Isolation Transformers

Why isolation matters on shore power

An isolation transformer breaks the direct electrical connection between shore power and your boat's AC system, which reduces the risk of galvanic corrosion caused by stray currents travelling through the marina earth and protects the boat if there's a wiring fault elsewhere on the pontoon. It's a different job to a simple RCD or breaker, and the two aren't interchangeable.

Sizing one correctly means matching its power rating to your onboard AC load, covering chargers, air conditioning and any galley equipment running at once, rather than just the shore supply's rated current. Installation position also matters: transformers are heavy and generate some heat in use, so they need a dry, ventilated spot with the cable runs to match.

If you're fitting one as part of a wider AC rewire, it's worth planning the transformer alongside your battery charger and inverter so the whole AC side of the boat is sized consistently.