Trailer has a ground fault

[Josparkz]

I finished putting in a new 30 amp RV outlet at the house to plug the trailer into. I used a GFI breaker. As soon as I plugged the trailer in, it tripped the breaker. I checked all the cords, nada. Definetly the trailer with the ground fault. Electric water heater off. I can't think of any reason why the trailer itself should trip the breaker. Unless it is from going from a 50 amp to a 30 amp circuit with an adapter. So, I'll call the dealer and see if maybe they have a clue, then I have to start checking every circuit and device in there see if I can find something wrong.

[Old and soft]

You might start by turning of the gfi protected breakers in the trailer and see if it stops. Something about a gfi outlet downstream from another gfi outlet.
The 15a gfi outlet I plug my 30a trailer into at the house would trip when the trailer was plugged in. Replaced the 15a gfi with a standard outlet, and no more problems.

[Marcm157]

Has the trailer been plugged in to other sources like at an RV Park before? Are you sure that you ha ve the 30 amp outlet wired correctly? Why did you use a gfci breaker? And lastly, why did you install a 30 am outlet if your camper is 50 amp?

[us71na]

Start by turning off all the breakers in the trailer. If your GFCI doesn't trip, turn on one breaker at a time until it trips.

[kirkelli]

switch out your GFI plug at the house to a non-GFI and you'll be fine. Running two GFI's in series will trip themselves.

[Josparkz]

Originally Posted by Marcm157

Has the trailer been plugged in to other sources like at an RV Park before? Are you sure that you ha ve the 30 amp outlet wired correctly? Why did you use a gfci breaker? And lastly, why did you install a 30 am outlet if your camper is 50 amp?

Yes to other breakers.
Yes to wired correctly.
My understanding is that all outlets near water or accessible from ground level require a GFI for protection.
I had a couple of hundred feet of 10/3 SO cord, the 30 Amp cord caps, and a 30 amp box. I did not have parts to run 50 amps to the trailer , nor did I feel like spending up to $500 to buy them now. It was an upgrade o ver the 20 amp outlet I had run my motorhome off of.

[Josparkz]

Originally Posted by us71na

Start by turning off all the breakers in the trailer. If your GFCI doesn't trip, turn on one breaker at a time until it trips.

GFI tripped with the main off. I haven't yet had the time to start ringing everything out. Maybe start today.

[Josparkz]

Originally Posted by kirkelli

switch out your GFI plug at the house to a non-GFI and you'll be fine. Running two GFI's in series will trip themselves.

I disconnected the pigtail on the breaker from the neutral bus disabling the GFI function. Solved that issue. There is bit of debate on GFI in series statement. I'm thinking that there are a few GFI outlets in that trailer and they all are on the same breaker. I think that would disprove that theory, but then again, all electrical energy is just theory anyhow.

[Josparkz]

Originally Posted by Josparkz

I finished putting in a new 30 amp RV outlet at the house to plug the trailer into. I used a GFI breaker. As soon as I plugged the trailer in, it tripped the breaker. I checked all the cords, nada. Definetly the trailer with the ground fault. Electric water heater off. I can't think of any reason why the trailer itself should trip the breaker. Unless it is from going from a 50 amp to a 30 amp circuit with an adapter. So, I'll call the dealer and see if maybe they have a clue, then I have to start checking every circuit and device in there see if I can find something wrong.

I am wondering if the 30 A to 50 A adapter is what's tripping the GFI. Of course I think of this after I have disabled the GFI breaker w/o testing the cord with the adapter on it. Whoops. My mind tells me that what the adapter does is not doing the thing that trips a GFI. Until I get motivated to work in a hot panel again to hook the GFI function back up just to test that adapter the best I could do is test the adapter on a 15 amp GFI with another adpter to make that fit. This would not replicate the actual condition though, as having some hundred odd feet of extension cord and the attendant resistance and voltage drop may be factoring in the situation. Apparently though trailers tripping GFI's is a real common thing. I may have to dig out my old electrical formula book and figure what splitting the hot into 2 parallel legs does to the current flow on the neutral which is basically what a GFI detects. And then again, a ot of people say having a GFI downstream from another one trips it. Personally I don't think that's true, especially since I think all the GFIs in that trailer are daisy chained off the same breaker. But I will delve into that some more, also. Thank you all for responding.

[Yooper906]

Originally Posted by Josparkz

This would not replicate the actual condition though, as having some hundred odd feet of extension cord and the attendant resistance and voltage drop may be factoring in the situation. Apparently yhough trailers tripping GFI's is a real common thing.

In your previous post you are using a couple of hundred ft of 10-3? Is that right?

I see a huge problem with voltage drop and resistance, if I'm reading this correctly.

[Josparkz]

Originally Posted by Yooper906

In your previous post you are using a couple of hundred ft of 10-3? Is that right?

I see a huge problem with voltage drop and resistance, if I'm reading this correctly.

Maybe 125'. I'd have to measure. I would have to get the millivolt meter out to measure the drop. I have a plug in voltmeter in an outlet in the trailer that's reading 125V with no air conditioners running, so that's not too bad.

[JFlightRisk]

I calculate the voltage drop at almost 8 volts at the end of 125'

[Old and soft]

Look in a newer residential houses. Outlets are marked gfi protected, by a gfi outlet up stream. They don't put gfi outlets downstream from other gfi outlets. Is it because they are cheap, or is there some kind of ac theory (smart peoples guess) behind it? Don't believe I have ever seen a gfi protected (115vac only) 30 or 50a outlet on a campground power pedestal.

[Josparkz]

Originally Posted by Old and soft

Look in a newer residential houses. Outlets are marked gfi protected, by a gfi outlet up stream. They don't put gfi outlets downstream from other gfi outlets. Is it because they are cheap, or is there some kind of ac theory (smart peoples guess) behind it? Don't believe I have ever seen a gfi protected (115vac only) 30 or 50a outlet on a campground power pedestal.

Well, you are right about the pedestals.
I have not been in a new residential home for since well into the last century.
And I never wired any residential houses, just powerhouses <LOL>
As for the electrical theory, unless they taught that the one day I missed in my electricians apprenticeship, I never heard it then or in the subsequent several decades of code updates and other classes I took whilst I was a working electrician. I did learn day one that no one can know it all and that certainly includes me. This is the first time I've had to deal with an RV issue like this, so it is a learning curve. Forgive my ignorance
Nothing in the codebook against having gfi outlets daisy chained. In application it would be the the practical cost. You can run multiple normal outlets on the output of a gfi and they are protected. One thing I keep seeing is a series gfi devices can cause each other to trip. That's a new one on me. Not sure if I can accurately measure devices in the trailer to find the 6mA leakage that is all it takes to trip one. I also hear that inverters and converters sometimes bond the neutral to the ground which will also do that.

[Vicr]

Originally Posted by JFlightRisk

I calculate the voltage drop at almost 8 volts at the end of 125'

Not 8 volts. I entered his parameters and threw out a wag of 12 amps load and here is the result. (PS, I'm a licensed electrician).

[Josparkz]

Originally Posted by Vicr

Not 8 volts. I entered his parameters and threw out a wag of 12 amps load and here is the result. (PS, I'm a licensed electrician).

Thanks. I'm a retired electrician. let all my licenses go and forgot all those formulas I learned when I was a cub. <LOL> I had to dust off my Ugly's book to jog my memory last week.

[Vicr]

Originally Posted by Josparkz

Thanks. I'm a retired electrician. let all my licenses go and forgot all those formulas I learned when I was a cub. <LOL> I had to dust off my Ugly's book to jog my memory last week.

I retired last June 1 but renewed my license for 3 more years "just in case". In Washington State they require 24 hours of Continuing Education so we all keep up on the latest codes etc. The tools available on line are incredible and I wished more people would seek them out. I haven't used an Ugly's in years but that book was once the "Standard" for calculations and formula's.

[Vicr]

OK, to the answer. And the OP had it in post #14 in his last sentence. The grounding and the bonded neutral in an RV will cause a current flow difference between the hot and the neutral which trips the GFCI. A bunch of posters here need to study up on how a GFCI works before posting. Google "how a GFCI breaker works".

[Josparkz]

Originally Posted by Vicr

I retired last June 1 but renewed my license for 3 more years "just in case". In Washington State they require 24 hours of Continuing Education so we all keep up on the latest codes etc. The tools available on line are incredible and I wished more people would seek them out. I haven't used an Ugly's in years but that book was once the "Standard" for calculations and formula's.

I had a Ut, Wy, Mt, Or., Wa,Id, and Ak. I needed 24 hours of CE every code cycle. Most of the states would honor each other's classes. I did most of them in person, It was more fun. The union usually did them, one time that electrical inspectors association did one. I did some online when I was in Boston for a couple of years. I don't think they had state licensing at the time so they didn't have many CE classes, at least not for travelers.
Congratulations on your retirement.
Back to the conundrum. I had a little with the service manager at the dealership I got my trailer from. He feels that none of the converters, inverters etc.have a bonded neutral. He maintains that multiple GFI's can put the Hertz to each other and trip. I guess I'll have to put some more study into that. The logic of that seems to be escape me. I guess they don't make thos with coils to balance them anymore and are all transistorized so maybe it could unbalance a neutral. I mean you really had to keep your 277 Volt loads matched up good so they'd balance. I'm certainly having to get some cobwebs out from between my ears lately :-)
Thank you.

[Josparkz]

Originally Posted by Vicr

Not 8 volts. I entered his parameters and threw out a wag of 12 amps load and here is the result. (PS, I'm a licensed electrician).

You certainly did a nice job writing that all up.
And then I get to the last line, and it's all null and void because I'm using SO cord.
"These calculations do not apply to flexible cords. "