Another circuit breaker problem

[djb75]

We have a 2018 GT27FB. Recently, it started tripping the 20A circuit breaker in our barn - it hadn't been doing that before. On inspecting the trailer's circuit breakers, I found the GFCI breaker was malfunctioning and replaced it. However, the trailer is still tripping the barn's circuit breaker as soon as I plug it in.

In an effort to track down where the issue is, I turned all of the trailer's circuit breakers off. However, even in this state the trailer trips the barn breaker as soon as I plug it in. It seemed to me that turning all of the breakers on the panel off should have prevented this.

The only electrical things I've changed since the trailer was out last are adding soft starts to both air conditioners (I was able to test them out successfully on the same barn circuit that is now tripping) and install new batteries.

Any ideas what the problem might be and how to test for them? Any suggestions gratefully accepted.

[Wazbro]

Is the barn breaker GFCI?
Can you plug anything else in to the barn breaker and have it work?

[djb75]

Yes and yes. It’s a GFCI breaker and I can plug the fence charger and a battery charger into the circuit without tripping the breaker.

[djb75]

My current working theory is possible rodent damage between the shore power connector and the main block. But I’m hoping someone will have a less involved explanation!

[tinstream]

Try unplugging the inverter. It seems the issue is between the barn and the trailer’s distribution. The inverter may be a direct connection to the shore power and if that’s correct, it could be a place to begin. Also check the power cable for breaks.

Tinstream

[jeffmc306]

djb75, do you have an onboard (hardwired) EMS on your trailer?

After I installed a Hughes Watch Dog inside our Globetrotter, it tripped the GFCI outlet on the garage. I finally installed a 30A dedicated circuit for the trailer to get around the issue.

[ITSNO60]

Switching off all the breakers will not eliminate a N-G fault, in order to do that you also need to disconnect all the circuit neutrals.

If you suspect the power cord, disconnect that first where it connects inside in your main panel and cap off the wires, then plug in your power cord. If the GFCI trips it's in your cord, if it doesn't trip it's in one of your circuits.

The 3 most common suspects are water heater, absorption fridge heating element and converter.

[djb75]

I tried plugging in the power cord without it being connected to the trailer, thinking it might have an internal short. But that didn’t trip the breaker. I’ll take a look at the inverter in the morning.

[PaulBristol]

I agree with Brian's post above.

Sometimes switching circuit breakers "OFF" will identify a ground fault. Sometimes not.

Both hot and neutral must be disconnected to test and isolate a circuit.

Any 120 volt appliance can cause a ground fault. Loose or corroded connections can cause a ground fault.

Some old design converter/chargers had a built in fault, but since your system worked before, then that is probably not it.

These things often develop ground faults:

Electric water heater. Heating element develops an internal leak that starts small and gets bigger. Disconnect hot and neutral at main breaker panel.
Absorption refrigerator. Again heating element develops a leak. Disconnect both hot and neutral at any convenient place. Some can be unplugged, easy.
Outdoor 120 volt outlets sometimes corrode causing current leak. Disconnect hot and neutral at outlet.

Failing that, systematically disconnect each main panel breaker and its corresponding neutral one at a time. I do it one at a time so I get everything back in place where it belongs.

I wish you good luck and happy trails ahead!

[djb75]

Jeff - no hardwired EMS, and I tried this with/without my external EMS - no joy.

Paul/Brian - thank you for the insight into N/G faults. I'll be pulling circuit breakers today. I tried unplugging the refrigerator, but it still trips the barn breaker. Based on your comments, I'll start with the breakers that cover the water heater and converter, then work outwards from there.

[uncle_bob]

Originally Posted by djb75

Jeff - no hardwired EMS, and I tried this with/without my external EMS - no joy.

Paul/Brian - thank you for the insight into N/G faults. I'll be pulling circuit breakers today. I tried unplugging the refrigerator, but it still trips the barn breaker. Based on your comments, I'll start with the breakers that cover the water heater and converter, then work outwards from there.

Hi

Pulling the breakers is no different than switching them off. It has no impact on a ground to neutral short.

To find a ground to neutral issue:

1) Unplug from shore power. Switch off all the breakers. Leave them off.
2) Put an ohm meter between ground and neutral on the plug. If you are lucky, you will spot the short that way. Head off and start pulling *neutral* wires on the panel. Eventually you will find the bad one.
3)If the ohm meter doesn't spot the issue, you are off to pulling the neutrals one at a time and using the ground fault to spot the issue.

This is not a "zero hazard" sort of thing to be doing !!!!

Bob

[NIdaho]

If a GFIC breaker is tripping -- DO NOT REPLACE IT A NON-GFIC Breaker

The way a GFIC breaker works is that it compares the current going out on the "HOT" conductor with the current coming back on the "NEUTRAL" if it is not the same (or at least very close to the same) then it knows that there is leakage to Ground (a problem) and trips the circuit off-line. This can save your life or the life of someone you love.

You said that the only change had been the addition of the soft-starts. Disconnect them and see if you still have the problem. If you still do then you will need to get into the trouble shooting.

Do you have the electrical schematic for the trailer? It will help greatly in trying to figure out the problem.

Later,

Bob
(FYI I am an Electrical Engineer as well as a HAM radio operator, . . .)

[JCWDCW]

Originally Posted by djb75

I tried plugging in the power cord without it being connected to the trailer, thinking it might have an internal short. But that didn’t trip the breaker. I’ll take a look at the inverter in the morning.

Quite probably this
Try to use your multitester to track continuity between the hot and ground
I'v seen this before and it was a cut 120V power supply grounding out after the trailer input

[djb75]

Just to make sure of our nomenclature, when you say "neutral wire", you're referring to the bare copper wires on the back row of the panel, yes?

And a followup question - they should correspond positionally with the circuit breaker they belong to - so the leftmost wire goes with the leftmost circuit breaker, etc?

I just want to make sure before I start pulling wires and plugging back in!

[NIdaho]

In a 120 Volt AC circuit you will have 3 wires:
[*]Hot -- wire will be black or red (or marked as such) per the National Electric Code[*]Neutral -- wire insullation will be white (or marked white)[*]Ground -- usually bare or sometimes Green or Green/yellow

The Neutral is bonded to Ground at the Service Entrance (first disconnecting means past the Meter)

There SHOULD NOT BE ANY OTHER Bonds/Connection between the Neutral and GROUND !

[ITSNO60]

Originally Posted by djb75

Just to make sure of our nomenclature, when you say "neutral wire", you're referring to the bare copper wires on the back row of the panel, yes?

And a followup question - they should correspond positionally with the circuit breaker they belong to - so the leftmost wire goes with the leftmost circuit breaker, etc?

I just want to make sure before I start pulling wires and plugging back in!

No, the neutrals are white. Follow your hot wire back to the jacket where it enters the load center and the white in that same jacket is your neutral. For testing disconnect it from the bus and cap it.

There is no specific order on the bus bars, just neutrals on one and grounds on the other.

[djb75]

At last, progress! I've traced this down to circuit #2, which the owner's guide identifies as the "front a/c". Of course, the other a/c is labelled "bedroom a/c". But we have an FB model and the "front a/c" is also the "bedroom a/c", so there's still some ambiguity. I'll see which one the thermostat can find and then start examining the other.
Thanks to all who have gotten me this far!!

[CBraun77]

Originally Posted by djb75

Yes and yes. It’s a GFCI breaker and I can plug the fence charger and a battery charger into the circuit without tripping the breaker.

If there is a GFI on the Airstream circuit and you plug that circuit into another GFI you will have two GFIs on the same circuit. That can cause one to blow...not always...but it does happen. I had a water distiller with a GFI plugged in to a GFI outlet and had that start happening.

Try plugging it in to a non-GFI circuit.

[sdavis2616]

Since you tested both AC’s I would suspect you might have pinched a wire when you installed the soft start. Sometimes a pinched wire will take awhile to break through to the copper. I would also recommend changing to a 30 amp breaker if your barn wiring can handle the current. The trailer inverter will probably pull more current when it’s first powered on than the battery charger so your 20 amp breaker may be weak.

[djb75]

I found the problem. It looks like one wire got scraped against the sheet metal while I was wrestling the strain reliever into position. Apparently it just took time for the wire to "relax" to short out. A couple of wraps of electrician's tape and all is well again.

Thanks for all of the guidance with this.