CAFCI/GFCI Gremlin on sub panel

Droopy said:

Ok, I've got an issue I can't figure out to save my life.

Background: I'm putting in a 100a sub panel in my detached 2 car high bay garage. Other than a 50a and a 30a 240v circuit(s), everything is on 20a circuits with CAFCI/GFCI Plug on Neutral Homeline circuit breakers (https://www.homedepot.com/p/Square-...and-GFCI-Circuit-Breaker-HOM120PDFC/204844661). I've got 2 circuits going to separate single pole switches that switch several outlet in the ceiling for lights. 6 more circuits are for wall outlets (Paired outlets every 4 feet or so with power from 2 different 20a circuits.)

So, got it all done. Powered up and checked each outlet with a circuit tester. They all show hot and wired correctly. However, one of the outlet circuits (labeled "C" on the attached photo) trips when I switch on either of the switched circuits ("A" or "B"). I've swapped breakers around to make sure it's not a bad breaker. The switched circuits go up to the ceiling in EMT to a junction box where I've spliced them into Romex running to the switches and outlets. The circuit that's being tripped goes up in a completely separate EMT conduit to a separate junction box before being spliced into Romex and going to its respective outlets. The Romex for the 3 circuits is only in close proximity for about 5 total feet and I've carefully checked to make sure a staple or something hasn't damage any of the wires.

When I check the DF fault code on the breaker, it shows a ground fault. Note that it only trips when A or B is powered AND switched on.

I can't think of what else to check. Ideas?

Thanks,

JohnView attachment 90483

Click to expand...