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.

Good that you got the switch and wiring fixed. The Reverse Polarity light can come on even with no leakage and the correct polarity. If there was any leakage, ie: current flowing in the safety ground (green wire) rather than all current flowing in the Neutral wire (white), the main breaker would trip. It acts like a GFI breaker for the boat. The Reverse P light comes on if Neutral is above the safety ground. (maybe if below ground too, not sure). This can happen on the dock due to loads or wiring not up to par. I don't think it should ever happen at anchor or unplugged from the dock. Good luck tracing it down.

Yesterday I replace my AC indicator lights with a new circuit board from Paneltronics. There is a resistor on the Reverse Polarity light that was bad. Replacing the board did the trick. I did hire some pros to check out the whole system. They did find and fix a couple of issues not related to the reverse polarity problem, but at least I know she is okay. Yeah!