Yacht shore power keeps tripping: RCD and ELCI faults

A shore-power RCD or ELCI that repeatedly trips is detecting a current imbalance, but the source may be one appliance, cumulative leakage from several loads, an earthing fault or damaged shore-power equipment. Repeatedly resetting the device does not identify the fault and may leave a serious electrical risk unresolved.

The immediate priorities are to keep swimmers clear, identify exactly which protective device opened and isolate non-essential AC loads. This guide explains what the trip means, which loads deserve attention and where crew checks must stop.

What an RCD or ELCI is detecting

In a correctly functioning AC system, the current flowing through phase and neutral is equal. An RCD measures that balance and opens its contacts when it detects a difference, indicating that current may be following another path to earth.

Insulation failure inside an appliance can produce this ground fault. The trip therefore does not, by itself, prove that the protective device is defective. The leakage source could be downstream equipment or part of the yacht's earthing arrangement.

An inverter/charger installation also depends on the correct earthing design for RCD protection to work. A double neutral-to-earth link can cause nuisance tripping, while a missing neutral-to-earth link can make the result of an RCD test misleading in a floating arrangement. Testing that relationship requires an electrical technician rather than trial-and-error switching by crew.

The protective devices also cover different parts of the installation:

• ELCI protection: The cited ABYC explanation describes an ELCI providing 30 mA whole-boat ground-fault protection beyond the main shore-power device. It refers to installation within 10 ft of the shore inlet.
• GFCI protection: GFCIs provide 5 mA branch-circuit protection in wet locations such as heads, galleys, machinery spaces and weather decks.
• Coverage limits: A GFCI does not protect a failing hard-wired appliance that sits outside the branch circuit it covers.

Blue Sea quotes ABYC E-11.11.1 as requiring an ELCI with or in addition to the main shore-power disconnect, at the relevant location nearest the shore connection. This is an ABYC new-construction reference, not a replacement for flag or local requirements. Questions about the yacht's installation should be handled through a proper electrical assessment and, where needed, compliance and flag-state support.

Identify which device is tripping

Start by recording the exact device that opened. A pedestal RCD, the yacht's main ELCI and a branch GFCI do not have identical coverage, so that detail helps define where the investigation should begin.

Do not report only that 'shore power tripped'. Record the label on the device, whether the trip was immediate and which AC equipment was operating or had just been switched on. Water heating and refrigeration are particularly relevant because electric water heaters and old refrigerator compressors are among the items Victron identifies for early isolation.

The trip may also depend on several loads running together. Victron notes that multiple small neutral-earth leakages can combine and produce unpredictable RCD operation, even where no single contribution has caused the trip by itself. Surge-protected boards are another item identified for checking and disconnection during diagnosis.

The following matrix helps organise the first report to the engineer. It is not a substitute for electrical testing.

Shore cords and earthing faults

Treat the shore cord as a safety-critical component. A loose or broken shore-cord ground can create a faulty grounding path, and Blue Sea warns that a simple continuity test may not reveal the problem. A continuity reading alone must not be used to declare the cord's earth safe.

The dangerous combination is ground leakage together with a faulty grounding path. This can energise metal parts on the yacht and underwater metal, exposing nearby swimmers to leakage current that can cause paralysis and drowning.

If an RCD or ELCI trips, keep people out of the water around both the yacht and dock until the fault has been assessed. Suspected energisation of any metallic part requires immediate isolation and professional attention. Do not touch suspect metalwork to investigate it.

Visible cord damage, moisture around the connection or a trip that began after a load change should all go into the fault report. These observations give the technician useful direction without asking crew to open panels or test live conductors.

Isolation and insulation-resistance testing

Useful fault-finding separates the installation into smaller sections and checks whether the trip follows a particular load. Repeated resetting without isolating loads is not diagnosis, particularly where cumulative leakage may be involved.

Crew can switch off non-essential loads using their normal controls and record what was operating. A hard-wired heater, refrigeration circuit or inverter/charger that appears to be associated with the trip should remain isolated for the engineer. Do not disconnect wiring or remove covers to continue the test.

An electrical technician may need to examine:

• Neutral-to-earth arrangements: This includes checking for a double link and assessing the inverter/charger earthing design.
• Protective-device placement: RCD or ELCI location and downstream coverage affect what the device monitors.
• Shore-cord earth integrity: A basic continuity check may miss a faulty ground, so the cord needs suitable assessment.
• Individual appliances: Water heaters, refrigeration equipment and other hard-wired loads may require separate testing.
• Cumulative leakage: Several below-threshold sources may combine to operate the RCD.

Insulation-resistance testing applies high DC voltage to de-energised conductors. Fluke states that electronic equipment must be disconnected first because the test voltage can damage it. This is not a suitable crew test on a connected yacht installation.

For repeatable insulation diagnostics, the equipment under test must be de-energised. Fluke also recommends using a temperature baseline or compensation when comparing results. That matters when a technician is comparing measurements rather than relying on a single reading without context.

What crew can check safely

Keep crew checks observational and use only normal installed controls. Do not open an AC panel, remove an appliance cover or disturb shore-power wiring.

• Clear the water: Keep swimmers away from the yacht and dock as soon as shore power trips.
• Identify the device: Record whether the pedestal device, main yacht protection or a branch device opened. Note its label rather than guessing.
• Isolate non-essential loads: Use normal controls and record each load switched off. Pay attention to whether the trip follows water heating or refrigeration.
• Inspect without dismantling: With power isolated, look for visible moisture and shore-cord damage. Do not open panels or equipment.
• Record load changes: Note which appliance had just started or been selected when the trip occurred.
• Use the test button correctly: The installed RCD test button simulates leakage and checks the RCD itself. Record whether it operates, but do not treat that result as proof that the complete installation is safe.

A successful test-button press does not verify the shore cord, appliance insulation, downstream wiring or neutral-to-earth arrangement. It is a device-function check only.

When to call an engineer

Electrical diagnosis is required when the protective device will not remain set or when the fault involves equipment crew cannot safely isolate through normal controls.

Call an engineer when:

• Trips repeat or occur immediately: This includes an RCD or ELCI that trips with all known loads switched off.
• The test button fails: The device needs professional assessment rather than further resetting.
• The shore cord or earth is damaged: A simple continuity check cannot prove the grounding path is safe.
• Metalwork may be energised: Keep swimmers clear, isolate power and treat any swimmer-shock incident as an emergency.
• Water has entered AC equipment: Leave the affected equipment isolated and do not remove covers.
• Specialist testing is required: Insulation resistance, neutral-to-earth links, protective-device placement and shore-cord earth integrity require suitable test equipment and procedures.
• A hard-wired load appears responsible: Water heaters, refrigeration circuits, inverter/chargers and other connected appliances need controlled isolation and testing.

For suspected energised metalwork, a swimmer-shock incident or another urgent electrical hazard in Mallorca, use the emergency yacht repair service rather than continuing onboard checks.

Blueward Marine provides marine electrical and electronics services from Palma de Mallorca. For planned diagnosis, book a service online with fault details and photos, or call the 24/7 emergency line on +34 971 251 374.