How do I install a shore power kit on my boat safely?

A safe shore power installation needs a marine inlet, correctly sized flexible cable, double-pole isolation, overload protection, a 30 mA residual current device and a continuous protective earth. Plan the layout and agree the mounting work with a qualified marine electrician, who should install the fixed mains wiring and test the complete system before connection.

Check supply and equipment

Start with the boat's wiring diagram, the marina supply and the appliances you intend to run. These determine the kit, cable sizes and circuit protection. The usual UK and European supply is 230 V, 50 Hz through a blue 16 A three-pin CEE connector. North American boats commonly use 120 V systems with different connectors and protection arrangements.

A plug adaptor changes the connection, not the voltage or frequency. Check imported boats particularly carefully, including the charger, immersion heater and existing sockets.

• List each appliance's input rating. A 2 kW kettle draws about 8.7 A at 230 V, leaving limited capacity for a heater and charger on a 16 A supply.
• Inspect existing wiring for household solid-core cable, unsupported joints, heat damage and missing earth conductors.
• Identify any generator or inverter supplying AC. It needs a suitable changeover arrangement to prevent backfeeding the shore connection.

Before starting installation work, disconnect the shore lead and isolate every onboard AC source, including inverter and generator outputs. Then prove the circuit dead.

Specify the marine equipment

Agree the following with your electrician. Use equipment intended for the boat's environment rather than a household extension arrangement:

• A weatherproof shore inlet with a secure mating connector and sealing cap, positioned clear of spray and places where water collects.
• A main device that disconnects both live and neutral, with overcurrent protection matched to the inlet, wiring and supply.
• A 30 mA RCD, or an RCBO combining residual-current and overcurrent protection. An RCD alone does not protect against overload.
• Separate protected circuits where appropriate for sockets, battery charging and water heating.
• Flexible stranded copper cable, suitable enclosures, cable glands, strain relief and protected sockets.

For an ordinary 16 A shore lead, 3G2.5 mm² outdoor flexible cable is a common choice. It has three conductors, including earth, each 2.5 mm². Longer runs, installation conditions and voltage drop may require another size. Internal wiring must also be sized for its circuit and routing.

A portable double-pole protection unit can provide additional protection; these units have typically cost around DKK 900. It does not replace a properly designed fixed installation aboard the boat.