- Safety Corner | April 17, 2017
Another swimming season is upon us, and so I must dive again in to a discussion of marina safety. As electrical professionals, we are in a position to help make marinas a safe place to work and play. Marinas can be quite a dangerous place when it comes to electrical hazards. Let's break the ice with some thought-stimulating information that you can build on during your next marina project.
Marinas in both fresh water and salt water can present challenging locations for the electrical distribution system. The distribution system has to to weather moisture and many other elements that act to deteriorate the electrical system over time. In addition to your standard electrical system components, these locations present possible fueling stations that present different challenges and hazards unto themselves. Much of this equipment is placed on a structure that rises and sways with the waves. This is a mix that can spell disaster for an electrical systems that is not maintained or designed correctly.
This potential for disaster is all too real. When a person succumbs to electricity while swimming, it is referred to as Electrical Shock Drowning (ESD). These issues are not contained to just large marinas; small, private marinas are probably more likely to have issues than the larger facilities.
Fresh Water vs. Salt Water
Water has a resistance usually referred to as "conductivity," which is measured by applying a voltage between two electrodes and measuring the voltage drop between the probes. The drop in voltage is used to calculate the resistance. The resistance is then converted to conductivity. Conductivity of water is quite complex and dependent upon what is in the water you are addressing. The more impurities you put in water, the more conductive it becomes. Saltwater offers a good conductive solution. When the resistance of a fluid around an object is less than the resistance of the object itself, current will take the path of least resistance, which is not through the object. When a human body is in fresh water that is energized, the fresh water has a high resistance due to significantly less impurities present. The human body offers a lower resistance, so electrocution is likely. This does not mean that there is no electrical hazard for salt water applications.
Hazards exist in any location where water and electricity are in close proximity to each other, from a pond on a golf course that may have employed pumps for fountain-like attractions to the private boat dock.
Codes and Standards
There are two key documents, from an electrical perspective, that command your attention when addressing marinas and boatyards: NFPA 70, the National Electrical Code, and NFPA 303, "Fire Protection Standard for Marinas and Boatyards." The American Boat and Yacht Council (ABYC) is another organization that offers safety standards focused primarily if not entirely on the boat.
When it comes to the National Electrical Code, chapters 1-4 apply generally and chapters 5, 6, and 7 apply to special occupancies supplementing chapters 1 through 4. Chapter 5 is where we find Article 555 for "Marinas and Boatyards," which was first introduced in NEC 1968 as "Boat Harbor Wiring" and consisted of Sections 555-1 through 555-6, taking up just about a half of a page. This Article has seen attention since then and NEC 2017 didn't disappoint. It was during the 2011 code cycle that Section 555.3, "Ground-Fault Protection," was added. NEC 2017 modified this section and more.
This first change is found in Section 555.1, titled "Scope." NEC 2017 added language that expands the requirements found inside Article 555 to "one-family dwellings, two-family dwellings, and multifamily dwellings." This is a welcomed expansion from a safety perspective. A good friend of mine told me one time that an electron doesn't know it's flowing through one structure over another, let alone who owns that structure.
The second change that NEC 2017 made can be found in Section 555.3, titled "Ground-Fault Protection." This section now requires ground-fault protection not exceeding 30mA, instead of the previous ceiling threshold of 100mA. Based on research that was conducted by th