In a properly functioning marine electrical system, the same amount of AC current flows in the hot and neutral wires.
However, if electricity “leaks” from this intended path in these two wires to ground, this condition is called a ground fault. A good example of this is an insulation failure in the wiring of an appliance.
Like GFI’s, ELCI’s (sometimes referred to as RCDs) must include a test feature, the blue button with embossed T.
While technically deemed “equipment protection”, because of their 30 milliamps trip threshold, the goal of ELCI’s is to interrupt current flow quickly enough to prevent electrocution, electric shock drowning or fire, and for the most part they do so very effectively, saving, much like GFIs, countless lives every year.
The adoption of the ABYC ELCI Standard was, much like the GFI, inspired by a number of electric shock drownings or ESD’s. Different than a conventional electrocution, an ESD can, with comparatively little current flow, paralyze a swimmer’s voluntary muscle reflexes, causing him or her to drown, which only serves to mask the underlying electrically-related cause of death. For more on ESD and how it occurs and differes from conventional electrocution, see this Marine Systems Excellence article.
“Electrocution” is a broad term, and the range of current has many differing effects. Those that may be non-life threatening ashore, such as muscles freezing, can lead to drowning while swimming.
While it’s true that virtually all documented ESD cases have occurred in fresh water, the risk of swimming around docks and boats that are energized with shore power, in salt or fresh water, remains extremely high. Some will say, “It can’t happen in salt water”, and I cringe each and every time I hear this. There are several reasons this “theory” represents dangerous folly. One, it’s impossible to determine the salinity level of a body of water before jumping in to cool off. In estuarial waters like the ones where I live, on the Chesapeake Bay, salinity changes seasonally and even daily after heavy rains. Two, it’s impossible to rule out the potential for ESD or electrocution in seawater provided the current flow is high enough. Do you want to risk your life or the lives of your loved ones by testing this belief? Some have also said that if an ELCI, leakage warning system or transformer is used, it’s then safe to swim in the vicinity of energized docks and boats. Again, this is incorrect; it’s dangerous and risky at best.
Ground fault interrupter receptacles have been around since the 60’s. Having saved countless lives in that time, they should be installed in a vessel’s head, galley, on weather decks and in engine rooms and machinery spaces. They provide local protection and are still required even for vessels equipped with an ELCI.
In addition to the trip threshold, the primary difference between the ELCI and its cousin the GFI, is the location in which it is installed. GFI receptacles are installed where power is to be used, galley, head etc, while ELCI’s are installed where power enters the vessel, near the shore power receptacle. Think of it as a whole boat GFI with some modifications. A primary shore power circuit breaker is already required for every shore power inlet, and in the case of an ELCI it is often installed either in conjunction with this breaker, or as a single combined unit, achieving the goals of over current protection and fault protection. It’s important to note that the presence of an ELCI does not negate the need for individual GFIs, both are still required for ABYC compliance.
ELCI’s, the blue-handles, are often combined or co-located with primary shore power inlet circuit breakers, the black two pole devices to the right of the ELCI. Don’t assume an ELCI trip current is correct, as they are available in a wide range, from 5 mA through 100 mA. ABYC compliant ELCI’s should be designed to trip at 30 mA, those seen here indicate this in the “I=0,03A” shown on their face.
ELCI’s got off to a rocky start when they were first introduced to the ABYC Standards and the marine industry in 2008. As is often the case, the intent preceded the hardware, and as a result the implementation was postponed for a couple of years. Now, however, proprietary marine ELCI circuit breakers are readily available from several manufacturers in a range of configurations. With few exceptions, new vessels that are built, or those that are being refit, to ABYC (or European CE) Standards must be equipped with ELCIs, and with good reason; they save lives. An ELCI can be added to virtually any vessel’s shore power system provided it is free of faults.
If the wire-run distance between the shore inlet and the circuit breaker panel is less than 10 feet, the ELCI may be located in the latter.
Folks often ask me when it’s OK to swim around docks, saying, ‘What if the vessel does have an ELCI?” or “The dock has a leakage warning system, is it OK then?”, or, “Can the water be tested before swimming?”. Unfortunately, the answer is no to all of these scenarios for a variety of reasons, including and especially because faults occur in a split second, one minute the water is safe, the next it’s deadly, and unless you can walk on water you can’t count on being able to get out of harm’s way quickly enough. Also, as wonderful as ELCI’s and GFCI’s are, they are not foolproof.
You might ask, “What about divers? I see them in the water in marinas all the time and they don’t get electrocuted”. Whenever I encounter one on a dock, and that’s often, I make it a point of asking, “Do you ever get shocked or feel a tingle?” Without exception every one has said yes, several have told me they can feel electricity coursing through their dental fillings. A dry, and even wet, suit does offer some protection against electrocution and ESD, which is why these folks probably haven’t become victims. They do this work at their own risk, hopefully knowing the hazards (one was killed recently in Florida, albeit by a bow thruster rather than ESD), a far different scenario from your child frolicking in the water on a seemingly care-free summer day.
Simply put, never swim around docks equipped with shore power in fresh or salt water. There are no exceptions to this rule.
Next month I’ll discuss shore power transformers and the role they play in electrocution prevention, and fault avoidance.