300.50(A) Interpretation

[bwat]

In 300.50(A), there are 3 categories of permissible installation that UG for >1000V must follow. The 3 options have the following titles:

300.50(A)(1) - Shielded Cables and Nonshielded Cables in Metal-Sheathed Cable Assemblies.
300.50(A)(2) - Industrial Establishments
300.50(A)(3) - Other Nonshielded Cables

Root Question: Does 300.50(A)(1) mean "Shielded Cables in Metal-Sheathed Cable Assemblies" and "Nonshielded Cables in Metal-Sheathed Cable Assemblies", OR is it "Shielded Cables" and "Nonshielded Cables in Metal-Sheathed Cable Assemblies"? The second way meaning that shielded cables without a metal sheath apply to this (A)(1).

My first interpretation of this section was that (A)(1) applies only to MC similar type... both for shielded and nonshielded... having that corrugated metal sheath like MC. But after looking at the rest of this section, I think (A)(1) applies to shielded cables without the metal sheath as well. So (A)(1) should be read as "Shielded Cables" and "Nonshielded Cables in Metal-Sheathed Cable Assemblies". Otherwise, what is permitted for a shielded 5kV cable without metal sheath? (A)(2) is only up to 2000V, and (A)(3) is only about other nonshielded cables.


Some colleagues and I had a debate on this a month or two ago, and now it has come up again on another project. Thank you in advance.

 

[electrofelon]

I have wondered this and find the wording rather ambiguous. I think (A)(1) must mean ""Shielded Cables" and "Nonshielded Cables in Metal-Sheathed Cable Assemblies" otherwise there would be many cables not covered. The only other option is is that they intend (A)(1) thru (3) to apply "as applicable" this allowing for other options , however with the use of the word "or" that doesn't seem to be what they mean.

 

[don_resqcapt19]

Yes, it applies to both. You can use a cable assembly consisting of shielded conductors without a metal jacket, or you can use a cable assembly consisting of non-shielded conductors in a metal sheath.

 

[bwat]

Thank you to both of you.

Perhaps if the CMP adds a simple comma in the future it may help clarify. Something like "Shielded Cables, and Nonshielded Cables in Metal-Sheathed Cable Assemblies"

 

[don_resqcapt19]

Thank you to both of you.

Perhaps if the CMP adds a simple comma in the future it may help clarify. Something like "Shielded Cables, and Nonshielded Cables in Metal-Sheathed Cable Assemblies"

You can submit a PI for that change to be made in the 2023 code. nfpa.org/70 and then click on "next edition" and then on "submit a public input online".

 

[bwat]

Done. Thank you. I didn't realize that it was so easy to submit public input.