NM cable and the outdoors

[all-power]

Definitions are there so people don't make up there own. Definitions explain and define the code. Some people look up at the sky and say it's a nice color blue, other's say it's more of a gray color. The insulation of the wire does matter because THWN is rated for wet locations and THHN is rated for damp locations, 310.104A. Romex was always dual rated. The material inside is not an issue. UF wire is black for outdoor use. Sunlight resistance. Not the same.

 

[Fred B]

Article 100 definition(s) are not the enforceable section of code, informational only.
300.9 clearly says inside of conduit is a wet area.
334.12(B)(4) clearly states NM cannot be used in a wet location.
Thus NM inside of conduit on exterior of building is a violation. Do it and you will fail an inspection. Like it or not, code is code. Don't like it, take it up with the NEC.

Grey area not adequately covered in code is as to NM entry directly into a box or fixture on outside of building. Personally I've seen several incidents of wet paper in NM terminating in outside fixtures here in the northeast.

 

[all-power]

If you look at the FPN for the def of wet location, it uses the term raceway and not conduit. A raceway is a channel where you run wires, like a trough. If they said conduit than maybe. They don't use the word conduit. Conduit is not a channel. Again, the definition of a wet location is something like a car wash and in an unprotected location exposed to the outdoors. Some of our inspectors no the difference others don't.

 

[don_resqcapt19]

If you look at the FPN for the def of wet location, it uses the term raceway and not conduit. A raceway is a channel where you run wires, like a trough. If they said conduit than maybe. They don't use the word conduit. Conduit is not a channel. Again, the definition of a wet location is something like a car wash and in an unprotected location exposed to the outdoors. Some of our inspectors no the difference others don't.

Please take a look at the definitions of all of the conduits in their respective articles in the code. They all define the conduits as a "raceway". For example:

Electrical Metallic Tubing (EMT).
An unthreaded thinwall raceway of circular cross section designed for the physical protection and routing of conductors and cables and for use as an equipment grounding conductor when installed utilizing appropriate fittings.

 

[readydave8]

If you look at the FPN for the def of wet location, it uses the term raceway and not conduit. A raceway is a channel where you run wires, like a trough. If they said conduit than maybe. They don't use the word conduit. Conduit is not a channel.

conduit is not a raceway? learn something new every day

 

[Fred B]

conduit is not a raceway? learn something new every day

If you look at the FPN for the def of wet location, it uses the term raceway and not conduit. A raceway is a channel where you run wires, like a trough. If they said conduit than maybe. They don't use the word conduit. Conduit is not a channel. Again, the definition of a wet location is something like a car wash and in an unprotected location exposed to the outdoors. Some of our inspectors no the difference others don't.

Better check for example 352.2 for those keen on definitions.
352.2 Definition.
Rigid Polyvinyl Chloride Conduit (PVC). A rigid nonmetalic raceway of circular cross section, with integral or associated Couplings, connectors, and fittings for the installation of electrical conductors and cables. (NEC 2017)

 

[don_resqcapt19]

If you look at the FPN for the def of wet location, it uses the term raceway and not conduit. A raceway is a channel where you run wires, like a trough. If they said conduit than maybe. They don't use the word conduit. Conduit is not a channel. Again, the definition of a wet location is something like a car wash and in an unprotected location exposed to the outdoors. Some of our inspectors no the difference others don't.

The reason they use the term raceway in that note is because if they didn't they would have to list all of the conduit types, tubing types and wire way types as they are all raceways.

 

[jaggedben]

Conduit is a subset of raceways.

 

[all-power]

So I reached out to Southwire which makes Romex. I know that the wires used to be listed THHN/THWN but now they are not. In fact they have no listing. MC cable wires are listed THHN/THWN. That is on the package. I thought all wires had to be listed for their use.

This is the response I received.

The conductors within NM-B Cable have no listing. Per UL, they are not listed apart from the compete NM Cable construction, therefore they are not marked and they are not recognized by the NEC. They are made with PVC insulation and a nylon jacket so they are similar to THHN/THWN(-2) conductors.

Dave
Dave Watson Principal Engineer Southwire Company LLC

 

[kwired]

So I reached out to Southwire which makes Romex. I know that the wires used to be listed THHN/THWN but now they are not. In fact they have no listing. MC cable wires are listed THHN/THWN. That is on the package. I thought all wires had to be listed for their use.

This is the response I received.

The conductors within NM-B Cable have no listing. Per UL, they are not listed apart from the compete NM Cable construction, therefore they are not marked and they are not recognized by the NEC. They are made with PVC insulation and a nylon jacket so they are similar to THHN/THWN(-2) conductors.

Dave
Dave Watson Principal Engineer Southwire Company LLC

They very well might be exactly the same thing as THHN/THWN, but the fact they are not marked means you can't strip the sheath off and use them as THHN/THWN. Conductors used in MC cable are not necessarily marked either. Sometimes they are though.

 

[all-power]

I was under the impression that it just had to be listed. We get high voltage cables that are marked on the outside but the cables inside are not marked. We use them to run from switch to switch out of the jacket and are not marked.