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Old 12-07-2012, 14:23   #1
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Reverse polarity nightmare

I was having issues with my shorepower that I traced to the rotary switch that switches my shorepower and generator. I bypassed the generator and hooked the shorepower wires and boat panel wires together while I found a switch, everything worked fine. After replacing the switch, exactly as the diagram says, I am now getting reverse polarity light when I'm on shorepower. Have checked wiring to the new switch 20 times. Only thing different is old switch was rated for 600v and new switch is 130v and I don't know if the polarity is bleeding through switch or even what that means. Any help would be greatly appreciated.
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Old 12-07-2012, 15:06   #2
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Re: Reverse polarity nightmare

The reverse polarity light is showing that somewhere before the switch the neutral (white) and hot (black) have been reversed. If you are certain that you've wired the switch correctly then either the dockside shore-power outlet is reversed or your extension cord is not wired correctly. If the red reverse polarity light is on then do not turn on the switch. Doing so could energize the cases of all the equipment on the boat, engine included, because the neutral and ground will be tied together.
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Old 12-07-2012, 17:24   #3
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Re: Reverse polarity nightmare

Greetings and welcome aboard the CF, alexandria.

Have you changed docks (shore power supply) lately?
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Old 14-07-2012, 13:03   #4
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Re: Reverse polarity nightmare

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Originally Posted by knots2u View Post
If the red reverse polarity light is on then do not turn on the switch. Doing so could energize the cases of all the equipment on the boat, engine included, because the neutral and ground will be tied together.
Don't think so. Neutral and ground are not/should not be, connected together anywhere on the boat.

Eric
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Old 14-07-2012, 13:15   #5
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Re: Reverse polarity nightmare

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Originally Posted by fairbank56 View Post
Don't think so. Neutral and ground are not/should not be, connected together anywhere on the boat.

Eric

They are connected through the reverse polarity light.
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Old 14-07-2012, 13:19   #6
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Re: Reverse polarity nightmare

As Knots2you said IF you wired the switch correctly,something is real wrong !! the only thing you changed is the switch, so therefor the switch is wired wrong or the switch is messed up !! if it's rated for less then the switch you changed out , that could be the problem ! If the shore power was right and no one touched it, then it's still wired right !! so then it has to be what you have done !! Maybe you need to change to the right rated switch?? I would sure do that first ! if you still get the reversed polaity light, then you must have switched a wire someplace, or you shore power cord is messed up ! ya might try another shore power cord, just to be sure !! wish I was nearer I would sure like to see this myself, as it should be right if it's wired right. just my 2 cents
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Old 14-07-2012, 14:11   #7
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Re: Reverse polarity nightmare

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Originally Posted by donradcliffe View Post
They are connected through the reverse polarity light.
That does not make them connected together!

Eric
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Old 14-07-2012, 15:25   #8
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Re: Reverse polarity nightmare

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Doing so could energize the cases of all the equipment on the boat, engine included, because the neutral and ground will be tied together.
sorry , what thats not good info. Thats doesn't happen. if it was as you said, the neutral would short to ground !!.


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Old 14-07-2012, 16:47   #9
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Re: Reverse polarity nightmare

Check the Blueseas notes on polarity indicators here Resources*—*Blue Sea Systems
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Old 14-07-2012, 16:55   #10
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Start with the basics, use a multimeter set to ac volts. Disconnect the line (black) and neutral (white) going out of your new switch to the panel. Plug your shore in turn your selector switch to shore power. Measure the voltage between shore / vessel ac ground and the neutral out connection on the switch you should have 0 volts, repeat with the line out between line out and ground you should have 120 plus minus volts. If this is the case then the switch is most likely wired correctly. Some things to check wiring numbers on different switches may not match. If the polarity sensing leads are external are they terminated correctly, does the new switch have external metal jumpers on terminals and are they connected correctly? For troubleshooting the best approach is to start at the beginning with the power off and a sheet of paper. Make a line diagram of your wiring starting with your shore power cable. Use your multimeter set to continuity or resistance in ohms. Check A to B and label. One meter lead on one end the other where the other end should be. You should read o ohms or close for the correct lead and open for all others. It is as simple as connecting the dots. If you read continuity on multiple points when you should not then you have a short or in correct terminations or jumpers. If you go slow write everything down you will be able to isolate the problem.
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Old 14-07-2012, 17:29   #11
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Re: Reverse polarity nightmare

as for the neutral and ground never connected on the boat is wrong. the neutral and ground should be connected at its source. thus a generator should have the neutral and ground connected at the generator. a shore power transformer should also have the neutral and ground connected together in the transformer, this is ABYC rules.
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Old 14-07-2012, 17:34   #12
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Re: Reverse polarity nightmare

as for the neutral and ground not connected together on the boat is wrong. the neutral and ground should be connected together at its source. thus a generator and a shore power transformer should have their neutral and ground connected together at the equipment. ABYC rules.
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Old 14-07-2012, 17:42   #13
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Originally Posted by tuberider
as for the neutral and ground not connected together on the boat is wrong. the neutral and ground should be connected together at its source. thus a generator and a shore power transformer should have their neutral and ground connected together at the equipment. ABYC rules.
Yes but when the shore power is connected the bond between the generator earth and neutral should be broken . Or more commonly the generator neutral is disconnected and therefore the bond is broken.

If a neutral goes hot nothing on a boat should become immediately unsafe.
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Old 14-07-2012, 18:37   #14
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Re: Reverse polarity nightmare

Which is why a reverse polarity indicator isn't even required if you are using an isolation xformer. It doesn't matter if the shore power is reverse polarity, it has no effect on your system as the polarity on your boat is established at the secondary of the xformer.

The biggest danger of reverse polarity on your boat is when your AC distribution panel only uses single pole breakers. If shore power is reversed, turning off a breaker does not remove the hot side from an appliance/load.

Quote:
as for the neutral and ground never connected on the boat is wrong
Since we are talking about reverse polarity devices which are not used with isolation xformers or generators, I assume we are talking about a straight thru shore power connection in which the neutral and ground would not be connected on board.

Eric
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Old 15-07-2012, 10:07   #15
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Re: Reverse polarity nightmare

I stand corrected. It bothers me when people talk off the top of their head and give incorrect information...and I've just done it! Now I've re-read my reference. Yes, neutral and ground should not be connected on the boat. The connection is at source either at the marina panel or at the on-board generator as has been mentioned. The selector should be a two pole switch which disconnects the generator's neutral when shore power is selected. Where my memory went off track is that the AC and DC grounds are connected on the boat and if the AC polarity is reversed due to improper wiring on board or in the shore power circuit and IF there is a connection between the neutral and ground on the boat the DC negative circuit will become hot. This is a hazard on board as well as in the surrounding water.
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