Is this the right way to ground fault protect both sides of an mwbc


is this the correct way to ground fault-protect both sides of an mwbc?
pigtail the (line) neutral to two separate gfci outlets, and pigtail the (load) neutrals to the neutral that's going outside.enter image description here

Best Answer

Close, but not quite. From the point of the two GFCIs onward, the neutrals must be kept separate.

Consider: if you had a device drawing power on the black hot circuit from a load farther down the line, and nothing on the red, which GFCI would its neutral return current flow through? Since they're just connected in parallel in your diagram, it would flow through both, and then trip both, since current out is not equal to current in within each GFCI. If you separate the neutrals, you can make sure all the current from the black hot flows back through its proper GFCI, and none crosses over to the other one.

Also note that this scheme will fail if you use any 240V devices on this circuit. The only way to do a mixed 120/240V circuit is with a 2-pole GFCI breaker.