For example, I have a 12/3 cable in which the red and black wires are controlled via separate breakers. The 12/3 drops into a single-gang outlet, out of which runs a 12/2 to another room. Is there a word/term for this (joined circuit, sistered circuit)?
I'm looking for a polite term 😉
(EDIT: Changed /4, /3 to /3, 2 – all cables mentioned contain grounds)
Best Answer
From Wikipedia
Notes:
These types of circuits must use a double pole circuit breaker
While the NEC recognizes this configuration, there is open debate as to weather or not this is a safe practice. For more information see Understanding the Dangers of Multiwire Branch Circuits
EDIT
Multiwire circuits for 3 and 4-way switches
Switch legs, also called travelers must now be in a different color to be easily identified. A few years ago the white wire could be used as a traveler but code changed that to lessen the confusion of identifying the traveler. Now instead of running a piece of 14/2W/GRD or 12/2W/GRD for 3-way you have to use 14/3W/GRD or 12/3W/GRD. Same goes for 4 Way's also.