How to wire a 50 amp shore power plug in the USA

[Lambretta]

Well I am at a loss ..... I bought a Hubbell Marine 50 amp male shore power plug to connect to my pigtail to connect my European plug to a shore power pedestal in the USA, but unfortunately even though the instruction pamphlet is written in English it makes no sense to me or too three other yachties on the dock I have spoken too!

On my pigtail wiring I know which is the Earth, Neutral and Live wire (I only have three wires as this is a single phase 230 v yacht with a Mastervolt system which takes care automatically of managing the voltage of either 110v or 230v and 50hz and 60hz issue.

However the Hubbell plug instruction for wiring make no sense.

I know which wire to connect to the Ground (earth) terminal on the plug and the wire to connect to Neutral (terminal W) as per the photo. However there are still two terminals on the plug marked X and Y ........ except in the instructions it does not mention which terminal I should connect the Live (positive) wire too as it could be either terminal X or Y and I sure do not want to get this the wrong way round

Does that mean that I could use either X or Y for the Live (positive) wire

I cannot believe how poorly the instructions are written as it tells one what not to do as opposed to what one should actually do for a three wire setup!

All help will be greatly appreciated

[SailingHarmonie]

To get 230V out of the 50 Amp USA plug is a bit different. The 50 Amp shore power system is what is callled a "split phase" system.

You CAN do it, but you need to be SURE you boat is set up for it.

The 50 Amp plug has FOUR wires. Two hots, a neutral, and a ground. The two hots have cycles that are 180 degrees out of phase. This means that between each of those hot wires and the neutral is 120V, and between the two hots is 240V. You wire the plug by connecting the ground wire, and then the boat Hot connects to one hot leg, and the boat neutral connects to the other hot leg. (usually black and red)

You now have 240 V (about) between the hot and neutral on your boat.

Now, you can ONLY do this if ALL the circuit breakers on your boat are 2-pole breakers. If they trip or are turned off, they MUST break both hot and neutral wires (because now they are both hot!)

If any of that is not clear, you should hire an electrician to help. Getting it work is very dangerous.

[Lambretta]

Originally Posted by SailingHarmonie

To get 230V out of the 50 Amp USA plug is a bit different. The 50 Amp shore power system is what is callled a "split phase" system.

You CAN do it, but you need to be SURE you boat is set up for it.

The 50 Amp plug has FOUR wires. Two hots, a neutral, and a ground. The two hots have cycles that are 180 degrees out of phase. This means that between each of those hot wires and the neutral is 120V, and between the two hots is 240V. You wire the plug by connecting the ground wire, and then the boat Hot connects to one hot leg, and the boat neutral connects to the other hot leg. (usually black and red)

You now have 240 V (about) between the hot and neutral on your boat.

Now, you can ONLY do this if ALL the circuit breakers on your boat are 2-pole breakers. If they trip or are turned off, they MUST break both hot and neutral wires (because now they are both hot!)

If any of that is not clear, you should hire an electrician to help. Getting it work is very dangerous.

Thank you for your detailed response. It is greatly appreciated I have taken your advice and will be trying to find a good electrician. Have tried two but they are both on holiday

[Sun and Moon]

I think you wire this by connecting the ground to the green, the white (neutral) to the opposite, then connect your live wire to either of the two sides. You will be getting 110V, which your Mastervolt system will deal with.

But I agree with "get help". Maybe start by reading the Mastervolt documentation and see if it says it can take US 220 input.

[s/v Jedi]

Do you have an isolation transformer?

Do you have double pole breakers for the AC circuits on your breaker panel?

If you can answer this, or supply pictures, you don’t need to hire an electrician as we can guide you here. Just post pictures if you’re not sure.

[HeywoodJ]

If you are in the US I doubt hiring a marine electrician will be helpful, few of them are aware of the nuances of connecting a European single-phase 230V system to an American split-phase 240V system.

Jedi’s question is the key, do you have an isolation transformer? If “yes” then this task is relatively simple. If “no” then there may be a few other questions about inverters, generators, how they are connected, and what you want them to be able to do while you are on shore power.

[Turtle Blues]

See Jedi post # 5.
You are euro single phase trying to connect a split phase plug.
Apples and Oranges, you just can't do it.

[s/v Jedi]

Originally Posted by Turtle Blues

See Jedi post # 5.
You are euro single phase trying to connect a split phase plug.
Apples and Oranges, you just can't do it.

But you can, the only question is which way and for that more info is needed. The OP wrote that his system auto-switches between 120V and 240V which indicates an isolation transformer, but he has vanished from the thread.

[Turtle Blues]

You are correct. I missed the sentence about the transformer. Picturing 3 pin euro plug in 1 hand and Hubbel in the other.

[shimari]

This is doable, and isn't that difficult provided you have everything that's needed installed already.

Finding an electrician that actually understands what to do is difficult both in the US and Europe. Even Mastervolt tech support has provided wrong information.

The questions asked by Jedi and others are important. You must have both an isolation transformer and double pole breakers. Make sure you have a double pole RCBO as well.

You also need to make sure that Neutral is not bound to ground at the isolation transformer and your inverter/charger as Mastervolt instructs for a single phase installation. The connection at the isolation transformer is physical and done by the installer. The connection at the Combi is controlled by software (master adjust) or the dip switch settings.

There is a lot of bad information out there. It took me a while to grok this.

Don't forget to make sure your 230v equipment can run at 60Hz also.

[smac999]

Do you want 120 or 240 from the dock to the boat? If it’s a 230v boat you probably want 240v from dock so take the 2 hots and no neutral.

[Turtle Blues]

"Do you want 120 or 240 from the dock to the boat? If it’s a 230v boat you probably want 240v from dock so take the 2 hots and no neutral."


Have you successfully done this?
Edit: Didn't mean this question to sound snarky. Should have said without changing the wiring at the inverter. Yes these are the lines the inverter wants to see.


OP's question was making the connection at the plug end, hence my comment, it's not possible to do it at that point.


As others have said it depends on what equipment is in place.

Inverters I have seen capable of taking us split phase to euro single have specific inlets and warnings about proper connection.

[shimari]

Originally Posted by Turtle Blues

"Do you want 120 or 240 from the dock to the boat? If it’s a 230v boat you probably want 240v from dock so take the 2 hots and no neutral."


Have you successfully done this?



OP's question was making the connection at the plug end, hence my comment, it's not possible to do it at that point.


As others have said it depends on what equipment is in place.

Inverters I have seen capable of taking us split phase to euro single have specific inlets and warnings about proper connection.

I wired our plug exactly like that. I used the original power cable (32 amp - 3 wire), and bought a Marinco 6365crn 50amp locking plug. I connected the brown wire (hot) to L1, the neutral wire (blue) to L2, and ground to ground. This leaves neutral on the dock side plug unattached.

Our RCBO is 32amps so we're good with a 32 amp cable. Our isolation transformer is a Mastervolt MassGI 7. It handles the split-phase fine, but it does not convert the phase. The power out of the MassGI is still split-phase. Thus, the need for double pole breakers as well as ensuring what is neutral in single-phase (now L2 in split-phase) is not tied to ground at the transformer.

You also need to ensure your inverter is off at the dock.

The wiring was reviewed and approved by a marine electrician prior to use.

[donradcliffe]

A lot of misinformation in this thread. The power output of the MassGI 7 is not split phase.

The Mastervolt instructions show the split phase L1 (red)and L2 (black)120v wires connected to the 230 v input L (brown)and N (blue). It doesn't matter which way. with the dock neutral (white or silver) unattached. Also connect the output neutral to the protective grounding wire on the boat. Do NOT connect the input and output grounding wires.

If you do this you do not need double pole breakers.

[shimari]

Originally Posted by donradcliffe

A lot of misinformation in this thread. The power output of the MassGI 7 is not split phase.

The Mastervolt instructions show the split phase L1 (red)and L2 (black)120v wires connected to the 230 v input L (brown)and N (blue). It doesn't matter which way. with the dock neutral (white or silver) unattached. Also connect the output neutral to the protective grounding wire on the boat. Do NOT connect the input and output grounding wires.

If you do this you do not need double pole breakers.

Agreed it doesn't matter on the wires.

I hear you about the transformer, but I've checked and re-checked with a meter. The output of our isolation transformer is: Brown to gnd is 120v and Blue to gnd is 120v. Brown to Blue is 240v. So, we see split-phase out of the MassGI.