Reverse polarity issue

[msu1966]

I plugged my shore power cord with a 15 amp adapter to my 20 amp garage outlet via an extension cord for the first time and got a red light on the 'reverse polarity' on the AC circuit panel. I immediately unpluged the shore power cord.

What could be the cause of the 'reverse polarity'?

Thanks,
Ken

 

[HookedUp]

If you used a 3 prong extension cord with manufactured connectors, I doubt it's the cord. I'd get a polarity tester and check the outlet as it could be incorrectly wired.

If the extension cord connector was hand wired to the cord someone could have switched the conductor and neutral. Or, if the extension cord is 2 prong it's easy to have them reversed when plugged in. Suggest a manufactured 3 prong cord to avoid polarity issues.

Outlets and cords with polarity reversed will work, but are unsafe and should be corrected. On a boat it is VERY unsafe to have reversed polarity.

 

[CaspersCruiser]

I hate to state the obvious, but it’s possible that your garage outlet has reversed polarity. Test it with one of these:

https://www.lowes.com/pd/Kobalt-Digital ... 1001799404

 

[Wee Venture]

The reverse polarity light is looking for a voltage drop between the neutral and ground wires of your shore power connection (which should theoretically both be at zero voltage with respect to earth ground). If there was actual reversed polarity, the “neutral” wire would in fact be hot and that would cause a 120VAC drop which would obviously make the light glow.

However even with correct polarity, if you have a long run back to your AC power source/service entrance, and undersized wiring, and your boat is drawing quite a few amps (think refrigerators, air conditioners, space heaters, battery chargers, etc.), the current running through the neutral wire can create a voltage drop with respect to the green ground wire. This can make the reverse polarity light glow, perhaps dimly, even when your polarity connection to shore power is correct.

Try turning off all AC power draws including any in your garage on the same circuit. If your reverse polarity light goes out, polarity is ok. You can also purchase an inexpensive plug-in tester. Or use a multimeter to test for AC voltage between neutral and ground. There have been other threads about the reverse polarity light coming on when people are plugging into long extension cords or with a long run back to the service entrance.

John

 

[msu1966]

It sounds like John may have the answer. I have a 50 ft. extension connecting from the garage to the 110 adapter then to my 25 ft. shore power cord. I did not have any circuits 'ON' on the AC breaker bank, I was just trying to charge the batteries.
I am not knowledgeable on using a multi-meter so I am going to have to get up to speed on that. Maybe my neighbor can give me a crash course on using one.

 

[knotflying]

My experience with this issue has been the GFI itself. I had the same issue at my house and checked the outlet for reverse polarity and it was fine. Using the same extension I plugged into a regular outlet in the house and all was good. So that ruled out the long extension. It has happened in other instances as well at friend's homes when visiting. I never investigated why since I overcame the issue by plugging in another outlet.

 

[msu1966]

Thanks knotflyung, your suggestion worked. Tried another plug and I got green light for battery charger, no red on the reverse polarity circuit. I guess I'm good to go.