Plain NM w/o any following designation is the old, original "Romex (tm)"
that used fiber insulation and hence was dry-only application. NM-C
followed w/ the plastic. NM is, for the most part, unavailable.
AFAIK, the "B" designation is for building application and is the
nomenclature for the color-coded sheathing of white/yellow/etc. designed
to aid in ensuring proper conductor size is used in appropriate circuits
and making for easier/quicker verification during inspection.
I'm pretty sure the main diff between NM and NM-B is the higher temp
rating of the insulation used. 90C vs. 60C IIRC. (remember back in the
day taking down light fixtures and having to keep heat shrink handy to
cover up the wire ends where they crumbled when you flexed them?)
replace "roosters" with "cox" to reply.
Nope, The "B" means it uses a 90c conductor, not really THHN but a
I doubt anyone here has ever seen NM-c. That is a NM cable listed for
If you look on any wire manufacturer's web page I have looked at NM-c
ends up referring you to UF (a wet location cable). I suspect there is
not enough of a market to make it generally available in the US. I
have heard you can get NM-c in Canada but I don't know that for sure.
A recent code change may make NM-c more common..
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