[AllanJ]

deleted .....................................

 

[AllanJ]

Here is a good shot of a panel and you can see how each phase is connect in a panel. Note all breakers on one side are on one phase as you might think. (snip)

Bolded word is a very bad typo. (Should read "Not".)

Thin breakers come in a variety of styles. The most common style is a two breaker tandem unit that fits in one breaker position. It snaps onto just one fin down the middle of the panel. Both halves are powered by the same leg (phase if you insist) and cannot be used together for a MWBC.

 

[AllanJ]

""A multiwire circuit shall be permitted to be considered as multiple circuits"" -- One (12 gauge 120/240 volt) MWBC can satisfy the requirement of two 120 volt small appliance branch circuits for the kitchen.

""For the purposes of this section a {MWBC} shall be considered a single circuit"" -- Where/when only one circuit is allowed to feed an outbuilding, one MWBC, both halves of which carry current and are breakered, is allowed.

""{G}rounded conductor"" -- "Neutral" is not an official term in the NEC code book. A circuit requires two conductors, plus and minus respectively if you insist. In some situations with metal all around you such as in an automobile, it has been expedient (saving the cost of and space occupied by extra wire) to use the chassis as one of the two conductors and that conductor, sometimes the positive, is for that make and model said to be the grounded conductor. There are a few situations, notably medium tension primary lines along the road in rural areas, where the dirt (earth, soil) below is the grounded conductor with just one metal conductor (the ungrounded conductor) carried on the utility poles.

Some three phase systems may have one of the 3 phases grounded and are called corner ground systems. These circuits do not have a neutral whose neutral to hot voltage is non-zero for any of the phases but may have a 4'th conductor as an equipment grounding conductor bonded to the phase that is the corner ground.