reverse polarity problem

sailingtime · #1 (**permalink**) 07-22-2008

I am new to the luxury of having shore power which also means I am clueless to dealing with any problems with it other than plugging in the cord. Up until last weekend everything worked great until I lost power and the “reverse polarity” indicator light came on. I discovered that the indicator light would go out and the normal “service” light would come on if nothing was plugged into any receptacles. As soon as something was plugged back in the “service” light went out and the “reverse polarity” light came on. Can anyone give me an idea of what I am dealing with and how best to approach fixing it?

hellosailor · #2 (**permalink**) 07-22-2008

It is possible that the marina has reversed the power leads on your dock, or that your own shore power wiring is crossed at some point. Go to any hardware store, for $5 you can buy a little power outlet tester with three lights on it, that plugs directly into a socket to test for these things. If necessary, get an adapter so it can plug directly into the dock power, or wire one up.

If you've never plugged into shore power before..odds are 50-50 whether it is your wiring, or the marinas. If no one else has a problem with the marina power--time to check your wiring out. If you find "household" grade power cords on the boat, that's a big hint right away.

sailingdog · #3 (**permalink**) 07-22-2008

If the reverse polarity light is off when you have the boat plugged in to shorepower, but it comes on when you plug something into the boat, you may have a bad appliance or outlet on the boat.

I would second HS's recommendation of getting a polarity tester at the hardware store.

It looks a lot like this:

Start by checking the marina's shore power outlet. Then check the shore power cord, while it is plugged into the outlet. If it is fine at these two points, the problem is on the boat someplace. Then check the boat when it is plugged into the shore power cord. Unplug all the 110 VAC devices and use the polarity tester to check each outlet. IF they're all fine, then it is one of the appliances on your boat.

BTW. DON'T FORGET THAT THE SHOREPOWER DOCK SIDE CONNECTION SHOULD BE THE LAST TO BE MADE AND THE FIRST TO BE DISCONNECTED. YOU DON'T WANT TO BE WALKING AROUND THE DOCK WITH A LIVE AC CORD IN YOUR HAND—SINCE IT MIGHT WELL KILL YOU IF YOU SLIP AND FALL IN HOLDING IT.

To plug the boat in:

Open the shorepower socket lid.
Connect the cord to the shore power outlet on the boat.
Tie or wrap the cord so that it can't fall in the water as you lead it back to the shore power outlet on the dock.
Connect the shorepower cord to the dock outlet.
Turn on the breaker.

To disconnect the boat:

Turn off the breaker.
Remove the shore power cord from the shore power outlet on the dock.
Unwrap and untie the shore power cord and coil it.
Disconnect the shore power cord from the boat.
Close the lid on the shore power socket.

Don't skip steps in this... 110 VAC and water don't mix nicely.

SteveInMD · #4 (**permalink**) 07-22-2008

The polarity light is there to protect you from ending up with revered polarity from shore power. Normally this is only an issue when you are in remote places and you have to wire up your own adapters to connect to shore power. If you didn't make any wiring changes on your boat and it was working before it's probably something your marina needs to fix. It could be a problem on your whole dock or just your connection point. Unless you are working with someone who knows electricity thoroughly, this is a job for a pro. AC power can kill you - your boats 12 volt DC system probably wont.

sailingdog · #5 (**permalink**) 07-22-2008

Steve-

You're making assumptions not in evidence... if the power went out due to a storm, he could easily have a fried piece of equipment on his boat that is causing the RP situation. He needs to check the AC at the shorepower box and at the end of the shorepower cable. If it is good at those two points, the problem is somewhere on the boat.

From his description, where the RP light doesn't come on until he plugs something in to the AC system on the boat, I seriously doubt that the RP problem is in the marina shorepower system.

A ten year old could run the simple checks I've described above.. They're not rocket science. While, I agree that working on a boat's 110 VAC system can be very dangerous.... doing basic trouble shooting like I describe should be something that all boat owners should be capable of.

Quote:

Originally Posted by SteveInMD

The polarity light is there to protect you from ending up with revered polarity from shore power. Normally this is only an issue when you are in remote places and you have to wire up your own adapters to connect to shore power. If you didn't make any wiring changes on your boat and it was working before it's probably something your marina needs to fix. It could be a problem on your whole dock or just your connection point. Unless you are working with someone who knows electricity thoroughly, this is a job for a pro. AC power can kill you - your boats 12 volt DC system probably wont.

SteveInMD · #6 (**permalink**) 07-22-2008

SD -

I don't disagree with anything you posted. Further, I wasn't responding to your post at all, as we were both writing our replies at the same time. The purpose of my post was simply to offer a little information about why the polarity light even exists on a boat in the first place. Also, since the polarity tester was already suggested, I was simply saying that once the problem has be identified, repairing the AC system should be left to a pro. (Of course this doesn't include unplugging and appliance.)

sailingdog · #7 (**permalink**) 07-22-2008

If the problem is in one of his AC appliances, an electrician may not be required.

Quote:

Originally Posted by SteveInMD

SD -

I don't disagree with anything you posted. Further, I wasn't responding to your post at all, as we were both writing our replies at the same time. The purpose of my post was simply to offer a little information about why the polarity light even exists on a boat in the first place. Also, since the polarity tester was already suggested, I was simply saying that once the problem has be identified, repairing the AC system should be left to a pro. (Of course this doesn't include unplugging and appliance.)

EO32 · #8 (**permalink**) 07-22-2008

Now I'm confused.

What does the "reverse polarity" indicator mean?

If it means the "Black" Line side of the AC and the "White" netural side are reversed, then why would it come on without shore power connected? Unless he has another source of power such as an Inverter.

If it never came on before, then I would agree with SD that something is broken.

If it refers to the DC system, then that's a whole new ballgame.

Chris

RAGTIMEDON · #9 (**permalink**) 07-22-2008

Realize that a competent professional was once a beginner--If you have the motivation to learn to do your own maintenance, simple electrical checks like SD describes are a good place to start. I am personally reluctant to "go with a pro" unless I know that professional well. I've seen and corrected some terrible mistakes made by professionals -- personally I prefer a truly motivated amatuer, so I do all my own work unless it calls for expensive specialized tools I do not posess! SD is right, if you are going to continue to be a boatowner, you need to develop some basic skills! Buy that polarity tester and go for it! Life is a learning process! 120VAC may burn if you are careless, but not likely to be fatal unless you are swimming when you touch the wire! If you are really nervous about it, wear rubber gloves to insulate your hands!

sailingdog · #10 (**permalink**) 07-22-2008

Sailingtime—

Just curious, but does your boat have an inverter/charger on it?? If the RP light is out when you power up the shorepower AC breaker, then it is pretty likely that the problem is on the boat someplace. If you had an inverter/charger that the outlets are connected to, and it got damaged, that might explain it. It might not...I really don't have enough information about the shorepower AC setup on your boat to say one way or the other... and anything we say will be pure speculation.

Quote:

I discovered that the indicator light would go out and the normal “service” light would come on if nothing was plugged into any receptacles. As soon as something was plugged back in the “service” light went out and the “reverse polarity” light came on. Can anyone give me an idea of what I am dealing with and how best to approach fixing it?

Chris-

A Reverse Polarity indicator on an AC panel is designed to show you if there is voltage coming in over the neutral line. It does not indicate whether the voltage is or isn't present on the black "hot" line, only whether any significant voltage is showing on the neutral "white" line.

The fact that it only comes on when he plugs something into the outlets on the boat tends to lead me to believe the problem is with something on the boat. Either the wiring, an inverter/charger, or one of the appliances.

AFAIK, none of this particular discussion has anything to do with the DC side of the boat.

Quote:

Originally Posted by EO32

Now I'm confused.

What does the "reverse polarity" indicator mean?

If it means the "Black" Line side of the AC and the "White" netural side are reversed, then why would it come on without shore power connected? Unless he has another source of power such as an Inverter.

If it never came on before, then I would agree with SD that something is broken.

If it refers to the DC system, then that's a whole new ballgame.

Chris