Don't see Romex (NM or NM-B) listed in Table 310.4(A)

[Sea Nile]

I'm sure this is probably an easy question to answer and probably asked here before.
But why isn't NM-B listed in table 310.4(A)?
Just to be clear, I'm not saying that Romex can't be used.

I also don't see it in Table 310.16, but I know that NM-B is pretty much the same as THHN, (90 deg C, and dry location), and NM is 60 Deg C dry location.

I'm not trying to say anyone in wrong, I'm just trying to understand. This is what confuses me: As long as Romex had been around, I would have expected that NM, NM-B be added to the table, or that Romex would start stamping their cable with one of the Letter Types listed in 310.4(A).

 

[wwhitney]

310.4(A) is a table of insulation types for individual conductors. So most cable types are not listed, such as AC, MC, or NM. UF is listed only because UF is available in a single conductor form in addition to as a multiconductor cable.

Cheers, Wayne

 

[xformer]

NM is manufactured with 90 C conductors.

 

[augie47]

NM is manufactured with 90 C conductors.

But note, they are not necessarily THHN or any other 310.4 conductor. They are simply insulated conductors meeting the standard for Romex.
This also means they have to follow the 334.80 limitation for 60°C termination.

 

[wwhitney]

But note, they are not necessarily THHN or any other 310.4 conductor. They are simply insulated conductors meeting the standard for Romex.

My recollection from a brief reading of the UL standard for Romex was that they have to either actually be THHN, or be PVC insulated and meeting all the standards that THHN has to meet, without actually being THHN.

Cheers, Wayne

 

[augie47]

echo ??

 

[wwhitney]

echo ??

My point was that the standard for Romex is actually THHN or the functional equivalent, as opposed to some other possible 310.4(A) type.

Cheers, Wayne

 

[kwired]

May or may not be same thing as THHN/THWN. Bottom line is it is already part of a listed assembly and doesn't need to be individually marked - therefore you don't know for certain what standards it may be equivalent to.

Have seen individually marked conductors in some AC or MC cables before though, which could have sheath stripped off and used in raceway methods since it is marked.

 

[tom baker]

NM is manufactured with 90 C conductors.

NM-B replaced NM in about 1984

 

[tom baker]

I found some old black jacketed NM, 1980 vintage, that the inside wires were labeled THW

 

[LarryFine]

I found some old black jacketed NM, 1980 vintage, that the inside wires were labeled THW

Then you can use them without the sheath.