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Ive run my EMT conduit and placed my boxes in my workshop and placed the wires. All is good except... my inspector says I cant use conduit as ground and must run a bare or green conductor to each box/outlet... I dont want to get into rules/lawyering but what NEC line tells me (him) that conduit is OK for residential grounding. My city (Tucson) is on the 2017 NEC rev. enter image description here

Am I reading this wrong?:

250.118 Types of Equipment Grounding Conductors. The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following: (1) A copper, aluminum, or copper-clad aluminum conductor. This conductor shall be solid or stranded; insulated, covered, or bare; and in the form of a wire or a busbar of any shape. (2) Rigid metal conduit. (3) Intermediate metal conduit. (4) Electrical metallic tubing. ...

and this:

358.60 Grounding. EMT shall be permitted as an equipment grounding conductor.

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    You're not reading it wrong. Your "inspector" is an idiot. 358.60 diy.stackexchange.com/q/74977/18078
    – Ecnerwal
    Oct 22 '20 at 22:23
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    I don't think it would do me well to fight him on it. Ill note the NEC articles on use of EMT for ground, as I 'prepare' my team to fish a ground wire into all the conduits... I wonder what else he has wrong.. uggg.
    – mark f
    Oct 22 '20 at 22:53
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    I found the one page Tucson variance page, nothing about this. Oct 22 '20 at 22:57
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    The only situations where EMT is not OK as an EGC are on a roof where it can get stepped on, or in a pool or body-of-water area where conduit simply isn't trusted for grounding at all due to deterioration issues. Oct 22 '20 at 23:42
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    NEMA technical article 97 - the link in my answer to the related question was broken, but I've fixed it.
    – Ecnerwal
    Oct 23 '20 at 0:39
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Yeah, that's wrong. The inspector ought to know better; clearly does not inspect a whole lot of commercial installations.

Gently stand up on the point and show him the code, and leave him a path to keep his ego intact (that is less than you pulling a bunch of pointless ground wires). That's part of negotiating.

By the way, if you do pull the trigger on pulling ground wires, the ground wires go to the boxes not the receptacles. They land on a 10-32 ground screw (which doesn't need to be green), which goes into the hole in the back of the box already tapped 10-32. When bringing a ground to any metal box, you must go to the box first. Once that's done, if you also want to bring ground to the recep, you can do that also e.g. via pigtailing. #1 mistake I see grounding metal boxes.

In cases like yours, where the recep will have hard flush metal contact between its yoke and the junction box mud ring or domed cover, that is a valid grounding path and ground wires are not needed. So remove that little paper square that captures the receptacle screw!

On switches it's even easier, you don't even need to remove the paper square and you only need screw-head contact with the yoke.

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  • "leave him a path to keep his ego intact" <-- a very critical part of the process!!!
    – FreeMan
    Oct 23 '20 at 16:44
  • So I had my inspection for the Service entrance today with a different inspector and he agreed EMT is fine for grounds but reminded me to tie the grounded boxes into the outlets (mine have a tie at the yolk mounting screw). Since I've already added that extra wire to bout 3/4 of my branches, I'm just going with it since I don't know which inspector ill get for that part....
    – mark f
    Oct 27 '20 at 22:58
  • @markf Yes, self-grounding receps can ground via the mounting screw. (all switches can too). Otherwise you need to run a ground jumper to the box, unless you have hard flush contact between yoke and metal box unimpeded by paint, rust, or those little squares that keep the screws from falling off... Oct 27 '20 at 23:45
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Legal or not, it's no longer a good practice to use only the conduit as the EGC (electrical grounding conductor) because of the predominance of electronic equipment. Electroni power supplies of all kinds create Common Mode Noise and that needs a solid ground path to avoid becoming a problem in your system. As conduit connections age and corrode, it adds resistance to the ground path and CM noise finds another path, sometimes through expensive sensitive equipment. The NEC is only concerned with safety, not equipment life.

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    I work exclusively in EMT, and I've never heard that. I can't imagine what difference that would make: proper EMT installation entirely envelops the current-carrying conductors with a Faraday cage. I can also assure you that 1960 era EMT that is tarnished and rusting is a fantastic conductor of hundreds of amps, having put that to a live-fire test due to an incident. Oct 23 '20 at 14:35
  • The Faraday cage issue is separate and no argument that EMT provides that benefit. CM noise however is a different issue and is a relatively new phenomenon because of the explosion in the use of electronics where electronics were not originally being used; chargers, CFL and LED lamps, EC motors, servos, VFDs, inverters of all kinds, etc. etc. etc.. But everyone is entitled to an opinion, I just like to err on the side of reliability. and longevity.
    – JRaef
    Oct 27 '20 at 19:04

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