On 2007-12-24, BobK207 wrote:

I have had trouble with motor loads tripping GFI's.

The fact that it trips when the fan is turned "off" leads me to
believe what you're seeing is not a true ground fault (current leakage
to ground) but "merely" a difference between the instantaneous
currents on the hot & neutral wires.

I'm an ME but I did study some motor & circuit stuff in
school.......here's my best attempt at an explanation, when the fan
is turned off, the magnetic field of the windings of the motor
collapses & induces a current back thru the neutral (since the hot
lead is switched & therefore open).

The GFI senses this slight current as mismatch between hot & neutral
currents & trios.

Hi Bob,

If this is the story, what is the proper way to deal with this? Is
there a type of motor that can be specified and which would minimize
this effect? Would it be acceptable practice to switch both the
neutral and hot to the motor? If so do double pole switches break
both connections sufficiently close to simultaneously to avoid the
induced current imbalance?

Thanks, Wayne