Connect RV to 20a outlet

Try turning off all of the circuit breakers in the trailer. Then plug the shore power cord in. Does the GFCI still trip? If not, then turn on one breaker at a time until it trips. The last breaker you turned on is the problem circuit.

Also, a defective water heater element can cause a GFCI to trip even though it doesn't trip the circuit breaker. Disconnect the water heater 120 connection and see if that keeps the GFCI from tripping.

Anything else on the GFI circuit? You may be trying to draw more than 20 with the addition of the TT.

Something in your trailer is probably wired wrong....maybe just the ground and neutral tied together. Need to get a qualified electrical person to help you find the problem.

Ozlander wrote:
Since the TT has a GFI also, you are plugging a GFI in to a GFI and I think that is a no no.

I asked that question a while back and was told, if it doesn't trip, no problem. here it trips, possibly a problem.
bumpy

Since the TT has a GFI also, you are plugging a GFI in to a GFI and I think that is a no no.

Maybe try one of those plug in GFCI circuit testers and see of there is a wiring issue...HD and Lowes sell them for under $10.

Does it always trip the SAME GVI outlet or is non specific? If it's always one circuit it's probably something ON that circuit. Could be as simple as a loose or disconnected ground wire.

Lots of possibilities. Process of elimination could take some time.

Are any high amp usage (electric heat, electric water heater, microwave, air conditioner, etc) items being used?

Are other items (power tools, air compressor, other trailers, etc) running on the same circuit?

Are you using an extension cord that is maybe too long, not heavy enough to carry the load, or, not in good condition?

Any electrical connections that might have moisture?

Something plugged into an outlet, in your trailer, that might be shorted or not grounded?

Still could be the outlet.

yep...even bought special gauge extension cord because of the distance from the outlet... thinking the CAMCO adapter is bad

Are all the extension cords, outlets, plugs wired correctly with 3 pins at each one? You have to have 3 wires or GFCI will trip.