reverse polarity

[Ron222]

Does anyone know what it means when you have "reverse polarity" on a boat? The light indicating this situation is flickering (not on steadily) which suggests something isn't right but not sure what to look for. Since the boat has been completely refurbished and much rewiring completed over the winter anything is possible. Is there someone with electrical expertise. Thanks in advance if someone has seen this before.
Ron
Paumanok A34
Westbrook, CT

[Russell]

This usually means that your ground and hot wire are interchanged on your AC circuit and you may receive a shock if you touch certain parts of the boat that are hooked to the ground circuit. The light is to warn about faulty marina wiring but if your boat has been rewired the hot and ground sides may have been reversed, especially if no one else in the marina is having a problem. You may wish to have an expert check your boat wiring to be on the safe side.

[Ron222]

Thanks very much for the tip. I'm sure it isn't the marina. Fortunately, I haven't received any shocks from touching anything on the boat. It sounds like a job for a qualified marine electrician. I wonder how long it will take to get an electrician this time of the year. I will update when I learn more. Still planning trips very soon.
Ron
1986 Albin 34 "Paumanok"
Westbrook, CT

[RobS]

Could be a bad ground connection, a loose or corroded connection, etc.. Get a plug in polarity tester like this and start with the dock power.

Outlet_Polarity_Tester.jpg

If your dock has a 30 amp twist lock you will need to also get an adapter to go from the 30amp to a standard 3prong 110 (15amp).

MAR-81A_med.jpg

Both are good items to have and keep on the boat. Especially if you visit transient marinas..

[jleonard]

I use the same tool.

[Drew]

Ron...any update on what you found. I now have the same issue when I turn on the generator.

[balance]

Hi Drew,

We have spent quite a summer trying to track down the cause of the reverse polarity from our generator. We've had 4 marinas with 6 different techs/electricians trouble-shoot. They were able to pinpoint <<Gen set output voltage is 80 volts on the lead leg and 40 volts on the neutral leg.>>

The short, and the last, so far: <<My technician has spoken to two different Northern Lights techs and both have suggested that the problem wit the generator is in the junction box attached to the side of the generator that was installed by the builder.>> We were quoted 10 - 16 hours for them to "get at it."

Hope you're having better luck with your search. Any info would be helpful. Does this sound likely? Does this sound like it would be resolved by replacing that junction box? Reasonable stimate?

Any help from anyone would be great.

[RicM]

Just want to say, be VERY careful with this problem. Last year year a guy was electrocuted here in RI because his shore power was screwed up. The newspaper account didn't call it "reverse polarity" but I don't know what else it could be. The boat was in the slip and he was working on it with his young son. Zapped him right in front of the kid. There's a reason why they put that light in every boat with shore power.

[balance]

Will do. We're not touching it and - although we miss the A.C. in Florida - are not using generator at all until someone knows exactly what to do. Thanks, Ric.

[Ron222]

In response to the responses regarding the reverse polarity I was observing on my boat, it turned out to be a very corroded "Y" 30amp electrical cord from shore. The previous owner installed a King AC/Heater unit in the bilge and instead of setting up a separate circuit onboard to the breaker panel installed a separate 30 amp plug in to shore. So, he had a 30 amp cord with a Y to 2-30 amp plugs. One plug to the boat main electrical panel the other directly to the AC/Heater. The Y was so corroded it created the reverse polarity. My boat yard decided not to do the wiring for the AC/Heater to the panel because of the lack of space and because there are two breakers already protecting the line (near the ac/heater and the shore power outlet). Anyway, the reverse polarity was solved although maybe not to national electrical code standards.

[RicM]

Is there an onboard breaker on the 30 Amp leg not going through the panel?

[Ron222]

No, I have to correct myself. There is a 30 amp breaker for the Honda 3kW generator that can power the AC/Heater while at anchor but there is no onboard breaker to the AC/heater for the AC shore power. The marina felt the 30 amp shore power outlet breaker was adequate to protect the circuit but not to code.

[balance]

Forgive my ignorance.... Does that mean you only showed the reverse polarity when plugged into shore power? or did it cause a problem on gen?

Ours is only on generator. We have someone who will look at it but they are pretty far away and charge travel time. Still trying to weed out the troubleshooting since so many have already looked at it.

[Ron222]

That it correct. It only showed the reverse polarity when attached to the shore power.