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Old 31-12-2011, 07:26   #1
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Reverse Polarity Light

My Chaparral Signature 31 is stored in my yard, and I wanted to plug in to the house current using a Marineco adapter. When I connect the extension cord from my house current to the shorepower connection the reverse polarity light comes on at the panel inside the boat. I'm afraid to turn on anything because of the warning indicator, so, I disconnected it.

Any idea why this is happening, and whether this is a risk to the AC or other systems in the boat? The engines and everything are already winterized (live in New York) and, so, I don't want to use the generator or anything else. Thanks.
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Old 31-12-2011, 07:28   #2
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The live and neutral are reversed in either the shore lead or the extension.( or the outlet) Swap them over
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Old 31-12-2011, 07:32   #3
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Re: Reverse Polarity Light

So, if that's the case, could I also safely try another outlet from the house? Is there any threat to the electrical systems if I do not turn on the panel?

Thanks for the help!
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Old 31-12-2011, 08:03   #4
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Originally Posted by martymalone3
So, if that's the case, could I also safely try another outlet from the house? Is there any threat to the electrical systems if I do not turn on the panel?

Thanks for the help!
Yes try another outlet or it could be the extension lead. No damage will be done once you don't power up. ( in fact no damage will be done if you do it'd just you should fix it ..

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Old 31-12-2011, 10:30   #5
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Re: Reverse Polarity Light

I would get one of those polarity testers from the hardware sotre and figure out where the reverse polarity is coming from. They are pretty cheap. You plug it into the receptacle and the lights on the tester tell you what the problem is with the wiring. http://www.amazon.com/s/?ie=UTF8&key...l_1mlf293if7_b (It is probably not a bad idea to have one of these on your boat and a little pig tail that you can plug into shore power so that a person could test the polarity of marinas when travelling)
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Old 31-12-2011, 11:01   #6
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you can use a volt meter to check the outlet.
switch to voltage AC

should have..
120 VAC from black (H) to white(N),
120 VAC from black(H) to ground,
0 VAC from white (N) to ground.

then check for ground.
Switch to resistance
look for 0 Ohms from white (N) to ground.

if it passes the first test, then power off and check that the wires are connected to the outlet in the correct locations. hot will have a copper screw, N will be silver and gnd will be green
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Old 31-12-2011, 11:41   #7
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Re: Reverse Polarity Light

The voltage drop in the neutral wire caused by the extension cord could be enough to turn on the reverse polarity light. This assumes that there is some load connected on the boat.
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Old 31-12-2011, 11:44   #8
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Re: Reverse Polarity Light

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Originally Posted by ChuckSK View Post
The voltage drop in the neutral wire caused by the extension cord could be enough to turn on the reverse polarity light. This assumes that there is some load connected on the boat.
explain that one to me, given that reverse polarity is typically a neon between neutral and earth.

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Old 31-12-2011, 11:49   #9
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Re: Reverse Polarity Light

The neutral and the earth are connected at the grounding point of the electrical service. Any voltage drop on the neutral would appear as a voltage across the neon reverse polarity light.
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Old 31-12-2011, 11:56   #10
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Re: Reverse Polarity Light

it would have to quite a drop to strike a neon

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Old 31-12-2011, 16:16   #11
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Re: Reverse Polarity Light

The reverse polarity light is powered, when lit, by the neutral and ground, neither of which are in normal conditions current carrying wires. There is no voltage to drop.

If neutral and hot were reversed the light would then be powered warning of the reversed polarity.
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Old 31-12-2011, 16:18   #12
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Quote:
Originally Posted by mitiempo
The reverse polarity light is powered, when lit, by the neutral and ground, neither of which are in normal conditions current carrying wires. There is no voltage to drop.

If neutral and hot were reversed the light would then be powered warning of the reversed polarity.
The neutral is of course carrying the full circuit current , the ground does not carry current except under fault conditions.

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Old 31-12-2011, 16:25   #13
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Re: Reverse Polarity Light

Blueseas technical note on
AC Reverse Polarity False Indicators
AC Reverse Polarity False Indicators
They also have tech notes on ABYC reverse polarity requiremnets.
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Old 31-12-2011, 16:36   #14
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Re: Reverse Polarity Light

The neutral is a grounded conductor. Followed back to shore it is connected the the green (grounding) conductor. Between neutral and ground there should be no measurable voltage.

These are the 2 wires going to the reverse polarity indicator light.
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Old 31-12-2011, 20:52   #15
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Re: Reverse Polarity Light

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Originally Posted by mitiempo View Post
The neutral is a grounded conductor. Followed back to shore it is connected the the green (grounding) conductor. Between neutral and ground there should be no measurable voltage.

These are the 2 wires going to the reverse polarity indicator light.
Put a heater on in the boat at the end of a 100' extension cord and draw 10 amps through the neutral. Depending on how heavy the cord was you would have at least a couple of volts drop in the neutral which you wouldn't have in the grounding conductor. Measurable voltage, but not enough to light a reverse polarity bulb.
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