I often deal with homes that were wired or rewired with the old style armored cable without the bonding strip. Most of them have had 3 wire receptacles added at one time using self grounding receps or pigtails to the box. Of course I know this cable is not approved for grounding, but now when I am called in for a new buyer I have to be the bearer of bad news and tell them the receps should go back to 2 wire.
There are probably millions of homes wired this way and whats more, the boxes are already grounded by the BX and there's nothing that can be done about that. And it seems that the most likely place for a H-G fault is going to be in that box, with all its old dried out insulation and perhaps a sharp edge on the BX to boot!
So am I doing the right thing here by telling homeowners they can't have grounding receptacles on this type of wiring? After all, it only extends the grounding six more feet from what's already there.
Or is the main risk that an uncleared ground fault will transfer to the user through the grounding pin?
