Dangerous Waters

istock / fotofrog
istock / fotofrog

In my first few years at NFPA, I met an electrical inspector who served as an expert witness in legal cases involving shock and electrocutions involving swimming pools. He told me that business was good, which was sad news. Were these the result of bad installations, damage or normal deterioration over time? Some fell into each of these categories.

Swimming is among the most popular recreational activities. According to the Association of Pools and Spa Professionals, there are 10.4 million residential and 309,000 public swimming pools in the United States. Others prefer to swim off the side of a boat or from a dock. According to the Statista, there were 11.9 million boats registered in the United States in 2016, and according to the University of Delaware, there are approximately 12,000 marinas in the country.

Electric shock drowning has been reported in pools, lakes, rivers and ponds. The occurrences in natural bodies of water have been getting much more attention lately. The 2012 Independence Day weekend was particularly deadly. Five incidents resulted in the electrocution deaths of four children and one adult. These incidents resulted in plenty of media attention.

Most electric shock drownings have occurred in fresh water. In fresh water, a body has higher conductivity than surrounding water, so current flow tends to be greater through the body than through the surrounding water.

In saltwater, the water may be more conductive. Saltwater dock areas are not immune to electric shock hazards. In 2017, several students felt tingling in their legs while they were wading in saltwater near a town dock in Menemsha on Martha’s Vineyard, Mass.

People are most vulnerable to the effects of electric shock when they are immersed in water. According to the National Institute of Occupational Safety and Health, dry skin has a resistance in the range of 100,000 ohms. Wet skin is more conductive and can be in the range of 1,000 ohms, allowing skin to conduct more current. Water can have varying degrees of conductivity, depending on what impurities are contained in the water. Saltwater is more conductive than fresh water.

Shutterstock / GerardvandeWerken
Shutterstock / GerardvandeWerken

Electrocutions have occurred in areas near docks and piers that are supplied by electricity. However, boats at the docks can also be a source of the problem. Not all equipment on boats and docks is correctly installed by professionals or properly maintained. Electrical equipment installed outdoors is subject to weather conditions for the area. It can be exposed to water spray and immersion. There are also the mechanical hazards of dock movement, which is worse in tidal areas. Some equipment locations can be subject to impacts from boats. The mechanical shock of boats impacting docks can also cause damage, even if the equipment is not directly struck by a boat.

Problems in pool areas have included underwater pool lighting and pool pump motors. Some faults have had nothing to do with the pool-related equipment. A utility fault may not clear immediately but may find a better path to ground through the pool area. According to the Consumer Products Safety Commission, there were 17 electrocutions involving pools, whirlpools and hot tubs from 2003 to 2014.

Pools don’t have the all of the same environmental exposures as marinas. In most areas, winterization of outdoor pools is necessary. The winterization process can involve removing equipment in the fall and subsequent reinstallation in the spring. Removal and reinstallation may damage equipment, and it is also possible that connections to equipment grounding or bonding conductors may not happen during reinstallation. Equipment can also be exposed to corrosive pool chemicals, especially if stored in the same room. Corrosive material damages enclosures, contacts and conductors.

How has the NEC addressed this?

Article 680 first appeared in the 1962 Code. Swimming pools were the first application that required ground-fault circuit-interrupter (GFCI) protection in the 1968 edition. Over many editions, Article 680 was revised to expand GFCI requirements to cover receptacles, pool pump motors and luminaires that exceeded the low-voltage contact limit. GFCI protection has reduced pool-associated equipment hazards as well as hazards from cord-and plug-connected equipment that may be used around pools. Equipotential bonding in the pool area has been effective in reducing voltage gradients.

Article 555 first appeared in the 1968 NEC under the title “Boat Harbor Wiring.” By the 1971 edition, the title was changed to “Marinas and Boatyards,” to align with NFPA 303, Marinas and Boatyards. The requirements for floating dwelling units were added as a new Article 555, Part B in the 1981 edition. Prior to the 1999 edition, article parts were Arabic letters rather than the roman numerals of today.

In the 1987 Code, the requirements from Article 555, Part B were relocated to a new Article 553. It was proposed by the Ad Hoc Subcommittee on Floating Dwelling Units, but were expanded to include other floating structures, so the title and scope was changed to floating buildings.

Pools are an easier environment to control than marinas. Marinas that supply power to docks may have multiple slips and docks. Each slip can contain a boat that may or may not be connected to the marina’s power supply. Most of these boats have their own electrical systems that can interact with the marina’s electrical system. The potential hazard for swimmers could be from the marina or from the boats docked at the marina.

Some states have enacted their own laws to require upgrades to electrical installations, such as the Noah Dean and Nate Act. This act was named for two boys who were electrocuted while swimming at a marina in Tennessee. The law requires GFCI protection, signs that warn of the dangers of swimming around docks and a marina-inspection program.

The 2011 edition of the NEC provides requirements for ground-fault protection of equipment. It required the main overcurrent protective device supplying a marina to have ground-fault protection not exceeding 100 milliampere (mA). The requirement permitted individual feeders protection or branch circuits as an alternative.

After media reports surfaced about electric shock drowning accidents at marinas and floating buildings, several members of Code-making panels identified electric shock drowning as an issue needing research by the Fire Protection Research Foundation.

For the first phase of the project, the research was conducted by the American Boat & Yacht Council. Their report was published in 2014. The second phase of research was conducted by Worcester (Mass.) Polytechnic Institute. The final report was published in 2017, and these reports were used as the basis for changes for the 2017 and 2020 NEC.

The limit for ground-fault protection was reduced from 100 mA to 30 mA in the 2017 Code based on “Assessment of Hazardous Voltage/Current in Marinas, Boatyards and Floating Buildings,” which was the report published by the Fire Protection Research Foundation. The Code-making panel also added a new requirement for signage. Section 555.24 was added in the 2017 Code to require warning signs to be posted at marinas to warn of shock hazards. The NEC cannot regulate swimming, but it can warn the public about electrical hazards. The sign is required to read: WARNING—POTENTIAL SHOCK HAZARD—ELECTRICAL CURRENTS MAY BE PRESENT IN THE WATER.

Many considered the 30-mA limit for ground-fault protection to be too low to be practical because there are many leakage sources in marinas and boatyards. A tentative interim amendment was issued that made the requirement apply to feeders supplying docks rather than the main. Furthermore, it permitted coordination so that the device closest to the fault would trip first. It also added definitions of the terms docking facility and marina to correlate with NFPA 303.

For the 2020 cycle, Article 555 was extensively revised to include all docks, including private docks at homes. Article 553 was deleted, and its requirements were consolidated back into Article 555. A number of additional definitions were added to 555.2 to correlate with NFPA 303. Bonding requirements were clarified so that all metal parts in contact with water, metal piping and all noncurrent carrying metal parts likely to become energized must be connected to the grounding bus in the panelboard. Requirements for ground-fault protection of equipment and GFCI protection were extensively rewritten. Feeders and branch-circuit conductors must have ground-fault protection equipment not exceeding 100 mA. Coordination with downstream devices is permitted. Receptacles supplying shore-power to boats must have ground-fault protection that does not exceed 30 mA. Other receptacles that are not intended to supply shore power must have GFCI protection for personnel.

If there are more than three receptacles that supply shore power for boats, a leakage current measurement device must be available and used to determine leakage current available from each boat.

A former colleague told me that he considered electric shock drowning among the most important electrical issues that we had dealt with in recent years.

Maintenance is key

The NEC is not a maintenance document, so it can’t contain maintenance requirements. However, inspection of pools and marinas is critical. There is discussion taking place to convert NFPA 70B into a standard, which would make its requirement mandatory. If that happens, maintenance requirements could be located in NFPA 70B.

Public pools in some areas are required by the jurisdiction to be inspected annually. A new requirement in 680.4 permits the authority having jurisdiction to require periodic inspection.

NFPA 303 requires periodic inspection of electrical equipment at docks so the electrical equipment is inspected annually. However, there are areas where it isn’t adopted.

For more on this topic, see “Protecting People from ESD” in the September 2019 issue.

About the Author

Mark Earley

Mark Earley, P.E., is the chief electrical engineer. Retired from the National Fire Protection Association, he was secretary of the National Electrical Code Committee for 30 years.

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