> Trying to detect 5ma of current going to the wrong place under a 48-amp load may be impossible
It's actually kinda easy - the way GFCIs work is pretty neat.
You pass the live and neutral through the same magnetic field sensor. So long as none of the current is escaping to earth, you get an equal current in each direction and the total magnetic field is zero.
The problem is you can get a 5mA leak to ground because of, say, condensation inside a socket. And ripping out your house's wiring in search of that is a lot of expense to deal with a relatively minor danger.
It's actually kinda easy - the way GFCIs work is pretty neat.
You pass the live and neutral through the same magnetic field sensor. So long as none of the current is escaping to earth, you get an equal current in each direction and the total magnetic field is zero.
The problem is you can get a 5mA leak to ground because of, say, condensation inside a socket. And ripping out your house's wiring in search of that is a lot of expense to deal with a relatively minor danger.