For the last 12 months my 2nd floor lighting + outlet circuit, with a Siemens Combo AFCI breaker, has tripped a few times. At the point of each trip I made a half hearted effort to work out what happened, but I couldn't reproduce it. Today it happened again and I decided to get properly in to it. After some time unplugging things and checking wiring in receptacles, I came up with nothing. I thought maybe the AFCI breaker was going bad, so I switched it with a dual function GFCI/Combo AFCi Siemens breaker. Much to my surprise with the DF breaker in, and the panel re-energized, the 2nd floor bedroom circuit tripped immediately and would not come on at all. I went through all my outlets and switches again and made sure everything was off and unplugged. Back to the panel, flip the DF breaker, and it comes on and stays on now. I set off plugging things back in and flicking lights back on and eventually I got to the problematic light switch. It was then that it became clear what was going on. Roughly around a year or so - maybe a little more - in this very same switch box, I had a contractor install a smart light switch which required a neutral pulling from a nearby outlet. What he either did not know, or did not care to mention, was that the outlet he pulled the neutral from was on a different circuit. The outlet he pulled from is dedicated to my washing machine. To be fair, I was not aware that the washing machine had a dedicated circuit. Never noticed it in the panel. Anyway, I've come up with what I think are few options for solving this, and I think I know what is probably the best one, but I would appreciate any feedback. For the sake of clarity I'll call the 2nd floor circuit A, and the washing machine circuit B. a) I could open the switch box on circuit A, cap the circuit A line coming in, and pull circuit B's line in, so the switch and light receives line/neutral both from circuit B. However, the neutral from the light fixture does not come back to the box. So in this configuration - does moving the switch on to the other circuit satisfy the AFCI safety on circuit A, and so could it maintain either a Combo AFCI or DF without further trip issues? And still in this configuration, presumably, circuit B (which presently has neither AFCI/GFCI) would still work, but then couldn't have AFCI because it'd trip in the same way Circuit A has been doing? b) Back in the panel, where there is a lot of junction wiring already, I could tie circuit A and circuit B together, the line and neutrals both, and then feed them in to a single pole AFCI or DF? The main issue here is one of load - there's not much on circuit A, until summer when we do have a couple of air conditioners on it. So I feel like I should probably keep the washing machine on its own dedicated circuit. c) Also back in the panel, I could tie the neutrals for A + B, and then feed that and the independent A+B circuits in to a dual pole combo AFCI? This gets me combo AFCI on my 2nd floor circuit, and gets me AFCI on my laundry circuit to. So I should eliminate my tripping, and I gain another circuit with AFCI protection. I think. Are there other options? I am thinking I should do C.

I googled and could not find a good answer for this one, I am replacing one overhead light, currently there are 3 sets of wires in the base , Set-a 3 wires (black and hot, white, bare copper) Set-b 3 wires (black, white, bare copper) - don't know what is it for Set-c 3 wires (black, white, bare copper) - to the switch itself I connect the black-a to white-c, and black-c to light, then light to white-a, the light works okay, but I am wondering if I am doing it correctly, what should I do with the rest wires? Especially the Set-b wires? Should I cap black-b with the (black-a|white-c), and white-b to white-a, and all the ground together?