A ground fault interrupter was designed for Bathroom and kitchen use. All about moisture creating a path from hot to YOU. If you have a motor with brushes, the carbon dust creates a leakage bridge to ground, or the metal dust in a non brush motor. Leave the GFI in the bathroom where it belongs. So years ago i sold a TP grinder to a guy from our group. It worked fine for me for years. When he got it he called to tell me the motor was shorted out. Wanted his money back. I asked him how it was hooked up, and he said through a GFI box. Lose the GFI box I told him. works perfect. now for years.