I have a job roughed in,it is an addition to a bedroom not a new room, the second floor is fed by multi wire circuits,and for ease/ diversety I used two different existing circuits.I know I at least have to provide afci for the work I did But does the afci function properly on a multi wire circuit? Does the NEC demand that I, regardless of cost/hardship,feed my work with a new circuit from panel witch would still not protect the existing outlets in the room. help!