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Old 12-02-2015, 08:04   #31
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Re: Reverse Polarity

I've got a table lamp in Texas with a plug I can push in both ways. Thing is that the metal socket is separated from the metal body by an insulator. Not the safest, but not instant death either.


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Old 12-02-2015, 08:05   #32
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Re: Reverse Polarity

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Originally Posted by K_V_B View Post
All table lamps in continental Europe come with reversible plugs... As explained above this does not lead to dangerous situations.
Whatever, Dude. You are comparing oranges to apples and arguing that apples are better. It's pointless.

Why don't you tell the guy how to fix his boat?
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Old 12-02-2015, 08:07   #33
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Re: Reverse Polarity

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Originally Posted by Sailmonkey View Post
I've got a table lamp in Texas with a plug I can push in both ways. Thing is that the metal socket is separated from the metal body by an insulator. Not the safest, but not instant death either.


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Old 12-02-2015, 08:26   #34
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Re: Reverse Polarity

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Originally Posted by rwidman View Post
Whatever, Dude. You are comparing oranges to apples and arguing that apples are better. It's pointless.

Why don't you tell the guy how to fix his boat?
No, I'm arguing that wiring your boat in a way that reverse polarity is not an issue is a better approach to electrical safety than assuming that shore power will be correctly polarised. And it appears that both AYBC and the European boating industry seem to be on agreement here.
A boat build to CE standard will not come with a reverse polarity warning light. Because it doesn't need one. Once you no longer require correct polarity you stop caring about it. That's why most plugs in Europe are reversible.

However, the OP appears to have an isolation transformer, which means that his problem probably has nothing to do with the shore power being incorrectly wired.
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Old 12-02-2015, 08:32   #35
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Re: Reverse Polarity

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Originally Posted by K_V_B View Post
A boat build to CE standard will not come with a reverse polarity warning light. Because it doesn't need one. Once you no longer require correct polarity you stop caring about it. That's why most plugs in Europe are reversible.
The other approach is to pay attention to polarity, particularly if your boat has a polarity indicator, and not listen to those who say polarity doesn't matter.

Either approach works fine, if you're well-informed.
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Old 12-02-2015, 09:08   #36
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Re: Reverse Polarity

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Originally Posted by K_V_B View Post
No, I'm arguing that wiring your boat in a way that reverse polarity is not an issue is a better approach to electrical safety than assuming that shore power will be correctly polarised. And it appears that both AYBC and the European boating industry seem to be on agreement here.
A boat build to CE standard will not come with a reverse polarity warning light. Because it doesn't need one. Once you no longer require correct polarity you stop caring about it. That's why most plugs in Europe are reversible.

However, the OP appears to have an isolation transformer, which means that his problem probably has nothing to do with the shore power being incorrectly wired.
This thread is not about whether the European standard for electrical wiring is better than the USA standard, it's about a guy whose boat is showing "reverse polarity" when it shouldn't. The reverse polarity light is a warning of an unsafe condition and that is what I believe he is asking for help with.

As for the isolation transformer meaning the problem is not with the shore power wiring, his boat seems fine everywhere else except at this marina. We don't have a diagram of how the boat, transformer and shore power are wired so we can only guess. As I posted above, my experience is that wires don't detach themselves from connections and reattach themselves to different connections by themselves so moving wires as the OP did is not the solution.

We don't know if the isolation transformer is permanently installed on the boat or if he plugs it into the dock pedestal and plugs the boat into it. Perhaps the problem is with his shorepower cable but one would think he would have tried another before posting here.

Perhaps his problem is that the ground is not being carried through from his boat to the power pedestal.

If you can provide a workable solution to the OP's problem, I'm sure he would be grateful. Rewiring his boat is probably not the solution he is looking for.
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Old 12-02-2015, 09:50   #37
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Re: Reverse Polarity

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Originally Posted by K_V_B View Post
No it doesn't.

Not if the boat is properly wired. Appliance makers have stopped making assumptions about which wire is live and which is neutral decades ago. You should do likewise.
Just install a double pole main breaker and RCD and you do t have to worry about reverse polarity. That is what my book about marine electricity tells me anyway...
This is incorrect. Some appliances, those not normally used in a "hazardous" environment do always make specific provision for reverse polarity. The primary reason for this is that households, here and in Europe I assume, are pretty well hard-wired and once correctly installed should not have reverse polarity to the panel. The neutral is required to be attached to ground. This makes the neutral a reference ground.

The Monk article cited above gives a very good explanation of, and scenarios where, reverse polarity can lead to electrocution, especially at the appliances which do not make a difference to polarity - AT THE PLUG. The standard in the US at least is to have the switch on the appliance interrupt the hot side and not the neutral so that the hot will be broken as soon as it comes to the appliance as possible. If the neutral is hot, more of the appliance wiring and circuit is hot.

Many devices, especially electronic, require normal polarity as their circuits are designed that way. Reverse polarity can cause them to permanently fail.

All the marine inverter/chargers that I am aware of void the warranties, and may not operate or completely fail, if reverse polarity is given at the AC input side.

Note: I just deleted a big section of this post to explain why US boats are wired the way they are (or should be wired). I was doing this to show why and how the safety ground is provided, why it connected to the neutral and where, the differences between US and European wiring systems (you have to consider the entire system regarding safety and standards, not just the incoming AC power), etc.

I was doing this to show how many of the posts on this thread are not only wrong but potentially dangerous (as in someone losing their life) should they be followed. I am amazed that some people are so sure of themselves regarding boat wiring because they know residential/commercial wiring, or in some cases power grid wiring, that they feel knowledgeable enough to advise other people how to wire their boats. Or just because they know better.

Short and sweet: It ABSOLUTELY matters about reverse polarity on US boats. It matters on European boats too but I am not expert on those but they are wired differently - not "better". See "systems" comment above.

If you have a reverse polarity indication on your boat, whether from the reverse polarity indicator at your panel, or from the little AC reverse polarity tester you can put into a 110/120v US outlet, or a similar tester (expensive) you can plug in to the 30A or 50A plug at the dock, then you have a potentially unsafe condition and you should find the fault and correct it. Period. If you don't please tell me you don't before I come on your boat, unless you want me or someone else who has experience with this to fix it for you. Seriously. Can you get away with it? Sure - if none of the various things that could happen to kill you don't kill you then your will be fine.

Some things are opinions and some aren't. Can electricity kill you? Yes, that is a fact not an opinion. I am seriously disturbed by some advice given on this forum. My skin is thick enough to take any misguided opinions thrown at me but I do worry that folks who don't will be persuaded by some of the fictions and opinions given here.

BTW - boat wiring for generators and inverter/chargers is a completely separate discussion and is more complicated. If you don't know what you are doing then don't.
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Old 12-02-2015, 10:12   #38
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Re: Reverse Polarity

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Originally Posted by rwidman View Post
OK, I get it, Europe is way better that the USA. Just remember though, you would all be speaking German today if it wasn't for the Good Ole' USA!
Not only are you incorrect regarding UK/Europe WWII "winner"-(Russian could well have been the current language),but you are doing an insulting dis-service to all those who fought &/or died in the European theatre,including,but not limited to,US military.As a Canadian,with relatives buried over there,I am deeply offended,as I'm sure other readers are.
This forum is no place for offensive remarks & sterotyping.
I apologize to other readers,but I could not let his remarks stand.
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Old 12-02-2015, 10:19   #39
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Re: Reverse Polarity

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Not only are you incorrect regarding UK/Europe WWII "winner"-(Russian could well have been the current language),but you are doing an insulting dis-service to all those who fought &/or died in the European theatre,including,but not limited to,US military.As a Canadian,with relatives buried over there,I am deeply offended,as I'm sure other readers are.
This forum is no place for offensive remarks & sterotyping.
I apologize to other readers,but I could not let his remarks stand.
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Old 12-02-2015, 11:47   #40
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Re: Reverse Polarity

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Originally Posted by letsgetsailing3 View Post
The other approach is to pay attention to polarity, particularly if your boat has a polarity indicator, and not listen to those who say polarity doesn't matter.

Either approach works fine, if you're well-informed.
Oh. I will pay attention when I get on board a yacht if it has a polarity indicator, as this seems to be a reliable indicator for sub standard wiring...

But it's unlikely that I'll ever have a boat that is not CE marked, so yes, for me it will remain largely a non issue.
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Old 12-02-2015, 11:52   #41
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Re: Reverse Polarity

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Originally Posted by exMaggieDrum View Post
Note: I just deleted a big section of this post to explain why US boats are wired the way they are (or should be wired). I was doing this to show why and how the safety ground is provided, why it connected to the neutral and where, the differences between US and European wiring systems (you have to consider the entire system regarding safety and standards, not just the incoming AC power), etc.
Why? And, more importantly, could you reconsider and bring it back to the forum? It is always good to read a well informed explanation and expand one's knowledge beyond what one knows from their local playground.
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Old 12-02-2015, 12:11   #42
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Re: Reverse Polarity

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Originally Posted by exMaggieDrum View Post

Many devices, especially electronic, require normal polarity as their circuits are designed that way. Reverse polarity can cause them to permanently fail.
We're still talking AC here, right?
Well, what you say is not true.

Again, in Europe most appliances come with a plug that is not polarised. Ie, it goes in the receptacle both ways.
If reverse polarity would cause damage then we would see a lot of damages. Half of the time when you plugged something in you would destroy it.
Appliance makers don't make separate versions for different markets anymore. The power supply that comes with my macbook will work worldwide, as long as I put the right plug on it. It certainly doesn't care about polarity here, so wouldn't do so in the US either.

The charger we have on our boat has a standard plug (just goes in a power socket that is connected to shore power). It therefore cannot be built in a way that it would be damaged by revers polarity.

I'm now looking at this thing:
EasyPlus - Victron Energy

Nice all-in-one solution, which would save me having to wire up a separate AC panel. And it has a RCD, so even with N and L swapped (as will often be the case) there should be no danger.

Quote:
If you have a reverse polarity indication on your boat, whether from the reverse polarity indicator at your panel, or from the little AC reverse polarity tester you can put into a 110/120v US outlet, or a similar tester (expensive) you can plug in to the 30A or 50A plug at the dock, then you have a potentially unsafe condition and you should find the fault and correct it. Period. If you don't please tell me you don't before I come on your boat, unless you want me or someone else who has experience with this to fix it for you. Seriously. Can you get away with it? Sure - if none of the various things that could happen to kill you don't kill you then your will be fine.
I know electricity. And I do inform myself. The odd think is that if I read books about yacht electricity written by Europeans the whole "reverse polarity" subject never even comes up.
It does come up in AYBC literature, where it is mentioned that if you have a RCD (or GFCI) that you don't need a reverse polarity indicator. You would install an RCD, wouldn't you?
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Old 12-02-2015, 12:15   #43
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Re: Reverse Polarity

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Originally Posted by mrm View Post
Why? And, more importantly, could you reconsider and bring it back to the forum? It is always good to read a well informed explanation and expand one's knowledge beyond what one knows from their local playground.

Yes, I would like to see it too and learn more.

back to the OP. no matter what, to say that someone will die my plugging in to a reverse polarity, with no other shorts. or issues, is simply wrong.

It still would take a short somewhere. Now you can say, that it is less safe.

The above lamp example is a perfect example.

And I don't stick my finger in a lamp socket no matter what the polarity.
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Old 12-02-2015, 12:40   #44
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Re: Reverse Polarity

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Originally Posted by Dauntlessny View Post
It still would take a short somewhere. Now you can say, that it is less safe.

The above lamp example is a perfect example.

And I don't stick my finger in a lamp socket no matter what the polarity.
It wouldn't take a short at all. See lamp socket example:

By contrast, a lamp socket connected to a reversed-polarity receptacle will have a ‘hot’ (ungrounded) screw-shell that is cycling at significant voltage to ground, while the spring-tab at the base will be ‘neutral’, and at zero volts to ground. Someone touching both the reverse-connected screw-shell and something grounded would become a conductor for significant current moving from 120V RMS ‘hot’ to zero volt ground
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Old 12-02-2015, 13:19   #45
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Re: Reverse Polarity

A lamp bulb is basically a resistance coil, so line/neutral is not that important, It is important with other electrical devices which have chassis grounds for instance. I stopped reading all the posts when it got screwy, but did anyone tell him if he is sharing the pedestal with another boat, it could be a polarity problem on the other boat feeding the neutral. Sorted this out in the boatyard just yesterday.
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