OK, let's take this from the top.
Say you've got a modern house, which, probably, none of the houses you mentioned are. Amongst the many things in the National Electric Code, there's this bit: Major 120 VAC appliances get their one and only socket. Got a stove? Even if it's gas, It Has But One Breaker On It. Got a microwave? Same. Same for a fridge. Or a garbage disposal. (An electrician and neighbor of mine who did some work for me on a kitchen reno told me that a kitchen, in general, is the Highest Current place is a house. After watching him correct a 1960's-era house to code, I believe him.)
As you'll find out hanging around here, garages built to current NEC, if they have a single wall plate in there, have but One Breaker on that wall plate. So, if that wall plate has a 15A breaker, you can figure, pretty much, that a Tesla plugged into that garage socket is the One And Only Load On That Breaker.
So, if that Tesla Mobile Connector is doing its thing on 120@15A, it'll draw 12A, the max for a steady load.
Thing is, if one goes to any other 120 VAC socket in a house, at least outside the kitchen, anyway, there'll probably be four or so sockets and some lights on that single 15A breaker. But the further back in time one goes, the fewer actual breakers one would find in a house, and the more sockets one would find on a single breaker.
So, say that a particular room, with the lights on, might have three 100W lightbulbs burning away. That's roughly 1A per lightbulb, more if they're three-way with 120W or something; add 12A from the Tesla and, sure, one is going to pop a breaker that way.
Um. You might ask if the homeowner has had other problems like this. I've got a relative in an older apartment in the Boston area; she already knows that turning on the toaster, coffee maker, and hitting the disposal will pop the breaker. You get the idea. If this isn't uncommon for that homeowner, then, well, you know.
Heck: late last year my daughter got married and a bunch of us got put up in an rental house. There were air conditioners in every room; and, yeah, we had breaker problems.
Now, having said all that, there's
always alternative explanations. Breakers do wear out over time. Wires get loose. And it's just possible that there's something screwy about your Tesla Mobile Connector. But you've already said that it works vaguely normally in other places... so I'm still thinking old construction.
The one that really got me in your story is that during one of these escapades the
main got popped. Um. Let's get clear: The Main Breaker is the one in the breaker panel labeled with something like "100A" or "60A" or "200A". Blowing one of
those is out of the penny-ante, "too much current on a branch circuit" and straight into horror story land. You said that happened when you used something like a computer surge protector-type extension cord. Um. My thinking is that you fried something inside of it, it shorted, and the Mains Saved The Day.
Is this what you're talking about? Or was it simply a $RANDOM 15A breaker on the panel?
Last thing, since you appear to be new to all of this. Most houses/apartments/what-all in the US tend to run something called, "split phase". Three wires show up at the house:
- A neutral, which is roughly ground (and is often bonded to a ground bus-bar in the breaker panel, which in turn has a hefty wire going to a 6' copper stake pounded into the Earth)
- A hot, which is 120 VAC to Neutral
- And another hot, which is also 120 VAC to Neutral; but when one of the hots is going up in voltage (sine wave, right?), the other is going down in voltage; so the voltage from one hot to the other is 240 VAC.
After these suckers make their way through the meter they show up in the breaker box. One hot ends up on one bus bar; the other hot ends up an another bus bar; and the neutral (and ground) end up on a ground bar that goes everywhere.
If one looks at the breaker box, there's typically a vertical stack of breakers. Here's the tricky bit: First breaker connects to one hot; next breaker connects to the
other hot; third breaker connects to the first hot, again, lather, rinse, repeat, all the way down. On a 120 VAC circuit, a particular breaker will have a black wire coming out of it; a white wire is connected to the neutral/ground bar; and then the two of them go off to wherever they go, along with a green wire also hooked to the bus bar. The black goes to the hot blade on a 120 VAC socket, the white goes to the other, neutral blade on the 120 VAC socket; and the green wire goes to the ground pin.
When you've got a 240 VAC load, like for Air Conditioning (or a Tesla), people will use a
duplex breaker where two, say, 40A breakers are ganged together and go in adjacent slots. One of the two gets one hot; the other gets the other hot, and the two wires coming out of the duplex breaker have 240 VAC across them. Add a neutral and/or ground and send them off to their load, be it a NEMA14-50, the HVAC, or whatever.
Adding a dedicated 120VAC 15A breaker to an empty slot, and having that go to a 120 VAC socket in a garage is pretty trivial. If the breaker panel is in the garage then it's more trivial than that. But if you haven't messed with AC power before in your life, Now Is Not The Time To Do It On Your Own. That's what electricians are for
.
