The 230 V system aboard runs at the same voltage as at home but lives with water, damp and vibration. The survey measures the line from shore socket to outlet, the protective devices and leakage current.
From shore to socket
- Shore cable and inlet
- Cable type and size, heat marks at the plugs, watertightness of the inlet on the boat.
- Main breaker and RCD
- The RCD is tried with its test button; pressing it must cut the supply.
- Polarity
- Live and neutral reversed can leave voltage in an appliance that looks switched off. A reverse-polarity indicator, if fitted, is tested.
- Source selection
- Shore power, generator and inverter must be separated so they cannot feed the line together.
- Galvanic isolator or isolation transformer
- Blocks galvanic current from other boats in the marina, protecting underwater metals.
- Sockets
- Type, mounting and corrosion of sockets in wet areas.
Readings
- Leakage: with the clamp meter on the protective conductor and the supply.
- Heating: with the thermal camera, switchboard and connections under load.
- Insulation: insulation resistance on suspect circuits.
- Cathodic effect: with the reference electrode, shore power connected and disconnected.
What we often see
- Overheating electrical connection: On the thermal camera, one pole of the main battery switch is markedly hotter.
- Leakage current on shore power: A steady current measured on the earth conductor with shore power connected.
Risks in the marina
A boat on shore power shares the pontoon's electrical supply and the same water with the boats around it. That brings two risks together. The first is to people: leakage current in the water is dangerous to anyone swimming near the pontoon. The second is to the boat: galvanic current between boats can waste underwater metals and anodes fast. The RCD guards against the first; a galvanic isolator or isolation transformer against the second.
Shore cable and plugs
The shore cable is the hardest-worn part of the electrical system: crushed on the pontoon, dropped in the water, left in the sun. A loose connection in plug or socket heats under load; blackening or melting on a plug means the connection needs replacing. The cable is connected to boat and pontoon without strain and clear of the water. Household cable or joints are never used as extensions.
With a generator and inverter
When a boat has more than one 230 V source, the arrangement that selects which one feeds the circuit matters. Two sources connected at once can damage both appliances and sources. On survey, the source selector is tried in every position, and how the inverter behaves when shore power arrives is checked too.
In marinas abroad
Socket types and pontoon supply arrangements vary between countries. When using an adapter, check that polarity stays correct and the RCD remains in circuit; on boats with a reverse-polarity indicator, watch it at every new connection.
Simple checks for the owner
Press the RCD test button once a month; if it does not trip, replace it. Give the shore cable a visual check at every connection. If you notice a hot smell or discolouration at the switchboard, switch off and have an electrician look at it before using the system again.
These checks do not replace an electrical survey, but they catch a problem early between surveys. With any electrical doubt, switching off is always safer than waiting.
Any electrical work aboard is done with the system off and the shore cable unplugged; the rule holds even for small jobs.