No exposed flex below 8 feet it’s part of a concealed wiring system.
Any building of 4 stories in height or more,
you need to use metal cable
instead of the plastic cable
Metal cable is harder to work and costs more in labor and materials
Nonmetallic sheathed cables in dwellings with more than three floors
Q: I wanted to respond to your commentary on Article 336 in the December 1999 issue of Electrical Contractor magazine. The question was " ... are we allowed by the National Electrical Code (NEC) to wire this four-story building with nonmetallic sheathed cable?" Your reply was "... yes if the enforcing authority in your jurisdiction has adopted the 1999 NEC without any amendments to Sections 336-4 and 336-5."
I believe your answer to the question is incorrect based on a reading of the Code Sections you included in the column and verified by examination of those same sections in my copy of the 1999 NEC.
Regardless of revisions to 336-4, Section 336-5(a) in the 1999 NEC, it is clear that NM, NMC, and NMS are prohibited in "any multifamily dwelling or other structure exceeding three levels above grade." The structure in question is four levels above grade, is it not? So where is there anything in the 1999 NEC that overrules this section to allow NM cabling in a structure more than three levels above grade? Maybe I am missing something, but I am sure there are many others who are confused in the same way. Could you clarify these issues for us?
A: The permitted uses for nonmetallic sheathed cable were expanded in the 1999 NEC. Types NM, NMC, and NMS cables could not be installed in dwelling occupancies that exceeded three floors above grade. An explanation indicated how the first floor of a building was determined and pointed out that a first level utilized only for vehicle parking, storage, or similar use was not counted in arriving at the three-story limitation. In other words, a four-story building with three stories designed for human occupancy and the first level designed for off-street parking could be wired with nonmetallic sheathed cable. There was also an exception that allowed conversion of an attic space, vehicle parking space, or storage space to a habitable floor level in a one-family dwelling without having to change the existing wiring method.
Permission to use nonmetallic sheathed cable in one-and two-family dwellings appears in Section 336-4(1) of the 1999 NEC: "USES PERMITTED. Type NM, Type NMC, and Type NMS cables shall be permitted to be used in the following: (1) One-and two-family dwellings (2) Multifamily dwellings and other structures, except as prohibited in Section 336-5 (3) cable trays, where the cables are identified for the use." Notice that there is no restriction on the number of floors for one-and two-family dwellings. Item (2) allows nonmetallic sheathed cable to be used as the wiring method in multifamily dwellings and other structures if the limitation specified in Section 336-5 is satisfied. Item (a)(1) in Section 336-5 limits the height of multifamily dwellings and other structures to three floors where the wiring method is nonmetallic sheathed cable.
Definitions in Article 100 explain what a dwelling unit is and the read out defines one-family, two-family, and multifamily dwellings.
Nonmetallic sheathed cables in dwellings with more than three floors
Q: I wanted to respond to your commentary on Article 336 in the December 1999 issue of Electrical Contractor magazine. The question was " ... are we allowed by the National Electrical Code (NEC) to wire this four-story building with nonmetallic sheathed cable?" Your reply was "... yes if the enforcing authority in your jurisdiction has adopted the 1999 NEC without any amendments to Sections 336-4 and 336-5."
I believe your answer to the question is incorrect based on a reading of the Code Sections you included in the column and verified by examination of those same sections in my copy of the 1999 NEC.
Regardless of revisions to 336-4, Section 336-5(a) in the 1999 NEC, it is clear that NM, NMC, and NMS are prohibited in "any multifamily dwelling or other structure exceeding three levels above grade." The structure in question is four levels above grade, is it not? So where is there anything in the 1999 NEC that overrules this section to allow NM cabling in a structure more than three levels above grade? Maybe I am missing something, but I am sure there are many others who are confused in the same way. Could you clarify these issues for us?
A: The permitted uses for nonmetallic sheathed cable were expanded in the 1999 NEC. Types NM, NMC, and NMS cables could not be installed in dwelling occupancies that exceeded three floors above grade. An explanation indicated how the first floor of a building was determined and pointed out that a first level utilized only for vehicle parking, storage, or similar use was not counted in arriving at the three-story limitation. In other words, a four-story building with three stories designed for human occupancy and the first level designed for off-street parking could be wired with nonmetallic sheathed cable. There was also an exception that allowed conversion of an attic space, vehicle parking space, or storage space to a habitable floor level in a one-family dwelling without having to change the existing wiring method.
Permission to use nonmetallic sheathed cable in one-and two-family dwellings appears in Section 336-4(1) of the 1999 NEC: "USES PERMITTED. Type NM, Type NMC, and Type NMS cables shall be permitted to be used in the following: (1) One-and two-family dwellings (2) Multifamily dwellings and other structures, except as prohibited in Section 336-5 (3) cable trays, where the cables are identified for the use." Notice that there is no restriction on the number of floors for one-and two-family dwellings. Item (2) allows nonmetallic sheathed cable to be used as the wiring method in multifamily dwellings and other structures if the limitation specified in Section 336-5 is satisfied. Item (a)(1) in Section 336-5 limits the height of multifamily dwellings and other structures to three floors where the wiring method is nonmetallic sheathed cable.
Definitions in Article 100 explain what a dwelling unit is and the read out defines one-family, two-family, and multifamily dwellings.
