You are correct Grasfulls,
A simple series circuit is does not equate to a househouse circuit with several parallel connected devices and/or circuit branches.
The current in the entire circuit is likely not the same.
A circuit element that is easy to understand this for is one that includes an EMI filter. A filter with common mode filter elements.
The current is not the same on both sides of the device.
With these dimmer devices they may likely produce additional high frequency currents on the line side as well.
Over many AFCI problem threads I have suggested adding an EMI filter to the device in question causing the nuisance trip ( like treadmills).
Adding an EMI filter to an entire circuit may well eliminate nuisance tripping but the question then becomes will you then prevent the ability of the AFCI to also detect a true arc signature and thus render the AFCI install completely worthless?
One thing that I have not seen any manufactures make obvious is the fact that AFCI's may indeed be rendered worthless if a circuit has enough high frequency impedance between it and the load outlets it is intended to protect.
I can see where given time to evolve, the algorithms used to detect arcs, that manufacturers would get better at distinguishing between a true arc and a common dimmer current signature.
In particular a true arc signature will have some random elements associated with it whereas a dimmer signature will be constant ( given a constant dimmer brilliance setting).
When the dimmer setting is changed it would then take some finite amount of time for the algorithm to recognize the change and adapt. This finite amount of time is what makes the task so difficult. Attempting to interrupt the circuit fast enough to prevent a fire, yet delay long enough to recognize and prevent nuisance trips.
Do the Eaton breakers you received have the diagnostic LEDs on them or is there another method used to read out the failure diagnostic information?
No manufacturer of AFCI's should ever have been allowed to release a device without some sort of diagnostic readout. At bare minimum the ability to distinguish between a GF or an arc signature is must.
