replying to Ed, Will wrote:
I know this is an old thread, but I just solved the exact same issue and
thought I'd post for future reference.

Turned out that I had a grounded neutral on the afci circuit. To test for this
turn off your main breaker for the panel and open it up. Disconnect the
neutral wire from the afci breaker. Use a multimeter to test the resistance
between the now loose neutral and ground. If it's close to zero then you have
a grounded neutral. Afci breakers will not carry a load if the neutral is
grounded. I didn't have anything plugged into that circuit so it only tripped
when the fridge or well pump turned on. The afci breakers are extremely
sensitive and I guess that the fridge and pump pull enough power that they
induce a small amount of current in adjacent wires and the breaker flips. You
then need to clear the grounded neutral. This could be a ground wire touching
an outlet terminal or a nicked wire. Mine turned out to be a neutral touching
a box that never had the drywall cut out around it. Cut it out, installed an
outlet, problem fixed!

--
for full context, visit https://www.homeownershub.com/mainte...on-141899-.htm