HAD A customer that had a gfci fire in bath. They had a elect toothbrush charger pluged into one of the rec. The owner got up in night to use bathroom and saw sparks coming from gfci. He reached and unplugged the charger, and had a large arc that burned the wall and melted the gfci. He told me it tripped 2 breakers in panel. After looking into things, i discovered there were 2 circuits hooked up to the gfci. The circuits were on opposite sides of the bus, so he had 240v between the two at the gfci. Ive never run across this before so im wondering what happens when you hook up 2 circuits to a gfci. I ran A new dedicated 20 amp circuit to the bath to fix problem, but im wondering if i should be looking elsewhere for a more serious problem. I know in older homes they ran 2 circuits to the kit area on a 3 wire and removed tab on recep. to seperate circuits, but how would this work on a gfci?