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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.

  • AC/BX (unless you're dealing with HCF, which is highly unlikely) doesn't have a green ground wire, are you talking about type MC cable instead? – ThreePhaseEel Apr 25 at 11:41
  • Yes. Armored cable. I connected the green into the bar above the neutral even though it still seems strange to me. – Zannon Apr 26 at 7:59
  • Can you post a photo of the cable where it enters the box? You are conflating two products with different construction standards, different installation rules in the Code, and different properties in general here... – ThreePhaseEel Apr 26 at 11:40
  • This was the last pic before closing everything up. i.imgur.com/IDlNZQD.jpg i.imgur.com/XUe200V.jpg Also asked a friend about grounding the box itself. He said it wasn't necessary since the ground wire attaches to the outlet screw which is now in constant contact with the metal box through the tabs. Tester shows continuity between the outlet prongs, box and armor. Also this is how it looks at the breaker panel. i.imgur.com/OnEQeVE.jpg – Zannon Apr 26 at 20:49
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    Your friend is correct that that's a legal ground path provided you have good metal-to-metal contact between the receptacle's mounting yoke and the mounting tabs on the box. Also, you have metal-clad cable (Type MC), not armored cable (type AC, formerly known as "BX") -- AC/BX has a thin bare wire "bonding strip" under the armor, and also requires the use of "redhead" insulating bushings inside fitting throats. – ThreePhaseEel Apr 26 at 22:43
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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.

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