Okay, we have had the discussion regarding using the same neutral for two ciruits. IIRC the upshot was “it’s the lazy way to do things but it’s okay as long as each leg is on a dif. phase. Any ‘real’ electrician worth his/ her weight would run two 2 wire lines.”
Well how about this:
Consider quad boxes along a kitchen back splash. Each of these boxes will be on 2 circuits. Each quad has two duplex outlets, one on circuit #1 and the other on circuit #2. Rather than run two pairs of BX between each box, it would be much easier, faster, and take up less room in the boxes if I use the 3 wire method.
Sounds okay……….. BUT how will it effect the effectiveness of a GFCI outlet at the first outlet of each circuit. Is that an issue? Am I not so smart after all?
F.
Replies
It's absolutely an issue. The GFCI will trip if both circuits are in use. It works by comparing hot and neutral current. With the usual caveat, you can share the neutral for the home run, but you need separate neutrals from the GFCI's onward. And you need to get them the right way around in every box. Otherwise they'll trip the instant you put any load on the circuit.
-- J.S.
The only way that you can do that is either use a GFCI at each location or a 240 GFCI CB.
Either one will run up the cost enough to not make it worth it.