Captain's Tips

Shore Power Paradox - Captain's Tips



New code requirements are causing marinas around the country to update their electrical service and address the risk to life safety caused from faulty or incorrectly wired boats. As a result, some boaters are experiencing trouble by tripping newly installed, more sensitive shore power breakers.

Understanding Electrical Safety Devices

Most people are familiar with a Ground Fault Circuit Interrupter (GFCI) outlet. For many years, we used them in home kitchens and baths or anywhere something plugged into an electrical outlet could come in contact with water. You know them by the small reset button built into an outlet. They are mandated in residential wiring by building codes for personal safety against electrocution.

Shore Power Diagram | Shore Power Paradox | Marinalife

Electricity flows from an outlet to an appliance and back again in a loop along the hot and neutral wires in a power cord. The GFCI monitors the electricity flowing through the loop. If the device fell into a bathtub or got wet, and allowed electricity to flow into the water, the GFCI would detect the loss or current imbalance in the loop and trip a highly sensitive breaker in the outlet. GFCI outlet receptacles detect an imbalance of as little as 4 or 5 milliamps and react quickly in as little as 1/13th of a second. Boats built to American Boat & Yacht Council (ABYC) standards also have GFCI outlets installed in the boat's heads, galleys and exterior spaces.

The updated code requires marinas to install devices called Ground Fault Protection (GFP) which are like GFCI outlets in your home. The GFP can detect electricity leaking from a circuit the same way a GFCI does and cut off the boat's electricity supply. The code requires ground fault protection not to exceed 100 milliamps of ground fault current leakage. However, most marinas are opting to install even more sensitive Ground Fault for Equipment (GFE) breakers at individual boat slips, which disconnects electricity to the boat at 30 milliamps of ground fault leakage.

Shore Power Electricity

When you link your boat to shore power, it's like connecting an appliance to an outlet: a flow of electricity travels in a loop between your boat and the shore power pedestal along hot and neutral wires in a shore power cord. A third wire in your shore power cord is the ground wire. If anywhere in the boat's wiring, or in an appliance on the boat, the neutral and ground are connected, current will be diverted from the loop, creating a leak of electricity from the circuit and into the boat's bonding or ground system.

Due to a prior lack of standards or variances in how a boat's appliances are wired, this condition could occur in many recreational boats. Electricity flowing through a boat's bonding system through the ground wire results in electrical current possibly flowing into the water around the boat. One of the primary reasons marinas post signs prohibiting swimming in the marina is the potential for electricity in the water and the risk of drowning by electric shock.

ABYC Boat Safety

ELCI Protects Tripped Wires | Shore Power Paradox | Marinalife

At the same time marinas are instituting new safety standards, ABYC is also recommending that boat manufacturers install a similar safety device at the boat's shore power entry point, called an Equipment Leakage Circuit Interrupter (ELCI). The ELCI monitors the electricity flow in a circuit in the same way as the previously mentioned devices. If the device senses an imbalance of more than 30 milliamps, it cuts off the electricity supply to the boat. All new boats should comply with this ABYC recommendation; however, an ELCI can also be installed in an existing boat's shore wiring circuit.

Frustrated Boaters

Boaters connecting to renovated marinas are becoming aware of their boat's wiring issues due to this newly installed, more sensitive equipment. Older boats aren't the only ones with problems; many late model boats have similar wiring issues. Finding the exact problem in the boat can be difficult, which elevates the frustration of boaters and marina staff.

Michael Giannotti, an ABYC-certified electrician and master technician from Hartge Yacht Yard who has investigated these problems, has discovered several likely causes including:

  • Inverters
  • Household appliances, such as washers and dryers
  • Ice makers and refrigerators
  • Generator transfer switches
  • Older or faulty galvanic isolators
  • Air-conditioning control boards
  • Corroded electrical connections
  • Faulty power cord, splitter or smart Y adapters.

Discovering the actual cause makes it especially important to follow the correct steps when connecting a boat to shore power. First, turn off the primary breaker in the shore power connection, then turn off all branch circuit breakers in the boat. Once the shore power cord is connected and locked into place, turn on the shore power connection at the dock pedestal with the boat's main AC breaker still off. If the breaker trips immediately, the problem is likely the shore cord or Y adaptor.

Next, turn on the boat's main AC breaker with all the branch circuits still off. If the shore power pedestal breaker trips, the problem is likely an improperly wired transfer switch or inverter. If the dock pedestal breaker trips after an individual branch circuit breaker is switched on, it is likely a device connected to the breaker or defective control board in an HVAC or refrigerator circuit. This procedure works in diagnosing at least where the problem lies for most boats, assuming they have two pole main breakers for 30 amp/125 volt inlets and three pole main breakers for 50 amp/250 volt inlets.

Whether investigating an electrical problem or installing new electrical equipment, all the work should be performed by an ABYC-certified electrician or with complete knowledge of and following ABYC standards.

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