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Old 07-01-2013, 11:32   #1
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120 & 220V Shore Power

My boat has capability to accept both 120 and 220V shore power, through two independent hook-ups.

It's a little difficult to pull all the wiring apart - since it's in conduits, behind bulkheads, etc., so I'm wondering if anyone can give me a likely wiring scenario - how does the boat sort out if it's being fed 120 or 220V - and does it matter?

The AC section of the main panel has the following brakers:
AC Main - Double
Water Heater - Single
Outlets Stbd - Single
Outlets Port - Single
Watermaker (220V) - Double
Charger Inverter - Double.

The watermaker operates on 220 (normally supplied by the generator). I believe that the Inverter and the separate charger both work with a range of voltage which would cover both.
Since the outlets are a single breaker, presumably only one leg is supplied - so it wouldn't matter what the shore power was delivering...

So: Does the 110 and the 220V supply both arrive at the Main double breaker on the panel?

Curious and confused...

Bill Balme
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Outbound 44 #27
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Old 07-01-2013, 11:57   #2
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Re: 120 & 220V Shore Power

Unless you happen to stumble on someone who is familiar with your specific boat model then it is impossible to say what happens inside the panels based on the information provided.

In general terms, 220 volt power supplies consist of 2 legs of 110 volts, 180 degrees apart. That gives you 220 volts between the legs or 110 volts between either individual leg and neutral. That also means that you can have 2 separate 110 volt buses inside a 220 volt panel. Either of those 110 buses can be independantly supplied with a 110 volt shoreline. So two 110 volt shoreline can feed the 2 x 110 volt buses. The twin 110 shorelines however cannot deliver the 220 volt supply that a 220 shore connection can.

I advise you to contact the manufacturer and ask for an electrical block diagram which should help you sort out where the power goes and how it gets there. Alternatively a day with a multi-meter can likely supply the same information in much greater detail. The chances that someone on the internet will know the specifics of your boat are slim to nil IMHO.

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Old 07-01-2013, 13:08   #3
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Re: 120 & 220V Shore Power

Like Bob said, figuring out what's going on behind the panels based on the information you give is uncertain. Also I would add that even getting information from the manufacturer may be problematic since a previous owner could have modified the original factory wiring.

A couple of comments and questions but DISCLAIMER don't start any wiring or installations based on these.

One physical breaker could be switching on/off the two 125V legs of a 250V input.

I assume your panel has a selector switch with GEN/OFF/SHORE or some similar wording that allows you to choose what source but only one that feeds the panel?

Is there a selector that allows you to select one shore power or the other?

I assume you have used your shore power cable(s) at a dock? Does the 250V water maker work when plugged into shore power?

Do you or have you connected both shore power cables at once? I would guess that you should not do this unless you have a selector switch for this on the panel.

If you really want or need to know you could probably sort it out with a meter and a couple of long wires. Connect the meter to various AC loads, shore power plugs, etc and turn switches on and off to see when and where you get volts, what circuits are linked, etc. Another DISCLAIMER. Don't do this unless you know what you're doing or you could produce smoke, sparks and potentially electrified owner.
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Old 07-01-2013, 13:12   #4
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Re: 120 & 220V Shore Power

Do you have a transformer? We have two shore power connections, one is 110 and the other 220. The 220 cable goes to a transformer where it becomes 110. There is also a large switch that chooses the input - direct 110 or from the trnsformer.
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Old 07-01-2013, 14:29   #5
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Re: 120 & 220V Shore Power

When you are connected to 110V shore power, do your two 220V devices still work?

If they do, then you probably have a transformer as alluded to earlier. The input to the transformer can be either 220V or 110V, and the output is always 220V split phase, i.e. two 110V circuits which if used together give 220V. The boat I'm building is set up exactly this way. It's the first time I had seen it before, and personally I really like it.
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Old 07-01-2013, 16:16   #6
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The 220V outlets might still work if powered by the batteries thru the inverter. Really, need more info. It might just be that the 110 goes to the inverter/charger. On my boat, I've got two separate circuits, with two inverter/chargers and 220v and 110v outlets throughout the boat. I didn't want to deal with the frequency issue.
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Old 07-01-2013, 16:53   #7
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Re: 120 & 220V Shore Power

Do you have a genny in this system as well? Is it 110 or 220? As well as previously mentioned does the WM work on 110 or just with shore 220 and genny. Doubt anyone would install a watermaker thats tied to the dock.

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