Riograndeelectric said:
what about 250.122 Tables
That's still using contemporary Code on an existing installation assembled under an earlier Code.
LarryFine said:
I'd say you absolutely can use grounding receptacles on the existing under-sized-EGC NM cable. It was compliant when installed, and if any original receptacles were grounding, they were installed using that same undersized EGC.
I agree with Larry, but with a caution.
When the requirement for NM to have an EGC manufactured in it went into effect, the installation techniques varied from electrician to electrician. The real question is whether the 16 gage EGCs, in the installation that is the subject of the Opening Post, are adequately spliced along the path back to the Service.
The first summer of my apprenticeship was the last summer that the reduced gage EGCs were manufactured. I was actually taught to do nothing more than twist the EGCs together for about five wraps and then to run one under the device grounding terminal. There was no bond to the metal boxes. There was no pressure connector, solder or anything else, used on the twisted EGCs. When we occasionally worked on weekends, outside of the local jurisdiction, the AHJ joined our crew (for a second job), and he instructed us on this exact technique.
Where I work now, the consensus is that
existing Flexible Metal Conduit, of any length, as originally installed, IS an effective EGC. On such a circuit, a 2 wire receptacle can be replaced by a grounding receptacle, with appropriate bonding at the wall case. However, if I add or change conductors in the FMC, I must pull in an EGC.
Also, old AC, with or without the drain wire, is an "effective" EGC. On such a circuit, a 2 wire receptacle can be replaced by a grounding receptacle, with appropriate bonding at the wall case.
IMO, the real question is whether the resistance of the EGC is low enough to be "effective" as an EGC under the original Code in effect at the time of assembly.