So I just found out that the Federal Pacific Stab-Lok main lug in my apt has got to go. After opening the cover, I was surprised to see no ground wires at all in there. There is only a neutral bar. The apt was built in 1960, and the main breaker is outside and only 30A. Perhaps there is a metallic conduit carrying the line, but why would there no ground wires coming from the circuits? What options do I have? Can I just replicate everything in the new panel?
Thanks!
Metal conduit, if complete from panel to circuit boxes, can be used in place of ground wires.
The different colours of hot wires in the panel supports this.
Can test if the ground path is good the same way as with ground wires.
A multi-meter at a light/receptacle should show local standard voltage between hot and box. Here it is ~120 volts.
If built in the 60's, grounds probably were not required on the individual circuits. I'd guess you have the two prong outlets all throughout the apartment. If you verify the metal conduit is in fact grounded in the panel, two prong outlets can be replaced with self grounding outlets where the mounting screws for the outlets provide a suitable connection to the grounded junction box. If self grounding outlets are not available, you can ground the standard grounded outlets to the junction box with some copper wire, bare or green, from the outlet ground screw to a new ground screw mounted into the junction box with a 10-32 grounding screw.
@Jimmy Fix-it made an excellent comment about older junction boxes might not have the ground screw hole. In that case you can use grounding clips to attach the ground wire to the junction box. See photo below from home Depot who I'm not affiliated with in any way.
For reference, this is from the NEC 2020 Article 406 Receptacles (etc) on replacement of non-grounding receptacles.
406.4 (D) Replacements. Replacement of receptacles shall comply with 406.4(D)(1) through (D)(7), as applicable. Arc-fault circuit-interrupter type and ground-fault circuit-interrupter type receptacles shall be installed in a readily accessible location. (1) Grounding-Type Receptacles. Where a grounding means exists in the receptacle enclosure or an equipment grounding conductor is installed in accordance with 250.130(C), grounding-type receptacles shall be used and shall be connected to the equipment grounding conductor in accordance with 406.4(C) or 250.130(C). A(2) Non-Grounding-type Receptacles. Where attachment to an equipment grounding conductor does not exist in the receptacle enclosure, the installation shall comply with 406.4(D) (2) (a), (D) (2) (b), or (D) (2) (c). (a) A non-grounding-type receptacle(s) shall be permitted to be replaced with another non-grounding-type receptacle(s). (b) A non-grounding-type receptacle (s) shall be permit¬ ted to be replaced with aground-fault circuit interrupter-type of receptacle (s).
These receptacles or their cover plates shall be marked “No Equipment Ground.” An equipment grounding conductor shall not be connected from the ground-fault circuit-interrupter-type receptacle to any outlet supplied from the ground-fault circuit-interrupter receptacle, (c) A non-grounding-type receptacle (s) shall be permitted to be replaced with a grounding-type receptacle (s) where supplied through a ground-fault circuit interrupter. Where grounding-type receptacles are supplied through the ground-fault circuit interrupter, grounding-type receptacles or their cover plates shall be marked “GFCI Protected” and “No Equipment Ground,” visible after installation. An equipment grounding conductor shall not be connected between the grounding type receptacles.
If you have an ungrounded system, and would like to replace the old 2 prong receptacles with grounded receptacles (3-prong) then there are code accepted methods to do so. Please refer to NEC Article 406.4 for these methods.
