Appears no one so far has ever wired a house or paid much attention to how its wired. Takes about 90 seconds and a flat blade screw driver to see for yourself what is going on. If you’re worried about your wiring mtrot this will be worth it for peace of mind alone.
Three great big utility cables bring power into the panel. Two are connected to the breakers, one to each row of circuit breakers. Think of these as one being the 120v positive half of a 60 Hz sine wave, the other being the 120v negative half. Connected together they give 240v.
Easy enough if you want to flip a breaker off and pull it, which if you do you will see two great big copper bus bars. All 120v breakers connect to just one of these. All 240v breakers connect to both.
The third big cable is utility ground. Notice the utility ground is connected to a great big bus bar. Notice all the hot black wires come off each 120v breaker. Notice all the white wires connect to the same utility ground bus bar. So each of these seemingly separate 120v circuits runs from its own individual hot breaker through the house and your outlets and completes back at the same utility ground.
Might want to read the above sentence one more time. Because this is kind of hard to sink in. Because people have this false notion that circuits are separate when they are in fact all wired together. Pull the cover and see for yourself.
