Yes, there's that as well lol, definitely have to isolate it. But when you don't have heat you gotta do something. I've since put a transfer switch on my furnace.Stuff in this case includes the electric techs who work on the distribution lines while fixing the power outage. If generators are not isolated from the main grid, techs will find hot wires where they should not be energized. I doubt many techs are dumb enough not to check, but the potential for an electrocution is real, which is the main reason transfer switches are required.
Codes aren't enforced out here so they're more like suggestions