On the issue of two fuses:
I might have told you this story before, I don't remember:
Anyway: We were doing some redecoration/repainting of a room (at the engineering school) In order to do this, I took the covers off the socket outlets after having removed the fuse for the circuit. Oh yes, I checked: No voltage on the circuit.
Well, about ten minutes later I came back into the room and the lights had come back on. (People were busy working with the walls) I rushed to the fusebox angry with the idiot who had put the fuse back. The fuse was still out, where I had put it!
From the back of my head I remember that the lights were somehow connected to the outdoor security lights.
I did eventually figure out what was going on: The fool who had installed the outside security lights had put them on a randomize timer fed from a panel at the other end of the building. He had then for some reason felt it would be nice if the lights in "our" room switched on and off too. In order to achieve this, he took the live wire from the security lights outside and sneaked into a junction box in the room.
This meant that "my" circuit (and fuse box) was back-fed via the timer from another panel with separate main fuses! Real "sparky-killer"...
