I recently replaced my home's load center. As part of that surgery, my breakers were also updated to (combination) AFCI breakers. My house has many Multi-wire branch circuits, so I also got a couple double-pole AFCI breakers to accomodate this wiring. I'll be re-wiring my house in the near future as part of a more comprehensive renovation that I'm planning, but I'm hoping to not have to do any re-writing currently since it'll be throwaway work.
My basement lights are on one of these multi-wire circuits. There is a three-way switch in the hall that, when turned on, immediately trips the (double pole) AFCI breaker. Are there any specific troubleshooting steps that I should take, or do I just investigate it like any other AFCI trip? All the other lights/outlets on the circuit are OK -- the breaker only trips (and will always trip) if the hallway light is turned on.
The second of the switches is the one on the right. I removed the switch on the left, it's not related (it controls a different light).