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I'm considering running EMT through my shop for outlets, etc. Does the NEC allow me to use EMT as ground (i.e. no need for ground wire)?

A related question: I may run wire through the shop's attic to get to the other side. This wire will not need conduit (NEC specifies wire must be protected if it is in a "high risk" area). Can I transition from EMT to 12/2 wire inside the attic, then transition back to EMT on the other side? I'm guessing I could use either a three-strand cable or just staple individual THHN wires along either the ceiling joists or rafters.

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NEC recognizes steel conduit as ground. One recently active ignorant inspector does not change code, unless you have the same ignorant inspector and opt not to fight them.

You can choose to transition to NM cable in the attic (ground wire connected to the steel box at each end of the cable), though I would not recommend that (I've seen far to many gnawed-bare NM cables to trust them in likely rodent habitat) but you absolutely cannot "staple up THHN wires" without conduit around them. While it may not matter for your application, you are also then limited to the 60C column for wire derate, and if it's a hot attic that might impact you.

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  • NEC 300.3 Single conductors...shall only be installed where part of a recognized wiring method... – NoSparksPlease Oct 28 '20 at 0:42
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    2020 is definitely the year to Bring back knob and tube yeah, that's the ticket! – Ecnerwal Oct 28 '20 at 0:48
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You're conflating two different things:

  • Use of the EMT metal conduit wiring method, allowing use of individual wires inside the conduit.

  • EMT metal conduit used as part of the NM Wiring Method as one possibility for a damage shield.

You are allowed to transition between wiring methods, but only in junction boxes.

So you are proposing a multi-method layout, where it'll be mostly EMT wiring method but you'll be hopping out of it at certain junction boxes to use the NM wiring method, perhaps with also using the same EMT conduit as a damage shield.

All sounds fine to me.

You can't run THHN outside conduit, though.

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