Reverse Polarity

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Veteran Member
May 29, 2019
United States
Vessel Name
Vessel Make
Bruno Stillman 42
Here's the story. I have a 5kw NL and a Xantrex freedom 458. This is a 30 amp / 120 system. It has been flawless till now.

Took the boat out the other day. Did my normal check list, started the gen and let it warm up for 10 min. Turned off the A/C, went to the switch and changed it to generator. Waited a minute and put a load to the generator by turning on the A/C (1600 BTU). The load meter went up to high (close to30 amps) and I flipped the switch off before it could start to strain the generator. This happens sometimes when the capacitor did not have time to load. Waited about 5 min and tried again, nothing.
At this point I have no AC power and the generator is running.

Returned to the dock, plugged in the shore power and still nothing.

The Investigation - I checked the following -

1. Starting from the shore power cord to the panel, no issues. I took the cord ends apart and checked with meter, no issue. Checked on all connections and no issue.

2 From the panel switch to the inverter no issue. The inverter and charging was still working on the Xantrex.

3 From the inverter out - No shore power

4 By-passed the inverter and connected the wires together. The reverse polarity light comes on at the panel. After a few minutes of playing with the 50 amp breaker the light goes off and everything works fine. A/C is blowing and fridge and freezer are running.

5 After running for 20 minutes the breaker pops and the Reverse Polarity light is on.

At this point I have no power coming from the generator, the shore power will not work. The Reverse Polarity light is on, the 50 amp breaker will hold but any load and it pops.

I think I have narrowed it down to the breaker now, but that is to be determined.

Has anyone experienced something like this?
I am at a loss to what happened. But would like to know myself!

I hope you find the problem quickly.
Bad 50 amp breaker.
you started playing with it and now it works. Corrosion inside or contacts are worn out. Change out. Corrosion causes heat, Heat causes fires.
Cheap fix.
I don’t think I am getting the whole story. You start off with this is a 30a 125v system but now you are messing with a 50a breaker. Is it really a 50a 125 system and shore is set up is a 30a 125v? What is the generator, 50a 125/250v or other? Is everything powered through the inverter or only certain circuits? There is a lot of missing info here.
I have 50amp service. My power cord needed to be so long I had to add an additional length. Sometimes that connection gets moved around and I lose one leg of my 2x115v. On my panel I’ll have 115v on one leg and 90v on the other. Polarity red light is on. It happened just minutes ago after a return trip back to the dock. I unscrewed it, re-screwed it and now I’m good. The main point is the polarity light.
Sorry for taking so long to get back. So after thinking my great land electrician could figure this out, i was wrong. I ended up getting a good marine electrician and find out it is the shore-power cord at the boat. I just stood there like a deer in the headlights, that is it? However every experience is a lesson learned.

As for the generator, the exciter decided to take a crap at the same time.

The Xantrex freedom 458 is back working just fine, still blinks off and on but works.

Charlie - it is from Paneltronics. Works fine but I wish I had 50 amp coming in.

tiltrider1 - it is a 30 amp system with a 50 amp main breaker. The system is flawless but its operator is not..

RickD - Your correct and thank you

I took her out on a day trip and everything works for now. Next week I will take her for a 4 night fishing trip with some friends, hopefully everything runs great.

Thanks Again
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