I’m trying to install a new light fixture in Chicagoland. From what I’ve read, junction boxes here do not have a grounding wire and are instead grounded through the junction box. Is there an easy way to confirm this? From what I’ve read it sounds like the threads and locknut in the junction box are telltale signs the box is grounded.

If so, is simply mounting the fixture enough (ie not connecting the light fixture’s grounding wire to anything). This seems to be what the previous fixture was doing. Is there any benefit to adding a grounding screw and tail?enter image description here

2 Answers 2


Your wiring method is conduit. Your box is grounded through the conduit.

The conduit is used as the grounding method.

You can see the locknut on the conduit in the box.

The other clue is colors, like the purple, in use meaning individual wire pulls through a raceway. Actually all the wires are labeled, which is another indication that individual wires were used.

If non-metallic conduit was used, there would still need to be a grounding wire to the box, but you can see it’s metallic.

  • "The conduit is used as the grounding method." -> "The conduit should be used as the grounding method." It's never a bad idea to test, just to be sure. You never know when a previous DIYer may have DIwrong
    – FreeMan
    Mar 26, 2021 at 18:00
  • @freeman in Chicago? Test a ground where you can see the metallic conduit end. I don’t even do that on commercial jobs but I might meg for a short on a feeder over 50 amps.
    – Ed Beal
    Mar 26, 2021 at 18:34
  • Thank you all for your comments. Any thoughts on whether I need to get a grounding screw and tail or will the fixture be connected to the grounded conduit via the mounting screws? The mounting screws appear to rest on a non-metallic surface on the fixture. Also, is it normal for there to be two black and two white wire to hook into? I was expecting to only see one of each.
    – RyanSlade
    Mar 26, 2021 at 22:48
  • Good answer Ed. Mar 27, 2021 at 5:46

When I want to see if something is conduit, I look for 2 things first: Is there writing on the sides of the wires; and do the wires go into a tube-like thing that lets it flop around. If I see that, plus all evidence of metal conduit, plus being in a jurisdiction where that's required anyway, I'd tend to assume you were all set.

If you really need to confirm it, then you can certainly go to the next box toward the panel, pop the receptacle out, affirm it's the same pipe by pushing and pulling the wires 1/2" and seeing if they move, rinse wash repeat til you're back at the panel.

If you aren't satisfied with the metal-metal contact the lamp provides, definitely ground it with a wire. In the back of the box should be a hole tapped #10-32 specifically for a grounding screw.

As far as 2 black and 2 white, that could be one of several things. Be careful no to disturb any evidence "the last guy" left you - in particular if you see a black and white wire-nutted together, that information is worth its weight in gold. (the white should be taped with black tape, but not all are).

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