2026 PI for 340.10 "Uses Permitted" for UF

[wwhitney]

Seems to me that subsections (3) and (4) don't match the commonly understood intentions, and would be better worded as:

(3) For wiring in wet, damp dry, or corrosive locations.
(4) In dry locations, where installed Installed as nonmetallic-sheathed cable. Where so installed, the The installation and conductor requirements shall comply with Parts II and III of Article 334 and shall be of the multiconductor type.

As currently worded, subsection (4) is meaningless, as subsection (3) provides a blanket allowance for dry locations. And the allowance for damp locations seems to be missing.

Cheers, Wayne

 

[Hv&Lv]

Seems to me that subsections (3) and (4) don't match the commonly understood intentions, and would be better worded as:

(3) For wiring in wet, damp dry, or corrosive locations.
(4) In dry locations, where installed Installed as nonmetallic-sheathed cable. Where so installed, the The installation and conductor requirements shall comply with Parts II and III of Article 334 and shall be of the multiconductor type.

As currently worded, subsection (4) is meaningless, as subsection (3) provides a blanket allowance for dry locations. And the allowance for damp locations seems to be missing.

Cheers, Wayne

Isn’t the definition of damp “slightly wet”?

 

[wwhitney]

Isn’t the definition of damp “slightly wet”?

No, the definitions are more specific and are generally understood to be mutually exclusive (see below for the 2017 definitions). I personally can't think of any equipment that would be suitable for a wet location but not for a damp location, but a priori there could be some. The phrase "wet or damp" occurs 11 times in the 2017 NEC, and absent a blanket statement somewhere that anything rated for a wet location may used in a damp location, that is the logical phrasing to use.

Cheers, Wayne


Location, Damp. Locations protected from weather and not subject to saturation with water or other liquids but subject to moderate degrees of moisture. (CMP-1)

Informational Note: Examples of such locations include partially protected locations under canopies, marquees, roofed open porches, and like locations, and interior locations subject to moderate degrees of moisture, such as some basements, some barns, and some cold-storage warehouses.

Location, Dry. A location not normally subject to dampness or wetness. A location classified as dry may be temporarily subject to dampness or wetness, as in the case of a building under construction. (CMP-1)

Location, Wet. Installations underground or in concrete slabs or masonry in direct contact with the earth; in locations subject to saturation with water or other liquids, such as vehicle washing areas; and in unprotected locations exposed to weather. (CMP-1)

 

[petersonra]

Seems to me that subsections (3) and (4) don't match the commonly understood intentions, and would be better worded as:

Just what is it that you think the commonly understood intentions actually are. That might be a place to start.

Personally I don't have a problem with explicitly requiring UF cable to be installed like NM when it is not underground.

 

[wwhitney]

Just what is it that you think the commonly understood intentions actually are. That might be a place to start.

Basically what you said, that if it's installed indoors it should comply with the requirements for NM. But as it stands now, subsection (4) could be deleted without changing the literal meaning of the section, since subsection (3) allows it in dry locations without further restriction.

Cheers, Wayne

 

[rnatalie]

Are you sure there isn't a comma missing there?

 

[wwhitney]

How do you mean?

Cheers, Wayne

 

[petersonra]

It seems to me that clause number four just says that if you are installing UF as NM you have to follow the NM rules. I don't see that that's particularly confusing.

 

[wwhitney]

Example of the logic problem with 334.10(3) and (4):

If I say "red wine may be paired with (a) any meat or (b) chicken with mushrooms," and then ask "may I pair red wine with a chicken dish without mushrooms?" then the answer is "yes" because (a) says I can pair it with any meat. I don't have to look at (b).

If I want to require the use of mushrooms when pairing red wine with chicken, then I had better modify my statement to "red wine may be paired with (a) any meat except chicken or (b) chicken with mushrooms."

Cheers, Wayne

 

[kwired]

Isn’t the definition of damp “slightly wet”?

Sort of but yet no. It is defined in art 100 and quoted in post 3.

 

[mbrooke]

Mike recently defined damp