Galvanic isolator for shore power explained

Why a galvanic isolator for shore power matters

When a boat or vehicle connects to shore power, its green safety ground bonds to the utility ground and to other rigs on the same grid. That shared path allows tiny DC voltage differences between dissimilar metals to create a galvanic circuit. The result is metal loss on underwater fittings, prop shafts, through hulls, and other bonded hardware.

A galvanic isolator sits in series with the safety ground and uses a back to back diode array to block low voltage DC potential while remaining transparent to safety faults. In plain terms, it stops the slow drip of galvanic current but still lets a large fault current reach the breaker and trip protection. The device preserves the essential safety function of the green wire while cutting off the corrosion pathway.

The unit does not replace breakers, ground fault devices, or surge protection. It is a corrosion control component that works alongside an ELCI main device, GFCI outlets, and proper bonding with sacrificial anodes.

Sources of galvanic trouble at shore

• Mixed metal fleets on one dock create uneven potentials that drift along the safety ground.
• Marginal marina wiring and aging connections can amplify galvanic differences.
• Poor bonding continuity or missing anodes makes a vessel the easiest path for current.

How the diode threshold works

Back to back diodes block current until a small forward voltage is reached, typically around one to one point four volts. That is above common galvanic potentials, so corrosion current is reduced. If a fault occurs, the higher voltage overcomes the diode threshold and allows enough current to flow to trip upstream protection.

Bonding, anodes, and the big picture

An isolator reduces galvanic current but does not eliminate the need for bonding and sacrificial anodes. Keep the bonding system intact, maintain zinc or aluminum anodes sized for your water type, and inspect connections for resistance or heat discoloration.

Isolator versus isolation transformer

An isolation transformer is the gold standard for boats because it completely decouples onboard AC from shore and creates a new neutral to ground bond onboard. That approach removes the shared ground path entirely, which stops galvanic currents and can reduce shock risks from shore side faults.

Transformers are heavier, larger, and more expensive. They also introduce inrush current and need careful mounting and ventilation. A galvanic isolator is compact, cost effective, and often a practical solution, especially for smaller craft or vehicles where weight and space matter.

Modern fail safe isolators include a monitoring circuit or a bypass element that maintains ground continuity if the diode stack fails. Many also include status indicators. For safety and code compliance, select a fail safe, ABYC E 11 compliant device that matches the service rating, such as 30 or 50 amp.

When an isolator is the right fit

• You want corrosion reduction without the bulk and cost of a transformer.
• Space and weight are limited, as in small cruisers or camper vans.
• You primarily tie into well maintained pedestals and want added assurance.

When a transformer is preferred

• You frequent older marinas with uncertain wiring quality.
• You need full galvanic isolation and additional shock protection benefits.
• Your installation can accommodate the weight and footprint.

Common misconceptions

• An isolator is not a surge protector or power conditioner.
• It will not correct reverse polarity or low voltage.
• It does not fix AC leakage from onboard appliances.

Installation and maintenance best practices

Mount the galvanic isolator in series with the green safety ground as close to the shore inlet as practical. Use tinned copper conductors equal to or larger than the safety ground size, and protect the wiring with secure strain relief and clean terminations. Follow manufacturer torque values and leave room for heat dissipation.

Choose a unit rated for your shore service and ambient temperature. Verify enclosure type for the environment and avoid areas exposed to standing water or spray. Keep cable runs short to minimize impedance, and confirm continuity from the inlet ground to the bonding bus through the isolator.

Testing methods vary. Some fail safe designs require a specific test module or built in monitor to verify diode health and bypass status. Check indicator lights, perform periodic continuity checks, and log your results. If your boat uses underwater metals, treat the isolator as one layer in a broader corrosion prevention plan that includes anode inspection, bonding verification, and regular haul out assessments.

For RVs and camper vans that connect to campground pedestals, a galvanic isolator can reduce nuisance galvanic coupling with other rigs and help protect chassis metal tied into the AC safety ground. Always use a pedestal tester to confirm correct wiring, rely on GFCI protection at outlets, and size the isolator to match the inlet rating.

Complementary protection to include

• ELCI main device at the service entrance to detect leakage.
• GFCI protected receptacles at required locations.
• An energy management or surge module for over and under voltage events.

Signs your system needs attention

• Fast anode depletion relative to past seasons.
• Unusual metal staining near underwater fittings.
• Intermittent ground faults or warm bonding conductors.

Standards to keep in mind

• ABYC E 11 for AC and DC systems on boats.
• ISO 13297 for small craft electrical systems.
• Manufacturer instructions and rating labels for your device.

How OZK Customs integrates smart shore power protection

We design shore power systems for custom adventure vans that mirror the discipline used in marine installations. Our team selects fail safe components, sizes conductors correctly, and routes the safety ground through the appropriate protection stack. When your van connects at a campground, you get quiet operation, clean wiring, and a system that respects the role of galvanic isolation alongside GFCI and ELCI protection.

If your travel style or gear requires more advanced power conditioning, we plan the right combination of converters, chargers, and distribution hardware. We also walk you through system handoff at our Fayetteville Arkansas shop so you leave with confidence.

Explore our builds and next steps:

• Recreational vans
• Custom van builds
• Finance friendly platforms

Ready to talk through a corrosion aware shore power plan for your van. Share your travel routines, power demands, and storage constraints. We will engineer a safe and tidy system that fits your platform and keeps you focused on the trip, not the pedestal.