I want to run a couple of dedicated circuits in my basement. Can I pass through outlet boxes basically making 180 degrees? The wire would go in and out of the back of the outlet box. I'm in Cook County IL so all wire has to be in EMT. I want to make sure this would pass the building inspector. enter image description here

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The wire would be run through the back of 5+ boxes. The dedicated circuits are for home theater equipment. To wire in the outlets I’m planning to use a pig tail. I’m want to make sure I can pass the electrical inspection.

  • 2
    I think the question becomes one of box fill. There is a limit to how much stuff - wires, connectors, splices, receptacles, switches, etc. can be in any box. If there was lots of extra room then you're fine. But if a particular box was already nearly full then you may not be able to include 2 additional wires passing through. Dec 13, 2021 at 1:26
  • I think you may also be required to have enough wire to reach the face of the box, even if you are "just passing through" as "things may change" (doesn't change the box fill calculation unless it's quite long, but it's another thing to watch out for when it comes to possibly failing inspection. You could not cut that white wire and make a legit junction with that little slack.)
    – Ecnerwal
    Dec 14, 2021 at 0:38

1 Answer 1


Any unused open knockouts must be plugged. The plugs are ten for $1.

There are rules for "box fill" in which the wires and devices are counted and compared to the box cubic inches (which is stamped in the box or a standard book size).

This type of 1-gang "Handy-Box" has just enough legal box fill for 2 wires in, 2 wires out and 1 device/yoke. You don't have room for more wires also.

Every wire transiting through that box will add 2 cubic inches to the box fill calculation. So your plan isn't going to work with these little 1-gang Handy-Boxes... (unless you put no devices or splices at all in them, in which case they follow the same rules as a conduit body: if it fits in the conduit it fits in the box.)

Also, as a practical matter these boxes are too tight to comfortably fit an AFCI or GFCI receptacle in - and I'd remind you, if a circuit needs AFCI and you have EMT metal conduit to the first receptacle, you're allowed to use an $18 AFCI receptacle instead of a $40 breaker.

What you should get in the habit of using, instead, is a 4x4 metal box with a 1-gang "mud ring". This gives you the spacious room of a 4x4 box + the mud ring, or about 26 cubic inches between the two - double the Handy-Box.

If you need even more than that, 4x4 "deep" boxes (2-1/8") are 30 cubic inches, plus the 5 for the mud ring. If you need more still, they make super-deep boxes.

These boxes have plenty of elbow room, both for thru wires and for AFCI/GFCI devices.

With mud rings, you mount the 4x4 box flush with the 2x4 stud (or even up to 1/8" shy of it) and then the mud ring protrudes through the drywall.

These boxes with flanges can be a bit specialty (at least, in the rest of the country) and the big-box stores tend to overcharge for rare stuff... a real electrical supply should be more in-line.

You might need to trim the conduit slightly for a 4x4 box, since it is flush with the wall, not proud by drywall thickness.

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    Once I finally started spending the few extra cents on deep boxes, I never thought to myself, "Dang, there's just too much room in here and it's too easy to get all the wires and nuts folded out of the way of the devices I'm putting into this box."
    – FreeMan
    Dec 13, 2021 at 14:05
  • 1
    I just did my basement with BX using the 4x4 boxes + mud rings, they are a treat to work with
    – element11
    Dec 13, 2021 at 14:34
  • Thank you so much for the help. This really helped clear up a lot of mystery for me! Once again thank you so much for the help I really appreciate it!!!
    – pehaada
    Dec 14, 2021 at 3:35

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