Wonder if this was ever code

[GerryB]

I was changing a few outlets in an older home the other day, 2 prong to 3. Bx wiring, all looked in excellent shape. So the 3rd one I changed when I tested it it said open ground. I pulled it out, looked at the bx clamp, etc, tested it right to the armor and no ground. In checking other outlets in that room and an adjacent room, (or trying to) the tester wouldn't go in on two outlets. They were 3 prong outlets and the ground prong was filled in with something. The room was redone she said a few years back due to a water leak. Being bx everything should be grounded which I informed her of. Question is if you did have an ungrounded system were you allowed to install a grounded outlet and disable the ground like that? I ask because an inspector told me you can disable one side of a duplex (break out the tabs) if a single receptacle is required.

 

[ptonsparky]

Ingenious method of making 2 wire devices out of 3. Most likely cheaper to buy the 3 and fill a hole vs buy the 2 wire. Should you? Probably not.

IMO, a duplex is still a duplex, connected or not. Again it's most likely cheaper than the single but where would you need a single that a duplex would not work?

 

[al hildenbrand]

Question is if you did have an ungrounded system were you allowed to install a grounded outlet and disable the ground like that? I ask because an inspector told me you can disable one side of a duplex (break out the tabs) if a single receptacle is required.

To my knowledge, this has never been a Code allowed practice (to block a grounding terminal of a grounding-type 15 or 20 Amp 125 Volt receptacle) on the old ungrounded wiring methods in lieu of using a two-wire nongrounding type receptacle. (I'm not talking about the "GFCI No EGC" exception of the GFCI era.)

The thing is, the wiring method is probably suffering from a discontinuity in the equipment grounding conductor (EGC) either at a loose BX cable connector, or, at a "rust through" of a portion of the sheath. Or some other break that might have been by a less than knowledgeable workman.

Historically, BX has been a grounded wiring method, and when the metal sheath bonding strip was added and BX became Armored Cable, even more so. The one exception in its use as a grounded wiring method was as the extension of existing Knob & Tube branch circuit in a dwelling.

 

[user 100]

I agree with al hildenbrand- you aren't allowed to fill/obstruct the egc slot on a grounding type receptacle. I would think that by doing this you would be modifying the device, and would violate its listing. And other than the armor being damaged if the bx is being be fed from an egc free wiring method-K&T, stone age nm etc, that could explain the open ground also.

 

[peter d]

One thing to keep in mind is that BX cable is not listed as a grounding path, and as such, should never be treated as such unless it's very short runs and integrity of the cable can be verified. I think the best course of action to take with old BX is to keep the system with ungrounded receptacles, as any current on the BX armor is a fire hazard.

 

[al hildenbrand]

One thing to keep in mind is that BX cable is not listed as a grounding path, and as such, should never be treated as such unless it's very short runs and integrity of the cable can be verified. I think the best course of action to take with old BX is to keep the system with ungrounded receptacles, as any current on the BX armor is a fire hazard.

BX that is still installed to the Code of its original installation (installed in the first half of the 1900s) was a grounding means, by those old Codes. If one were to reuse old BX by re-installing a salvaged length in a new assembly under today's Code, it is no longer acceptable as a grounding means.

Click Here for some Code citations for early BX.