How do you decide if an old existing non-grounding receptacle can be replaced by grounding receptacle? What do you look for and where do you look for it? Does the old BX cable without a bonding strip provide an adequate grounding path?
Reason I'm tossing this out to you is I visited a customer today where the homeowner is receiving financial aid in order to make home repairs, roof, plumbing, electric, etc. Basically, a building inspector looks at the property and makes very general recommendations. The homeowner then must get three bids from each of the trades required. The recommendation for the electric was to have a licensed electrician survey the property for faults and provide a price to correct them.
Another electrician had previously visited the home and gave them an estimate which included replacing 18 duplexes with grounding duplexes. I noticed the fairly new panel had one knob 'n tube circuit exiting out and up to the second floor. It was the sole circuit for the floor including a new gfci receptacle in the bathroom...eek! I removed a cover plate in one of the bedrooms and found a single BX cable entering without the bonding strip and of course the old RH type wires ready to shed their insulation. Somewhere someone had extended the knob n' tube with some BX. Nothing new here right? The thing that amazed me was that the homeowner said the other electrician didn't open the panel cover or any cover plates the whole time they were there. BTW, the home was built in 1903.
Obviously, aside from code issues here there are some business ethics issues also.
If it is the old BX without the bonding strip, that should automatically disqualify the use of a grounding outlet.
Usually, I'm looking at K&T or the really old cloth covered NM cable. I will install a GFI receptacle if the outlet does not serve one of the items in 250.114 If an equipment ground is called for, I do not run a, EG as permitted by 250.130(C) since, for a few bucks more, I can generally pull in a new circuit for the same amount of work.
Few things are harder to put up with than the annoyance of a good example.