Whats the difference between Romex NM Electrical Cable and Romex NMC Electrical Cable
taras1
| Posted in General Discussion on
Whats the difference between Romex NM Electrical cable and Romex NMC Electrical cable ?
What is each used for? (What application)
I know NM is romex simpull and it is for indoor use.
I was told romex NMC is for inside or outdoors.
My local electrical store does not know about romex NMC.
Maybe it stands for non metalic cable.
I reside in NYC and do not know the code for this NMC and what application it is within code.
I am wondering if romex NMC can be used directly under vinyl siding in a 2 family house for lighting?
And within NYC code?
I have tried and can’t seem to get answers to this on line.
Thanks for your help.
Replies
"Type NM. Insulated
"Type NM. Insulated conductors enclosed within an overall
nonmetallic jacket."
"Type NMC. Insulated conductors enclosed within an
overall, corrosion resistant, nonmetallic jacket."
"Type NMC cable is for use in dry, moist, damp, and corrosive locations, and Type NM cable is for use in normally dry locations."
It's not clear whether NMC is a unique type or just another designation for UF.
NM-C defaults to UF
If you look for NMC on most wire manufacturer's web sites that is where you end up. NM-C is basically regular Romex with a plastic packing instead of paper but I am not sure anyone in the US actually makes it. I have heard it called "barn cable" so there may be a supplier in rural areas.
For most users, buy UF if you are not using it in a dry location.
http://books.google.com/books?id=ZlsHKuq4eBoC&pg=PA711&lpg=PA711&dq=nm+nmc+uf&source=bl&ots=aZoJ3eXzTC&sig=ojA0Lk29k36C3h_4vrVonuNb4cM&hl=en&ei=aCbcTLmCD8jPnAfx17kW&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCgQ6AEwAg#v=onepage&q=nm%20nmc%20uf&f=false
NMC and UF cable are entirely different things.
NMC is a corrosion resistant type of NM cable that is permitted for use indoors.
UF cable is restricted to use underground only and outdoors above ground where it is designated as UV resistant. It is prohibited from being installed on the interior of a building.
Reason NMC is sometimes called 'barn cable' is that agricultural buildings housing animals are subject to the caustic effects of urine and its by-product gases. This urine/gas is corrosive and will damage the cover and insulation of standard NM cable.
NMC can also be used in other types of building environments where corrosive gases may affect electrical wiring.
We installed UF inside in Puerto Rico since it better withstands rats. Kept all of the wiring above 18" in the walls as well.
"UF cable is restricted to
"UF cable is restricted to use underground only and outdoors above ground where it is designated as UV resistant. It is prohibited from being installed on the interior of a building. "
Cite that.
I see this
340.10 Uses Permitted.
Type UF cable shall be permitted as follows:
(1) For use underground, including direct burial in the earth. For underground requirements, see 300.5.
(2) As single-conductor cables. Where installed as single-conductor cables, all conductors of the feeder grounded conductor or branch circuit, including the grounded conductor and equipment grounding conductor, if any, shall be installed in accordance with 300.3.
(3) For wiring in wet, dry, or corrosive locations under the recognized wiring methods of this Code.
(4) Installed as nonmetallic-sheathed cable. Where so installed, the installation and conductor requirements shall comply with Parts II and III of Article 334 and shall be of the multiconductor type.
You are correct and I am wrong.
I wrote my comments yesterday morning from memory and without access to my copy of the NEC.
Once I got to my office and looked up Art. 334 for UF I realized my memory isn't very good anymore. :)
Came here to change my comments and see that others had already done that for me.
Thanks for the heads up and again, my apologies for any errors.
Gee, you're the only one I know having memory problems. For the rest of us our memory gets better the older we get. Mine's damn near perfect.