I was trying to replace a fan/light in my living room with a new led light, and have found that the living room branch circuit (lights and outlets) is actually fed by a Multi Wire Branch Circuit (14-3) that powers both the living room and a second branch circuit that only powers two kitchen lights. As an MWBC, The two circuits share one neutral and one ground.
I had suspected something might be funky, because a tester in a living room outlet had indicated a bad ground, which I understand would happen in this case, though it is also my understanding that both circuits would actually have a working ground.
At the panel, the MWBC is properly attached to two adjacent slots but the two breakers are not linked together, as code says they should be. After turning off the living room circuit, I was fortunate to check for hot wires before touching anything, so I was able to figure this out and turn off the kitchen lights branch circuit before I touched a hot wire.
Anyway, my question is, how can I fix this? Two options I was thinking about were: replacing the two breakers with a dual pole breaker so that they trip together and no one risks touching a hot wire like I almost did. I have been slowly adding GFCI/AFCI protection to other circuits; would I be able to find a dual function, dual pole 15A breaker like that? (Square D Homeline panel). Would the shared ground and neutral being shared cause problems with this? Secondly, I was thinking about just eliminating the branch circuit that powered the kitchen lights (disconnecting and wire nutting the hot wire at the panel and the junction box, and labeling them as such), and combining the kitchen lights and living room lights and outlet onto one circuit. I will be replacing the two kitchen lights with leds totalling only about 35 watts, so am I correct in thinking that the extra power draw from adding the kitchen lights to the living room circuit would be negligible and OK to do?