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Old 06-09-2019, 12:55   #1
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Plugging a 120v boat into 240v

I have run into an interesting problem that has me a bit baffled. I am in a marina in 240v Chile with my 120v American electrical system. The dock has 240v service via a 2 prong receptacle. I bought a 2 prong plug and adapted it to my 120v 30 amp 3 prong plug by connecting each of the hot wires from the dock to the hot and neutral wires of my 120v system, reasoning that this should give my 240v at the panel, and it does. I can plug in, turn on the AC main and all is well until I try to throw the breakers on any of my outlets or my battery charger. When I do this the breaker at the base of the dock trips. Nothing is plugged in when this happens. I have tried reversing the polarity of the hot wires and it makes no difference (which, of course, it should not). All of my breakers are "world breakers" by Bluesea and are rated for 250v. All of my wiring is specced for 120v so no worries there. My charger is rated up to 250v as well. My question is: What is my boat doing to anger the breaker at the base of the dock?
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Old 06-09-2019, 14:54   #2
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Re: Plugging a 120v boat into 240v

One possibility is a connection between neutral and ground somewhere on your boat. There shouldn't be, but that doesn't mean there isn't.
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Old 06-09-2019, 15:48   #3
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Re: Plugging a 120v boat into 240v

You do realize that Chile offers 230V 50hz service, you won't get 120V without a transformer.
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Old 06-09-2019, 16:06   #4
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Re: Plugging a 120v boat into 240v

There is no ground on a boat. That should be obvious. There is only a neutral.

For 120v you have a hot wire and a neutral wire. For 240v you have two hot wires.

You cant run a hot wire down a neutral.

The reason it is fine up to the panel is because it is just wires up to the breaker. After the breaker one of the wires goes to the neutral.

What you can do is wire a pigtail for 240v off your panel but since you didn't know this already I would suggest you don't.

P.S. You probably fried some stuff.
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Old 06-09-2019, 16:29   #5
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Re: Plugging a 120v boat into 240v

You need one of these, 240 Volt transformer to 110 Volts,
You plug it into your 240 volt mains and run your 110 Volts off it,
Works great on my 110 Volt fridge,
Around $50-00 on Fleabay,

Cheers, Brian,
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Old 06-09-2019, 16:59   #6
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Re: Plugging a 120v boat into 240v

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Originally Posted by ttex View Post
There is no ground on a boat. That should be obvious. There is only a neutral.

For 120v you have a hot wire and a neutral wire. For 240v you have two hot wires.

You cant run a hot wire down a neutral.

The reason it is fine up to the panel is because it is just wires up to the breaker. After the breaker one of the wires goes to the neutral.

What you can do is wire a pigtail for 240v off your panel but since you didn't know this already I would suggest you don't.

P.S. You probably fried some stuff.
Thanks, but I am still not understanding this. Why can't you run a hot wire down a neutral path? Isn't this exactly what happens with reverse polarity? Wouldn't the 2 hot wires of a 240v supply simply use the hot and neutral wires of the 120v system as 2 hot wires as well?
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Old 06-09-2019, 19:17   #7
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Re: Plugging a 120v boat into 240v

Another thought is what kind of battery charger do you have? Many of the newer ones will work anywhere in the world. We plug the charger into the dock and then run our inverter to power any of the 110v items on the boat.

If you do have one that will work then it may solve your dilemma.

Good luck

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Old 06-09-2019, 21:05   #8
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Re: Plugging a 120v boat into 240v

> "each of the hot wires from the dock to the hot and neutral wires of my 120v system"


Chile, like much of the rest of the world, has a 220V 50Hz single phase power supply. That is a very different thing to US 240V 60Hz split phase power supply.


You can't do to a 220-240V single phase supply what you would do with a US 240V supply.


No matter how you try to wire it, you will end up with 240V going somewhere - quite likely into your 120V appliances


You need a voltage converter.


> "Wouldn't the 2 hot wires of a 240v supply simply use the hot and neutral wires of the 120v system as 2 hot wires as well?"

The single phase 220V 50Hz supply doesn't have " 2 hot wires". It has one "live" wire and one "neutral" wire
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Old 06-09-2019, 21:15   #9
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Re: Plugging a 120v boat into 240v

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For 120v you have a hot wire and a neutral wire. For 240v you have two hot wires.

In the US, that's true. Not so in Chile.
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Old 06-09-2019, 23:10   #10
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Re: Plugging a 120v boat into 240v

I think people are missing the point. He says nothing is connected.

It could be that your insulation is breaking down probably due to moisture. The breaker will trip at 30ma . You normally only have 120v but with 240 the insulation is more deeply tested.

You need to get someone with a megger and do an insulation test.

I am a licensed electrician in Australia.
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Old 06-09-2019, 23:24   #11
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Re: Plugging a 120v boat into 240v

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Originally Posted by mikereed100 View Post
I have run into an interesting problem that has me a bit baffled. I am in a marina in 240v Chile with my 120v American electrical system. The dock has 240v service via a 2 prong receptacle. I bought a 2 prong plug and adapted it to my 120v 30 amp 3 prong plug by connecting each of the hot wires from the dock to the hot and neutral wires of my 120v system, reasoning that this should give my 240v at the panel, and it does. I can plug in, turn on the AC main and all is well until I try to throw the breakers on any of my outlets or my battery charger. When I do this the breaker at the base of the dock trips. Nothing is plugged in when this happens. I have tried reversing the polarity of the hot wires and it makes no difference (which, of course, it should not). All of my breakers are "world breakers" by Bluesea and are rated for 250v. All of my wiring is specced for 120v so no worries there. My charger is rated up to 250v as well. My question is: What is my boat doing to anger the breaker at the base of the dock?
Quote:
Originally Posted by ben373 View Post
I think people are missing the point. He says nothing is connected.

It could be that your insulation is breaking down probably due to moisture. The breaker will trip at 30ma . You normally only have 120v but with 240 the insulation is more deeply tested.

You need to get someone with a megger and do an insulation test.

I am a licensed electrician in Australia.
I am not an electrician but I see that the power is on until a circuit breaker is thrown to connect a 120 volt appliance at which point the power to the boat is disconnected. These breakers are surely designed for 120 volts not 240 volts so the system is working as designed. As others have noted, US power systems differ markedly to those of much of the rest of the world. I would consider firstly a step down transformer or a battery charger for the available supply and run everything from the batteries.
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Old 07-09-2019, 05:46   #12
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Re: Plugging a 120v boat into 240v

Quote:
Originally Posted by ben373 View Post
I think people are missing the point. He says nothing is connected.

Correct. There are no loads on any of my circuits, which has me wondering why the breaker is tripping. At first I thought it may have something to do with my GFCI outlets, but the breaker at the dock trips when I close the breaker for the battery charger as well. The charger is rated for 120-240v and 50-60hz.

It could be that your insulation is breaking down probably due to moisture. The breaker will trip at 30ma . You normally only have 120v but with 240 the insulation is more deeply tested.

Interesting thought, but all of my AC system is marine wire, rated for 600v and is only a few years old. All of the wiring is bone dry and the humidity doesn't get much above 60% inside. Also, the breaker at the dock trips no matter which breaker I close. It would be odd that all of my insulation had broken down?

You need to get someone with a megger and do an insulation test.

I am a licensed electrician in Australia.
I am still confused as to why everything is OK at the panel until I try to send power to any of several unloaded circuits?
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Old 07-09-2019, 06:15   #13
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Re: Plugging a 120v boat into 240v

Quote:
Originally Posted by StuM View Post
> "each of the hot wires from the dock to the hot and neutral wires of my 120v system"


Chile, like much of the rest of the world, has a 220V 50Hz single phase power supply. That is a very different thing to US 240V 60Hz split phase power supply.


You can't do to a 220-240V single phase supply what you would do with a US 240V supply.


No matter how you try to wire it, you will end up with 240V going somewhere - quite likely into your 120V appliances

Actually, this is what I am trying to accomplish. I would like to run my battery charger and dehumidifier, sourced locally, while I am away. No need for 120v.

You need a voltage converter.


> "Wouldn't the 2 hot wires of a 240v supply simply use the hot and neutral wires of the 120v system as 2 hot wires as well?"

The single phase 220V 50Hz supply doesn't have " 2 hot wires". It has one "live" wire and one "neutral" wire

Thanks for that clarification.
That actually has me more puzzled. If the Chilean service has a 'hot' and 'neutral' wire, similar to North American 120v service, it would seem that simply increasing the voltage through the wires within the rating of the wire and breakers should not cause a problem?
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Old 07-09-2019, 06:40   #14
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Re: Plugging a 120v boat into 240v

Why would you want to run 230 vac or whatever single phase hot wire into a boat system with appliances set to run at 120 vac anyway? That wont be good for them.

bypass the breaker to the battery charger, wire direct thru the main breaker only, and see what happens.
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Old 07-09-2019, 11:27   #15
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Re: Plugging a 120v boat into 240v

I'm with Jammer on this one; 220v systems take the ground back to the generating station whereas the US 120v system will ground locally and on a boat this can mean that the neutral bus is connected to ground at the distribution panel. Have a really good look and if you can find it disconnect. On board grounds must be connected to the shoreside ground only.
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