Can a TDR be used to find faults in electrical installations. I know they'll work on long cable runs but if you tried to use one to find an open wire in a building, would you get a bounce off of every wire nut, lug, and terminal screw between you and the open?

Yes, you would see every splice and tap, but the reflections from those would be a lot smaller than the reflection from the open conductor.

I don't think that it would be the technology of choice to hunt down an open in a building though. I would think that some sort of signal injection and sniffing scheme would serve better than a TDR in that application.
Joe