I ran 10/3 BX cable to my attached garage for an outlet. The BX has its own green wire for grounding, but since my home is grounded all through the conduit/outlet boxes and is bonded to the neutral in the breaker panel, do I still need to connect the ground wire from the BX cable in the breaker panel? I connected it on the outlet end just because.
Electrical – Should I connect the ground wire to the panel when the conduit is grounded
circuit breakerelectricalgroundinggrounding-and-bonding
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Best Answer
First, don't use obsolete cable because it may not comply with current Codes.
Rule of thumb: If the cable has a ground wire, you have to use it. Only certain types of metal-jacketed cable are allowed to use the jacket as the ground wire. On the types that are not, they include a ground wire.
Since you are in all metal boxes, you ground this cable to the ground screw in the back of your junction box. Most junction boxes do not come with a ground screw, but they do come with a hole tapped #10-32 for the purpose of adding a ground screw. Any #10-32 machine screw will suffice -- however they make cute little green ground screws, with or without pigtails preattached.
If there is no hole tapped, add a mounting screw and then remove each of the existing mounting screws in turn, just to make sure they didn't accidentally use the tapped ground hole for a mounting screw. Otherwise, you can tap one yourself, it must be #6 or larger and -32 or finer. Common sheetmetal screws are Right Out.
If you need to land more than 1 wire on the ground screw, pigtail it.
Lastly on the panel's neutral-ground equipotential bond, don't misinterpret that. Neutral Is Not Ground. That one bond in one location in your electrical system (at the source) has a special purpose. Neutral and ground must never connect anywhere else, and one should never be used as a substitute for the other. Each wire has an independent job to do (one returns normal current, one diverts fault current) and conflating them creates a dangerous situation.