Another inverter/solar grounding question for the experts

My tests are not definitive but I have powered the trailer via shore power cord to a GFCI on my house and run the microwave 3-4 times without tripping the GFCI, so it seems to only happen on the transfer switch GFCI. I'll do some more exhaustive testing. Sounds like there is nothing "obviously" wrong with my setup which is what I wanted to originally confirm.

smkettner wrote:
I would plug the micro into a GFI on utility power.
See if it trips 50% of the time or even once in ten.