Neutral Ground Fault on ciruit 1

[ViewRVs]

I started this conversation off-line but I thought I'd take it to a larger venue.

Prior to my paint job and power transfer switch installation, I always plugged in my Argosy to a GFI outlet on the back of my house to keep the battery charged and the vent going as needed. When I returned from Florida, I plugged it in and the GFI popped. I suspected the automatic transfer switch but when I rewired the coach directly to the GFI (bypassed the switch), it still popped the GFI.

I then went to the main panel and disconnected the neutral wires. When circuits 2 and 3 are wired, everything works with the GFI. When I connect the #1 neutral, even with the breaker off, it pops the GFI.

Circuit 1 powers three outlets including the old Univolt (TU-440-6 Converter Charger). I still get the fault when I unplug the Univolt (which uses a three-prong plug). I did try plugging the Univolt into to a cord with a GFI and it does not pop the GFI. For some reason, the voltage on the 12v panel is running 18 volts though. Normally my readings are 12-13 volts. Ideally I'll replace the aging Univolt but it looks nearly impossible to remove in it's current location.

The three outlets are the old mobile home outlets that actually use a continuous wire through the box. It's kinda hard to troubleshoot those old boxes. I guess I am going to have to pull out the boxes and replace them with more modern ones in order to troubleshoot.

If I plug the unit in to an outlet without the GFI, everything works fine. What concerns me is that there is a fault somewhere and I'd like to get it fixed instead of getting electrocuted one day!

[ViewRVs]

Two little details.
1) We did have a roof leak while we were out. I guess there is a possibly of a wet connection causing the fault. Those old boxes have lots of paper around the wires as insulation that they cut back when pushing in the wire. We ran a dehumidifier for the last day to help dry out the coach. We were also in the Smokies which tend to be damp all on their own!

2) A lightening bolt hit a tree about 40 feet from us while in North Carolina. We were not connected to shore power (just tires on the ground). I thought there was hail afterwards but it turned out to be a shower of wood chips from the poor tree! That was a terrifying experience and we are from Florida and have seen lots of lightening!

[ViewRVs]

Well I reinstalled the automatic transfer switch today with the circuit 1 neutral off at the RV's breaker panel and the GFI does NOT pop. I think that rules out the transfer switch. Circuits 2 and 3 are operating just fine on the GFI protected shore power.

[richinny]

do you have an exterior outlet? i've seen posts about trapped condensation there cause gfci's to trip. i've also seen posts on refrigerator elements tripping gfci's too.

[ViewRVs]

I do have an exterior outlet. I did open it up to air out. I have opened the junction boxes at the reverse polarity light and the bathroom outlet. I think the issue is the wire between the reverse polarity light and the bathroom outlet. I am going to bypass that segment in the AM and see if the rest of the circuit tests out OK.

[richinny]

do a google search using the search tab above. i remember something about the reverse polarity light being a shock hazard. it may not be related to your problem but should be looked into.

[ViewRVs]

richinny - Good idea! Here is what I found.

The reverse polarity light is wired to the ground and the neutral. I guess normally you would not have hot power on the neutral (light off). If you did, it would light the bulb indicating a possible safety issue.

This thread is actually for a boat (but applicable to our land yachts )
Shorepower and Reverse Polarity - SailNet Community

The real danger with reversed polarity is that the "neutral" wire is now "HOT" and on the side without the breakers. So if you decide to shut off the shore-power, but leave the cable connected, the "neutral" terminals at all of the outlets are still going to be live and electrocution is a good possibility.

I have tested my shore power (home outlets) and they check out fine. Since my issue is only with circuit 1, I think the fault is located there. The reverse polarity light is obviously a safety feature and not a cause of the problem.

Based on the research, folks today typically test the outlet PRIOR to plugging in the RV cord so the light is not as critical. Going forward, that is what I plan on doing. I'll use my 30/20 adapter and my standard $3 outlet tester. Similar to this:
30-amp RV outlet Tester

I better get out there and continue my investigation before it gets too hot.

[ViewRVs]

By George I think I've got it! The wire between the reverse polarity light and the bathroom outlet must be damaged. I tested for continuity and all three wires check out OK. The problem lies in the fact that when I check for continuity between the neutral and ground on the same end of the wire, I actually get some continuity! I also get continuity on the other end of the wire between the ground and neutral.

I am guessing that a sheet metal screw or something else damaged the wires over the last 36 years (or recent exterior renovation) and exposed both the ground and neutral wires.

Everything after the bathroom outlet appears correct since my temporary bypass does not throw the GFI.

And now the challenge of replacing a wire in a monocoque constructed unit!

[Wazbro]

Try removing the bulb from the reverse polarity light and check for continuity again before digging too deep. The light is an old fashioned safety device which may not be fully compatible with new technology.

[ViewRVs]

Done!

Using my voltmeter, a 120v tester, the wiring diagram, and a BUNCH of testing, I have resolved my issue. Fortunately I was able to pull a new wire (12/2) through while pulling out the old wire!

After an inspection of the old wire, there was a spot on the wire that broke the outside wrap and the cover of the neutral wire. It is pretty amazing to actually see the source of the problem!

My coach is now plugged in properly to the house GFI and the wiring is showing correct on my outlet tester. The power is also going through the automatic transfer switch.

I am not sure when the issue occurred. I think there have always been multiple electrical issues with the coach. The reverse polarity switch lit up partly because one of the power cords with the coach was wired BACKWARDS. It also had several 30 amp marine twist fittings. All of the old power cords are gone and I have new cords. I also have a 30a/15a adapter to always test the campground post prior to plugging in.

Now on to the leaking radiator......

[bkahler]

Super! It's always nice to work through a problem like that and be able to see the actual cause.

Any time you drill through the skin on one of these rigs there is a risk of hitting a wire, especially if you're drilling into the ceiling.

Congrats on solving your problem!

Brad