circuit breaker peak amperage

My understanding, not necessarily accurate, is that the GCFI trips if there is more than only a few milliamps of stray induced current flowing through the circuit's ground wire. The current measured by the clamp-on ammeter measures current flowing through any two of the three wires in the circuit. The surge that's tripping the breaker is flowing through the hot and neutral wires and doesn't involve the ground wire (probably green in color but it could also be an un-insulated, bare wire. GCFI is designed to detect a bad ground connection. It is not a surge protector. If your dehumidifier draws an excessive surge when starting up, it would trip a normal, non-GCFI 15 amp breaker as well. It's not the GCFI feature that's causing that breaker to trip. I'm sure I'll be corrected if I've got this wrong.

The GFCI trips on _tiny_ <milliamp> _imbalance_ in the current carrying wires or tiny flow in the ground wire. Breakers and fuses have a time-curve to allow short duration "overload" for starting surges. I've heard that breakers can go weak if they have been tripping a lot .. if it wasn't a warranty job replacing the breaker might be a first-step .. John T.

The GFCI is not a circuit breaker. It detects ground faults, not overcurrent conditions.

Had the same problem with my central vac. It was determined to be the surge current on startup - which required a "high magnetic" 15 amp breaker. Single 15 amp high mag breakers are not carried in Ontario and I wasn't about to order one from Quebec. I called Square D and they told me all 2 pole Squsre D breakers were high magnetic so I just threw in a 2 pole in (thankfully I had space) and the problem was solved.