I am renovating part of my house, and taking the time to update some old wiring that is now exposed. The old wiring is primarily #14/2c WITH NO BARE BONDING CONDUCTOR. This means that no device boxes are bonded to earth ground, and neither are the receptacles on those circuits.
I have run a new feed from a circuit breaker to a device box which now contains a UL/CSA approved Leviton AFCI/GFCI receptacle. This box is now bonded to earth ground. From this first device on the circuit, I ran a new cable, 14/2 with bare bonding conductor, to another device box for light switches (now bonded), with feed through to another device box with switches and junctions to old wiring. This last box has older wiring that feeds lights and receptacles that have no equipment bonding conductor. Are these last devices protected by the upstream AFCI/GFCI device (the ones with no equipment bonding)?? My understanding of this AFCI/GFCI device is that it detects differential current between the hot and neutral. If there is no equipment bonding to earth, and if a fault exits, where does that current go, and how would the AFCI/GFCI device function?