Re: Two 15 amp breakers Vs 15 amp double pole

"Inside your main breaker box are two bus bars, one powered by the large
black wire, and one powered by the large red wire.  These two wires are
opposing 1/2 phases of the alternating current.  "


We are talking about the US, no? Then that is incorrect.

There are two buses, each 120v, that is how you get 240v. But they are not out of phase, the "phase" never enters into it. They are both the exact same phase.

Is the phases were opposed, voltage would always be zero.

It's confusing, because the term "3 phase" is used a lot, implying that there are two other phases. But house current is all one phase.