I've got some outdoor conduit within which are three separate branch circuits:

  1. A general purpose, 20A outdoor receptacle circuit
  2. A 15A HVAC circuit
  3. A 40A EVSE circuit

I am using NM-B for each circuit on the indoor segment that connects the breaker to the conduit, at which point I transition to THWN. The NM-B has a ground wire included, and I know that I only need to ground the conduit to the 8AWG wire from the EVSE circuit. My question is, should I not connect the ground wires on the 15A and 20A circuits to avoid creating a ground loop, or does it not matter?

  • 1
    You shouldn't have to worry too much about ground loops if you're lined up on runway centerline. Seriously though current does not normally flow through ground so it should be fine. Mar 21, 2017 at 2:44
  • "Ground loops" are almost a non-issue in AC building wiring that some folks feel the need to make a big stink out of. If you were wiring a commercial recording studio with tons of sound equipment, maybe. In a home, don't even give it a second thought. Mar 21, 2017 at 16:30
  • That was my impression, however, I am fairly used to electronics design (including some PCB fab) where ground loops are sources of endless frustration. That said, the closest equivalent here would actually be neutral loops, not ground loops.
    – Hari
    Mar 21, 2017 at 18:00
  • @SpeedyPetey -- even for a recording studio, the ground loops themselves are not a problem until you add gear that has pin 1 wired wrong on its audio connectors. Fix the Pin 1 problems, and the hum will go away, ground loop or no ground loop. Mar 22, 2017 at 2:01

1 Answer 1


The "ground loop" in question does not matter one bit -- the NEC assumes all involved EGCs are connected together at all junctions, even. (It's impossible not to have them all connected together in a metallic conduit system, for one.)

Note that there are a few exceptions for isolated grounds for certain sensitive equipment, but the benefits of isolated receptacle EGCs are unclear. (Note that the redundant earthing requirement in patient care areas is not an isolated equipment grounding requirement!)

  • @Kris -- there is sensitive equipment that recommends isolated grounding, but it's not medical equipment -- patient care requirements are for redundant EGCs not isolated ones Mar 21, 2017 at 3:31
  • @ThreePhasEel after i typed the comment I remembered just that! Thanks !
    – Kris
    Mar 21, 2017 at 11:55
  • @ThreePhasEel A dedicated circuit is basically an isolated ground, no?
    – Kris
    Mar 21, 2017 at 11:56
  • @Kris -- not necessarily, especially in a conduit/metal framing environs Mar 21, 2017 at 22:12

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