Why is it incorrect that "the neutral wires are not connected together before connecting to the outlet on the left" on the following image?
Multi-Wire Branch Circuit Incorrect Wiring
The two left outlets do not meet the NEC for a multi-wire branch circuit. If the neutral wires are disconnected with B phase power turned on, the neutral wire from the B phase outlet has line voltage.
Here's the correct wiring:
The neutral wires are connected together before connecting to the terminals on the left outlet. It is preferred that the line (black) wires be connected together before connecting to the terminals on the left outlet, even though it is not required by the NEC.
On the first image, if one would want to replace the left outlet and thus disconnect the neutral/white wire, all without disconnecting "Line B phase", wouldn't the neutral wiring be energized in both images? In what way does the first wiring then pose additional risk?
Moreover, I presume this would only pose a danger if NEC 210.4(B) would also be violated:
Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.
Since when following above code, "Line B phase" would have to disconnected "simultaneously" as well.
Side question: why is it "preferred that the line (black) wires be connected together before connecting to the terminals on the left outlet"? I think this referring to a "pigtail". But is this really "preferred", even if a receptacles has dual screws? Or just easier for the electrician?
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