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Making Progress on Electric Shock Drowning

Some experts believe there should be more training for technicians in the area of electrical current leakage
Marina Rowena on Lake Cumberland has a shore-power network with ground-fault monitoring to keep boats from leaking stray current.

Marina Rowena on Lake Cumberland has a shore-power network with ground-fault monitoring to keep boats from leaking stray current.

About 12 years ago, Dave Dyson was swimming in the water behind a houseboat. “I reached up and grabbed a ladder, and it sent a shock up my arm and into my body that made me immediately let go of the ladder,” he says.

Today, as manager of a new facility, Marina Rowena on Lake Cumberland in Kentucky, Dyson has done everything he can think of to ensure that his experience doesn’t happen to customers. “Our electrical system is state of the art,” he says. “We have elected to set our system at the 30-mA threshold because that is the new standard.”

The figure 30 mA refers to the maximum permitted milliamps for ground-fault protection, and it’s what a 2017 revision to the National Electrical Code, Marinas and Boatyards, requires — with 30 mA being down from the previous requirement of 100 mA. For boaters, the change means that plugging into a shore-power pedestal should include finding a 30 mA circuit breaker. The previous rule required protection not exceeding 100 mA at the main electrical power source feeding the marina and allowed protection at each pedestal as an alternative. The 2017 rule requires that all overcurrent protective devices in marinas, boatyards and non-commercial docking facilities include the 30 mA protection.

The reason for this protection is to prevent stray current from getting into the water, which can cause electric-shock drowning. The Electric Shock Drowning Prevention Association estimates that 60 people have died from ESD since experts began identifying the incidents as such earlier in this decade. According to the Missouri Electric Cooperatives, there have been at least seven ESD deaths in the state since 2004, and six of those occurred at popular Lake of the Ozarks.


ESD is dangerous because it’s undetectable. You can’t see it from the docks, and you don’t feel it until you’re in the water. The situation becomes exacerbated when people jump in to help; now there are multiple people in the water confronting the same problem. The Electric Shock Drowning Prevention Association is trying to get marina owners and managers to be more forceful about prohibiting people from swimming around boats that are in slips and plugged in.

Marina Rowena’s electrical system was designed by Maffett Loftis Engineering in Cookeville, Tenn. The system is set up to monitor power channels. Each channel consists of two pedestals. If more than 30 mA of stray current is detected, it trips the breaker. “There’s an alarm light on the panel, and when any of the channels trip, it flashes the light at that beacon, and the power goes out to those beacons,” Dyson says.

As soon as a boat comes into the marina and plugs into a pedestal, he adds, the owner will know if there’s a problem. “Everyone tests his system as soon as he plugs into one of our pedestals. We haven’t had a single cruiser or runabout or pontoon boat plug into our system that has caused a problem.”

However, he says, every houseboat that has plugged in has had an issue. The primary cause was a neutral-to-ground bond within an appliance — usually a dryer wired the way it would be in a home, instead of with proper grounding for the marine environment. (When there is a problem aboard a cruiser, experts often find that the water heater is the culprit.)

Initially, it was thought that the 30-mA monitoring systems would cause multiple breaker trips, which might frustrate other boats plugged into shore power. “A lot of states are incorporating that code, and the world hasn’t ended,” says Kevin Ritz, who founded the Electric Shock Drowning Prevention Association and is a lead systems instructor at the Northwest School of Wooden Boatbuilding in Port Hadlock, Wash.

In Washington, the Port of Poulsbo is updating the electrical system at Poulsbo Marina, even though the port is on saltwater Puget Sound and ESD occurs in fresh or brackish water. “We have so much transient activity, and we have a lot of rowing clubs and paddleboarders coming in,” port manager Carol Tripp says. “We just need to be proactive.”

In 2017, the port received a $115,387 grant from the Washington State Recreation and Conservation Office to upgrade the guest docks with 30-mA breakers on moorage pedestals, with a total of 68 Eaton Newport Camp Mate pedestals being installed. “It means that some boaters might not be able to get power, but it also tells me they have an issue on their boats,” Tripp says.

In addition to the 30-mA monitors on the docks, Tripp says, the marina added four isolation transformers, so a boater who can’t plug into the main system won’t have to run his generator. The transformer isolates the boat so it can’t leak current. Additionally, there’s a 100-mA monitor on the main power transformer.

An isolation transformer at Poulsbo Marina lets transient boaters plug in without endangering other vessels. 

An isolation transformer at Poulsbo Marina lets transient boaters plug in without endangering other vessels. 

Most marina operators and boaters seem to be getting the message. Earlier this year, when water levels were high at facilities on the Great Lakes, some boaters were annoyed because marinas had to shut down the power to their pedestals. The plug-in sites were above the water, but the lines that fed them were beneath the surface. “We encouraged the marinas to shut off the power regardless of inconvenience,” Ed Lethert, an ESD expert, said during a webinar held by the American Boat and Yacht Council in July.

Ritz says he would like to see more training for technicians in the area of electrical current leakage. “The problems are on the vessels most of the time,” he says. “We need to be training our technicians to find those problems and solve them early.”

One accessory that marina owners may consider acquiring is Shock Alert, a low-voltage tester that retails for about $175. Lethert says he uses it on a fiberglass pole and slowly drags the device around a boat. A green light on the Shock Alert means everything is good, but a red light means current has been detected, and the device sounds an alarm.

If power is detected, marinas need to let boaters know how to turn off the power to a given dock. The Electric Shock Drowning Prevention Association recommends swimming at least 150 feet from any AC electrical equipment, and it encourages facilities to post signage that instructs people how to turn off the power. 

This article originally appeared in the September 2019 issue.



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