Lessons Learned – by Pat Carson
Shorepower – ELCI, GFCI and GFD
Almost any of us who work, live or play on boats have experienced the occasional dreaded and usually embarrassing slip and fall into the water. A captain “friend,” who shall remain nameless, tells me he has been known to fall in a few times a year and his worst fear isn’t the cold water or being injured. He is most concerned with…
On July 21, 2010 the ABYC (American Boat Yacht Council) standard E11.11.1 took effect which recommends an ELCI (Equipment Leakage Circuit Protector) be installed in addition to the main shorepower disconnect breakers. Think of this system as a whole boat GFCI (Ground Fault Circuit Interrupter) that we see in the vessel’s galley and heads or in your home kitchens and bathrooms. The ubiquitous GFCI is a protective device that will open a circuit when a leakage current of four to six milliamps is detected as required by the UL943, Ground Fault Circuit Interrupters, requirement. Both the GFCI and ELCI operate on the same principle of measuring any imbalance of current between the hot and neutral lines of the AC power and tripping the circuit breaker in a prescribed amount of time when an imbalance of a specified limit is detected. While a GFCI will trip with a leakage current exceeding six milliamps, an ELCI is less sensitive and will trip when the leakage current exceeds 30 milliamps. Why is this important? ESD, electric shock drowning and the potential for fire.
Electric shock drowning refers to in-water injuries or fatalities resulting from an electrical shock. ESD generally occurs when low levels of AC current are present in the water and pass through a person’s body. When an electrical fault condition on a boat or dock occurs and a voltage source comes into contact with the water, an electric field is developed that radiates out from the source. As a swimmer approaches the electric field current begins to flow through their body. Since the human body has a much lower resistance than fresh water and acts as a better conductor, current begins to flow through the person and not the water. Currents as low as ten milliamps can cause paralysis of the muscular and skeletal systems while immersed in either fresh or salt water. When paralyzed, the victim is unable to swim or move to safety and will ultimately drown. Unfortunately, it is a person’s natural instinct to swim towards the boat or dock, but just the opposite is best and the victim should swim away from the source of current.
ESD can be deceptive since the victim may not be exposed to the stray voltage field when first entering the water. They can then believe that the water is safe for swimming and will unintentionally enter the voltage field. It does not take much current to have an effect on a person. At just one milliamp a person will feel a tingling sensation. At only 10 to 15 milliamps, he or she can experience paralysis and drown. At 60 milliamps, heart failure is imminent. I know what you are thinking, and the answer is yes, any boat can be retrofitted with the addition of an ELCI.
When you connect your boat to shorepower, there is a flow of electricity traveling in a loop between your boat and the shorepower pedestal along the hot and neutral wires in your shorepower cord. Anywhere in the boat’s wiring or in any appliance on the boat the neutral and ground are connected, current can be diverted from the loop creating a “leak” of electricity from the circuit and into the boat’s bonding or ground system. Electricity flowing through a boat’s bonding system by way of the ground wire results in a potential for electrical current to flow into the water around the boat. One of the primary reasons marinas post signs prohibiting swimming in the marina is due to the potential for electricity in the water and the risk of drowning by electric shock.
I receive several calls per month from boat owners with older boats that do not have an ELCI system installed and are having shorepower issues while traveling away from their home marina. Most recently I received a call from an owner with a large motoryacht who, when he connected to the marina’s power pedestal his breaker would trip and not reset. As I explained, the most likely cause is a ground fault with one or more of his vessel systems leaking current and the marina ground fault device, GFD, detecting that leakage and providing circuit protection as designed.
While the ABYC standards are recommended best practices for yacht manufacturers, most but not all, follow their recommendations. To address these shorepower safety issues the NEC (National Electrical Code) in 2014 changed article 555.3 which then required marinas to install GFP (Ground Fault Protection) in their shorepower system. You may have already visited one of the Bay and Delta marinas that have installed shorepower equipment meeting this standard which, just like the GFCI or ELCI, measures the imbalance of current and trips the circuit. In this case, the power is cut off if the imbalance exceeds 100 milliamps.
Based on research conducted by the Fire Protection Research Association the NEC in 2017 changed article 555.3 again. The new rule requires that all over current protective devices (circuit breakers for example) in marinas, boatyards and at commercial and non-commercial docking facilities provide ground fault protection not exceeding 30 milliamps. This is the same protection level as an ELCI that the ABYC recommends new boats have. This marina rule will protect older boats that do not have onboard ELCI, but will not protect the vast number of older boats that are berthed in older marinas that do not meet either the older 2014 NEC 555.3 or the newer more restrictive 2017 version. And it is important to remember that a person in the water will be incapacitated with currents as low as 10 milliamps and the new marina rule calls for no more than 30 milliamps of leakage current. Perhaps this new requirement is not stringent enough. Keep in mind that compliance with codes and safety standards will help to protect an individual that inadvertently enters the water around a dock or boat equipped with electric power, it is not meant to be the green light for in water activities around a boat or dock.
The more common cause of leakage current in the vessel’s bonding system is from household appliances being used on the boat. In most home appliances the ground and the neutral are bonded or tied together inside the appliance. On a boat the neutral and ground are never bonded and must be separated. Therefore, the offending appliance has by default tied the vessel’s electrical system’s neutral and ground together, leaving open the possibility of ground currents. Your boat can be perfectly OK leaving the dock, but it is possible for a wire to vibrate loose or chafe and short as the boat pounds over the waves. A heating element in the hot water tank can bend enough to come in contact with the tank side. Elements in a heater or toaster can short from a ride in rough water. Any loss of correct wiring can result in current taking a different and potentially dangerous path and very often the circuit breaker will not trip, yet the electrical field is now in the water. If your boat is tripping the marina GFD or the vessel’s own ELCI, the best course of action is to diagnose the vessel’s wiring, find the offending device or devices and either replace them with products designed to be installed in a vessel or break the internal neutral to ground bond. This process is neither easy nor quick. When the owner asks for an estimate to do the troubleshooting and repairs, it is unfortunately not possible to give an exact cost or time estimate; it is essentially open ended. The offending device could be the first system you look at or it could be the 20th.
If your vessel is tripping the marinas GFD then it is almost certain that your vessel is not equipped with an isolation transformer. The isolation transformer is installed between the vessel’s shorepower inlet and the first electrical device. Often times it is the main shore disconnect breaker or ELCI. This effectively isolates your vessel from the marina shorepower and does not allow any ground currents from the vessel to travel back to the marina since the ground wire from the marina is not connected to the vessel’s bonding system. An isolation transformer has two or more windings that couple AC power magnetically between shorepower and the vessel and are by design isolating the system. There is a voltage loop from shorepower to the transformer and back to shorepower and another from the transformer’s secondary winding through the boat and back to the transformer. The power is conducted through a magnetic field inside the isolation transformer rather than across a solid wire connection, effectively breaking the dangerous electrical connection through the water to earth or ground. The current that originates within the isolation transformer will never travel back to shorepower. Isolation transformers may be a good solution for ground fault problems aboard your boat and may offer additional benefits like correcting reverse polarization in the shorepower and providing galvanic protection.
The beauty of an isolation transformer is that because it has taken over duties as the boat’s power source, any leaking current will simply return to the transformer on the boat, protecting everyone in the water. A great side benefit is that the transformer automatically corrects polarity problems from the shorepower. Reversed polarity can be dangerous because AC appliances that should be off when their power switch is turned off will still have current flowing into them. Even worse, when polarity is reversed on some household appliances such as refrigerators, the metal case may be energized with 120VAC. Anyone who comes in contact with that refrigerator and a ground could be electrocuted. Need more convincing? Isolation transformers also prevent galvanic corrosion that can occur between boats in a marina that share a common ground through the AC shorepower. This connection can cause neighboring boats to damage or destroy each others’ less noble underwater fittings like aluminum outdrives, bronze thru hulls and NiBrAL propellers and rudders. Finally, isolation transformers supply clean power to such sensitive AC electronics as computers and TVs. It is sometimes easier and less costly to install an isolation transformer than to diagnose the vessel systems and re-wire portions of the boat to eliminate any offending devices that are putting current into the grounds.
Many yachtsmen with older boats, boats that have nonmarine rated equipment installed or new boats with faulty electrical wiring have been discovering issues with their boats when connecting to a renovated marina. Finding the exact cause of problems can be difficult, however the more likely culprits are household appliances on the boat, improper inverter wiring, corroded electrical connections and faulty power cords. Ground faults onboard our vessels that are connected to marina power with cuts, breaks or poor connections can be a serious shock and fire hazard.
Do not take AC power around your boat or dock lightly. If there is any sign of a worn connection anywhere in the shorepower system, inspect closely and replace any component that is suspect and have a marine electrician inspect your boat’s AC system. Do not blame the marina if you are having problems. Another solution would be to install an isolation transformer on board your vessel. If your boat is having power issues at one of the new marinas with ground fault protection, a transformer may be the first line of defense for your vessel. As the name implies the isolation transformer “isolates” your vessel from the shorepower and any ground currents that appear on board will not be carried back to the shore and trip the GFP device. These transformers have other advantages as well as compensating for low marina voltage such as correcting reverse polarity problems and providing galvanic protection. Getting angry with a renovated marina that has installed modern shorepower equipment designed to protect you and your guests will not solve the problem.
The danger of electric shock drowning comes when a boat that has experienced a short or fault is connected to shorepower and is not isolated with a transformer. Away from the marina shorepower, for example when swimming at an anchorage, you are unlikely to be in any danger because there is no route for the current to find a path to earth. Remember, electricity must have a complete circular path. With shorepower, the shorepower system is connected to earth. The path is from the power pedestal, through the shorepower cord, into the faulty system, out through the ship’s bonding system to the underwater metals and completes the route back to earth through the water that may only be a few feet deep in the marina. Even with your generator running and a faulty system there is only one path to earth.
According to one marine insurance company most AC electrical fires start somewhere between the shorepower pedestal and the vessel inlet connection. Use only marine grade power cords and connectors and use the locking rings and collars to make the connections watertight and mechanically secure. Do not ignore the other high-risk area; the back of the shorepower receptacle. It is recommended that these connections be inspected at intervals not exceeding 10 years. If your boat is older than 2013, when did you last inspect the back of the shorepower connections? Installing an isolation transformer will not prevent problems caused by faulty wiring, it will just mask them until that smell of burning wire becomes apparent. The best practice is to have an isolation transformer installed if you do not have one, and if you are experiencing ground currents tripping the marina shorepower, have the vessel inspected and the offending systems addressed. Remember, it might not be a faulty appliance but instead may be faulty wiring or loose connections.
Time for me to grab my favorite dock chair and decide between a Montecristo #2 Torpedo or a Davidoff Year of the Dog Gran Churchill cigar, pour a large port and relax while my transformer transforms dirty shorepower into clean shorepower.
That is it for this month. If you have a good story to tell or want to discuss the installation of an isolation transformer, send me an email at email@example.com. I always love a good story.