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Old 21-04-2010, 00:28   #1
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New Boat Electrical Set-Up

I am currently about 33% of the way through getting a semi-custom 42' cruising yacht built at Newcastle. I intend to use it on some long passages and would want to be able to anchor out as much as possible. The engine ordered is a 75hp Yanmar with twin alternators, 1 X 80 amp & 1 X 130 amp. With 1100 litres water tankage and valves to direct deck water into storage, I am hoping not to need a watermaker. I am OK with only being able to have A/C & microwave on shore power. I am trying to follow the KISS principal and not build in unecessary complication. Is it practical to hava a completely 12 volt boat (plus shore power) or do I have to run an inverter? I would love to hear suggestions from experienced cruisers. I definately don't want a generator. Thanks in advance.

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Old 21-04-2010, 04:30   #2
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Your answer will be self-evident once you decide on the size A/C you want and check out it's power draw. There is such a thing as a 12v A/C but very limited in capacity.

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Old 21-04-2010, 04:56   #3
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You would not be asking the question, if you had made a list of electrical equipment, both 12v and 230v. You should do that before doing anything else.

Typical 230v equipment on board a largish cruising boat:

chargers for phones and laptops
air conditioning
tea kettle
washing machine/dryer
hot water heater
electrical heaters

Obviously, a generator will run any of these. Besides that, a generator has the extremely useful function of charging your batteries.

Some of these things can be practically run off an inverter:

power tools

Those are things which are either small loads, or large loads run for short periods of time. Things which are large loads run for extended periods of time: air conditioning, watermaker, washer/dryer, hot water heater, electrical heaters -- are not practical or possible to run from an inverter.

For large loads run for brief periods: kettle, microwave, power tools -- you want a large built-in inverter.

If you don't want the ability to run things like that, then you can get away with a small, perhaps not built in inverter, for the chargers and the TV.

It all depends on what equipment you will use, in what way.

Even though our boat has a generator, I find the electric kettle and microwave to be so extremely useful on board (among other things, they reduce the hazardous and somewhat awkward use of propane), that I am planning to install a large built-in inverter sometime this year.

KISS principle or not, I wouldn't want to be without the generator. There are different circumstances, where you want 230v power on board, beyond what an inverter can provide. Air conditioning is far less useful, if you can only run it on shore power. And you save your main engine from the potentially damaging job of charging your batteries at anchor. Besides that, you have a backup redundant way to charge your batteries, should something happen to the main alternator, which is a frightening thought since all of our navigational equipment, autopilot, nav lights, etc., depend on having power.

That's why a typical large cruiser, designed for autonomous use away from marinas, will have a generator and a large, built-in inverter.

But if you really want to be without those complications, then, of course you can live without 230v power on board, or even 12v power. If you really wanted to go whole hog, you can buy oil-fired navigation lamps, oil lamps to light your cabin, and you can steer by hand and use a hand-held battery-powered GPS. Only you can decide what items of electrical equipment you need or want.
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Old 21-04-2010, 05:42   #4
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Well said, Dockhead.
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"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

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Old 21-04-2010, 08:39   #5
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Many thanks for the opinions Dockhead and S/V Illusion. I have not previously researched generators. I've just hoped that I wouldn't need one. I'll do some more homework and see what I can come up with. Regarding the size of A/C, I actually don't want one, but I need some plan for really hot nights or else I might be singlehanding, which is not my preffered option.

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Old 21-04-2010, 15:03   #6
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You can also buy 12V kettles, 12V tellys etc.


Battery operated Fridges and Freezers for use on Yachts, Cruisers, Canal Boats, Motorhomes, Horseboxes, Caravans and Trucks.

You can kettles, lighting, etc, etc. Just start Googling 12V appliances. Many domestic applicances step the 230V mains feed down to a much smaller DC voltage. All these products have done is to remove the mains transformers.

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