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Old 27-11-2014, 09:25   #1
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240v Shore Power Connection

Our boat(of 16 years) was built and used in Asia and the Med--until now. She is wired for 240v AC power,with a 3 wire sysyem-hot, neutral, and ground. We just arrived in the USVI, and plan to spend the next several years here in the Caribb. Unfortunately, the 240v(220-240v) available is based on a 4-wire system; 2 hots, neutral, and ground. Is there a way I can connect my 3-wire AC system to the 4-wire system we've found on marina power poles? We tried putting 2 wires to the "hot" and the third to gnd....we got 240vAC on the boat, but is shows reverse polarity, and switching the 2 "hot" wires did no correct the reverse polarity. Help!!!
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Old 27-11-2014, 09:40   #2
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Re: 240v Shore Power Connection

Your polarity light/sensor sits between ground and neutral, hence it will show reverse anytime there is a potential/voltage difference between ground and neutral. The way you connected it, there is a 120v potential, hence the reverse indicator.

The fear I would have connecting the way you describe is if you have a polarized appliances, something that may depend on neutral and ground to be the same potential. I'm not very familiar with EU power appliances, so there may not be any as I describe, but if there is it could cause a problem.

If all your appliances have 2-wire plugs, I would think you'd be OK.

Obviously, you'd be operating everything on 60hz vs 50hz. Some appliances (motors) may not like that.
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Old 27-11-2014, 09:41   #3
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Re: 240v Shore Power Connection

You'll never get rid of the reverse polarity simply wiring it straight... The ORIGINAL neutral to ground is supposed to be zero potential, and you're now loading it up with 120v (1-240 hot to neutral or ground)...

The best way to do this is an "isolation transformer" 240 any which way into the transformer.... AND... you can wire your original hot-neutral-ground out of it...
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Old 27-11-2014, 09:45   #4
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Re: 240v Shore Power Connection

I don't really know much about electricity. But My boat was wired the way yours is. My guess is you will find that yours is also 50hz not 60hz. The 4 sire system is most likely 60hz. You may have an issue with whatever you normally use the 240v for. My understanding is that some motors don't like running on the wrong hz.

In my case I removed everything 240v (electric distribution panel, air con, refrig, bat charger) including the shore power. I switched refrig to 12v and replaced the electrical panel with a standard USA 125v 30amp service, although not hooked up to any shore power yet. Since I have solar and wind I don't need the bat charger. I will eventually install 125v shore power but for now I don't need it. When I get to the Caribbean I'll have to deal with not having air cond.

I asked around just as you but could not find a good solution other than removing/replacing it.

Larry
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Old 27-11-2014, 11:35   #5
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Re: 240v Shore Power Connection

A transformer is the simplest and safest way to take care of this except for the possible 50hz thing. This is not something you're going to find at Radio Shack, it needs to be something made for marine applications and something that can safely handle your boats power needs, not just the voltage conversion.

I would start here: Marine: Isolation and Boosting Transformers and give them a call to see if anything they offer will meet your needs.

I think you probably should have this done by a qualified marine electrician as well. A mistake here could cause a lot of damage or even electrocute someone.
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Old 28-11-2014, 09:02   #6
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Re: 240v Shore Power Connection

I agree with the advise to get qualified boat electronics person on-board who knows ABYC guidelines. Changing a 3-wire 240 boat back to US 4-wire is serious stuff. Every boat/ electrical panel/ foreign purchased/ installed appliances, AC wiring has its irregularities and giving advice on this complex/ important project without seeing, measuring things is risky. A mistake not only risks you and your boat, but if you inadvertently energize the ground (green) wire back on the dock you could cause serious issues to nearby boats, divers, swimmers. Also if you get it wrong, it can in a short period of time eat your and nearby props and thru-hulls... zinc or no zinc.


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Old 28-11-2014, 09:54   #7
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Re: 240v Shore Power Connection

The simple answer is NO!

U.S. 240v is three phase. European and Asian 230v is single phase. You can't mix the two in any way. Never mind!

You have three choices:

1. Just hook the existing system up to 120v, change the breakers and sockets, and change out all the AC equipment from 230v to 120v. Note well: you must review all the wiring to be sure that it is sufficient for 120v power, and replace any of it which is not up to spec. That's because the amperage -- and hence the capacity of the wire -- is double with 120v, for the same power.

2. Install an isolation transformer (like the Victron one) which steps up the voltage to 230v. You get a bonus of isolation, which may help with corrosion. Change out any 230v electrical equipment which can't tolerate 60 cycles (some things can, others can't). You don't have to change wiring, sockets, or breakers in this case, but you won't be able to plug in any new 120v equipment.

3. Install a 120v battery charger with enough capacity to cover the maximum power you will take from AC and DC systems combined (or maximum power you expected to get out of shore power, whichever is less). Install a 230v inverter of capacity enough to run all your AC systems (does not have to be the same capacity as the charger, as the batts can cover any short-term deficit). Wire the boat so that AC panel is connected only to the inverter, not to shore power. Then you don't have to change any sockets, breakers, or equipment, but you can't plug in any new 120v equipment.
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Old 28-11-2014, 10:07   #8
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Re: 240v Shore Power Connection

[QUOTE=Dockhead;1688082]The simple answer is NO!

U.S. 240v is three phase. European and Asian 230v is single phase. You can't mix the two in any way.

Nope. US is single phase but you are right about the mixing part.


3 phase is commercial or industrial applications.
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Old 28-11-2014, 10:21   #9
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Re: 240v Shore Power Connection

[QUOTE=Sand crab;1688093]
Quote:
Originally Posted by Dockhead View Post
The simple answer is NO!

U.S. 240v is three phase. European and Asian 230v is single phase. You can't mix the two in any way.

Nope. US is single phase but you are right about the mixing part.


3 phase is commercial or industrial applications.
Unless I am badly mistaken (not an unknown phenomenon ), all four-wire AC power is 3 phase. Yes, there is single-phase 240 power in the U.S., but the OP was talking about a four-wire system and I think marina 240v everywhere is three-phase.
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Old 28-11-2014, 10:26   #10
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Re: 240v Shore Power Connection

Quote:
Originally Posted by HappyMdRSailor View Post
You'll never get rid of the reverse polarity simply wiring it straight... The ORIGINAL neutral to ground is supposed to be zero potential, and you're now loading it up with 120v (1-240 hot to neutral or ground)...

The best way to do this is an "isolation transformer" 240 any which way into the transformer.... AND... you can wire your original hot-neutral-ground out of it...
This is how we are wired. Shore power 240 using only the two 110 hot wires powers the primary on the isolation transformer. The secondary is two 110 volt outputs & a floating ground. You may need to pay particular attention to make sure your generator is not in conflict with your wiring solution. The plus side is that you are isolated from the marina ground with respect to corrosion issues.
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Old 28-11-2014, 10:27   #11
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Re: 240v Shore Power Connection

Wow
A lot of bad info...

Standard US commercial power can be a lot of things
208/3 is quite common but in marinas 120/240 50a single phase is the norm

Large yachts use 100-200a 3 phase but not small ones

Hire a good marine electrician and this can be easy if not cheap

Yes, I do this for a living
No, I don't want to do yours, unless the job includes travel to the VI! <grin>



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Old 28-11-2014, 10:30   #12
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Re: 240v Shore Power Connection

Quote:
Originally Posted by Dockhead View Post
The simple answer is NO!

U.S. 240v is three phase. European and Asian 230v is single phase. You can't mix the two in any way.
It is if there's three hot leads of 120v potential to neutral/ground 120 degrees apart... Otherwise the 99.9% of US 240 service is simply single phase 120v, 180 degrees out... This of course does not include the majority of industrial electric service which usually is 3 phase...
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Old 28-11-2014, 10:33   #13
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Re: 240v Shore Power Connection

Use it as you have it and disconnect your reverse polarity light.
We have a 230/50 boat and have been on 110/110 (220) systems many times, without a problem. The microwave clock was wrong, and one pump got hotter, but everything else just worked.
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Old 28-11-2014, 10:38   #14
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Re: 240v Shore Power Connection

[QUOTE=Dockhead;1688103]
Quote:
Originally Posted by Sand crab View Post

Unless I am badly mistaken (not an unknown phenomenon ), all four-wire AC power is 3 phase. Yes, there is single-phase 240 power in the U.S., but the OP was talking about a four-wire system and I think marina 240v everywhere is three-phase.
(edit-the quote button referenced the wrong source)

The 4 wire gotchya... All depends on how it comes from the panel to the equipment:

Quite common=4 wires, 3 hot and a ground = 208-240 3ph
Quite common= 4 wires, 2 hot, ground and neutral = 120/240 1ph

Most "pleasurecraft" marinas are single phase...
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Old 28-11-2014, 10:45   #15
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Re: 240v Shore Power Connection

[QUOTE=Dockhead;1688103]
Quote:
Originally Posted by Sand crab View Post

Unless I am badly mistaken (not an unknown phenomenon ), all four-wire AC power is 3 phase. Yes, there is single-phase 240 power in the U.S., but the OP was talking about a four-wire system and I think marina 240v everywhere is three-phase.
Yes, badly mistaken.

Generally 240 VAC marina power is single phase 240 hot to hot and 120 hot to neutral. The four wires hot, hot, neutral, and ground. Ground and neutral are bonded together somewhere (e.g., panel feeding dock) and should be very close or at same potential as each other. Note that some docks will provide 240 single phase with 3 wire outlets (no ground, just grounded neutral) while other with 4 wire outlets (separate neutral and ground). In USA the 3-wire outlets no longer meets electrical code requirements so only seen in older marinas.

There is 3-phase at some marinas for mega yachts, but usually 480.

The above are USA/Canada/Mexico electrical outlets I have seen.
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