What happens when I take my 120 volt
US boat to Europe and want to plug in to 240 volts?
Boat electrical systems in US and Europe
European boats tend to have smaller shore power systems than are typically found in the US. Even boats of 45ft (15 meters) will often just have a battery charger, water heater and a few AC receptacles. In the US it is quite common to have air conditioning, refrigeration, microwaves, TV's and all the comforts of home and so power requirements tend to be more demanding.
Typical shore power in the US and Europe
For small and medium sized recreational boats cruising in Europe it is normal to find a shore power connection with a 16 Amp service delivering 240 volts at 50 Hz. Larger boats in larger slips will encounter a 32 Amp service. The total power available from a 16 Amp service is 3840 Watts ( Watts = Volts x Amps) and from a 32 Amp service is 7680 Watts. The frequency of the shore power in Europe will be 50 Hz or 50 cycles per second.
In the US will find a 30 Amp 120 volt service for the smaller boats. Larger boats will typically find a 50 Amp 120/240 volt service, or occasionally a 50 Amp 120 volt service. The total power available from a 30 Amp 110 volt service is 3300 Watts and from a 50 Amp 120/240 volt service is 12000 Watts. In the US the frequency is 60 Hz.
Bringing a US boat to Europe
The least expensive way is to get a multi input voltage battery charger and use it to charge the boats batteries while using an inverter on board to continue to make 120 volt 60 Hz power as needed. This allows you to keep batteries charged and use appliances on board as needed. It works best for small power demands; if your boat has three air conditioners and a washer dryer this is not going to work so well.
The next way is to get a transformer to convert the voltage. The snag with this is that transformers are big and heavy and expensive and won't convert the frequency. A transformer for a 30 Amp 120 volt service will cost about $600 and one for a 50 Amp 12/240 volt service will cost around $1750. The frequency may not matter for many pieces of equipment but for some it could cause overheating or other problems. If you have a new boat under construction you can specify dual frequency motors for air conditioners and refrigeration and avoid this problem.
US boats going permanently to Europe will be required to comply with CE requirements. What this means in practice appears to depend on who is doing the certifying. If the boat is to be rewired at least it should be possible to keep most of the existing wires as they will be adequately sized to support the lower currents and higher voltage.
Bringing a European boat to the US
Permanently bringing a European boat to the US may involve rewiring because the wire size within the boat is likely to be too small to give adequate power with the lower voltages. For temporary visits the methods outlined above apply. What is definitely not recommended is that you "jury rig" US 120/240 volt shore power to go into your 230 volt boat without understanding the consequences. In the US 120/240 volt system there are two hot legs but in the European 230 volt system there is only one hot leg. If you plug a European boat into 120/240 volt system there may well be all kinds of unintended consequences when this is used with appliances not designed to work in this manner.
There are a number of voltage and frequency converters available but the cost, size and weight considerations are normally prohibitive for all but "Mega Yachts". Atlas Marine Systems and ASEA Power Systems are manufacturers of such systems. At Peter Kennedy Yacht Services we do not deal with such large and expensive systems and the information that is included here is just for information purposes because we get asked about this so often. Here is a sample pricelist:
12 KVA 1 Phase - 1 Phase 20 x 23 x 10 230 Lbs $17,630.00
AC15 15 KVA 1 Phase - 1 Phase 22.4 x 29.13 x 12 230 Lbs $19,910.00
AC18 18 KVA 1 Phase - 1 Phase 22.4 x 29.13 x 12 300 Lbs $22,950.00
AC24 24 KVA1 Phase - 1 Phase 41 x 17 x 30.25 490 Lbs $34,350.00
AC25-1 25 KVA 1/3 Phase -1 Phase 42 x 18.5 x 28.25 350 Lbs $34,880.00
AC25-3 25 KVA 1/3 Phase - 3 Phase 42 x 18.5 x 28.25 350 Lbs $34,880.00
AC30 30 KVA1/3 Phase - 1 Phase 42 x 18.5 x 28.25 350 Lbs$41,470.00
AC36 36 KVA 1 Phase -1 Phase 41 x 17 x 30.25 530 Lbs $43,370.00
AC36-1 36 KVA 1/3 Phase -1 Phase 42 x 18.5 x 28.25 350 Lbs $43,720.00
AC36-3 36 KVA 1/3 Phase -3 Phase 42 x 18.5 x 28.25 350 Lbs $43,720.00
AC50-1/2 50 KVA 1/3 Phase -1 Phase 41 x 18 x 30.25 1150 Lbs $57,640.00
AC50-3/2 50 KVA1/3 Phase - 3 Phase 41 x 18 x 30.25 1150 Lbs $57,640.00
AC75-3 75 KVA 3 Phase - 3 Phase 50 x 23.88 x 30.25 1240 Lbs $72,760.00
AC75L-3/2 75 KVA 1/3 Phase - 3 Phase 57.68 x 18 x 21 1650 Lbs $75,280.00
Blue Sea Systems page on the differences between US and European electrical systems
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Peter Kennedy Yacht Services
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