NM Question

[bjp_ne_elec]

Say you have a panel with a conduit that goes out the top (ref. 312.5 (C) Exception), through a 30" nipple and in to a wireway. Say there are six (6) 12/2 cables.

First, what's the ampacity of the 12/2 in this situation? Secondly, can the sheath of the NM be removed once it enters the wireway?

Thanks

Brett

 

[Pierre C Belarge]

The 12 AWG, NM cables would have an ampacity adjustment to 15 amperes.

Yes you can remove the sheathing inside of the wireway.

 

[bjp_ne_elec]

Pierre - thanks.

How did you derive 15A? I was thinking, using 334.80, where it states to use the 90 degree C column if you are going to derate. Then, I was thinking that you would derate 50%, referring to Table 310.15(B)(20(a) - as there are twelve current carrying conductors in the scenario. My opinion (and God have I been wrong before) that you would need 10 AWG for this 20 A circuit, that would be then allow you to take the 40A (90 degree C column), derate 50% --> 20A. Do you agree with this?

Also, I saw a test question like this - specifically showing the sheath removed in the wireway. This threw me, as first I couldn't see any reason to remove the sheath, and I mistakedly thought 312.5 (C) Except - at least at first read - disallowed the removal of the sheath. After re-reading it, it specifically talks to the fact that the portion in the conduit SHALL have the sheath installed.


Back to the scenario - have you seen anything similar to this, as far as an application? What I saw was a drawing, not an actual photo - and again, I'm just wondering what application would have this scenario. It's probably been run in to on numerous occassions - as it was in a review session that someone saw it - and I have to admit that I have never seen an actual scenario like this.
Thanks

Brett

 

[George Stolz]

(e) The cable sheath is continuous through the raceway and extends into the enclosure beyond the fitting not less than 6 mm ( 1 /4 in.).

I am confused. Is everybody else saying they can remove the sheath? :?:

 

[don_resqcapt19]

Pierre,

Yes you can remove the sheathing inside of the wireway.

312.5(C) Exception ... (e) The cable sheath is continuous through the raceway and extends into the enclosure beyond the fitting not less than 6 mm ( 1/ 4 in.).

Don

 

[bjp_ne_elec]

George - I'm also confused, thus the post. I've been getting mixed feedback, and really want to get a firm understanding of what the NEC really says here. I am struggling with why the sheath would even be removed.

Curious what the consensus is on this one.

Thanks

Brett

 

[bob]

bjp

Say you have a panel with a conduit that goes out the top (ref. 312.5 (C) Exception), through a 30" nipple and in to a wireway. Say there are six (6) 12/2 cables.
First, what's the ampacity of the 12/2 in this situation?

You started off using #12 and Pierre correctly answered you question.

The 12 AWG, NM cables would have an ampacity adjustment to 15 amperes.

Pierre - thanks.
How did you derive 15A? I was thinking, using 334.80, where it states to use the 90 degree C column if you are going to derate. Then, I was thinking that you would derate 50%, referring to Table 310.15(B)(20(a) - as there are twelve current carrying conductors in the scenario. My opinion (and God have I been wrong before) that you would need 10 AWG for this 20 A circuit, that would be then allow you to take the 40A (90 degree C column), derate 50% --> 20A. Do you agree with this?

You started with #12 and in the middle of the question, while we were not looking, you switched to #10. Pierre gave you the correct answer for #12.
#10 is rated at 40 amps 90C. With a 50% adjustment factor the rating is 20 amps. Which size are you using?

 

[bjp_ne_elec]

I'm not using any size, just trying to make sure I could answer a quiz question that I saw on a review. I'm also just wondering why you would do something like this - especially stripping back the sheath. Don't see the advantage to stripping it back.

Thanks

Brett

 

[George Stolz]

I say no, you can't strip back the sheath, by the section cited above.

As for a desireable reason to do so, I can't think of one.

 

[bjp_ne_elec]

Boy am I confused. Removing the sheath - allowable by the code or not?

 

[izak]

wow... i hope article 312 never makes it to arkansas.... nobody would know what to do..
heh
"how can i fit 6/2 wg into a 1/2 carflex if i cannot strip the sheathing off??"
hehee

 

[jwelectric]

Boy am I confused. Removing the sheath - allowable by the code or not?

George has answered your question and cited the code section that would apply.

 

[infinity]

He is asking if the NM cables installed in a raceway can have their jacket removed. His 30" nipple is between the wireway and the panel. 312.5(C)(e) does not apply.

 

[bjp_ne_elec]

Infinity - you're saying that 321.5 does not apply to the situation I laid out? Why is that?

Has anyone out there actually had a situation where they stipped the sheath on NM, other than tailing in device and junction boxes?

THanks

Brett

 

[jwelectric]

He is asking if the NM cables installed in a raceway can have their jacket removed. His 30" nipple is between the wireway and the panel. 312.5(C)(e) does not apply.

If this is not a raceway please tell me just what it is;

Raceway. An enclosed channel of metal or nonmetallic materials designed expressly for holding wires, cables, or busbars, with additional functions as permitted in this Code. Raceways include, but are not limited to, rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquidtight flexible conduit, flexible metallic tubing, flexible metal conduit, electrical nonmetallic tubing, electrical metallic tubing, underfloor raceways, cellular concrete floor raceways, cellular metal floor raceways, surface raceways, wireways, and busways.

 

[infinity]

Infinity - you're saying that 321.5 does not apply to the situation I laid out? Why is that?

Has anyone out there actually had a situation where they stipped the sheath on NM, other than tailing in device and junction boxes?

THanks

Brett

What I'm saying is that the exception to 312.5(C) is for a conduit stubbed up out of a panel with the NM cables entering it without, in this case, a wireway.

 

[bjp_ne_elec]

OK - if that's your interpretation, then where would the NM wires (as they have the sheath stripped back) be going?

Thanks

Brett

 

[infinity]

OK - if that's your interpretation, then where would the NM wires (as they have the sheath stripped back) be going?

Thanks

Brett

If your installation met all of the requirements of 312.5(C)exceptions, than the sheath must extend into the panel at least 1/4". Since you've installed a wireway your installation now is a raceway nipple between the panel and the wireway. You could remove the outer jacket from the NM cables and install the conductors within the nipple but now you may have an issue with the conductors installed in the raceway without marking as to the size and type of insulation, etc. This information would appear on the outer jacket of the NM cable but may or may not appear on the individual conductors which are now installed in the raceway. This requirement is in 310.11.

 

[jwelectric]

Brett
In 312.5(C) it states that NM cable MUST be secured to a panel period. The exceptions gives relief if this panel is surface mounted and the raceway is used as protecrtion only.

In 314.17(B)[metal boxes] and (C) [nonmetallic boxes] we are required to secure NM cable to the enclosure.

Both sections require the sheath to enter the box at least ? inch. Based on these sections I it would be a violation to strip out the conductors for any reason.

I know that you are hearing that it has been done and passed inspection, but based on the forum that you have posted in Exam Prep I think that an answer from the NEC is the only one that will be accepted on an exam.

 

[George Stolz]

You could remove the outer jacket from the NM cables and install the conductors within the nipple but now you may have an issue...

For a volley of references to fail such an installation, look at my last post in this thread. What do you think? Am I stretching it, or interpreting the quoted sections appropriately?