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I'm looking to transition NM cable out of 1" EMT using a transition coupling. In the usual case, I read that the right product looks like the photo below. I find many of those for 1/2" EMT (like the photo), but nothing for 1". Is there a common way to do this with 1"? I'm planning to put one or two 10/3 NM cables from a receptacle box, up a cinderblock wall protected by conduit, and then transition them in the ceiling joist area. Many thanks.

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    When you say "transition NM cable out of 1" EMT" do you really mean you intend to run NM in EMT? You'll probably need bigger EMT than 1" for two 10/3 cables - fill calculations are extremely unfavorable for cable in conduit. It would also be extremely unpleasant to pull (unless your conduit is only a short, straight run). You should really run individual wires (THHN/THWN) through the conduit to a junction box, where you splice to NM.
    – nobody
    Feb 13 at 0:42
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    Running individual wires will also let you use much smaller conduit, between the more favorable rules and the fact that you only need six wires instead of 8 with NM (instead of two ground wires you can have zero - just use the conduit itself). Six 10AWG THHNs will fit in 1/2" EMT.
    – nobody
    Feb 13 at 0:49
  • I believe fill calculations are more favorable when the EMT is used as a protective sleeve, which is my use case. What I don't know is how to exit the EMT properly.
    – Brent
    Feb 13 at 0:56
  • So have you done the calculation?
    – nobody
    Feb 13 at 1:06
  • If I'm not mistaken, for short sections of EMT used as a protective sleeve, no fill calculation is required at all. Short seems to be undefined, though some people seem to put it at two feet or less. (The inspectors in my area allow longer than two feet.) I'm happy to be corrected if I have this wrong...
    – Brent
    Feb 13 at 1:32

3 Answers 3

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I think the connector you are looking for is hard to find because it isn't required.

334.15 Exposed Work. In exposed work, except as provided in 300.11(B), cable shall be installed as specified in 334.15(A) through (C).

(B) Protection From Physical Damage. Cable shall be protected from physical damage where necessary by rigid metal conduit, intermediate metal conduit, electrical metallic tubing... Conduit or tubing shall be provided with a bushing or adapter that provides protection from abrasion at the point the cable enters and exits the raceway.

It says "bushing or adapter". Most electricians just use Arlington EMT100 push on bushings for 1" emt. They are cheap and readily available at any electrical supply house.

Conduit fill limits are a little tricky, I would use an online calculator using manufacturers "major diameter of the ellipse as a circle diameter" as required by the NEC.

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    Thanks for this helpful info. I did the conduit fill calculation, and if I'm not mistaken, two 10/3 cables of my size (422 mils) are allowed in 1-inch EMT, even when using it as conduit and not as a protective sleeve.
    – Brent
    Feb 13 at 3:02
  • Two 10/2 sounds right. FWIW sleeve exception accepted as being defined in note 4 of chapter 9 table 8 : "(4) Where conduit or tubing nipples, not including connectors, having a maximum length not to exceed 600 mm (24 in.) are installed between boxes, cabinets, and similar enclosures, the nipples shall be permitted to be filled to 60 percent of their total cross-sectional area, and 310.15(C)(1) adjustment factors need not apply to this condition." Feb 13 at 3:41
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NM routed through a protective metal sleeve (as opposed to a conduit system) doesn’t need to be clamped to the sleeve. You can just put an anti-chafe bushing on the end of the sleeve (so the NM doesn’t get cut on the edge of the metal sleeve) and then staple it down per usual outside the sleeve.

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The obvious answer would be a small box, or a fitting with an access panel that can be used as a box, to contain the splices between the individual wires in conduit and the BNC, with appropriate fitting in each side. Don't forget to make sure safety ground is carried through properly, including grounding the metal conduit and connection box. Note that the box must be accessible for maintenance; you can't bury it behind a wall surface.

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    Between the OP's wording and the 1/2" clamp they showed, it sounds like they're planning to run NM in EMT.
    – nobody
    Feb 13 at 0:44
  • Ah. Missed that, if so. In that case the only question would be how to exit E MN T cleanly, which would be more about avoiding risk of sharp edges than about clamping, right?
    – keshlam
    Feb 13 at 0:46

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