I am experiencing a very strange, intractable ground fault issue. I have a bandsaw that runs on a GCFI/ACFI-protected branch. It has a standard capacitor-start induction motor. Every OTHER time I start the motor, it causes a ground fault, like clockwork (NB: not an arc fault.) I will turn it on, it trips, I reset the breaker, turn it on again, it runs, turn it off and on again, it trips, ad infinitum. It's an old motor, and the wiring is a recent installation. I have another squirrel cage motor on the same branch for a drill press, and it never causes a trip. What on earth could be causing this ground fault on every OTHER motor start?
Edits to address comments: I know it's not an arc fault because the breaker has lights that indicate whether it's an arc or a ground fault or an overload fault that tripped the breaker. It's definitely a ground fault. I haven't tried it on other GFCI branches because it would be a pain in the but to get the saw over there, but I will look into doing so. It does not trip a non-gfci breaker.
The idea that it might be time running, and not the fact of starting it twice is an interesting idea mentioned in the comments. But I don't think that this is the case because I can run the saw for 20 minutes, turn it off, turn it back on again, and have a trip.
Best Answer
Well, it's not so much every other time as it is every second time. This suggests that something inside, be it a cap or something else, is storing charge which back-EMFs the second time you start it up. Then the breaker trips, everything dumps, and you start clean. If you can, see if you can :
I know from my days messing with CRT televisions that caps can hold charge for days.