April 8

Understanding Marine Electrics: Converting a 230V SHORE POWER system to 120V

If you are looking to import your European-built boat into the U.S., one question that may come to mind is whether you can convert your boat's AC circuit to make it compatible with U.S. AC shorepower. 

The Importance of Sizing Conductors for Lower Voltage

First thing to note is European shorepower is at a frequency of 50Hz while U.S. is at 60Hz. You will need AC equipment that can handle the different frequency.

Then there’s voltage. The base voltage in Europe is 230 volts, while in the U.S. it's 120 volts. This means that for a given load, if the voltage is cut in half, the amperage must be doubled to get the same power. Higher amperages require larger conductors, because if not you may fry the conductors on your boat. Unfortunately, the boat may need to be rewired for it to safely function on U.S. shorepower. The critical issue is the size of the conductors: whether or not they are sized for the lower voltage in North America. If they are not, even if the different frequency is not a problem, ssimply changing the plug on the shorepower cord won't work.

Using the Wire Sizer App for Cable Sizing

To make sure that the conductors are sized appropriately for the lower voltage, use the Wire Sizer App found at BoatHowTo.com. This free app is considered the best in the marketplace, and it helps boat owners ensure that they have the right-sized conductors for any given task.

Importance of Safe AC System Installation

Make sure you follow the relevant boat building standards when installing or converting your boat to U.S. AC. Aside from frequency and conductor sizing issues, there may be grounding, residual current device, and galvanic isolation issues. Converting a European-built boat to U.S. AC shorepower is certainly possible, but it does require careful planning. Ensure that you have the appropriate conductors and follow all safety protocols when installing the new system.

If you want to learn everything you need to know about AC shorepower, you should have a look at our Advanced Marine Electrics course, containing an entire module on this important topic.

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