IP 350: Reverse Polarity Light goes on when Air Conditioner is running -- Fixed

Has anyone had issues with reverse polarity light on?

1) When I bought the sailboat, the owner said the reverse polarity light on is normal for an IP. Also the boat inspector said there was no reverse polarity issue. My video's of the inspection showed the light was on. (2 years ago)
2) I have hired a technician to check it out.
a) with charger and air conditioning on there is 3 volt leakage
b) with charger, air conditioning and water heater there is 6 volt leakage
3) They have a new a/c and generator switch on order -- there were some loose wires & heat marks
4) After about 6 hours, the reverse polarity issue has not been found. The technician will run some more tests after replacing the switch.

Does anyone have any ideas? Is this a known problem with IP?

The reverse polarity light is connected between neutral and ground. When there is significant electrical load the neutral voltage drop will increase and a voltage difference will develop between neutral and ground. If you hired a marine electrician and he didn't know this, find a different electrician.


Frank

The voltage measurements mentioned in the original post are between the neutral and ground wires.

The neutral and ground are connected together at the electrical service entrance (house or dockhead). Normally the only current flowing in the ground is the current through the indicator lamp (next to nothing). Think of the indicator lamp and your voltmeter as measuring/ indicating the voltage drop over the neutral conductor ( maybe 5 or 10 volts under heavy load). I am not going to tell your system is fine as I am not there to examine the entire system, but what you describe is not at all unusual.

Frank

We often see the reverse polarity light on dim on Shawnee. But I think this is due to the dock wiring and load from other boats on the dock. This load can cause a drop in voltage on the neutral return, lifting above ground level. And that makes the light go on somewhat. Loads on your boat can cause increased drop as well, due to dock wiring. If you did have leakage on the safety ground (green wire), the AC Mains breaker would trip out.

Thanks for your response. I did hire a contractor to check out the electrical system. They did find that the shore / generator switch needed to be replaced. There were some loose wires, some were burnt. They have not found the leakage yet and will be working on it later this week. I am going to check the generator while at anchor to see if the reverse polarity light goes on. It does at the dock.