Reading the 2018 NEC, near as I can tell, a conduit nipple from an electrical panel to a junction box doesn't need to be straight, only 24" or less in length. Is that right?

My house is old and the panel is in a challenging location where only the bottom knockouts are readily accessible. Because it's a split panel with meter, there aren't many knockouts in the bottom. I could run a couple more circuits through some 1 or 1.25" flex to a junction box in the crawlspace less than 24" away, and then run properly-filled conduit from that box. I think this meets code, but can anyone weigh in?

  • 3
    Just in case it helps: you're not limited to using only the factory-provided knockouts. You can drill your own holes in blank metal wherever you like. A hole saw may work, but a punch or step drill are better suited for this task.
    – Greg Hill
    Commented Sep 20, 2022 at 20:21
  • Yeah, and I've done this. It's getting harder, what with the concentric knockout rings and dwindling area.
    – Rick
    Commented Sep 21, 2022 at 0:10

1 Answer 1


"nipple" is just a buzzword used to describe a pipe or conduit run that is short. Nothing says conduit runs can only be 24".

The only 24" related rule I can think of is that If the conduit run is <=24", then "thermal derate" owing to numbers of circuits in the conduit does not apply. i.e. 310.15(B)(3)(a).

However, that rule already allows:

  • up to 4 circuits in a conduit if all are 15-20A.
  • up to 3 circuits in a conduit if all are <=40A

It doesn't say that explicitly, this must be derived from 334.80, 310.15(B)(16) and 240.4(D).

So the issue doesn't come up much, except with heavy feeder (or dual EV circuits which you should not be doing anyway, ask us why).

But if your intention is to install a large number of circuits, then yes, keep that conduit <2' long between junction boxes.

As far as curves, that doesn't matter. That's not mentioned in the rule.

However, remember the rule with conduit: All access covers must be accessible forever without tools or damaging the building finish, and all conduit pipe must be built out complete before ANY wires are added in. Thus, conduit must be built to be pullable. Corners must either be sweeps, certain listed elbows right at the end, or conduit bodies whose lids must remain accessible forever.

  • This is great, thank you. Yeah, I have a 40A EV circuit in the largest knockout, and the nipple derating exception will let me run another 30A circuit through there.
    – Rick
    Commented Sep 21, 2022 at 0:12
  • About access covers being accessible without tools…that doesn't mean the screws holding the cover on the junction box, right? These will be accessible in the crawlspace.
    – Rick
    Commented Sep 21, 2022 at 0:14
  • And why not run multiple EV circuits in a single conduit?
    – Rick
    Commented Sep 21, 2022 at 0:14
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    @Rick actually if the pipe is <2' you have no thermal restriction whatsoever, and conduit fill can go to 60%. Yes, the junction box cover must be accessible without tools. Obviously you need tools to get the cover off. Code is saying "don't use the cover's need for a screwdriver to rationalize also needing a screwdriver to get the panels off to reach the cover". Commented Sep 21, 2022 at 2:19
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    @Rick because when you get to that point, there are MUCH better ways of supporting multiple EVs and we should have a conversation about that. Really, most EV level 2 charger installations are woefully underinformed by knowledge, craft, and understanding of how EV charging works. Money is spent unnecessarily and in some cases services are overloaded. Commented Sep 21, 2022 at 2:24

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