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Solved problems · Shore power · Crew answer

Why does my boat trip the dock's GFCI or ELCI breaker?

An ELCI trip means leakage current, not overload. Usual causes: a neutral-to-ground bond aboard, a failing water heater element, or moisture. Add loads one at a time to find it.

Symptom

The shore-power breaker on the pedestal, or the boat's own ELCI main breaker, trips as soon as you plug in, or when a particular load such as the water heater or battery charger switches on.

Likely cause

Ground-fault and ELCI breakers trip when current going out on the hot wire doesn't all come back on the neutral. Typical causes are neutral and ground joined aboard (often a miswired inverter, generator transfer switch or household appliance), a water heater element leaking to ground, an old battery charger, or water in the shore inlet, cord or an outlet.

Stop now if

Never swim near a marina or a boat connected to shore power; leakage into the water can cause electric shock drowning. If anything is hot or smells burnt, or you feel a tingle from metal fittings, unplug and call a qualified marine electrician.

Why an ELCI trip matters

An ELCI or GFCI trip is not a nuisance trip: current is leaking somewhere other than back through the neutral. ABYC E-11 has required a main-feed ELCI on new boats since 2015, typically 30 mA, and many marinas now have ground-fault protection at the pedestal under NEC Article 555. Several small leaks can add up to one trip. A galvanic isolator does not stop ELCI trips. An isolation transformer stops shore-side trips because it breaks the direct connection to shore, but the leak is still there and must be found. The transformer's boat side needs its own correct bonding and protection, installed by a qualified marine electrician.

The fix, in short

  1. Switch everything off, then add loads one at a time. Turn off all AC breakers aboard. With the pedestal breaker off, connect the boat end first, then the pedestal, then switch on. Now turn the boat's circuits on one by one, waiting a moment after each. The circuit that causes the trip is your suspect.

  2. Check the shore inlet and cord. Turn the pedestal breaker off and unplug before inspecting the inlet, cord ends and adapters. Look for water, corrosion or burnt pins, and dry or replace any damaged parts.

  3. Test the water heater element. A cracked element can leak to ground even while it still heats normally. If the water heater circuit causes the trip, have the element tested and replaced.

  4. Look for a neutral-to-ground bond aboard. On shore power, neutral and ground should only be joined ashore. Inverter-chargers, generators and transfer switches must handle that bond correctly. Testing and correcting it is work for a qualified marine electrician who follows ABYC standards.

  5. Don't bypass the protection. Moving to a pedestal without ground-fault protection, or using adapters to stop the trips, hides a real shock hazard rather than fixing it.

Written by Sailor Cruiser crew. General guidance, not an inspection of your boat.

Equipment involved

  • Shore power: Inlet, cord, main breaker or ELCI
  • AC loads: Water heater, battery charger, inverter-charger, generator transfer switch

Related guides

Sources

Background reading we checked while writing this answer. The wording above is our own.

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