I’m looking to run 3 circuits 20A 120VAC (3 wires per circuit; H,N,& G, 12 gauge THHN) together through 3/4” FMC. Circuits will have ground fault and arc protection breakers. Residential basement run to power kitchen outlets.

Code requires earth ground cable (EGC) for ground fault since exceeding 6’ length.

Each of the circuits ground wire will have a jumper connection to ground screw at each junction box.

I’ll be using listed connectors to connect the conduit to each junction box.

What I don’t understand is how to connect the EGC to the FMC. Since the FMC is not considered suitable for ground faults, I don’t see how to protect for ground fault inside the FMC. Is it enough to run a 12 gauge bare copper wire and jump it to circuit ground at the junction box, same as the box?

I have the NEC 2023 handbook.

  • I'm pretty sure the standard ground (bare or green) is all you need, but someone who really knows FMC can answer that. But what I am very sure of is that if you are running all three circuits together that you only need a single ground wire, not 3. And with that (well actually, even with 9 wires, but all the more so with only 7 wires) you can go down from 3/4" to 1/2" and save a bit. Nov 19, 2023 at 22:20
  • 1
    Metal junction boxes? Nov 19, 2023 at 22:29

1 Answer 1


The listed connector used to attach the flexible conduit to the (grounded) box is all that is needed to ground the conduit. The conduit only needs to contain a single Equipment Ground Conductor (EGC) of the appropriate size.

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