I'm remodeling a place built in the 80s and found that the dishwasher and disposal are on a multi wire branch circuit - i.e. live wires come from separate breakers but shared neutral.
AFAIK in California to bring this up to code i only need to gfci the dishwasher (although if they have already adopted newer nec's maybe its disposal now too + afci - ill need to talk to my inspector).
I was originally hoping I could just throw a GFCI in place of the existing outlet at the box above the counter there - but seeing as how the neutrals are shared I don't think this will work.
At the breaker, the two circuits are on separate breakers one right on top of the other but oddly enough there is no bar/linkage piece to ensure that they flip together - perhaps they forgot it?
So what are my options for doing a GFCI correctly for the dishwasher? So far all I can come up with is:
a) install a double pole gfci breaker (very expensive, prefer not)
b) run another wire from the counter box to the box below the sink to allow me to do something like the below (running another wire would be really difficult in this situation):
c) install another box below the sink to give seperate boxes for dishwasher & disposal and then install GFCI on the dishwasher one (maybe disposal too?) - I am not actually sure if this would work, but if it did it would be the easiest/cheapest of these options: