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AC Ground Faults, the Boater, and ABYC

Understanding Equipment Leakage Circuit Interrupters (ELCIs) and Ground Fault Circuit Interrupters (GFCIs) to make your boat safer.

April 27, 2009

There are two potential failures in a boat's electrical system that can put people on or around the boat at risk of lethal electric shock.

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.

In addition, a faulty ground can occur when the grounding path is broken through a loose connection or broken wire. For instance, a shore power cord ground wire may fail due to constant motion and stress.

Faulty grounds can be undetectable; a simple continuity test will not necessarily reveal a problem.

When these two conditions occur at the same time, the results may be tragic. The combination of a ground fault and a faulty ground can result in metal parts in the boat and under water becoming energized.

In addition to the hazard to people on the vessel, there is a larger danger to swimmers near the boat. While people on board are likely to receive a shock from touching energized metal parts, nearby swimmers could receive a paralyzing dose of electricity and drown due to involuntary loss of muscle control. A Coast Guard sponsored study showed numerous instances of electrical leakage causing drowning or potential drowning even though the shock did not directly cause electrocution.

Given the seriousness of the problem, ABYC requirements now include specific measures for avoiding this danger.

ABYC regulation E–13.3.5 states:

If installed in a head, galley, machinery space, or on a weather deck, the receptacle shall be protected by a Type A (nominal 5 milliamperes) Ground Fault Circuit Interrupter (GFCI).

ABYC regulation E–11.11.1 states:

An Equipment Leakage Circuit Interrupter (ELCI) shall be installed with or in addition to the main shore power disconnect circuit breaker(s) or at the additional overcurrent protection as required by E– whichever is closer to the shore power connection.

ELCIs, and the more familiar GFCIs, are part of a larger family of devices that measure current flow in the hot and neutral wires and immediately switch the electricity off if an imbalance of current flow is detected. ELCIs and GFCIs that are also Residual Current Circuit Breakers (RCBO) provide overcurrent tripping protection characteristic of a normal circuit breaker.

GFCIs are used as branch circuit ground fault protection at the 5mA threshold in potentially wet environments. GFCIs protect against flaws in devices plugged into them, but offer no protection from the danger of a failing hard-wired appliance, such as a water heater or cooktop.

In contrast, an ELCI provides additional whole-boat protection. Installed as required within 10' of the shore power inlet, an ELCI provides 30mA ground fault protection for the entire AC shore power system beyond the ELCI. ABYC regulations still require the use of GFCIs in environments described above.


Although ABYC regulations apply only to new boat construction, the dangers and liabilities exist for any boat owner with a shore power connection. Retrofitting an ELCI to an existing AC system can be worthwhile “insurance” against risk. Since an ELCI/RCBO can serve as the main shore power circuit breaker, it can replace a standard circuit breaker in this application. Alternatively, an ELCI/RCBO can be added between the shore power inlet and the existing main shore power circuit breaker.

Safety ground system failures on boats are safety and liability disasters waiting to happen. ELCI protection on each shore power line, combined with protection afforded by GFCIs, will reduce risk to those on the boat, the dock, and in the water surrounding the boat.

Blue Sea Systems Offers Solutions for Mounting ELCI Breakers to Comply With ABYC July 2010 Requirements

February 17, 2011

In response to a 2008 Coast Guard sponsored study entitled In-Water Shock Hazard Mitigation Strategy, ABYC standards now require boatbuilders to install an Equipment Leakage Circuit Interrupter (ELCI) on each shore power line on new vessels. Although refit of older vessels is not required as of 2011, prudent boatowners will consider installing an ELCI to protect themselves from liability and nearby swimmers from potentially lethal electric shock, muscle paralysis, and drowning.

Most boaters are familiar with the GFCI (Ground Fault Circuit Interrupter) outlet. GFCIs provide 5mA branch circuit ground fault protection in wet locations. An ELCI, installed as required within 10’ of the shore power inlet, provides 30mA ground fault protection for the entire AC system beyond the ELCI. GFCIs are still required in heads, galleys, machinery spaces, and weather decks.

Blue Sea Systems offers several options to help boatbuilders and boatowners comply with ABYC regulations. Three of those options will be discussed here.

If a boatowner has an existing AC Main panel, it may be possible to retrofit an ELCI breaker into that panel. Blue Sea Systems PN 3106 is a toggle breaker designed for Traditional Metal panels, and PNs 3102, 3103, and 3104 are large-frame circuit breakers intended for use with the 360 Panel System.

ELCI Main Circuit Breakers


Alternatively, Blue Sea Systems offers several standard panels with ELCI breakers, both in the Traditional Metal line and the 360 Panel System. These panels are available in standard sizes and with and without AC Voltage metering.

Traditional Metal Panels

360 Panel System


For the boatowner with special considerations, Blue Sea Systems’ Custom 360 Panel Program offers the ability to fit ELCI breakers into a custom panel. Panels can be created in many sizes and configurations, and generally ship within ten days of order finalization.

Consider viability of a retrofit, cost, and future expandability when choosing between these options. Since ELCI breakers are physically larger and have more poles than their standard AC Main counterparts, some modification is likely to be required to an existing panel, whereas starting fresh with a standard or custom panel allows more choice in configuration.


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