Does anyone know if that's a true sine wave inverter, or just modified sine wave? (which really should be called modified square wave!)
It should, but there is more than one way to wire a 3 pin plug to a 4 pin socket. The "normal" way seems to be to wire the hot blade on the 15 amp, 120v plug, to both of the hot poles of the 240 volt socket. This will give you 120 on all of your 1 pole breakers. None of your 220 stuff will work. No harm if you turn them on, they just won't work. (however, if you turn on some 220 stuff and forget, you can burn your house down when the power comes back on. Happened to someone in my town. There is a bit more to the story of course.)
This should be mandatory applied to the
I think he means turn off all the breakers as a means of load control. The OP said the electrician installed an interlock. However, I agree, back feeding the mains is very dangerous. Being "careful" is not enough, you have to have an interlock. I have enough electrical experience that I "know" how to backfeed a panel safely, but for that same reason, I'd never do it. It's way to easy to forget. And if you think you are smart enough to do this, keep in mind that when you screw up, and backfeed your pole transformer, it's going to put ~10,000 volts on the street line.This should be mandatory applied to the main circuit breaker. You don't want to back-feed power into a "dark" grid, if anything for utility workers' safety reasons.
The size of the circuit is pretty much irrelevant. That's just your basic circuit for anything, and the furnace gets it's own circuit. The issue is the motor starting load(s). I have a oil burner, and I've tried to start it with a 1500 watt inverter, and it does not work. However, I also have a stack fan, which is not common. And it all starts at the same time. So the questions are- what kind of furnace, gas or oil? Hot air, or hydronic? Stack fan or natural draft?Would the built-in 1500W power supply power my house's furnace? It uses 120V 15A breaker. It seems like it would probably work? I wouldn't try it until summer when I don't need the furnace in case I blow up it's circuit board.