In a Dark Attic

[al hildenbrand]

. . . does this mean that prior to the installation of the bonding strip in AC cable you could use the outer jacket as an EGC?

Yes.

I know, for the wide variation of BX installations I've seen the patterns in, if the BX was mechanically connected, with a BX connector and anti-short bushing, to an enclosure that was already bonded in some manner to the EGC, then the sheath on the BX was considered an adequate grounding means for the BX connector on the far end of the cable, and whatever the connector was mechanically connected to that was conductive.

The one real caveat involves the widespread practice of extending K&T circuits with BX, in the installations I see. I see a lot of simple extensions to add one new outlet (a duplex receptacle or a switch loop for a light) that are not grounded because they used the Code exception that cites "isolation", or "insulation" as alternatives to grounding the sheath of the BX. That is, in a typical wood frame dwelling, in the first half of the 1900s, one could wrap tape around the outside of the BX were it crossed near a heating or plumbing pipe and then the rest of the run was considered isolated by only being in a wood, plaster and lathe structure.

Back then the installation of a three prong self-grounding receptacle was always considered to improve the safety of the installation.

I still hear this.

Of course, a polarity tester needs to read correctly when plugged into that newly installed grounding type receptacle.

 

[pfalcon]

The plumbing looks so much newer. You don't suppose he installed over those wires?

 

[Pierre C Belarge]

The plumbing looks so much newer. You don't suppose he installed over those wires?

Taking another look, you may be correct. Maybe the plumber respliced, because the wiring was in his way.

 

[LarryFine]

It would be better to cut the ground prong off the attachment plug than have an install where the hot conductor faulted to the box and apply voltage thru the ground wire attached to the screw on the faceplate and end up on the equipment on the other end. A three wire receptacle on an ungrounded circuit can create the same hazzard.

That's why EGC are not to be connected when using GFCI's on ungrounded (i.e., 2-wire) circuits and extensions.