Before I built my pole building, I would plug in my Super C with a 50A to 15A dogbone to a GFCI outlet that convenient from where it was parked in the driveway. My stock WFCO Converter would trip the GFCI occassionally. Never had any issues when I was plugged into a regular 15A outlet.
I eventually replaced the WFCO with a Progressive Dynamics Converter because I wanted a better Converter / Charger. I can't remember if I ever tried it on the GFCI once I got the garage built. In any case, I did check all the wiring in the coach, including the outlet the Converter was plugged into and everything checked out.
The total length of the wire in a GFCI circuit can have an effect on the GFCI outlets performance. When you get over 100 - 150' capacitive leakages can occur due to the wire length of the circuit and may exceed the threshold of the GFCI. The actual length limitations vary depending on wire type and size. If you have a 50' extension cord and long wire runs through you house on that GFCI circuit, it could be contributiing to your issue.
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