[AT] engine heater

[Al Walker]

Hi Folks,
I've got an engine block heater that trips my ground fault outlet.  I am not able to explain it to myself.  My understanding is that current should flow from one flat blade in the plug to the other. Alternating, of course.  In between those two flat blades in the plug is the heating element.  I did not think this would leak enough current to the ground wire to trip a ground fault breaker.  If I disconnect that ground wire, it seems to work, but the plug gets pretty hot.  Is this normal behavior for a resistor heating element?
Al in NW MN