Reverse Polarity

[Half Off]

OK so here's the deal. I ran a 100' extension cord to the 110 shore power adapter last weekend while the boat is on the hard to do some dewinterization. Didn't notice the reverse polarity light on but could have been. We left it plugged in for 2 days while charging the batteries, powering a sander, small portable heater in the cabin, had TV on for a couple hours and also ran the radio. When we got ready shut everything down I noticed the red reverse polarity light on. I had replaced the male end on the cord I used before using it, could it be possible I had the wires turned around? Can low amperage cause the problem? One last question, what kind of damage does reverse polarity cause?

 

[jrcinnh]

Reverse polarity is detected using a lamp between neutral and ground. Normal polarity means there is no voltage difference between neutral and ground so the lamp never lights. If the lamp is lit then you probably swapped neutral and hot. It is also possible that you have a poor ground. Sometimes floating grounds can cause enough stray current to light the lamp. So go check your wiring.

The good new is that reverse polarity usually doesn't damge anything. The reason its important is safety. While you were using all that gear in you boat with reverse polarity, you were under a much greater chance of getting a shock, or starting a fire. In good condition, modern equipment the risk is pretty low but any wiring fault could have been very dangerous.

As to low amperage causing the problem, anytime you draw more amperage than the wire or circuit is rated for you can get weird results. So if you hooked up your 30 amp boat to a normal 15 amp wall outlet with a 15 amp cord. The circuit breaker in your house should blow when you turn on enough gear to get well above 15 amps, but things may be a little squirrelly if you're right around the limit.

 

[Stray Cat]

1/2 -Off It sounds like it is going to get down into the low 30's this weekend, don't dewinterize too much! Next week sounds like spring again.

You bring up a good point about replacing the plug on an extension cord...is the neutral supposed to be on the wide or narrow spade? I can't remember....I presume the narrow one because it would carry less amperage.

 

[2000SEARAY280SS]

The narrow blade gold screw lead is for the hot the wide blade silver lead is for neutral and the green is for ground.

 

[Half Off]

The narrow blade gold screw lead is for the hot the wide blade silver lead is for neutral and the green is for ground.

2000SEARAY280SS,
Thanks, that's the first thing I'm checking when I get back to the boat.

1/2 -Off It sounds like it is going to get down into the low 30's this weekend, don't dewinterize too much! Next week sounds like spring again. You bring up a good point about replacing the plug on an extension cord...is the neutral supposed to be on the wide or narrow spade? I can't remember....I presume the narrow one because it would carry less amperage

Stray Cat,
This weather is getting a little old isn't it. We had planned on finishing up the maintenance this weekend and splash next week but it looks like we'll have to push that back a week.

Reverse polarity is detected using a lamp between neutral and ground. Normal polarity means there is no voltage difference between neutral and ground so the lamp never lights. If the lamp is lit then you probably swapped neutral and hot. It is also possible that you have a poor ground. Sometimes floating grounds can cause enough stray current to light the lamp. So go check your wiring.

The good new is that reverse polarity usually doesn't damge anything. The reason its important is safety. While you were using all that gear in you boat with reverse polarity, you were under a much greater chance of getting a shock, or starting a fire. In good condition, modern equipment the risk is pretty low but any wiring fault could have been very dangerous.

As to low amperage causing the problem, anytime you draw more amperage than the wire or circuit is rated for you can get weird results. So if you hooked up your 30 amp boat to a normal 15 amp wall outlet with a 15 amp cord. The circuit breaker in your house should blow when you turn on enough gear to get well above 15 amps, but things may be a little squirrelly if you're right around the limit.

jrcinnh,
Thank you very much for taking the time to explain this to me. Electrical is not my strong suit.

 

[Half Off]

.......If the lamp is lit then you probably swapped neutral and hot.

Got back to the boat yesterday and that was the problem, switched them around and no more warning lamp.

Thanks again for the help.

 

[J Levine]

Two years ago I stored my boat is a very old yard with crap wiring. I ran a extension cord same as you to power up the boat while it was still on the hard and I was working on it. I never noticed the reverse polarity light was lit up on the panel. I am under the boat laying on the damp gravel/sand ground and I go to reinstall one of the propellors. I have one hand on the ground and when I touch the propshaft with the other hand I get the very distinctive shock of AC power. At first I say to myself WTF? and then of course I touch it again thinking I was dreaming or somthing and sure enough I get wacked again. I crawl out from under the boat and go down into the cabin to check the reverse polarity light and sure enough it is lit up. I chase the extension cord (with its orginal factory ends) back the old building where I pluged into a outlet and figure that the outlet was wired backwards. I check with another guy who had his boat plugged into the same outlet and his reverse polarity light was also lit. I moved the cord to another outlet and the light went out. Now I check it anytime I am in a new place. If the boat had been in the water I would have probably really gotten wacked.