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frani

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Retired electrical contractor/instructor/inspector
I just have three questions and would like some imput. The insulation on romex is not approved for wet locations. So with that you are not allowed to strip the sheathing off and use the conductors inside of sealtite to wire from a weatherproof disconnect to an AC compressor in a home. So.....is it against the code to wire the weatherproof disconnect that is mounted to the house with romex that is feed from inside?
The second question is SEU/SER cable is used on the exterior for services. The insulation is XHHW-2 (printed on the sheathing) so this means the cable is approved for use in wet locations (outside). If you were to install SER in PVC and run it outside and underground to a garage for a sub-panel (10' away from house) this would be against the code. Is the only reason that this is against the code is because each conductor in not labeled with XHHW-2 only the outer sheathing? If this is the case then why can it be installed for services?
The third question is anit-short bushings (redheads). They are installed on BX cable but not required to be installed on MC cable. I realize that the casing on the BX is the ground and MC has it's own insulated grounding conductor, but isn't the anti-short used to prevent the sharp edges of the metal from possibly cutting through the insulation (or chaffing) on the conductors.
 
I can only comment on questions one and three as I haven't used any XHHW-2 wire in a long time. Question 1-No the installation is code compliant because the conductors are inside of an approved box and (I believe) are THHN/THWN rated which would allow the installation.

Question 3-Refer to manufacturer's instructions. I believe we have a few threads on the red heads and MC/BX. Remember that the MFG's instructions trump the NEC in certain areas. I have never needed them on BX, only MC.

Edit to add: Though I don't see any problem with the proposed installation in Question 2, I do not have my NEC handy to check it out. I would think that in this case piping the XHHW-2 like using UF in pipe in an exterior application is permitted, but I will let greater minds then mine comment on that.
 
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1) It is not a violation to terminate NM cable on the outside of a dwelling in a weatherproof disconnect. Just use an approved NM clamp to enter disconnect.

2) I believe the reason SER cable is not approved for underground use is because the aluminum EGC is not insulated. It is only protected by the outer sheath of cable.

3) The fittings listed for MC cable by design may not require an insulating bushing or may have a bushing included in the fitting. The installer should note the instructions with the fitting to determine if a bushing is included with the fitting. The fitting manufacturer may have listed the fitting as usable with Type AC or Type MC cable and thus a bushing is included with the fitting. The bushing in this case may not be required but the installer should verify with the fitting manufacturer if the fitting was listed with or without the bushing for Type MC cable.
 
Don't try to think through uses permitted/not permitted for cables by looking at the types of individual conductors. On NM most of the time the conductors aren't labeled individually. If they're labeled as THHN/THWN, great, you can strip the sheath and use them individually as THHN/THWN. One issue with NM in wet or damp locations is the paper in the cable. There was also a thread on here a while back where somebody (480sparky I want to say) had an installation where a piece of NM went from an outdoor bell box to an ordinary JB inside. Water from the bell box got through the romex, whether by wicking through the paper or capillary action, and caused a short in the indoor JB. This is a case where even if the conductors in the romex were THWN rated it wouldn't have made a difference. Individual conductors in conduit wouldn't have done the same thing because of the lack of paper strip and they're too far apart to have a capillary effect.
 
Jd-

you are right. I was just parroting back something someone told me at one time....But that brings up this question next...If I have conductors labeled THHN/THWN and I strip them out out the NM jacket, is that a violation?

Edit to add: I'm asking because of an issue a friend is going through right now because of this.
 
kkwong said:
Jd-

you are right. I was just parroting back something someone told me at one time....But that brings up this question next...If I have conductors labeled THHN/THWN and I strip them out out the NM jacket, is that a violation?

Edit to add: I'm asking because of an issue a friend is going through right now because of this.
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Nope, not a violation as long as the unsheathed conductors meet the same labeling requirements as THHN bought on a spool. If the inspector never knew it used to be a cable they wouldn't have any reason to red tag it.
 
I agree with JD, but have to add that I have never seen NM Cable with the conductors labelled inside the sheath. Not saying that it does not exist, just that it would be fairly rare.
 
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