discussion for determining acceptable levels of leakage current in marinas. The report lists 30 milliamps of leakage current as an acceptable threshold to safely limit current in the water for nearby swimmers. While this amount of current through the body is more than enough to cause electrocution, this is not generally the case due to how leakage current is distributed in the water. Swimmers are rarely subjected to the entirety of the leakage current. Therefore, it seemed to make sense that the NEC could safeguard people in the water with ground-fault protection set at 30mA or less.

Action taken in the 2017 NEC applied the 30mA level of ground fault protection to all overcurrent devices that supply marinas, boatyards, and docking facilities. This becomes a logistical problem when the protection is at the feeder and service level. For instance, a vessel might be leaking only a single milliamp of current into the water; according to the research, it would appear that this is acceptable and doesn’t pose a significant risk to people in the water. But what if a marina is hosting boats in each of its 100 slips? The level of current each boat leaks is only 1mA, but the service overcurrent device is going to detect all 100 of the faults and it will appear at the service that a fault is leaking 100mA, a value far over the threshold established by the 2017 NEC.

The challenge is to draft language that limits the amount of leakage current to 30mA while allowing a functional installation. One suggestion proposed that the 30mA ground fault protection only be applied to the shore power receptacle while allowing a coordinated 100mA of ground-fault protection at the main or feeder overcurrent protection. The environment around these installations is unforgiving; faults in feeders and other branch circuits are going to happen, and without ground-fault protection they could pose a serious hazard. Other discussion points put more emphasis on the boats themselves, and suggestions were made to allow on-site testing of vessels. Many new boats are built with leakage current considerations in place, but many watercraft currently in use include no such protections.

While the 2020 NEC is still in the first-draft stage, these are valuable discussions intended to mitigate the dangers swimmers face around boats and docks that are powered from shore, and to reduce and eliminate electric shock drowning. To learn more about the discussion, visit the First Draft Report on the document information webpage.

DEREK VIGSTOL is an NFPA technical lead, Electrical Tech Services.