Type NM in EMT

[LarryFine]

I thing Wayne is saying if you use an nm connector in a panel box then you don't have to have 1/4" sheathing in the box.

I got the impression that he was saying that a connector of some sort at the conduit entrance negates the requirement for the sheath to even extend to the enclosure, or like with my example above.

The transition fitting effectively changes the wiring method from a cable into a wire-in-conduit method.

 

[wwhitney]

312 does not have a blanket requirement for the sheathing to enter a cabinet (e.g. panelboard enclosure). Unless someone can point to wording in 312 that I missed?

312.5(C) requires the cable to be secured to the cabinet. You can do that with a metal NM clamp of the style shown below. The clamping mechanism is outside the enclosure, you could cut the sheath flush with the (cabinet-side) edge of the clamping mechanism, no sheath in the enclosure. [Not a good practice, I would find it annoying if I ran into it, but not a violation.]

312.5(C) Exception just says that if you don't want to secure the cable to the cabinet, you can instead do an installation that meets a bunch of other requirements. One of those is that the sheath needs to extend into the cabinet. But if you've complied with 312.5(C) via a clamp, the requirements of the exception have no bearing.

Cheers, Wayne

 

[Fred B]

312 does not have a blanket requirement for the sheathing to enter a cabinet (e.g. panelboard enclosure). Unless someone can point to wording in 312 that I missed?

312.5(C) requires the cable to be secured to the cabinet. You can do that with a metal NM clamp of the style shown below. The clamping mechanism is outside the enclosure, you could cut the sheath flush with the (cabinet-side) edge of the clamping mechanism, no sheath in the enclosure. [Not a good practice, I would find it annoying if I ran into it, but not a violation.]

312.5(C) Exception just says that if you don't want to secure the cable to the cabinet, you can instead do an installation that meets a bunch of other requirements. One of those is that the sheath needs to extend into the cabinet. But if you've complied with 312.5(C) via a clamp, the requirements of the exception have no bearing.

Cheers, Wayne
View attachment 2558685

312.5(C) doesn't specify the extent of sheath clearance with the clamp you have shown but 314.17(B) does and it states the sheath shall extend not less than 1/4 inch inside the box and beyond any clamp. (language added to 2017 NEC)
Thus your second statement above if applied would be a violation.

 

[wwhitney]

314.17(B) does and it states the sheath shall extend not less than 1/4 inch inside the box and beyond any clamp. (language added to 2017 NEC)
Thus your second statement above if applied would be a violation.

Agreed for enclosures within the scope of Article 314, boxes, used as "outlet, device, junction, or pull boxes." That does not include panelboard cabinets or other enclosures subject to Article 312: "cabinets, cutout boxes, and meter socket enclosures."

Cheers, Wayne

 

[Fred B]

Agreed for enclosures within the scope of Article 314, boxes, used as "outlet, device, junction, or pull boxes." That does not include panelboard cabinets or other enclosures subject to Article 312: "cabinets, cutout boxes, and meter socket enclosures."

Cheers, Wayne

Agreed for enclosures within the scope of Article 314, boxes, used as "outlet, device, junction, or pull boxes." That does not include panelboard cabinets or other enclosures subject to Article 312: "cabinets, cutout boxes, and meter socket enclosures."

Cheers, Wayne

So are you saying that even if every other reference related to NM installation all require the 1/4 inch of sheathing minimum to extend into an enclosure because you don't see the the added reference in 312 other than the exception in 312.5(C) the sheathing is exempt from the requirements. And even though it is also mentioned in 334, because the reference is in 334.15(C) any other area is also exempt from the 1/4 inch.
So your also ok with getting out of the drivers seat of your winnebago while in cruise control to make some popcorn because it didn't specifically state so in the owners manual.
No wonder we have almost a thousand pages of code and growing, and attorneys are getting rich.

 

[wwhitney]

So are you saying that even if every other reference related to NM installation all require the 1/4 inch of sheathing minimum to extend into an enclosure because you don't see the the added reference in 312 other than the exception in 312.5(C) the sheathing is exempt from the requirements.

Precisely.

And even though it is also mentioned in 334, because the reference is in 334.15(C)

That's only in the context of installation on basement walls.

Now I'm happy to say that best practice would be to bring the sheath at least 1/4" into any enclosure. But if one doesn't do that in a cabinet, there's no language in the NEC to justify calling it a violation.

Cheers, Wayne

 

[wwhitney]

So here's a related question. What do 312.5(C) and 314.17 have to say about pulling NM cable through a complete conduit run from enclosure to enclosure?

Seems like the cable shouldn't require securing to the enclosures, just like individual conductors don't require it. 314.17 has a reference to 300.15(C), so it's reasonable to read that as not requiring the cable to be secured to an outlet or device box when 300.15(C) applies. But 312.5(C)'s exception is very limited.

Does that mean that if I take a panelboard enclosure, run a short nipple to a four square box with a receptacle in it, and pull NM in the nipple, it's a violation of 312.5(C)? If not, why?

Cheers, Wayne

 

[Fred B]

So here's a related question. What do 312.5(C) and 314.17 have to say about pulling NM cable through a complete conduit run from enclosure to enclosure?

Seems like the cable shouldn't require securing to the enclosures, just like individual conductors don't require it. 314.17 has a reference to 300.15(C), so it's reasonable to read that as not requiring the cable to be secured to an outlet or device box when 300.15(C) applies. But 312.5(C)'s exception is very limited.

Does that mean that if I take a panelboard enclosure, run a short nipple to a four square box with a receptacle in it, and pull NM in the nipple, it's a violation of 312.5(C)? If not, why?

Cheers, Wayne

312.5(C) indicates a minimum 18 in raceway up to maximum 10 ft of raceway. Does your "short nipple" meet the minimum? But even if it does, the condition of the exception in 312.5(C) exception(1) cannot be met if raceway is continuous box to box. Also the general condition of the exception indicates the raceway comes out the top of the enclosure, thus your suggestion fails that point as well.
Even if your premise is accepted, the requirements remains that at least a 1/4 inch of sheathing protrude from the ends of the conduit into the enclosure. Also if NM sheathing is not visible or present the conductors of NM are not marked and would fail identification criteria unlike THHN or other individual conductors that all have marking on the conductors.
Both 312 and 314 have a part of the conditions the securing of the NM within 12 inches of entering the enclosure or raceway (where allowed). Thus a box to box conduit wouldn't allow for that condition to be met. Don't particularly see the safety issue in having a short box to box run as suggested but do see the identification issue if sheathing is not visible or present. Is it 12 or 14? NM or NM-B? A, old vs new, mfg vs mfg, had different insulation thickness and making quick visual identification difficult or impossible without the markings.

 

[wwhitney]

I decided to start a new thread for the "related question," as I decided it wasn't related enough and didn't want to confuse the question with other details from this thread:

312.5(C) and Cables in Raceways

A hypothetical: say we have a cabinet, a raceway connected to it, and another enclosure at the end. So a complete raceway from enclosure to enclosure, not a sleeve. And for whatever reason we use the raceway to pull in a cable instead of individual conductors. The raceway is properly sized...

xenforo.mikeholt.com

Cheers, Wayne

 

[roger]

I thought the OP was talking about a complete raceway but for the discussion at hand here is an illustration that I agree with.



Roger

 

[wwhitney]

I thought the OP was talking about a complete raceway.

Well, for a complete raceway, that brings up the "related question" I asked, does the cable still need to be secured to a panelboard enclosure to comply with 312.5(C)?

here is an illustration that I agree with.

That is just illustrating 312.5(C) Exception, which lets you skip securing the cables to the panelboard enclosure. Many of those requirements can be skipped if you instead figure out how to secure the cable coming out of the sleeve to the panelboard enclosure.

Cheers, Wayne

 

[roger]

For another possible never-ending argument, if you are standing on your head outside, is the sky up or down?

Roger

 

[wwhitney]

For another possible never-ending argument, if you are standing on your head outside, is the sky up or down?

If the 312.5(C) cable in complete raceway to panelboard enclosure question has come up before, I'd be happy to review any threads you can point me to.

Is this in the category of "common enough practice, should be allowed, 312.5(C) is missing the appropriate exception?" Should I prepare a 2026 PI?

Cheers, Wayne

 

[LarryFine]

Well, for a complete raceway, that brings up the "related question" I asked, does the cable still need to be secured to a panelboard enclosure to comply with 312.5(C)?

I responded there with:

"I agree with you that a cable in an enclosure-to-enclosure conduit may be treated as single conductors."

Then you said that you might not be agreeing with me. Too bad; I'm right.

Many of those requirements can be skipped if you instead figure out how to secure the cable coming out of the sleeve to the panelboard enclosure.

Such as the NM-to-EMT transition fitting or my NM clamp-and-female adapter method.

 

[LarryFine]

View attachment 2558687

This is a very specific installation, and different from a general box-to-box conduit.

 

[wwhitney]

Such as the NM-to-EMT transition fitting

Are you suggesting that if the transition fitting secures the NM to the sleeve, and the sleeve is secured to the cabinet, the NM is thereby secured to the cabinet? A transitive property of securement? Regardless of the length of the sleeve?

or my NM clamp-and-female adapter method.

Yes, I certainly agree than a clamp connector inside the panel, screwed into a coupling or female adapter outside the panel, would secure the cable to the enclosure.

Cheers, Wayne

 

[roger]

This is a very specific installation, and different from a general box-to-box conduit.

Did you read post #50?

Roger

 

[LarryFine]

Are you suggesting that if the transition fitting secures the NM to the sleeve, and the sleeve is secured to the cabinet, the NM is thereby secured to the cabinet? A transitive property of securement? Regardless of the length of the sleeve?

Yes, and more specifically, that the sheath need not reach the cabinet interior.

I connected NM to NMFC with a 2-screw clamp and a female adapter, effectively making a transition fitting, and stripped the sheath inside the flex, within 1" of the clamp, and all the way to the disconnect.

What's the functional difference between these two fittings from the cable's point of view?

Yes, I certainly agree than a clamp connector inside the panel, screwed into a coupling or female adapter outside the panel, would secure the cable to the enclosure.

And I'm saying that such a clamping assembly on the other end of the conduit would provide the same function (if not better), and allow a standard connector at the enclosure end.

 

[LarryFine]

Did you read post #50?

Yes, and I'm suggesting that those rules do not apply to an enclosure-to-enclosure conduit, regardless of the wiring method within.

 

[wwhitney]

I connected NM to NMFC with a 2-screw clamp and a female adapter, effectively making a transition fitting, and stripped the sheath inside the flex, within 1" of the clamp, and all the way to the disconnect.

So why isn't that a violation of 310.120(A)? Otherwise, I agree that the NM to conduit transition fitting, along with stripping the NM sheath, would be a change in wiring method, and so then 312.5(C) becomes moot, as a cable is no longer entering the cabinet.

If you don't strip the NM sheath, there's no 310.120(A) issue. But I think if the switchover clamp connector is far enough away from the cabinet, it's hard to argue that the cable is secured to the cabinet, making a 312.5(C) issue.

Cheers, Wayne