Shore Power Connection - Tell Me Why I Can't Do This

[SVNeko]

Our boat is US-wired 240V/60hz (ie, 4 wires with 2 hot legs of 120V each). We will put ashore in Grenada with 240/50hz shore power (ie, 3 wires with 1 hot leg of 240V). All we want to do is power our battery chargers.

Is there a reason I cannot wire up a shore power adapter that puts the 240v single leg over both hot legs of my shore power inlet? To avoid side issues, we can assume all 240V appliances can handle the frequency difference and that we will shut down in a tamper proof way all 120V circuits.

[Jd1]

Your 240V US boat is powered by two circuits that are 120V each and out of phase with each oher. To get 240V, they connect the device that requires 240V across the two 120V hot legs and they do not use the neutral leg.
If you were to connect the 240V shore power to the two hot 120V hot legs you would effectively have zero volts across any device that is currently hooked up for 240V.
Other than that obvious problem, I would also be concerned about putting 240V on 120V circuits. In theory that 'should' work but I could see many possibilities of issues and I would recommend against that.
If you have an inverter, chances are that it senses shore power and switches to shore power when hooked up and uses it's inverter function when not hooked up to shore power. Chances are that the sense circuit would get fried. You really do not know how exactly the wiring is set up in the boat - you could inadvertently cause heaps of issues and even burn down the boat.
Get yourself a properly rated battery charger, hook it up to the batteries and only connect shore power to it. Leave your regular shore power disconnected.

If you really know what you are doing you could possibly hook your current battery charger directly to shore power but then if you really knew what you were doing you would not have asked the question in the first place.

Good luck!

[smac999]

Originally Posted by Jd1

If you were to connect the 240V shore power to the two hot 120V hot legs you would effectively have zero volts across any device that is currently hooked up for 240V.

no he would have 230v on his 240v bus and the 240 stuff would work (assuming it can handle 50hz) however I doubt the boat has anything on 240v bus. maybe electric heaters or stove. even if the charger is 120/240 50/60hz safe, it's probably on the 120v bus which wouldn't be getting power as it would need the N leg to complete the circuit.

if you chargers are actually wired for 240v on your panel (super rare) then you'd probably be ok.

but the other issue is you don't only want to take the two currently carrying wires into the boat. (2 wires only) that work's but wouldn't be too safe. I'm not sure where you would want to take the 3rd ground wire too. as over there it goes to one of the 240v wires which is different then here going to our N. if you don't have a N-G bond on the boat you'd probably be ok tying ground to ground at plug, but if you did, it would likly cause havoc on the boat as your N line would then have 240v to hot. depends on if boat is wired correctly or not. I still find N-G bonds on boats.

ideally you would have a center taped 240v iso transformer in the boat. and you'd be making your own 240/120 and ground on the boat in any country. then all your 50/60hz stuff would work even the 120 stuff.

[SVNeko]

The boat was originally a European boat and certainly has items on the 240 bus - 2 chargers, 2 water heaters and air conditioners. They can all handle both frequencies. The generator output is 240/60. In fact, very little is on the 120 circuit - another charger/inverter and a W/D. I don't have a transformer and am not going to add one for this short stint. I have to understand the ground issue better.

[s/v Jedi]

Connect the shore 230V phase to your L1
Connect the shore Neutral to your L2
Connect the shore Ground to your Ground

Leave your Neutral unconnected. Only feed power to the 230/240V 50/60Hz devices you have and you will be fine.

[sailorchic34]

What JEDI said....

Make sure that any 120V breakers are off as you will have 230V which might let the smoke out of some devices, which would be bad.

[Redline452]

Your 240 v devices should be OK, but without a "neutral" for the 120v circuits, you could end up severely unbalanced, say 200 v on one side and 40v on the other. Swith ong o. Any 120v load would do strange things and likely damage other devices drawing less current on the opposite leg. Even 120v GFI outlets with nothing connected could be damaged.

[Sardean]

Battery charges must be 240v and be rated for 50hz.
One option is to buy a local extension lead and new local plugs for chargers then plug chargers direct to shore power.
If chargers are not compatible by a cheap local charger.

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[k. michael marquardt]

Depends how the people on shore generate their 230V 50Hz

1. If its a power net you will have three AC strands of 380 Volts between each plus a neutral(center) plus a ground (safety).

You will have 230Volts between one 380 strand and neutral.

2. If its a locally generated net you will have two strands of AC 230 both.

And no, I would not try to tamper with shore power if you don't know exactly what you're doing - least could fry your gadgets - maximum burn your boat.
Cheers

[SVNeko]

OK, again, 120 circuits will be kept OFF and, yes, the chargers can take 230v/50hz.

[s/v Jedi]

Originally Posted by SVNeko

OK, again, 120 circuits will be kept OFF and, yes, the chargers can take 230v/50hz.

Yes Neko, people are adding irrelevant info. Just take my post above, follow your procedure as in keeping 120V circuits off and you will be fine.



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[fgd3]

Are your battery chargers dedicated 240V appliances or are they 120V appliances that can handle a broad voltage range? It makes a difference.

Dedicated 240V appliances are connected to two hot legs. In the US those hot legs carry 120V each and are 180 degrees out of phase so their voltage sums to 240V. You can simulate that in Grenada by making an adapter as Jedi described.

If your battery chargers can accept 100-240V input you don't need an adapter at all. The circuits will be the same, only the voltage will be higher.

Fabbian

[SVNeko]

Originally Posted by s/v Jedi

Yes Neko, people are adding irrelevant info. Just take my post above, follow your procedure as in keeping 120V circuits off and you will be fine.

Thank you. Now I just need to figure out what size wire to use. I have a 50hz 32A adapter but its wires are much lighter than my 50A shore power cord. I think if the adapter is sized for 32A and 230V, it should be OK. I may run the aircon (16kbtu) for a few days on it.

[s/v Jedi]

For a short adapter, the wires may be smaller diameter than for a long cord. A 30A US 120V shore cord has 3x AWG10 conductors I think while a 50A US 120/240V cord has 4x AWG8.


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[SVNeko]

OK, this seems to be getting quite complicated for me. I have, I think, correctly wired up the adapter and I am getting 230v into the shore power breaker on the boat. However, it is not getting to the panel for some reason. Between the breaker and the panel I have an ABB AE30-30 contactor to select between the genset and shore power. I was last on genset and I think it may not be switching over to pass the shore power through. I am trying to figure out why.