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Old 15-07-2013, 05:33   #16
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Re: Can't find cause of Reverse Polarity.

I am assuming he is using 120 aboard or he probably wouldn't have the RPI. I know from many experiences surveying different vessels where transformers and generators do not have the neutral and green ground connected they will give no indication of that configuration using the onboard panels or tests.

I find ungrounded appliances when I plug in my test meter or attempt to trip a GFCI using a button type three light tester. My Suretest meter will indicate there is no ground. My three light tester will show normal condition of two yellow lights but when its button is depressed all three lights will glow and the fixture will not trip; however, the test feature on the fixture itself will work.

The preceding doesn't answer why the OP has RP now but may shed some light as to whether his transformer is grounded on its output side. It is very possible it is not since he would have no way to know without a special meter or use of a push button three light tester.

I assisted a client with sorting this issue out on a vessel with a pair of isolation transformers that were not grounded according to US ABYC standard. He emailed me the transformer diagrams and pictures inside the transformers and it was clear the vessel ground was attached to the transformer case but not connected to the neutral. It was a quick fix.

It would be a good idea for the OP to review his installation or get help doing so to insure his transformer was properly configured from the start. Most of the cases I found had been in operation ungrounded for many years...
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Old 15-07-2013, 15:42   #17
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Re: Can't find cause of Reverse Polarity.

I'm the one that started this post. Here's what's been going on.
The marina brought their electrician to the boat. He's not a boat electrician. The wires I've been using also plug into my Yamaha generator and that power comes through just fine. The set up I have is a cord with a Marinco plug on it plugged into the dock fixture. It goes out to a standard 110 female outlet. The stepdown transformer has a three prong plug that plugs into it. Out of the stepdown transformer comes another three prong female outlet. I plug in my cord into it and it takes the power inside the boat.
Last year when we were in Fiji, we had the same problem but found after having local electricians work on the set up that Fiji doesn't wire their plugs the same way they do in the US. With some rearranging, we got it all straightened out and had no problem for the remaining 10 months we were there.
With that being said, I think with a good degree of certainty that there is no problem with the stepdown transformer. The problem must lay in the wiring. I'm just not sure what that might be.
I figure to sit on the dock with all the cords and transformer and just keep sticking wires into the Marinco fitting and testing what comes out of the transformer. Eventually I may get it right. The marinas electrician told me that I don't really need the ground and disconnected it at the power post. That made no difference in the RP I just keep on getting. I do have one of the little plugs that tell you if your wiring is set up correctly so I'll be trying that when I start playing with the wires at the plug.
If anyone has any suggestions on how this should actually be wired(at the plug) I'd love to hear them.
Thanks for the feed back.
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Old 15-07-2013, 16:18   #18
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Re: Can't find cause of Reverse Polarity.

Philippines (at least at my vacation house) is 2 wire 220v 60 hz

from the connection at the house, coming from the street to the house meter, one non insulated ground/neutral and one hot wire at 220 v 60 hz

John
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Old 15-07-2013, 17:12   #19
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Re: Can't find cause of Reverse Polarity.

Marinco makes a bunch of different plugs. If you can get me a part number, or better yet, the NEMA number off of the plug, I can look up the standard wiring configuration for that particular plug. A NEMA number would be something like L5-30, L6-20, or L14-30. It is often (but not always) on the face of the plug, next the the prongs.

If you have a volt meter kicking around, the first thing that I would do is set it for an AC range that is good to at least 300v & poke the probes into the available service outlet to see where the power poles are. I would then look at the primary wires on the step down transformer & see what colors they are. I would then change the meter over to ohms & check for continuity from each wire on the primary side of the transformer to the transformer case. If you get a hit on only one of them, that is most likely your ground connection. If the other two wires ohm out to something that is not a dead short, but does have some continuity from one to the other, then they are probably your power wires. I would not just randomly poke wires into an outlet until you get the desired results. You run a good change of getting a dead short on the main feed that way & that can be a bit exciting in a bad way.

Please also let us know what country you purchased the transformer in. That will help us understand what wiring standard it was probably built to & what colors to expect.

Not knowing what kind of switchgear you have on board, I would disconnect the generator before attempting to attach shore power.

If your transformer has 6 wires & you ohm them all out to find that 1 pair is a dead short, 1 pair is about 15 ohms & the other pair is about 30 ohms, with no other continuity, then the 30 ohm pair is probably your primary, the 15 ohm pair is probably your secondary, the dead short pair are probably ground wires in & out and you have an isolation transformer. The actual number of ohms on the power wires is not important. The 2:1 ratio is. DC resistance is not always an accurate indicator of AC impedance.
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Old 15-07-2013, 17:45   #20
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Re: Can't find cause of Reverse Polarity.

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Originally Posted by mestrezat View Post
The tech took his multi meter and stuck the wires into my outlet and still got a reading even though there was no wires attached to the plug
Could you please elaborate on this statement from your first post a little bit? Maybe the plug itself is bad or has a small strand of wire creating a short somewhere? Or maybe I am misunderstanding what you are saying.

With no wires attached, none of the prongs on any plug should show continuity to any other prong.
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Old 16-07-2013, 06:55   #21
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Re: Can't find cause of Reverse Polarity.

"wires. I would not just randomly poke wires into an outlet until you get the desired results. You run a good change of getting a dead short on the main feed that way & that can be a bit exciting in a bad way."
I would like to repeat this.
Use your volt meter to check each "leg" on the dock pedestal to ground. Determine if one is actually neutral. Both may possibly be hot to ground.
Then connect and do the same at transformer.
Do you have a neutral to ground?
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Old 26-08-2013, 08:19   #22
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Re: Can't find cause of Reverse Polarity.

We finally resolved the problem. We got a third electrician to come on board with the second electrician. Along came the manager of the marina, another cruiser and myself. My wife hung back just outside the cockpit taking pictures to document how many guys it takes to solve a problem like this.
The new electrician took his multi meter and tested everything from the outlet on the dock to the plug where it comes into the boat. The wires ran from the dock came in at 240 volts or there abouts. The outlet coming out of the step down transformer came out at 110-120 volts or there abouts. The strange thing is that every plug prong hole showed 110-120 volts coming out of it! That included the ground prong! As it was explained to me by the electrician, the step down transformer I was using(made for the US) requires a Ground wire. In the Philippines, no such thing is used. All outlets have only two prongs. My step down transformer got "confused" and grabbed the current coming in since it couldn't find a "ground" wire and added it to the circuit. I was pushing 110-120 volts onto the boat on all three wires! The marina manager went up to his shop and got one of the locally made step down transformers that only uses the two pronged plugs and it worked just fine. No more "reverse polarity". Problem solved.
Now this explanation seems a bit strange to me but what do I know. The biggest thing I know is that I now have 110-120 volts coming into my boat. I do have to replace all six of my house batteries as the charger I bought from the hardware store to keep them charged till be could find the solution fried my batteries. It has no regulator(none of them do in the Philippines). Hey, they were five years old any way.
So that's what I was told. Make any sense to all you folks out there?
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Old 26-08-2013, 10:50   #23
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Sounds to me like you just have a split phase 110-0-110 output 240 vac input transformer.

Hence the 110 everywhere with 240 between the two hot wires.

Alternatively you have a 240 to 110 step down with a floating neutral. That measures 110 everywhere



How did he measure the output of the transformer.

Doesn't sound like any of those people there knew what they were doing

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Old 26-08-2013, 16:25   #24
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Re: Can't find cause of Reverse Polarity.

He took his volt meter and stuck the prongs in each of the slots for the prongs of the plug. Positive to negative=110 volts, Positive to ground=110 volts, Negative to Ground=110 volts. Every where we looked we had 110 volts. The wires are set here at the marina that each wire coming in carries 110 volts but there are only two wires hence the 220 volts. Or so I have been told.
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Old 26-08-2013, 17:46   #25
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If each wire feeds comes in at 110 volts how does it return?
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Old 26-08-2013, 20:59   #26
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Re: Can't find cause of Reverse Polarity.

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Originally Posted by goboatingnow View Post
Doesn't sound like any of those people there knew what they were doing
At the very least, I think that a few key details are still missing.

Quote:
Originally Posted by goboatingnow View Post
Sounds to me like you just have a split phase 110-0-110 output 240 vac input transformer.

Hence the 110 everywhere with 240 between the two hot wires.

Alternatively you have a 240 to 110 step down with a floating neutral. That measures 110 everywhere
Since he said that it was a made-for-us transformer, I would expect that the secondary could also be 0-110 with 0 tied to the ground prong. In the US, per NEC, neutral gets tied to ground at the service entrance & the secondary of an isolation transformer counts as a service entrance. 110-0-110 secondary transformers (as you suggest) also exist in the US with that 0 (neutral) being tied to ground at the service entrance. In that case however, he would have two different outlets with 220 across the 2 hot prongs on the two separate outlets, which was not reported. Maybe nobody measured that. In the event of a 110-0-110, he should still read 0v from ground to one power prong of each outlet if the transformer is wired to standard US NEC.

I agree about the possibility of a floating neutral being the cause of "110 everywhere". We're not talking 3-phase here & you need a return leg on every circuit. The high impedance of the meter could be just picking up floating voltages that are caused by some sort of inductive coupling or something like that.
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Old 26-08-2013, 21:44   #27
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Re: Can't find cause of Reverse Polarity.

In the Philippines it is 2 wire 220v. One is ground and the other is 220v.

I would guess his original transformer was not intended for this... That is why the local transformer works.

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Old 27-08-2013, 02:22   #28
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Re: Can't find cause of Reverse Polarity.

Quote:
Originally Posted by mestrezat View Post
He took his volt meter and stuck the prongs in each of the slots for the prongs of the plug. Positive to negative=110 volts, Positive to ground=110 volts, Negative to Ground=110 volts. Every where we looked we had 110 volts. The wires are set here at the marina that each wire coming in carries 110 volts but there are only two wires hence the 220 volts. Or so I have been told.
Yeap thats right for floating neutral. on the output of the transformer, just tie local boat earth to the designated "neutral". The boat side earth shouldnt be connected to shore earth BTW.

I suspect all he did was sell you a traffo, with the secondary neutral and earth tied together.


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