All right. I'm going to admit something: Up to this minute, I wasn't really sure how the breaker on a 240 VAC mains breaker works. See the below picture:
So, note that a Standard house picks up three wires from the pole transformer:
- A Hot, 120 VAC with respect to Neutral, at 0 degrees. (It's a sine wave, so sue me.)
- A Hot, 120 VAC with respect to Neutral, at 180 degrees. (That is: When #1 is going up, #2 is going down.)
- A Neutral.
Say you've got a 100W lamp plugged into the wall. The NEMA5-15 socket has Neutral on one blade and #1 or #2 on the other, so it's 120 VAC across the blades. Current flows in on the Hot (more or less, yeah, it's AC), and out on the Neutral. When one goes outside the house with a clamp on ammeter, and say we're playing with #1 HOT, then, when somebody flips the switch and turns the light on, one will see 0.83A additional on #1 Hot and 0.83A additional on the Neutral, and #2 Hot will Not Change.
So, take a look at that picture. There's not a breaker on the Neutral: There's a double-pole breaker on the Mains breaker, with each pole passing Line1 or Line2.
Implication: Say that that's a 100A Mains Breaker. Run 150A on Line 1 and Neutral, but not Line 2, and the breaker should trip. Run 150A on Line 2 and Neutral, but not Line 1, and the breaker should trip. Implication: There's actually
two physical breakers in that Mains Breaker, and if either one of them trips, they
both trip.
So: Run 150A on Line 1, 150A on Line 2, and no current on the Neutral (which is the way it works with a 240 VAC load: It's 120VAC to neutral on each Line, but 240 VAC from Line 1 to Line 2), and
both of the breakers in the Main Breaker trips and it pops open.
One more bit of interest. So, on a standard breaker panel, say one is looking at breakers, vertically, and the wire coming out of single, 120 VAC breakers. Starting at the top, the output of the first breaker will (picking one) be Line 1; the output of the next breaker down will be coming from Line 2. The next breaker's output will be from Line 1 again, and so on, all the way down.
So, say one has three 100W lightbulbs turned on in different areas of the house. Depending upon completely random wiring, all three might be on Line 1; all three might be on Line 2; or there could be one on Line 1 and two on Line 2; or, finally, two on Line 1 and one on Line 2. In other words, all over the map and depending upon how the wiring electrician was feeling that day. (Any real electricians who feel like chiming in right now, have right at it.)
So, imagine that one has a 60A main breaker. And, for some insane reason, one has seventy 1A loads turned on in the house. (That's 70 120W lightbulbs or the equivalent: Kind of insane. But there are such things as 500W lightbulbs.) In principle, if one manages to pick the Right Sockets, one will pop the Main Breaker since it will have 70A on it. Or not: If one manages to get a 50/50 split on Line1 and Line 2, there will be 35A on each Line - and the breaker won't pop.
Deep breath, worst case. Say one puts in a 40A 240 VAC breaker pair in there and hooks it up to a Tesla. The Tesla does its thing and draws 32A on Line1 and 32A on Line2, simultaneously, and nothing on Neutral. How much headroom we got before the Mains at 60A pops?
Well, there's two breakers in there on Main, each is 60A, so 60-32 = 28A. On each.
So, say one has the Air Conditioning. the A/C is high power, so everybody likes to run 240 VAC to that thing. Say it's got a 30A breaker on it; max load would be 80% of that, so 24A. On each of the two Lines.
So, 28+24 = 52A. that leaves, with our 60A breaker, 60-52 = 8A.
100W lightbulbs, coffee makers, refrigerators, and the garbage disposal.. if the lights are running, the microwave is running (1500W!), and somebody is doing the dishes and runs the disposal, and Pop! goes the Main.
And now one knows why the Electricians were giving the OP a shifty look.
